USGS Professional Paper 993, text - USGS Publications Warehouse [PDF]

Youd, T. T. L., L., and and Hoose, Hoose, S. S. N. N. (1978). (1978). "Historic "Historic ground ground failures failures in in northern northern California California triggered triggered by by Youd, earthquakes." U.S. U.S.Geological Geological Survey Survey professional professional paper paper 993, 993, U.S. U.S.Govt. Govt. Print. Print. Off., Off., Washington, Washington, iv, iv, 177 177 p. p. earthquakes."

Historic Ground Failures in Northern California Triggered by Earthquakes By T. L. YOUD and S. N. HOOSE

GEOLOGICAL

UNITED

STATES

SURVEY

GOVERNMENT

PROFESSIONAL

PRINTING

OFFICE,

993

PAPER

WASHINGTON

:

1978

UNITED STATES DEPARTMENT OF THE INTERIOR CECIL D. ANDRUS, Secretary

GEOLOGICAL SURVEY I

W.A. Radlinski, Acting Director

Library of Congress Cataloging in Publication Data Youd, T. Leslie Historic ground failures in northern California triggered by earthquakes. (Geological Survey Professional Paper 993) 1 Bibliography: p. 68-71. 1. Earth movements-California. 2. Earthquakes-California. I. Hoose, S. N., joint author. 11. Title. 111. Series: United States. Geological, Survey. Professional Paper 993. QE598.2.Y68 624'.176 77-608366

FOI sale hy the Superintendent of ~ o c u m e " t s ,U.S. Goiernment Printing Office Washington, D.C. 20402 Stock Number 024-001-03060-8

CONTENTS Page

Abstract .................................................. 1 Introduction .............................................. 1 Area of investigation ...................................... 2 Rainfall and ground water conditions in 1906 .............. 2 Ground failure types ...................................... 4 Limitations of ground failure data .......................... 5 Distribution and character of ground failures . . . . . . . . . . . . . . . . 9 Monterey Bay counties region .......................... 13 San Francisco Bay counties region ...................... 23 Santa Cruz Mountains ............................ 23

Page

Distribution and character of ground fai1ures.X ontinued San Francisco counties region-Continued San Francisco Bay. Santa Clara Valley and east bay hills area ...................................... San Francisco City and County .................... North bay counties region .............................. North coast counties region ............................ Summary and conclusions .................................. References cited ..........................................

ILLUSTRATIONS [Plates are in pocket1

1. 2 3 4. 5

PLATE

. . .

FIGURE

Location map of ground failures in the Monterey Bay counties region . Location map of ground failures in the San Francisco Bay counties region Location map and of ground failures in San Francisco City and County. Location map of ground failures in the north bay counties region . Location map of ground failures in the north coast counties region

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1. 2. 3 4. 5 6 7.10

Map of northern California showing areas in which earthquake-triggered ground failures have occurred . . . . . . . . . . Graphs of monthly rainfall data for the 190&06 water year compared with average rainfall data ................ Map showing rainfall distribution in California during March 1906 ............................................ Graphs of daily rainfall data for March and April 1906 ........................................................ Map showing 1906 earthquake intensities for San Francisco County ............................................ Map showing 1906 earthquake intensities for Western United States .......................................... Photographs showing: 7 . Damage a t Spreckels sugar mill as a consequence of lateral spreading during 1906 earthquake .............. 8. Barley field near Spreekels disrupted by slumping and lateral-spreading failures . . . . . . . . . . . . . . . . . . . . . . . . . . . . ............. 9 County road along Salinas River, south of Salinas, disrupted by slumping and lateral spreading . . 10 South terminal pier of bridge over Salinas River . Surficial deposits shifted about 6 ft (2 m) toward the river . 11 Geotechnical section across the Salinas River ................................................................ 17-29 . Photographs showing: 12. Damage a t Moss Landing caused by lateral spreading .................................................... 13. Ground failure scarp near the south bank of Pajaro River across from Watsonville .......................... 14 Graben and damaged buildings caused by lateral spread in Watsanville .................................... 15. Slump scarp and sandboil near Pajara River .............................................................. 16. Sandboil near Wat~onville.............................................................................. 17. Ruptured abutment of county road bridge over the Pajaro River near Chittenden ............................ 18 Hillside landslide in a redwood forest near Alma .......................................................... 19. Deer Creek landslide that destroyed the Hoffman Shingle Mill and took one life ............................ 20. Flow failure in hills southeast of Half Moon Bay .......................................................... 21 . Flow failure east of Half Moon Bay ...................................................................... 22. Flow failure 4 mi (6.4 km) east of Half Moon Bay ........................................................ 23. Rockfalls along coastal bluffs between Ocean Avenue, San Francisco, and Mussel Rock ...................... 24 Landslide an ~ t e e phillside near Mussel Rock ............................................................ 25. Cavity of flow failure above Mt Olivet Cemetery near Colma .............................................. 26 Rails of electric railway on marsh west of San Bruno that were buckled by compression ...................... 27 Ground cracks in the "icinity of Coyote Creek west of Milpitas ............................................ 28. Sand boils in field between Milpitas and Coyote Creek .................................................... 29. Geotechnical section across Coyote Creek a t the Alviso-Milpitas road bridge . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

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In

23 24 60 66 67 68

IV

CONTENTS

FIGURE

30 . 31. 32 33 .

.

34 .

35. 36 . 37

.

38-41.

42 . 43-50 .

Aerial photograph of commercial and shipping district of San Francisco showing ground failure zones ............ Photograph showing cracks and separations in roadway pavement near San Francisco water front ................ Geotechnical section beneath Market Street .................................................................. Photograph showing dlstruprion of block pavement and sidewalk on Columbln Street just sourh of Folsom Street ... Photograph shuw~ng. pulled-apart rails on Flfth Strert near Harrlson Street ................................ . Photograph showing damage to San Francisco Post Office caused by ground failure .............................. Geotecbnical profile across south of Market zone a t James Lick Skyway between Third and Sixth Streets ........ Schematic diagram of area between Ninth andTenthStreets andBryant and Brnnnan Streets in lower part of Mission Creek zone, San Francisco, showing locations and directions fmm which photographs in figures 3 U 1 were taken .. Photographs showing: 38. View along Dore Street from Bryant Street toward Brannan Street ........................................ 39. Scarps and right-lateral displacements caused by lateral spreading a t two points on Bryant Street near the intersection of Ninth Street .......................................................................... 40. Views along Ninth Street between Bryant and Brannan Streets ............................................ 41. View northeastward an Brannan Street, corner of Ninth Street ............... Schematic diagram of area between 17th and 18th Streets and Capp Street and South Van Ness Avenue in the central part of Mission Creek zone, San Francisco, showing locations and directions from which photographs in figures 43-47 were taken ...................................................................................... Photographs showing: 43 Buckling of rails by compression an Howard Street (South Van Ness Avenue) near 17th Street .............. 44. South Van Ness Avenue in San Francisco with rails offset by lateral-spreading ground failure .............. 45 . Scarps showing vertical movement and northward lateral movement on 18th Street ........................ 46. Scarps with lateral and vertical displacements in Capp Street between 17th and 18th Streets ................ 47 Buckled curbstone on Capp Street near 18th Street ........................................................ 48. Valencia Street between 17th and 18th Streets ............................................................ 49 Photograph of San Francisco in fiames after 1906 shack.................................................... 50. Lateral-spread at the Youth's Directory on 17th and Guerrero Streets ...................................... Geotechnical section across Mission Creek zone .............................................................. Photographs showing: 52 Distruption of Van Ness Avenue over a filled-in ravine .................................................... 53 Slump in Union Street between Pierce and Steiner Streets ................................................ 54 Flow failure along shoreline of Lake Merced triggered by the 1957 Daly City earthquake .................... 55. Cracks a t Bolinas Lagoon ................................................................................ 56. Cracks along the edge of a sag pond near Bolinas ........................................................ 57 Tipping of buildings into the water a t the Balinas waterfront .............................................. 58. Cracks and settlement a t the head of a lateral spread between Olema and Inverness ........................ 59. Cracks generated by lateral spread southwest of Point Reyes Station ...................................... . . . . . . . . . . . . . . . . . . . 60. Cracking and subsidence of road grade across a marsh southwest of Point Reyes Station . 61. Ridged bottom of Tamales Bay after 1906 earthquake ...................................................... 62 Shifted sediments of Tomales Bay ........................................................................ 63. Boat piers a t Invernessdisplaced duringearthquake ...................................................... 64. Hillside Row failure near Inverness ...................................................................... 65. Hillside landslide in roadcut west of Inverness ............................................................ 66. Landslide on east side of Garcia River Valley ............................................................ 67 . Cape Fortunas (False Cape) landslide, one of the largest landslides triggered by the 1906 shock .............. ~

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51. 5 2 6 7.

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TABLES Page

TABLE

1. Northern California earthquakes of 1769-1970 associated with reported ground failures ........................ 3 2 . Excerpted notes containing general descriptions of the types, character, and locations of ground failures associated with the 1906 San Francisco earthquake.................................................................. 6 3 Excerpted notes containing general descriptions of ground failures in the Monterey Bay counties region .......... 14 4 Excerpted notes containing general descriptions of ground failure and consequent pipeline breaks in San Francisco .... 26 5 Specific deseri~tionsof mound failures in the Monterev . Bay . counties r e ~ o n........................................ 74 6 . Specific descriptions of gmund fadurcs in the S m Francisco Bay counties refion ................................... 88 7. Specific dcscnptions of ~ w u n dfailures in San Francisco City and County ......................................... 125 8. Specificdescriptions of ground failures in the north bay counties region . ........................................... 147 9 Specific descriptions of gmund failures in the north coast counties region ...................................1 . . . . . . 164

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HISTORIC GROUND FAILURES IN NORTHERN CALIFORNIA

TRIGGERED BY EARTHQUAKES By T. L.

you^

and S. N. H o o s ~

ABSTRACT

/

A major source of earthquake-related damage and casualties in northern California has been ground failures generated by the seismic shaking, including la~dslid~J,,la~ef.a~~~f~~d~!, .gr~unr.~sLIs: ment, andsurface cracks. The historical record shows that, except far ashore shocks, the area affected and the qu~antityand general severity of ground failures increase markedly with Richter magnitude. Hence, the largest historical event, the 1906 San Francisco earthquake, has been the most important generator of ground failures. Because of recent population growth and land development in northern California, the potential for damage in future events is enormous compared with that existing in 1906. Reports of the 1906 San Francisco earthquake and other northern California earthquakes and descriptions of ground failures therein mound failures asare used to (1) identifv and clarifv the tvoes of sociated with earthquakes, (2) provide a guide for engineers, planners, and others responsible for minimizing seismic hazards, and (3) form a data base for other geotechnical studies of earthquaketriggered pound failures. ~;alogie,hydrologic, and topographfc setting have an important influence on ground failure development as well as distance from the causative fault. Areas especially vulnerable to ground failure in northern California have been oversteepened slopes, such as mountain cliffs, streambanks, and coastal bluffs, and lowland deposits, principally Holocene fluvial deposits, deltaic deposits, and poorly compacted fills. Liquefaction has been the direct cause of most lowland failures. The historical record suggests that ground failures during future large earthquakes are most likely to occur a t the same or geologically similar locations as failgres during previous earth-

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m,rka. y--.."".

INTRODUCTION

Earthquakes are one of the most perilous natural hazards affecting northern California. One great (Richter magnitude, M, greater than 8) and several major (M greater than 6) earthquakes have struck that region in historic time (last 200 years). These shocks caused extensive property damage and inflicted several hundred casualties. Because of large population growth and land development in recent years, the potential for damage in northern California is enormous today compared with that existing in 1906, the date of the last major destructive shock. A principal cause of past earthquake damage and casualties has been seismically generated ground failures in the form of landslides, lateral spreads, differ-

ential settlements, and ground cracks. In this study, earthquake reconnaissance reports and newspaper reports from past events in northern California are reviewed, and ground failures described therein are identified, classified by present criteria, and located on modern maps. The purposes of this study are (1) to identify and clarify the types of ground failures associated with earthquakes, (2) to provide a guide for engineers, planners, and others responsible for minimizing seismic hazards, and (3) to form a data base for further geotechnical studies of earthquake-triggered ground failures. Each reported ground failure site has been given a location number, and descriptions of that failure excerpted from the literature are tabulated by location ndmber in tables 5-9. The location number is entered on the appropriate plate near the location of the failure, and a symbol indicating the inferred type of failure is placed as accurately as possible on the plate over the corresponding failure site. This classification symbol is also entered in the descriptions of failures a t that location number along with a letter symbol indicating the geographical accuracy with which the failure can be relocated on modern maps. Ex~lanationsfor the classification symbols are given on each plate and in the notes to the descriptions of failures; also, explanations for the accuracy symbols are listed in these notes. Acknowledgments.-We gratefully acknowledge the psistance of the following individuals and organizations who contributed to this study by providing information, photographs, and helpful suggestions: Grace Curtis, Pajaro Valley Historical Society; Clyde Arbuckle, former San Jose City historian; Jarvis McGowan, resident of Monterey County; Albert T. Vierra, Sr., resident of Moss Landing; Hans Struve, resident of Moss Landing; John Hughes, resident of Salinas; Salinas Valley Historical Society; Henry J. Degenkolb and Associates, San Francisco; The Bancroft Library, University of California, Berkeley; Stanford University Archives; San Francisco Public Library; Humboldt ~

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HISTORIC GROUND FAILURES IN NORTHERN CALIFORNIA TRIGGERED BY EARTHQUAKES

area affected by the 1872 Owens Valley, Calif., earthquake was thus excluded from consideration in this report. Although earthquake vibrations have been felt historically over all of northern California, ground failures of greater than very slight severity (table 1)have been reported only from a narrow strip along the Pacific Coast that lies almost entirely within the Coast AREA OF INVESTIGATION Ranges province (fig. 1)(Bailey, 1966, p. 2). This does The region considered in this study (fig. 1) extends not mean that severe earthquake-induced ground failfrom the southern parts of Monterey, Kings, and Tuures cannot occur in other areas, but rather that they lare Counties (approx lat 36' N.) on the south to the have not in recent times. Oregon border (lat 42" N.) on the north and from the Geographically the Coast Ranges province forms a Pacific Ocean on the west to the Nevada border or crest band along the coastline of northern California that of the Sierra Nevada Mountain range on the east. The extends inland as far as 70 miles (110 km) from the Pacific Coast. The province is composed of several northwest-trending mountain ranges and intermontane valleys. The ranges are made up of Mesozoic and Cenozoic rocks that have been faulted and folded (Christensen, in Bailey, 1966, p. 305313). The larger valleys commonly are deeply alluviated and traversed by meandering rivers and streams. The most important structural feature in the province is the San Andreas fault, which strikes approximately N. 35" W. and cuts across the general trend of the mountain ranges a t a small angle (Oakeshott, in Bailey, 1966, p. 357-3721, Most northern California earthquakes are associated with movements on this fault or subsidiary faults in the San Andreas fault system. Historic earthquakes in northern California that have triggered ground failures are listed in table 1, and approximate epicentral locations are plotted on figure 1; for the 1906 San Francisco and 1868 Hayward earthquakes, the approximate zones in which ground failures occurred are delineated. This figure confirms that the 1906 San Francisco earthquake is by far the most significant event for ground failure studies in this region because of the vast area affected and also the,, number and severity of the failures generated. The1 i tabulation also shows that earthquakes with mag-! nitudes less than 4 have produced no reported (and1 i thus no consequential) ground failures. Above magnitude 4, severity of generated ground failures gener- ; ally increases with magnitude. State University Library; Mary Lou Malhern, Bay Area Rapid Transit District; George Litros, Berkey Photos (formerly Bear Photo); Charles A. Smallwood, resident of San Francisco; M. G. Bonilla, Albert T. F. Chen, Jackie Freeberg, Edwin L. Harp, and Julius Schlocker, U.S. Geological Survey.

: 1

RAINFALL AND GROUND WATER CONDITIONS IN 1906

Ground water conditions are an important factor controlling development of many seismically generated ground failures, especially those associated with FIGURE 1.-Map of California showing Coast Ranges province, areas liquefaction. In most upland areas, ground water concovered by regional maps, and areas in which ground failures have ditions at any given time are dependent on antecedent climatological conditions, particularly precipitation. occurred during historic northem California earthquakes.

3

RAINFALL AND GROUND-WATER CONDITIONS IN 1906 TABLE1.--Northern California earthquakes of 1769-1970 associated with reported ground failures

ISeverity of ground failure is dnssified as fallowa: Very s l i g h t i a few minor ground cracks or landslides in a small localized srea: Slight-several instances of minor ground crack and lnndslides over an area of several square milcs; Moderstdamaging or potentially damaging ground cracks and landslides aver an area of several tens of square miles; Severe-. large gmund cracks and landslides over an area ofacvcral hundreds of square miles or more. Laeation numbers are assigned to ground failure sites in areas covered by plates 1-5. Dcseriptions of failurea nre given by location number in tables 69. Data fmm Corman and van Hake (1973); Holden (1898);Townley and Allen (1939); Wood. Allen, and ~ e e k (193911

Year

1800 1836 1838 1852 1853 1855 1857 1861 1865 1865

Date

Oct. ll(?) June 10 June Nov. 2%24 Oct. 23 Jan. 24 Jan. 9 July 3 Oct. 1 Oct. 8

1866 Feb. 17 1868 Oct. 21

Epicentrsl area

Maximum Modified Mercali intensity

Richter magnitude

Severity of

K:

Location No.

San J u a n Bautista .................................... San Francisco Bay . . . . . . . . . . . . . . . . . . . . . . . . IX-X San Frnnclsco Bay area ............... X San Francisco peninsula ............... VIll Eureka ............................ VlIl Downieville .......................................... Fort Tejon . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . IX Contra Costa-Alameda Counties .......... VIII Fort Humholdt and Eureka ................ VIII-IX VIII-IX Santa Cruz Mountains ....................

Maderate(?) .......... Moderate(?) .......... Moderate to severe(?). Moderate(?) . . . . . . . . . . Very slight . . . . do-............... . . . . do................ . . . . do................ . . . . do-----........... Moderate ............

Klamath River ........................................ Hayward ................................ IX-X

Moderate(?) .......... Moderate ............

1883 1885 1890 1892 1892 1898 1898 1906 1908 1915 1915 1919 1923 1926 1927 1932 1933 1947 1953 1954 1954 1954 1954 195'7

Oet. 22 Mar. 30 Apr. 24 Apr. 19 Apr. 21 Mar. 30 Apr. 14 Apr. 18 Aug. 18 Feb. 21 Apr. 5 Jan. 4 Jan. 22 July 25 Aug. 20 June 6 May 16 June 22 Dec. 16 Apr. 25 Aug. 12 Sep. 15 Dec. 21 Mar. 22

Merced River ............................ ............ Southeast of Hollister .................... VII VII Monterey Bay region ...................... Vacaville ................................ IX IX Winters .................................. VIII Mare Island .............................. East of Mendocino ........................ VIII-IX XI San Francisco ............................ Eureka .................................. VII Near Lassen Peak ........................ Coleville region .......................... Shasta County ............................ ......... Upper Mattole & Petrolia .................. IX Near Idria, San Benito Co ................ VII Humboldt Bay . . . . . . . . . . . . . . . . . . . . . . . . . . . . VIII Humholdt County ........................ VIII Fremont .................................. VII VI Gilroy .................................... Watsonville .............................. VI East of Watsonville . . . . . . . . . . . . . . . . . . . . . . VIII .--.do .................................... VI East of Merced ............................ VI Eureka-Arcata .......................... VII West of Daly City ........................ VII

1958 1959 1961 1962 1963 1965 1967 1968 1969 1970

Dec. 11 Mar. 2 Apr. 5 June 6 Sep. 14 Sep. 10 Sep. 28 June 25 Oct. l May 18

Southwest of San Francisco ................ Near Gilroy .............................. Humboldt County ..........I............. Near L a k e ~ o r. t........................... ........... East of Watsonville ...................... VII Pittsburg ................................ VI Morgan Hill .............................. VI Petrolia-Honevdew ...................... VII Santa Rosa .............................. VII-VIII Fort Jones area .......................... v

Precipitation varies considerably in the Coast Range province, both in time and in location. Average rainfall is in excess of 100 in. (2,500 mm) per year in some areas near the Oregon border but generally decreases southward to as little as 12 in. (300 mm) per year a t some points in the southern Coast Ranges. Locally the average rainfall is variable, generally being greater nearer the ocean and at higher elevations. Rainfall over the entire area is seasonal, with the bulk of the

.....7....

Very slight .......... . . . . do---............. Slight ................ . . . . do................ . . . . do................ Very slight .......... . . . . do................ Severe .............. f&t locations Very slight .......... 348. Slight(?). . . . . . . . . . . . . . Very slight .......... --do .. -----........... . . . . do--.............. do6 ..... ........-. ------.... . . . . . . . . Slight to moderate . . . . 353 6.4 Slight ................ 345 . . Vew slight .......... 165

. . . . do................ .............. Moderate ............ 340,34%354 . . . . do................ 132, 133,232, 235242 Very slight .......... 132 Slight ................ 31,47 Very slight .......... 334 . . . . do................ near 310 -..do ---...........29,30 .. ..-.do ................ 180 . . . . do ................ 48 --..do ---...........338 .. -... do---........... .. 295 . . . . do................

major storms occurring in the months of October to May (Sprague, 1941, p. 795796). Of special interest to this study are the rainfall records for the winter immediately preceding the 1906 San Francisco earthquake, (McAdie, 1906; U.S. Weather Bureau, 1912.) The 190506 monthly rainfall i records for five stations in the coastal section of north- j : ern California (fig. 2) indicate that precipitation during '; j the 190506 year was from 7 to 76 percent greater than !

HISTORIC GROUND FAILURES IN NORTHERN CALIFORNIA TRIGGERED BY EARTHQUAKES

4

Monthly precipitation MARCH 1905

SCALE OF SH,AOES,

00

TO

2.00 in.

2.00 to 4.00 in. 400 10 6.00 in.

6.00 to 8.00 in.

1 9 0 6 4 21.15 in.

19054 59.7710.

FIGURE3.-Map showing rainfall distribution in California during March 1906 (after McAdie, 1906, p. 35).

OSM 05M JUI~

0 5 M 0 5 M 0 5 M O E M 0 6 M 0 5 M 0 6 M 0 6 M 0 6 M 06M

A " ~ .sPpt. act.

N ~ " . D ~ = . la". mb.

M ~ , . A ~ . I I M~~

J~~~

EXPLANATION

0

~ o n t h i yrainfail for month indicatedduring 1 9 0 5 4

El

nveiage monthly rain far^

T ~ r a e of s rdnfatl. not maarurab~s

2.-Monthly rainfall data from several northern California stations for the 1905-06 water year (U.S. Weather Bureau, 1912), compared with average monthly rainfall data (Environmental Data Service, 1971) for those same stations.

FIGURE

period immediately preceding the earthquake. This information suggests that the ground water level was probably high a t the time of the earthquake and that the soils above the water table probably were fairly ' : well drained. These soil moisture conditions contributed to the development of ground failures during the 1906 earthquake.

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GROUND FAILURE TYPES

Ground failure is defined as a permanent ground movement (Youd, 1975). In this report only those ground failures triggered by seismic shaking are sidered, including various types of landslides, spreads, ground settlement, and ground of these failures are commonly caused by liquefaction, which is defined as "the transformation of a granular material from a solid state into a liquefied state as a 1 conse~uenceof increased pore-water pressures" (Youd, 1973, 1975). Ground failures are categorized herein as follows: Hillside landslides include rotational slumps, block glides, soilfalls and rockfalls, shallow debris ,i landslides, and flows (Varnes, 1958,1978; Youd, 1975); valley floor-failures include lateral spreads, slumping of streambanks, and ground settlement (Varnes, 1958, 1978; Youd, 1975); miscellaneous ground cracks in-

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normal a t the selected stations and that March was an exceptionally wet month with rainfall ranging from 50 to 200 percent above normal. A statewide rainfall map March 1906 is plotted on figure 3. March and April, 1906, daily rainfall records from three coastal stations are plotted on figure 4. These data show that the last major storm prior to the 1906 earthquake occurred during the last few days of March and that no significant precipitation fell in the 17-day

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LIMITATIONS OF GROUND FAILURE DATA

descriptions; however, in some instances classifications . were inferred from descriptive evidence such as cracks and vertical separations along stream channels. Evidence used to categorize ground movements as lateral spreads include notations of lurching (most phenomena generally termed as lurching are, in fact, lateral spreads associated with liquefaction (Youd, 1973, 1975j); ~ ~ n t r a c t i oofnstream channels; lateral, extensional or compressional displacements of fences, sfreets, pipelines, rails, and other constructed works; and laterally shifted intertidal marsh deposits. Published notes describing the typical character and extent of lateral spreads during the 1906 event are given in notes %18 of table 2. Ground movements were classified as settlement on thebasis of vertical displacements not apparently associated with landslide movements. Evidence of a,,, n o m a b e ground.settlement includes relative downward movement of the ground surface around well casings and structural pilings and relative vertical displacement of the earth's surface beneath structures such a s roadways and buildings. General notes concerning settlement during the 1906 earthquake are included in notes $18 of table 2. The category of miscellaneous ground cracks includes ~~~~h A~.~I cracks and fissures that on the basis of published de, FIGURE 4.-Daily rainfall data at three coastal stations for March scriptions cannot be related to tectonic faulting, landslid April 1906 (data from McAdie, 1906, p. 32-45), slides or ground settlement. General descriptions of the character and distribution of many such cracks generated during the 1906 event, both on hillside and in valley floor deposits, are given in notes I S 2 4 of table 2. cluae all surficial fissures triggered by seismic shaking ! (cracks caused by direct tectonic movements were not j generally considered) that were, apparently, not genAlthough there are many notations of ground failure ,! erated by another form of ground failure. Other i 'phenomena considered because of their relation to in the historical record for northern California, the 'ground failure include sand boils arid disturbances of data still are limited and incomplete for the five followI artesian wells. All the classifications given on the ing reasons: (1)Most postearthquake investigative efplates and in the descriptions of failures (tables 5 9 ) forts were applied to assessing the extent of structural are those inferredby the authors from written descrip- and other damage or tracing out ruptured faults; hence tions and modern geological and geotechnical reports notations concerning ground failures are commonly of incidental nature, and many ground failures not critiand maps. Hillside ground failures generally are easily recog- cal to constructed works may have been neglected. (2) nizable in the literature from the terminology or de- The incidences of ground failures, particularly landscriptions given. Most authors referred to hillside land- slides, were so numerous in some localities during the slides as "landslides" with no further details given. In 1906 shock that careful noting of each occurrence was :the State Earthquake Investigation Commission re- practically impossible (see note 1, table 2). (3) The port (Lawson, 1908) the subclasses slumps, rock av- areal coverage of postearthquake investigations has alanches, and earthflows are used. Some general de- been uneven, and some omissions exist. Areas in and scriptib;iis-af the character and distribution of hillside near centers of population, along major transportation landslides triggered by the 1906 San Francisco earth- routes, and along major faults have generally received much more attention than less developed, less relequake are contained in notes 1-8 of table 2. Descriptions of valley floor ground failures vary vant, or more remote areas. (4) Several major earthgreatly in their clarity and detail. sj.umped .stream; quakes occurred before modern investigative procebanksgenerally , are easily recognizable from published dures were developed or before it became routine to sari ~

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HISTORIC GROUND FAILURES IN NORTHERN CALIFORNIA TRIGGERED BY EARTHQUAKES

6

TABLE ?..-Excerpted Note

notes containing general descriptions of the types, character, and locations of ground failures associated with the 1906 Sun Francisco earthquake

Relerence

Quotation

Hillside landslides 1 Lawson and others, 1908,

p. 390.

2 Lawsonand others, 1908, p. 385. 3 Lawson and others, 1908, p. 394.

4 Lawson and others, 1908, p. 398.

By far the most common manifestation of landslide phenomena was that here referred to as earth-slump. It would be wearisome to attempt to mention all the various earth-slumps stimulated by ttiee-eartliquake, even if information were sufficient1 detailed to make this ossible. Thruout the Coast Ranges of zalifornia the small resiiual stability of many earth-slumps was overcome by the I vibration of the ground a t the time of the earthquake of April 18 and they were caused to slump forward. In many other instances new earth-slumps were started, owing to the same general cause. Earth-flows originated in valleys, in gullies, or on hillsides. Where the weight of the earth, combined with the weight of the add$ water, was sufficient and the substratum of the soil was rendered plastic, gravity caused it to creep like a lava-stream, leaving a hollow in the place from which it came and a fan or tongue of debris down the slope below. Movement was especially apt to ensue where the ground had been previously wet, the intensity of the earthquake shock being particularly great a t such points and the tendency ofthe vibrations being to set the mass in motion. Earth-flows occurred in many places in the Coast Ranges, and probably throughout the region in which the shock was heavily felt. The writer found many of them, large and small, on the San Francisco Peninsula and in the Santa C m Mountains, also in the Mount Diablo and Mount Hamilton Ranges. Similar [flow] landslides, tho usually of smaller size, occurred throughout the region neighboring the fault vlslted by the writer, and even in districts at a considerable distance from the fault. Frequently they werenot definitely referable to the earth-flow type, but resembled more closely earth-dumps formed without the aid of a suddenly increased water supply. It was often difficult, especially in cases where the movement was slight, or the slide was in the embryonic stage, to determine whether the earthquake a t those points had caused a flow ofwater or not. *** Many slips were formed on hillsides and along the embankments of mountain roads, and along the cracks formed by the shock in moist and lwsened soil. O&en these slips were arranged one above another, the perpendicular faces due to slipping having the appearance of step faults. In such cases the weight of the moved mass and the amount of water was not sufEcient to cause the material to flow. *** In some places bare ridges . had their lines oCjynlmctry broken into .ittle knolls and irrcgularrties by these dips, a common occurrence rn the hills of.i~Rsand formntluns in the nonhcrn pan ofthe Snn Francjsco Peninsula. All the sl~psjustreferred to illustrated the rradntinn benvren eanh-s1umo.i -~ r - and eanh-flowr;. ~ .-- Doubtlesi in man" of them a small amount e of water did eather as a result of the earthauake. Earth-flows weFe of frequent occurrence in tke Coast ranges, the writer finding them numerous on the San Francisco peninsula and in the Santa C r u mountains with," a scoreafrn~lcsol'ihefault, and what appeared tu be flows ofs:milar arigtn at a much grcatsr drstance from the epicentrum. They were formed on gmtle as well as s t e e ~ l u ~ ennd s , hoth in orev>ouslvdrv druln:lee dc~resslunsand on convex hillsides in the laruest llowd thousands iftoins of earth and rock detritus were re&v& and carried hundreds of yards, leaving g r e a cavities. In one case a hole ten feet deep was excavated over a n area of nearly an acre o n a five-degree ilope, and the materinl removed was spread over two acres -"'There is still another [type of landihdr], which is ~mmediatclysssociated wlth eanhquekcs as n cause of movement. 'This 1s the shdc of drv eanh and ruck upon ~recrpitousslopes or thew fit11 from cllffj.Soil or uther loose forms of earth may articiiate in such IandsIides; but-the material is usually composed chiefly of rock which becomes increasingyy shattered with the progress of the slide. Earth-avalanches lsoil and rock falls1 were caused chieflv alone the sea-cliffs of the coast an the morning of the earthquake, tho'some also accurr~don steep canyons withyn the zone of high intensity. On the mast the earth-avalanches were for the most part simply an exceptional incident in the normal process of cliff recession. Where the u land ofthe Coast Ranges approaches the shore, the horizontal corrasion of the waves maintains a steep sea-cli8: and the recession of the sea-cliff is effected bv the repeated occurrence of earth-avalanches due to the undermining by the sea, combined with the disintegriting action of atmospheric agencies. There are thus always upon the face of the cliff masses of earth or rock, the fall of which is imminent and may easily be preci itated by a severe shock of earthquake. Along t g e seashore immense landslides accwed, throwing vast quantities of earth and rock into the sea.

-~

5 Anderson, 1907, p. 643.

6 Lawson and others, 1908, p. 386.

7 Lawson and others, 1908, p. 387.

8 Gilbert, Humphrey, Sewell, and Soul6, 1907, p. 133.

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Lateral spreads and ground settlement

.

9 Lawson and others, 1908, p. 386.

Besides these three types oflandslide, another ought perhaps to berecognized. This is the form ofsuperficial earth movement which occurred in conseauence of the earthauake shack on the alluvial bottom-lands of manv

or. 11 may bc, toward an abandoned slouih, the lurch ~ s u d l h&ng l ~ accompilnied by a rotation of the prism:

They arc dirtlnguished from all other forms of landslidui by occurring on perfectly flat pound and by the fact that-they arc appnrently referable directly nnd solely to the horizontal jerk of the eanh muvement during the earthquake shock. 10 Lawson and others, 1908, EARTH-LURCHES. Of the three kinds of landslides thus far referred to, the first two, earth-avalanches and p. 400. earth-slumps, occur quite commonly independent of earthquakes. Of the third kind, or earth-flows, the only examples that have been presented are immediately connected in genesis with the earthquake of April 18, although it is conceded that sudden accessions of water to loose earth might arise in other ways and occasion earth-flows. As regards the fourth type, the earth-lurch [lateral s ~ r e a dit l is difficult to conceive for i t anv other . origin than an c.irthquake, since i i is caused dlrectlyby the f i n r i ~ ~ ~ njerk t a l of the ground and canmot bc produced in any other way. [Authors in 1906 were n ~awareofthe t liquefaction process.] In thcdctniledaccount of the distribution of apparent intensity, a brief nrcount d t h e s e superficial movemenu: ofthe ground has been

7

LIMITATIONS OF GROUND FAILURE DATA

TABLE2.--Excerpted notes containing general description of the types, character, and locations of gmund failures associated with the 1906 S a n Francisco earthquake-Continued Note

Reference

Quotation

Lateral spreads and ground settlement-Continued

Greotdam;~gewas sustained by water work; in the rupture of matns, and the w reservoirs, plants and equlpmcnts. Elevated water tanks supported by steel and timber frrming were frequently wrecked. 'The railways also suffered cnorm,~usdamage through d~;plnccmcnts of the roadbed and serious lnjurica to the bndgcs. The surface movements s e r e very much more apparent ln the cities and uwn5 where the alignment of the streets, rallwn tracks, pole lines,etc., wcre matrrinlly altered. Strect rails werescvered by tension i n some plnces and b u c k l e ~ a rothers. Large areas, constituting m.my acres, sctrlcd as much ns from ten to liflecn feet, badly diston~ngthe buildrngs which drd not have deep foundations. -*- I t ir cvidcnt that the whole region ailcctrd moved eenerallv N 3 unit. and thin the sudden and iarrine motions had the effect oicauslnc local disturbances a d displ&ements wllerever the soil was soft, incoheknt and deep, as in the river bGtoms, artifically filled areas, etc. Marked disturbances and deformations of the softer material always resulted along the lines skparating a hard, compact material from one that was soit as, for example, the line of contact of the rock formations with the silt of the vallevs. -~ Lawson and others, 1908, ~ e i o n dthe zone i f the ~ i f t , ~ & a c kwere s observed a t many localities. These were most common on the hottomlands of the streams, notably the Eel River (plate 138A, B), the Russian River (plate 139A, B), Coyote Creek p. 401. (plate 140A, B), and other streams a t the south end of the Bay of San Francisco, Pajaro River (plate 141B),San / Larehu,River, and the Salinas River. Many other smaller streams might also be mentioned. In these cases the' cracks were usually associated with the phenomena of lurching of the alluvial deposits, though many cracks also occurred where no such association was apparent. They were in nearly all eases found to be parallel or sub pa+alllel.G the nearest portion of the streamJr.e~h.They very commonly extended for several hundred feet, in some instances for sevel'al~hundredyard< and were characteristically arranged in linear series. The cracks in the series in some eases overlapt en echelon, and in others they were in groups of parallel cracks in belts a few hundred feet wide. In no case was there any suggestion that they were more than purely superficial phenomena. Duryea and others, 1907, Embankments-Embankments across marshes, or with soit strata underlying them, settled more or less. In same p. 258. cases the settlement was vertical; in other cases there was considerable horizontal with the vertical movement. Duryea and others, 1907, Settlements ofthis character [embankments an tidal marshlands] and of more or less severity were common on all p. 258. railroads operating about the Hay of San Francisco and its tiihutarics. It is evxdenr that structures pcrta:nmg w railroads sun'ercd Severely in common with others. It is a -,ell-known Hyde, 1906a, fact that many cmbankmcnts were seriously distoned m nlignmrnt and were rc.dueed in elevation through p. 705. srrrlcment duo to the vlbrarion. Landslides were not uncommon on hillsides and in curs where both rallronds and hrghwnys, prlnclpally the former, were located. Thc disturbance had the effect oflowering the general lcvcl ofalluvial land and opening in it numerous crocks. In Carey, 1906, scveral instances in the Santa Clara Vellcy rvater plpcs in wells dug through the uncompnetcd and unconsolip. 299. dnmd vallev sanda, mnvels and clnvs showed, aflc.r the shock. a foot ur more of the DIE above the ecncral Himmelwright, 1906, p. 21.

~.

".

e."-.".

Lawson and others, 1908, Along rlvcr horwms andun valley flooos, panieularly where the ground water is abundant, structures werc much more susceptible to damage than s~milarstructures founded on the firm rocks of the valley slopes. Thjs p. 162. nu~arentlvhich intcnsitv nfthe shock in the vallcv lands was in oan duc to a n actual slumoine ofthe ~ r u u n d . d i c h w r i e k d the buildings inde~endentlyof an; elastic vibration communicated to the& fGm the mound: Duryea and others, 1907, Draus-Brrdges.-Draw-brid es a c r o g the littic creeks and inleti around San Francisco Bay, heins geneF;lly qn " a ' sl~ght . ' movement of their pier&,in many cases resulting in the bri gc blndlng so p. 259. sol? ground, were offecte by that it could not be opened until some repairs werc made.

f

' Ground

cracks '

--

19 Lawson and others, 1908, Within the mne of high intensity no marshes and no bottom lands were seen which did not exhibit cracks, and I regard their tracking as a general phenomenon. The elaborate cracking of a roadway across one of the marshes p. 74. seems saeciallv simificant. In the adiacent soft marsh close attention was necessarv to discover cracks. To a large exicnt th>y \;ere concealed by [lie vegetat~on,nnd i t is probable also ttlpt many which were opened during the earthquake agitation immedlstely closed agaln and werc practically ublltcrated by the weldlnp; of the mud. Hut the road embankment. bcinc free from \.ceetation and comooscd of com~arativelvrrcid and brittle matcrial, retained all the cracks maze durine the &itation, and t h b served ta recard th"e tKoro shattering of an un&onsolidated formation when subjectd to s&ng vibration. (Plate 50.) Another class of superficial cra& affected hillsides, penetrating only the coating of loose materialrock e those that follow eantaurs. Along rleromnn~ed -.. .=. ..... and talus. The eons~ieuousindividuals of this t v ~ are these there was often a notabl? w;dth ofcraek, accom anicd by d&ttling an thc down-hlll ~ i d eand , many cracks ofthiri type are still vlsrble. They arc in effect tRe heads of incipient landslides and mlght wlth equal propriety be described under another caption. They are numerous throughout the Rift belt and fairly nbun~~~

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8

HISTORIC GROUND FAILURES IN NORTHERN. CALIFORNIA T R I G G E ~ DBY EARTHQUAKES

TABLE2.--Excerpted notes containing general description of the types, character, and locations of ground failures associated with the 1906 S a n Franci.xo earthquake-Continued Note

Quotation

Reference

Ground eracks--Continued dnnt on jterp hills~des(nurthofSan Francisco Hay] for more than a mile to the west. East ofthe Riti they are mconsplcuuus and believed to bc rare. Some of the best evnmples are on the northeastern slope of Mount Whittenberg, about a mile from the fault-trace, the locality being favorable for observstron because of the absence of forest. Superficial cracks of a third type are connected with side-hill roads. (See plate 51.) In such roads there is usually a notch cut in the hillside and the excavated material is thrown outward so as to make a n embankment. The roadbed thus consists in part of the natural formation and in part of an artificial and relatively loose embankment. In the loose material, and frequently along the line separating it from the firmer ground, cracks were extensively developed, often accompanied by evident settling of the outer bank. Their magnitude depended in part on the character of the material, but in large part also on the intensity of the earthquake. Where they were of such magnitude as to injure the roadway they were soon obliterated by road repairers, and elsewhere they tended to disappear in consequence of the traffic; but while they lasted they constituted an excellent age of intensity, and much use was made of them in districts where there were few buildings. Lawson and others, 1908, All thru t h e s i f t there is associatibn of earthquake cracks with fault sags; probably half of the sags were bordered by such cracks on one side or the other, the crack usually following the line of separation between the side slope p. 75. and bottom slope. In some instances there was a crack on each side of the sag, but more frequently on one side only. Where the sag eontained a pond the crack was usually present. With little or no exception these cracks exhibit downthrow on the side toward the sag. (See plate 52B.) Lawson and others, 1908, In the bottom-lands of creeks it happened a t many places that a slice of the alluvium was separated by a crack p. 77. parallel to the bank and slid into or toward the stream. In some cases alluvium lying with a gentle slope adjacent to a marsh slid toward the marsh opening a crack along its u p r edge: Mention has already been made of numerous hillside cracks which mar ed mc~plentlandslides. In such cases the downward motion apparently began during the earthquake agitation, hut the momentum acquired was not sufficient to continue the motion after the earthquake stopt. In a very large number of these localities motion was resumed and landslides occurred during a period of excessive rainfall in the spring of 1907. (Plates 54A and 55A.) So far as mv observation goes, all of the landslides having this history were wet, the material usually florvh freely down the ilupe a& thin mud. Gilbert, Humphrey, All through the area of high intensity crack6 wrre made, and these wrre specially numerous near t h e Sewell, and Saul&,1907, ~~~~~-~ fault trace. werc. more numerous in solt alluvrum ~ - The -~ ~ cracks ~ ~ . - . ~-~ ~ also ~~-~ - ,-.-.x:. than in hard mound, but the number which p. 7. d e e ~ l v~enetratedthe bed rock was~l&ge.Perhaps thls featurcls better expressed by saying that the bed rock wa; &ierally and profoundly sharterea, but without lmportatlt dislorntioi except on the old fault plane At the surface the cracks had grcnt variety of expression. Somc were barely perceptible as partings; others caoed so widelv that onc mieht look down th+m several vards. Somc were mere ~ u l l i n a apart; s uthers showed small differengal movemen& of the nature of faulting. Some were solitary: others, especiaily those exhibiting faulting, were in groups. Some straggled and bmnchea irregularly; utheffi~were nenrly stra~ghtfor hundreds of feet. Theoreticall , some cracks were prlmary as regards the earthquake and othc~.ssecondary; that 1s to say. some wcrc enuseKdirect~vbv the oreexlstent strejses whlch oroduced the maln fault and others were cawed bv the waves co&tituting tke karthiuake. Lawson and others, 1908: Cracks.-In preliminary reports I have classified the earthquake cracks as primary and secondary, the primary being occasioned by strains which existed before the earthquake; and the secondary being caused by the p. 73. earthquake. With the multiplication of observations this classification has become increasingly difficult, and I now find it more convenient to group the cracks as superficial and deep, or superficial and bedrock. Many of the superficial cracks are in alluvium. In the field excursions of April and May, 1906, they were seen in all alluvial formations within the RiR belt and for some distance on each side. The greater number appeared to be merely partings without vertical or horizontal throw. In general they were not parallel with one another nor were they otherwise systematically arranged, except that some of them were apt to occur along the boundary between alluvium and a firmer formation. They were rambling rather than straight and were oRen branched. They ranged in width from a fraction of an inch to several inches. Lawson and others, 1908, T** I t may be well to direct attention more particularly than has hitherto been done to the behavior of water contained in the alluvium of the river-bottoms. One of the most common phenomena in such situations was the p. 403. expulsion of water in jets from apertures which suddenly appeared in the flat-lying ground. The water was usiXljTth7G-ih2 air far several feet; in some cases it was reported to be as much as 20 feet, and the ejection continued for several minutes aRer the earthquake. The continuance cf the ejection after the shock indicates that an elastic stress had been generated in the saturated ground, which thus found relief in the emulsion of the contained water or that there was a mavitational settling together of the material, which diminished the spaces occupied by water. The vents th;s established were Gery-numerous, and were in many instances closcly~spaced;mbrr fr&usntly a few to the acre, and oeensianally isolated. These vents \\ere cnsily recognmble for W L - L . ~and S even months after the c.arthquake, in the, form ol'eratrrlets. The water in lupassagc to the surfaec broueht uo considerable aunntities of fin? sand. whlch, from its orsvailinclv llcht blulsh-pray color, was evidently deriGed from considerable depth, On theflood plain of t h i SalinasRiver, the sandwas recognized by the people of the neighborhood to bethe same ns that bf a stratum of sand pierced by wells at a depth of 80 feet. The craters were usually distinctly funnel.shape-d and were rimmed by a circular flat ridge of sand which. bv rt.a.ion of its lraht color. was in marked contrast to the surroundine surface. Thev varied in diameter from1 to perhaps l0'ket. In &me instance.; the funnels wrre several f e e r ~ c e pin ; other;, the feeble actron in the closing stages of the eruption had caused them to fill up with sand. They were quite snalogouv ta the cra~er1et.sdescribed and pictured in Duttan's account ofthe Charlejron earthquake. (See plates 142A, Band 143A, B.) These craterlets occurred on practically all the saturated alluvial bottoms of the streams within the zone of destructive erects, and also onihc tidalmud flats ol'Tomales Bay. They are significant of the compression ta which such water-laden, incoherent formations were subjected by the passage of the carth.waves at the time of the earthquake or by the consequent settling of the ground.

CRACK^

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DISTRIBUTION AND CHARACTER OF GROUND FAILURES

',

make postearthquake investigations; hence the amount and quality of information decrease with the entiquity ,of the event. .For events prior to the 1906 sliock the record is very fragmentary. (5) In a t least one instance, the results of a postearthquake investigation appear to have been intentionally suppressed. Concerning the 1868 earthquake, A. C. Lawson (1908, p. 434) noted Shortly after the earthquake of 1868 a committee of scientific men undertook the. collection of data concerning the effects of the shock, but their report was never published nor can any trace of i t be found, altho some of the members of the committee are still livine. I t is stated that rht report was supprest [src]hy the authorities, thru the fcar rhnt its oublicnrion !voulddamacc - the rcoutarion ofthe clty. Our knowledge of that earthquake is therefore not very full, and is eontained chiefly in the newspaper reports of that day. ~~~

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9

evidence of more than minor ground cracks include (1) the Oct. 8,1865, earthquake on the San Andreas fault, which generated ground cracks and sand boils in San Francisco (loc. 202), Santa Cruz (loc. 461, and Watsonville (loc. 25), and small rockfalls and ground cracks in the Santa Cruz Mountains (loc. 60); (2) the 1868 earthquake on the Hayward fault, which caused ground cracks and lateral spreading in San Francisco (locs. 19%202) and cracks and sand boils along Coyote Creek a t the south end of San Francisco Bay (locs. 149, 151, 153) and near Hayward (loc. 171) on the east side of San Francisco Bay; (3) two earthquakes two days apart in 1892, which triggered landslides in the mountains and ground cracks and sand boils in creek bottoms in a strip along the west margin of the Sacramento Valley between Vacaville and Capay (locs. 255259); (4) several moderate shocks in 1890, 1953, and 1954, which generated minor landslides in the Pajaro Gap area (locs. 28-30); (5) shocks in 1853, 1865, 1908, 1927, 1932, and 1954, which generated landslides, settlement, and ground cracks of up to moderate severity in the Eureka area; and (6) the 1957 Daly City earthquake, which generated landslides and ground cracks around Lake Merced (locs. 23Z242) and near Daly City (locs. 132-133). A full list of earthquakes causing ground failures is given in table 1. Mapping of earthquake intensities has been useful in delineating areas of ground failure. Specifically, criteria used for mapping 1906 earthquake intensity are based in part on occurrences of ground failures and, hence, have aided in delineating areas in which ground failures occurred. Two intensity scales, quoted below, were used for mapping the 1906 event--the "San Francisco scale" and the modified Rossi-Fore1 scale:

The use of one word to describe two genetically different phenomena and ambiguous descriptions of damage are two additional factors that limit, o r a t least confuse, the interpretation of the historical record. For example, many investigators of the 1906 earthquake referred to the fault rupture as "the crack." Because of ,-thisusage, it is d e l t in many instances to distinguish between cracks generated~bytectonic faulting and those generated by ground shaking. For this reason, nearly all cracks within the fault zoneare omitted from consideration in this report. Some recorded descriptions are inadequate to differentiate whether damage to a structure was caused by deformation wholly within the structure or whether ground failure was also a factor. For example, a typical description might indicate that a building was shifted laterally during the earthquake. Such movement could have resulted from any of several sources including "walking" of the structure off of its foundations, col- San Francisco scale (Lawson and others, 1908, p. 224): lapse of underpinning, or ground failure. Grade A. Very violent.-Comprizes the rending and shearing of In spite of the above limitations, the published rerock masses, earth, turf, and all structures along the line of faulting; the fall of rock from mountain sides; ports provide an adequate sample of data for determinnumerous landslips of great magnitude; consistent, ing the general type, character, and distribution of deep, and extended fissuring in natural earth; some ground failures triggered by earthquakes in northern structures totally destroyed. California. In several instances, the data are adequate Grade B. Violent.-Comprizes fairly general collapse of brick for nearly complete delineation of ground failures in a and frame buildings when not unusually strong; serious cracking of brick work and masonry in exparticular area. DISTRIBUTlON AND CHARACTER OF GROUND FAILURES

The 1906 San Francisco earthquake triggered ground failures a t numerous locations throughout a 370-mi (600-km)-longsegment of the Coast Ranges extending from southern Monterey County on the south to Eureka on the north (see fig. 1).Most of the failures tabulated in this report are from that event. Several other events for which the historical record contains

cellent structures; the formation of fissures, step faults, sharp earnpression anticlines, and broad, wave-like folds in paved and asphalt-coated streets, accompanied by the ragged fissuring of asphalt; the destruction of foundation walls and underpinning structures by the undulation of the ground; the breaking of sewers and water-mains; the lateral displacement of streets; and the compression, distension, and lateral waving or displacement of well-ballasted street-car tracks. Grade C. Very strong.-Comprizes brick work and masonry badly cracked, with occasional collapse; some brick and masonry gables thrown down, frame buildings

10

HISTORIC GROUND FAILURES IN NORTHERN CALIFORNIA TRIGGERED BY EARTHQUAKES

1

I

-

The "San Francisco scale" was used onlv for mauuine intensities in San Francisco City and County (fig. 5). The highest intensity grade, grade A, is based almost exclusively on the occurrence of fault ruptures, large l landslides, and deep cracks. Grade B is based partly on :( 1 I the occurrence of severe structural darnaee - and uartlv 1 I On the occurrence of mound failures of lateral-- 1 spreading and ground settlement types. Grades C through E are based entirely on damage to constructed works. Hence, zones of grade A and B intensity gener- -' I ally delineate areas where faulting and ground failures disturbed the ground surface. Areas zoned grades C through E delineate areas with varying severities of Modified ~ossi- or el scale (Lawson and others, 1908, structural damaee -p. ,C,\. ! - but with a -eeneral absence of sieIVL,. nificant ground failures. Hence, areas zoned A and B ,! In the first blace, the scale upon which the gradation of intensity is generally coincide with zones of ground failure in San indicated, tbdt known as the Rossi-Fore1 scale, is more or less arbiFrancisco, whereas intensity grades C through E detrary. At the outset of the inquiry, the Commission revised and simplified thfs scale somewhat, with the object of adapting it for lineate areas where few significant ground failures ocgeneral use, and its present form, as amended by the Commission, is curred. as follows: I The modified Rossi-Fore1scale was used to map 1906 earthquake intensity throughout the Western United I. ~e!!eeptible, only by delicate instruments. 11. ~ e slight, b shocks noticed by few persons a t rest. States. Criteria used to assign intensity grades I-IX on 111. ~ l i k h shock, t of which duration and direction were noted the modified Rossi-Fore1 scale do not include ground Gy a number of persons. failure effects.T~.~highe_st,grade(X),ho.weev.ee~,.is.based IV. ~ d d e r a t shock, e reported by persons in motion; shaking of I almost exclusively moveable objects; cracking of ceilings. . . . .on occurrences . . of fault -- rupturing, . -la;ids_kd_e_s,..and deep .. ground ..~.. cracks. . On the maps pred a r t shock, generally felt; furniture shaken; some clacks V. &opt; some sleepers awakened. pared by the 1906 investigatordfie. and - 6). (Lawson . VI. ele ere shock, general awakening of sleepers; stopping of / others, i908. atlas. D. 21-23). onlv a narrow zone alone ., " Clocks; some window glass broken. the ~ n d r e a f&t s is mapped as intensity grade X. VII. v i b ~ e nshock, t overturning of loose objects; falling of plasThis zone generally coincides with the zone of 1906 {er; striking of church bells; some chimneys fall. fault ruptures. Other areas where severe ground failVIII. Fall of chimneys; cracks in the walls of buildings. IX. partial o r total destruction of some buildings. ures occurred, such as along the Salinas kiver, were X. ~ r k adisasters; t overturning of rocks; fissures in surface of given a lesser intensity, indicating that averaging of , I earth; mountain slides. intensities within a given area probably occurred durI It is aDDarknt .. that the scale leaves room for wide variation in the ine- comuilation of the man. For delineation of areas personal eqdation. Different reporters interpret the same experi- subjected to ground failure, such averaging reduces the 1 ences and the same phenomena differently. It was also found that in usefulness of the map to almost nil because it obscures the peripher$ of the region affected, where the earth waves were of slow period, ipendent objects and liquids were more sensitive indic- the data and falsely infers, from direct reference to the ators of eartA movement than direct nerce~tion . . bv individuals. altho scale, that major ground failures did not occur in areas the latter is iplaced first in the scale. characterized by intensities less than X. lurched or .listed on fair or weak underpinning structures, with occasional falling from underpinning or collapse; general destruction of chimneys and of masonry, brick or cement veneers; considerable cracking or crushing of foundation walls. Grnde D. Strone.-Comorizes eeneral but not universal fall of chimneys; cracks i;masonry and brick work; cracks in foundation walls, retaining walls, and curbing; a few isolated cases of lurching or listing of frame buildings built upon weak underpinningstrudures. Grade E. Weak.-Camprizes occasional fall of chimneys and I 1 damap-e to plaster, partitions, plumbing, and the like.

A.

E

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1

/

8

an

I

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DISTRIBUTION AND CHARACTER OF GROUND FAILURES

FIGURE 5.-1906

11

earthquake intensity m a p prepared for San Francisco County using San Francisco intensity scale (aRer Lawson and others, .. . . . .:. .. 1908, map no. 19). ~

12

HISTORIC GROUND FAILURES IN NORTHERN CALIFORNIA TRIGGERED BY EARTHQUAKES

...-

FIGURE 6.-1906 earthquake intensity map for Western United States based an modified Rossl-Fore1 scale (aRer Lawson and others, 1908, map no. 23).

DISTRIBUTION AND CHARACTER OF GROUND FAILURES MONTEREY BAY COUNTIES REGION

13

spreading were as large a~d&&4&7-m). The largest displacements were no&-near Monterey Bay at and Monterey and San Benito Counties, the southern north of Moss Landing (locs. 19, 21). Inland along the parts of Santa Cruz and Santa Clara Counties and the Salinas and Pajaro Rivers lateral displacements as western parts of Fresno and Merced Counties form the large as 10 ft (3 m) were common. These movements Monterey Bay counties region (pl. 1 and table 5, locs. considerably damaged bridges and pipelines that 1-44; figs. 7-17). (Regions in this report were selected crossed the rivers and highways and railroads that largely on the basis of available map sheets and paralleled the rivers. Photographs of 1906 ground failamount of data for any given area.) This region has ures along the Salinas and Pajaro Rivers and the dambeen shaken in historic times by several moderate- to age they caused are shown in figures 7-10 and 12-17, large-sized earthquakes; however, only two events, the A geotechnical section across the Salinas River in October 8,1865, shock for which we have but fragmen- the zone of 1906 ground failures (fig. 11) was compiled tary information, and the 1906 shock, have produced from foundation investigation borehole logs for the more than minor local effects. Hence, the discussion in State Highway 68 bridge over the river. This bridge is this section is limited almost exclusively to ground located 0.5 mi (0.8 km) upstream from a bridge that failures caused by the 1906 SanFrancisco earthquake. was severely damaged during the 1906 shock (fig. 10, A summary of statements excerpted from reports on loc. 12). The geotechnical section shows several layers . the 1906 shock containing generalized descriptions of of loose to dense sands, sandy silt, and clay in a comground failures in the Monterey Bay counties region is plex configuration extending to depths as great as 80 ft reproduced in table 3. Specific descriptions of individ- (24 m). The area is characterized by a high water table ual failures are contained in the descriptions of failures that ranges in depth from several feet beneath the God (table 5, locs. 1-44). plain to the ground surface at the river. The evident Plates 1 and 2 show that the density and severity of cause of ground failure at this location was liquefaction ground failures generated by the 1906 earthquake within a loose granular layer below the water table generally decreased with increasing distance from the (Youd and Hoose, 1976). j causative fault rupture (the southern limit of which Effects similar to those along the Salinas and Pajaro ; was near San Juan Bautista). Thus, the density and Rivers, but of much lesser extent and severity, also severity of failures decreased southward from S a n occurred along the San Lorenzo Fiiver (locs. 43,44) and Juan Bautista. The southernmost reported failure was Soquel Creek (locs. 41,42) in and near Santa Cruz and slight settlement beneath the Bradley, Monterey Capitola, respectively. These latter failures caused no County, railroad station (lac. 1).Bradley, not shown on significant damage. plate 1, is located near the Salinas River, 12 mi (19 km) Buildings and other works sited on deep unconsolisoutheast of San Ardo, which is located near the south- dated deposits generally were damaged more. than ern edge of the map. those sited on shallow unconsolidated deposits over On a local basis, geologic setting had a greater effect bedrock. This was true even a t localities where ground on the density and severity of ground failures than failure was not a factor. For example, A. S. Eakle distance to the ruptured fault. Areas with the greatest ..,... (Lawson and others, 1908, p. 296) reported that "the density and s t y c t ~of " ground failures included & I town of Salinas suffered greater destruction than any place in the county." Nevertheless, no evidence lying alluvial deposits - . - along-., the Salinas and Pajaro other Rivers andbeachand dune .. . . d.eposi$,necth,e. .. mouths of was found during this study of any significant ground these rivers. In fact, one investigator stated that the failures in the city of Salinas during the 1906 event. Salinas River valley was "fissured and disturbed more Most of the older section of Salinas is located in the than any other district in the state" (note 5, table 3, Salinas River valley, which is underlain by unconsolithis report; Gilbert and others, 1907, p. 133). dated Holocene sediments to considerable depth. .~ ,.... failure ...., types~. in the riverv_aLepwere Amplification of bedrock ground motions by these sedThe principal ~~~l of7iHt- iments likely led to the great damage. Great damage V r slumping of ~ t r e a r n b a n kl'at&lspreading . . land~_tow.ard~chann_e~ssina,m_anney,s~,m~lar,~o. that-de- was also reported from Del Monte and the Pacific scribed in reports from the 1964 Alaska earthquake Grove Light House (A. S. Eakle in Lawson and others, (Kachadoorian, 1968; McCulloch and Bonilla, 1970). 1908, p. 291, 343), Santa Cruz (Lawson and others, I! These failures were accompanied by considerable 1908, p. 3431, Hollister, and other parts of the lower :I :!, ground cracking and differential settlements and by Santa Clara valley (Lawson and others, 1908, p. 28& 290) as well as parts of the San Joaquin Valley, par,. i ; the pervasive eruption of sand boils. The sand boils are j. !, evidence that liquefaction played a major role in these ticularly the area surrounding Los Banos (G. F. ..failures. Lateral displacements associated with lateral Zoffman, in Lawson and others, 1908, p. 316, 345).

--

14

HISTORIC GROUND FAILURES IN NORTHERN CALIFORNIA TRIGGERED BY EARTHQUAKES

Local geology may have been an important factor in amplifying or modifying ground motions in these areas, which led to greater-than-normal damage. Ground failures, however, were apparently not a factor. Other than some cracks along steep bluff faces, upland alluvial terrace and eolian deposits were apparently unaffected by ground failures during the 1906 earthquake. This conclusion is supported by notations and maps (fig. 6) showing that damage was less in the upland areas than in the river valleys and by the absence of ground failure reports from the upland areas, which is considered to be positive evidence because several investigators traveled through those areas and most likely would have noted any significant ground failures. Some specific notes do show an absence of ground failures in some areas. For example, G. A. Waring (Lawson and others, 1908, p. 292) noted that "Castroville [loc. 171 being on solid ground was unaffected" TABLE3.-Excerpted Note

and A. S. Eakle (Lawson and others, 1908, p. 292) reported that "On the road eastward to Salinas from Del Monte [loc. 121, no visible signs of the earthquake were encountered until the Salinas River was reached." The mountains in the Monterey Bay counties region apparently were only slightly affected by ground failures during the 1906 temblor. The largest failures reported were landslides near the fault trace west of Chittenden (loc. 31) where several large rockfalls and debris slides filled the lower part of the canyon. A linear array of landslides occurred near the west margin of the San Joaquin Valley (loc. 71,which led some investigators to speculate that there might have been sympathetic movement on a fault in that region. However, no evidence was found to support this speculation (G. D. Louderback in Lawson and others, 1908, p. 319). Many small landslides occurred in the mountainous areas, including a dislodged boulder that crashed through a house, killing one man (loc. 38).

notes containing general descripLions of -ground . failures in the Monterey Bay counties region ~

Rearen""

~~

Quotation

1

Lawson and others, 1908, p. 343.

2

Lawson and others, 1908, p. 296.

3

Duryea and others, 1907, P. 311.

4

Lawson and others, 1908, p. 409.

5

Gilbert, Humphrey, Sewell, and Soul&,1907, p. 133. Lawson and others, 1908, Effect upon structures, objects, etc. (G. A. Waring).-It is remarkable how closely the disturbance followed the p. 295. river channel throughout the Salinas Valley; 2 or 3 miles away from the stream on both sides the intensity was very slight. Southward up the valley the shock gradually lessened, and rapidly died out in the foot-hills on either side.

6

I

Text continued on pace 23

1

DISTRIBUTION AND CHARACTER OF GROUND FAILURES

FIGURE7.-Damaged

rails and pulp flume a t Spreckels sugar mill as a consequence of lateral spreading during 1906 earthquake (loc. 11). A. Pulled apart rails showing 3 ft (0.9 m) of differential lateral movement. (Photograph by A. C. Lawson, courtesy of an photograph states "wrecked The Bancroft Library, University of California, Berkeley.) B. Displaced pulp flume-aption pulp flume and leaning tower; ground moved 4 ft [1.2m] south." (Photograph courtesy of K. A. Meserale, Menlo Park, California.)

15

16

HISTORIC GROUND FAILURES IN NORTHERN CALIFORNIA TRIGGERED BY EARTHQUAKES

FIGURE8.-Barley field "car Spreckels drsrupted by slumprng and lateral-sprcoding failures ildc. 12). I'reviously published in Lawson and others (1908, ~ 1 137,\1 . wirh captlun "Lurching toward Slllnas Iiiver, with consequent collnpse." \Photo~.;rph by J.C. Bron.of mound . ner, courtesy of Stanford University Archives.)

DISTRIBUTION AND CHARACTER OF GROUND FAILURES

FIGURE 9.-County road along Salinas River, south of Salinas, disrupted by slumping and lateral spreading (loc. 12). (Photograph courtesy of K. A. Meserole, Meulo Park, California.)

FIGURE 1 0 . S o u t h terminal pier of bridge over Salinas River 4 mi (6.4 km) south of Salinas (loc. 12). Surficial deposits shifted about 6 ft (2 m) toward the river. (Photograph by J. C. Branner, egur\tesy of Stanford University Archives.)

.y

.-

fiq

" [)

.-

(\\ > .,

18

HISTORIC GROUND FAILURES IN NORTHERN CALIFORNIA TRIGGERED BY EARTHQUAKES +TO

MONTEREY

0

10

20

30

40

50 METERS

FIGURE11.-Geotechnical section across the Salinas River at State Highway 68 bridge; (lac. 12) 0.5 mi (0.8 km)

DISTRIBUTION AND CHARACTER OF GROUND FAILURES TO SALINAS

0 Sand

Water table in borings at time of drilling (January 1963)

El clay

Approximate water table

0 Interbedded sand and chy

Standard penetrationblowslft

upstream from the bridge damaged during the 1906 shock (fig. 10) (data from Division of Highways, 1964).

20

HISTORIC GROUND FAILURES IN NORTHERN CALIFORNIA TRIGGERED B y EARTHQUAKES

FIGURE 12,Damage

at Moss Landing caused by lateral spreading (loc. 191. A. Damaged railroad bridge. Photograph previously published in Lawson and others (1908, pl. 135A) with caption "Lurching of ground toward Salinas River, to left, carried piles from beneath bridge timbers and caused bridge to collapse. Displacement 9 feet [2.7 m]."B. Displaced building. Photograph previously published in Lawson and others (1908, pl. 134Al with caption "House, tree, and fence moved 12 feet [3.7 m] by lurching of ground toward Salinas River." (Photographs by A. C. Lawson, courtesy of The Bancroft Library, University of California, Berkeley). C. Ground ruptures in Moss Landing between Monterey Bay and old Salinas River. View eastward toward bluffs between Elkhorn and Moro Cajo sloughs. (Photograph courtesy of Monterey County Historical Society, Inc., Salinas.)

DISTRIBUTION AND CHARACTER OF GROUND FAILURES

FIGURE13.-Ground

failure scarp in a former community called Chinatown located near south bank of the Pajaro River across from Watsonville (lac. 25). (Photograph courtesy-of Pajaro Valley Historical Association, Watsonville.1 ~

FIGURE14.-Graben

21

~.

.

. . .-

.... .

and damaged buildings caused by lateral spread near t h e Pajaro River a t the foot of Marchant Street in Watsonville (lac. 25). (Photograph courtesy of Pajara Valley Historical Association, Watsonville.)

22

HISTORIC GROUND FAILURES IN NORTHERN CALIFORNIA TRIGGERED BY EARTHQUAKES

FIGURE 1 5 . S l u m p scarp and sand boil near Pajaro River (lac. 27). Similar photograph previously published in Lawsan and others (1908, pl. 141B) with caption "Secondary crack, with drop of 7 feet, in alluvial flood-plain of Pajaro River." (Photograph by Livennon, courtesy of The Bancroft Library, University of California, Berkeley.)

16.-Sand boil near Watsonville. Part of this photograph previously published i n Lawson and others (1908, pl. 143B) with caption "Craterlets near Watsonville" (lac. 27). (Photograph by J. C. Branner, courtesy of Stanford University Archives.)

FIGURE

FIGURE 11.-County road bridge over the Pajaro River near Chittenden (loc. 30). Abutment displaced and fractured by lateral spreading of sediments toward the river channel. (Photograph by Livennon, courtesy of The Bancroft Library, University of California,. Berkeley.)

DISTRIBUTION AND CHARACTER OF GROUND FAILURES SAN FXANCISCO BAY COUNTIES REGION

23

SAN FRANCISCO BAY, SANTA CLARA VALLEY, AND EAST BAY HILLS AREAS

SANTA CRUZ MOUNTAINS

The Santa Cruz Mountains comprise the northern part of Santa Cruz County and the western parts of Santa Clara and San Mateo Counties (pl. 2 and table 6, locs. 4kL135; figs. 18-25). Ground failures in the form of hillside landslides, flows, slumping of streambanks and ground cracks, both on the hills and in the creek bottoms, were numerous and widespread effects of the 1906 San Francisco earthquake in this area. The most common damage caused by these failyres was to highway and railroad grades and to bridges. Rockfalls and dry sand flows along the coastal bluffs were particularly disruptive in this respect. For example, the ocean shore railway grade between Lake Merced and Mussel Rock (locs. 131, 132,133, fig. 241, then under construetion, was a1 ost entirely destroyed for a distance of 3 mi (5 km). S ,mewhat similar landslides were triggered in this sa , e area during the 1957 Daly City earthquake. Two catastrophic rockfalls occurred in the southern Santa Cruz Mountains. One on Hinkle Creek, a branch of Soquel Creek (loc. 501, buried the Loma Prieta Mill killing nine men, and the other on Deer Creek (loc. 74, fig. 19)became a rock avalanche that moved about 0.25 mi (0.4 km) down a narrow canyon destroying a shingle mill and killing one man. A number of flow failures were triggered in the Santa Cruz Mountains by the 1906 earthquake (locs. 110-114, 135; figs. 20-22, 25). These failures occurred in wet surficial materials, anct many were associated bith conspicuous amounts of surface water. In some instances these flows traveled considerable distances at relatively high velocities (for example loc. 135). In other instances the flows traveled rather slowly (for example loc. 113). Because the flows were generated in wet unconsolidated' sediments, generally as a consequence of liquefaction, precipitation records for the Santa Cruz Mountains for the winter preceding the 1906'shock are relevant. Monthly and daily rainfall data for San Francisco, Santa Clara, and Santa Cruz (figs. 2 4 ) show that precipitation was unusually heavy during the winter, particularly in March, and that a17_dday Had hhe shock ocrain-frekp-eriod p~e~d_e.d-th.e-sh~k. curred when ground water conditions were significantly different, such as during the dry season of the year, the number of flow failures most likely would have been greatly reduced; on the other hand: had the shock occurred when the ground was even wetter, such as during or immediately after a major storm sequence, even more flows might have developed.

4

. .

i !

Included in the San Francisco Bay counties region are Alameda County, the southern part of Contra Costa County, and the eastern parts of Santa Clara and San Mateo Counties (pl. 2 and table 6, locs. 136182; figs. 26-29). (San Francisco City and County is considered separately in the next segment of the report. Locs. 183-192 are discussed in the section on the "North Bay Counties Region.") The most common failures on the alluvial plain surrounding San Francisco Bay were lateral spreads, slumping of streambanks, ground setrtlement, and ground cracks (figs. 2628). These failures were located chiefly along stream channels and margi; nal to San Francisco Bay. Lateral movements of 2 6 ft (0.6-1.8 m) were reported in the Colma Valley (loc. 1361, on the San Bruno Marsh near Baden (loc. 137), along Coyote Creek north of San Jose (locs. 149, 150), a t a point on the railway line between Niles and San Jose (loc. 1621, and along Alameda Creek (loc. 170). These failures were mostly in sparsly populated areas; however, they caused considerable damage to railroad and highway grades and to bridges. Similar types of failures occurred along the lower reaches of Coyote (l'ocs. 149,151,153) and Alameda (loc. 170) Creeks during the earthquakes of 1868 and 1906. Figure 29 shows a geotechnical section across Coyote Creek a t the State Highway 237 bridge. This bridge is very near the site of the old bridge (loc. 149) that was damaged by lateral spreading during the 1906 temblor. The section shows that a loose granular layer just below the water table extends at least 800 ft (240 m) westward from the creek. Cracks and sand boils were reported as far as 2,000 ft (600 m) west of the creek after the 1906 shock (lac. 149). Liquefaction in this or similar granular layers was most likely responsible for the sand boils and ground failures that occurred in that area. Ground settlements of up to 2 ft (0.6 m) occurred around two well casings 4 mi (6.4 km) apart (locs. 147, 148) near the south end of San Francisco Bay. Flow from these and other wells in the vicinity (locs. 146, 149)was temporarily increased. Settlement of highway and railroad fills was also reported from several locations near the margins of San Francisco Bay (locs. 138, 141; notes 11-18, table 2). No significant ground failures were reported on late Pleistocene and-mxlc-Holocene alluvial fan deposits a t points well removed from active stream channels. These older, more consolidated and denser materials (Youd and others, 1975) apparently resisted the shaking of the 1906 event without significant yielding. This inference is supported by several specific notations of lack of ground movement. For example, Derleth (in

24

HISTORIC GROUND FAILURES IN NORTHERN CALIFORNIA TRIGGERED BY EARTHQUAKES

Jordan, 1907.. D. 188) stated that "San Jose's water works,like that of ~ a n t aRosa, was not injured; its sewers were left intact, showing that there was no unequal displacement of the ground [loc. 1571." Other ground failure are listed statements showing. lack of under locations 144, 156, and 164 in the descriDtions of ground failures (table 6). The lgo6 earthquake reports indicate that ground failures in the hills east of Sari Francisco Bay and the Santa Clara Valley were few in number and not very severe. Ground cracks were generated at several locitions north of Livermore (loci. 166, 167, 180). In addition several shallow debris slides occurred along a road in the hills east of San Jose (loc. 160), and an accelerated movement of an already active slide occurred east of San Pablo (loc. 179). ~

A

~

I

I

I

SAN FRANCISCO CITY AND COUNTY

The eventual construction of the streets in the lower section of the city caused the existence of many blocks surrounded on all four sides by high earth embankments, undrained, unsightly, with many stagnant pools, and gradually filling with rubbish and trash of all kinds. Captain Folsom was the first to fill in one ofthe water lots, a n expent of the sive dece of work on California Street west of the ~ r e s e n site ~ a nofi California. Despite the cost, i t was recognized as a valuable undertaking and others speedily followed. James Cunningham realized this was a jab for a steam shovel (or "steam paddy") and had one brought in by steamer. From 1852 to 1854 and from 1859 until 1873 a steam shovel was working constantly, loading into small railway cars and dumping in the bay, moving more than fifteen hundred cubic yards per day. As the shovel could work profitably only in sand and where there were comparatively long hauls, a large portion of the work was moved more economically by horse and cart even though a man with a horse and cart was paid $15.00 a day. There are no official firmres on the amount of material moved. Hittell (1878) assumed atransfer of 21,000,000 cubic yards, while Bancratt (1882) estimated this to be 22,000,000 cubic yards. These figures are probably conservative.

Three major ground failure zones have been identified in the filled areas of San Francisco. These zones Because of the considerable amount of damage that are designated here as (1)foot of Market zone, (2) south occurred in San Francisco (pl. 3 and table 7, locs. 19% of Market zone, and (3) Mission Creek zone (fig. 30; pl. 248; figs. 3LL54) and the greater development of that 3). These zones are generally congruent with three community compared with the surrounding region, conspicuous zones mapped as intensity grade B after more thorough 1906 postearthquake investigations the 1906 earthquake (fig. 5). The most common ground and more quantitative reports were prepared than for failure types in these zones were lateral spreads and most surrounding areas. This was generally true for differential ground settlements. Because of the critical earthquakes in 1865 and 1868 as well. Ground failures locations of these failures, they were responsible for in San Francisco have been limited mainly to areas considerable damage including the breaking of several underlain by filled over marsh and bay mud deposits, major water pipelines that, in turn, left the city largely filled-in ravines, loose sand deposits near Lake Merced, defenseless against the conflagration (fig. 49) that folsand dunes, and steep slopes. Locations of failures are lowed the 1906 earthquake. (See notes 14-19, table 4.) shown on plate 3 and for the downtown and waterfront In the foot of Market zone, settlements as large as 4 sections on figure 30. General notes describing these ft (1.2 m) occurred during the 1906 earthquake (loc. failures are listed in table 4. 193). During the 1868 earthquake settlements of 1-2 ft Before examining the nature of seismically triggered (0.3 m-0.6 m) were reported (locs. 199-2001, and some ground failures in filled over marsh and bay mud deposits, a brief review of the methods and materials settlement also was reported during the 1865 earthused in constructing the fills is provided from Brown quake (loc. 202). Near the waterfront, permanent lateral movements as large as 2 ft (0.6 m) developed durand others (1932, p. 29): ing the 1906 shock (loc. 193, fig. 31). The magnitude of these displacements decreased with distance from the Many difficulties were experienced in grading the streets in the swamp areas. Hittell [I8781states: "When streets were first made the waterfront. Some horizontal movements also apparweieht of the sand Dressed the eat down so that the water stood ently occurred in the foot of Market zone in 1868 (locs. where the surface-was dry before. Sometimes the sand brake 1 198, 200). Before a thorough investieation could be through, carrying the peat down under it, ieaving nothing but water made, evidence of 1906 ground failures and most or thin mud near the surface. More than once a contractor had put on of the consequentdamage in the foot of M~~~~~ zone enough sand to raise the street to official grade, and gave notice to Were by the fires that devastated the area t.h-e..work. the Citv Eneineer ~= ~. .---, but in ... *he .... lnnse ~~- to insoeet =-- of -- 2- dav --, between the notice and inspection, the sand had sunk down six or I and by workers during cleanup operations. eight feet; and, when a t last a permanent bottom had been reached ( A geotechnical section beneath Market Street from the heavy sand had crowded over the light peat a t the sides of the the bay to Second Street (fig. 32) shows that a layer of street and lifted it up eight or ten feet above its original level, in fill mostly ofloosefine sand with some rubble muddy ridges full of hideous cracks. Not only was the peat crowded particles the foot of Market 'One. The is UD . by . the sand in this wav. .. but i t was-also ~ u s h e dsidewise. so that houses and fences built upon itwere carriedaway from theirbrigina1 approximately 20 ft (6 m) thick near the waterfront positions and tilted up a t singular angles by the upheaval." and thins with distance inland, feathering out near

. - - ~ ~ ~ ~

~

~

~

~~~

~~

1

DISTRIBUTION AND CHARACTER OF GROUND FAILURES

'

Sansome Street. In March-July 1964, the ground water level was a t a depth of about 8 ft near the waterfront and increased in depth to about 18 ft at Sansome Street. The ground water level was probably a t about the same depth in 1906. Beneath the fill are layers of soft silty clay (bay mud) with some sand lenses. These sediments are in turn underlain by more firm materials. Liquefaction within the sand fill or an underlying sand layer is the only tenable explanation for the ground failures that developed in this area (Youd and Hoose, 1976). One evidence that liquefaction occurred in the foot of Market zone during the 1868 earthquake was the ejection of water from cracks and fissures (loc. 201). These ejections were probably a form of sand boils. No sand boils were reported in the foot of Market zone in 1906. However, some could have occurred only to be destroyed during the fire and ensuing cleanup operations orfor-.someother reason were not reported. The\south of Market zondlies in an area of filled-over marshland extending from Rincon Hill near Fourth and Brannan Streets westward approximately 1 mi (1.6 km) to near Market Street (locs. 205-212; figs. 3%36). Differential settlements in this zone were as large as 5 ft (1.5 m), and lateral displacements as large as 6 ft (1.8 m). The ground failures in that area were remarkable in two respects. First, the slope down the axis of the zone (from near Eighth and Mission Streets to Fourth and Brannan Streets) was only 0.8 percent (0.5"). Second, the lateral movement was not into a free face, but rather into Rincon Hill, a sandstone outcrop (Schlocker, 1974). At the head of this lateral spread, extensional features such as open cracks and pulledapart rails, sidewalks, and curbs (loc. 205) were common. Where the failure butted into Rincon Hill, compressional features such as buckled rails and curbs indicated that the lateral displacement was absorbed by compression. The U.S. Post Office Building at the corner of Seventh and Mission Streets (loc. 210, fig. 35) is astride the north margin of the south of Market zone. During the 1906 earthquake the ground in front of the Post Office settled 4 or 5 ft (1.2 or 1.5 m) and moved laterally about 2 ft (0.6 m), damaging the stone skirting around the base of the building (fig. 35A, C) and pulling the sidewalk apart a t the construction joints (fig. 35B). The building, which is apparently founded on a grillage foundation carried down to a firm granular layer (Gilbert and others, 1907, p. 97-98), sustained little structural damage and is still (1977) in usei A geotechnical profile across the south of Market zone a t the latitude of the James Lick Skyway (fig. 36) shows a 5-8-ft (1.5-2.4-m)-thick layer of rubble fill in the ground failure area. The rubble is underlain by a 7-114% (2.1-3.4-m)-thick layer of generally loose sand ~

.

,'

7:

b ' L~:, -A

I

,., a'

.'. , .

.,.

0' / ;: ,. ,

.

25

that is also probably artificial fill. Underlying the sand is a deep'layer of soft peaty clay (bay mud). The water table in March 1952 was only a few feet deep across most of this section. Liquefaction within the loose sand layer is the only tenable explanation for the ground failures iRthis area (Youd and Hoose, 1976). The l ~ i ~ s i Creek on which apparently contained several ground failure segments, extended up the sinuous former channel of Mission Creek from Old Mission .. Bay to near the intersection of 19th and Guerrero Streets (locs. 21P217; figs. 37-51). Settlements as large ad6 ft'(1.8 m) and lateral movements a t least as large ask6-ft,?l.8m) occurred a t several locations within this zone. The average slope from 19th and Guerrero Streets to the freeway is 0.6 percent or 0.3". Ground failures within this zone were responsible for some serious and spectacular damage, much of which is well recorded on photographs. Figure 37 is a schematic diagram of present streets in the lower part of the zone showing approximate locations and directions from which the photographs in figures 3 5 4 1 were taken. These photographs show southwestward lateral spreading across both Ninth and Dore Streets between Bryant and Brannan Streets. The lateral spreading did not extend as far 'south as 10th Street, where there was but little evidence of ground failure (loc. 214). Figure 42 is a schematic diagram of several streets in the midsection of the Mission Creek zone showing approximate locations and directions in which photographs in figures 4%47 were taken. These photographs show the magnitude, location, and character of the lateral-spreading ground failure in this area. Lateral movements of up to several feet developed down the axis of the zone and in some areas toward the axis, causing compressional deformation a t some locations (figs. 43, 44, 47) and extension features a t other locations (figs. 45, 46). The damage at Valencia Street was the most catastrophic of any that occurred in the Mission Creek zone (loc. 216; figs. 48A, 48B). Vertical and horizontal displacements here were both as large as 6 ft (1.8 m). Two main arterial water pipelines laid beneath the street were severed by the ground failure cutting off the water supply to a major part of the city which was soon to be in flames (fig. 49). Also, the catastrophic collapse of the four-story Valencia Street Hotel (loc. 216; fig. 48A) occurred at this location. This collapse may have been a t least in part a consequence of the large ground movements that extended beneath the structure. Tens of people were killed in the collapse and the ensuing consumption of the building by fire. At the head of the Mission Creek zone, a substantial three-story brick building (fig. 50) was carried laterally

, ,

26

HISTORIC GROUND FAILURES IN NORTHERN CALIFORNIA TRIGGERED BY EARTHQUAKES

the lake. Liquefaction within natural and artifically placed sand surrounding and beneath the lake has been identified as the cause of many of the 1957 failures (Bonilla, 1960) and is the probable cause of the 1906 failures. After an earthquake in 1852 fissures were found between Lake Merced and the Pacific Ocean (loc. 244) through which the waters of Lake Merced were flowing into the sea. It is unclear whether these ruptures were generated by an earthquake or by other factors such as previous heavy rain storms that may have caused overtopping of or piping through the natural embankment between the lake and the ocean (Soul6 and others, 1854). The sand dune section of western San Francisco was very sparsely developed ,in 1906. As a consequence, only fragmentary descriptions of ground failures in that section are available from the 1906 reports, and some of these descriptions are vaguely stated. The reports indicate that some areas of instability developed near the ocean (locs. 246, 247) and some cracking and lateral spreading occurred farther inland (locs. 230, 243). Liquefaction probably contributed to the development of these failures as evidenced by the eruption of sand boils a t several locations (locs. 243, 247). Several hillside landslides occurred on the steeper slopes in San Francisco during the 1906 event (locs. 218, 22G229). These failures were responsible for structural damage to the Cyclorama, a building in Golden Gate Park (loc. 228), and a retaining wall at Laguna Honda reservoir (loc. 229).

6 ft (1.8 m) along with the curb, walk, and street in front of the building (loc. 217). There is no evidence indicating that lateral spreading continued up the old Mission Creek channel beyond this location. A geotechnical section across the Mission Creek zone a t Mission Street (fig. 51) shows a layer of very loose fine sand fill underlain by layers of soft clayey sand and soft silty sand, which are in turn underlain by alternating layers of firm clean clayey sand. In February 1964 the water table was as shallow as 5 ft (1.5 m) beneath the ground surface in that part of the section where the 1906 lateral-spreading failure took place. Liquefaction wtihin the loose sand fill or possibly the soft silty sand layer beneath the fill is the evident cause of ground failure in this zone (Youd and Hoose, 1976). Two ground failures in filled ravines, though small in size, produced rather spectacular results. One near the intersection of Vallejo Street and Van Ness Avenue (loc. 221, fig. 52) was characterized by differential settlements as great as 2 ft (0.6 m) and lateral displacements as great as 3 ft (0.9 m). The other, on Union Street between Pierce and Steiner Streets (loc. 222, fig. 53), had vertical and lateral displacements as great as 10 ft (3 m) and moved down a rather steep slope into an unfilled vacant lot. Several lateral spreads and rotational slumps, some of which were converted into flow failures, occurred around the shoreline of Lake Merced during both the 1906 and 1957 earthquakes (locs. 232, 242; fig. 54). These failures caused considerable damage to highway embankment and bridge structures around and across TABLE4.-Excerpted Note

notes containing general descriptions of ground failure ond consequent pipeline breaks i n S u n Francisco quotation

Reference

1 Lawson nnd others, 19Ud. It is evident that the intcnsaty vanes with the grulogy, or with the areal distribution of rucks and soils The areas that suffered most scvcrcly were those u p m filled ~ r d ~ n d . p. 253. Arras uoon marsh" eround showed destruotlve effects ilmllar to u r r ~ f i c ~ filled el land &as of filled land are those w o n incoherent sands. The damage in sandy areas was Next in;ntensity due partly to thc .\,thickly b u i l t up. The earthquake caused a settlement of f o m 6 t o 8 f t . f o r a distance of from 150 t o 200 f t . along t h i s s t r e e t , and a t t h e same time s h i f t e d t h e e n t i r e s t r e e t , with adjacent l a n & e a i t r r r d through a naximm distancalof 9 t o 10 f t . This change i n alignment and grade could, of course, mean nothing l e s s than t h e e n t i r e destruction of a l l water and gas mains, e l e c t r i c l i g h t i n g and telephone conduits, sewers, cable conduits, r a i l r o a d t r a c k s , e t c . The breakage of these important l i n e s , e s p e c i a l l y t o t h e water mains, w w o f g r e a t e s t significance. I n t h i s case the destruct i o n of t h e water pipes, o f which a 28-in. and a 16-in. were found i n t h i s s t r e e t a t t h i s point, meant t h e c u t t i n g off of a large p a r t of t h e water supply of t h e portion of t h e c i t y which was &on t o be i n flames.

A

1906

Lawsan and others, 1908, P. 239, p l a t e 938.

A t Eighteenth and Valencia S t r e e t s t h e r e was a serious break i n t h e water;pipe. Here, on both s i d e s of t h e s t r e e t , tile ground sank about 6 feet;'causine t h e roadway t o arch i n a verv noticeable way. Teninch car r a i l s were bowed up i n t o arches from 24 t o 30 inches i n height. The Valencia S t r e e t Hotel collapsed s o t h a t occupants of t h e fourth s t o r y could s t e p out i n t o t h e s t r e e t . Casualties i n t h i s d i s t r i c t can never be known accurately, owing t o t h e immediate onset of t h e f i r e , and t h e complete devastation i t produced.

Duryea and others,

I n f i l l e d - i n t i d a l areas, marsh-lands and swamps t h e r e was considerable movement i n a n m b e r of places [the g r e a t e s t near 16th Sr. [ l a t h S t . ? ] and Valencia S t . , where t h e settlement was 5 f t . and t h e l a t e r a l movement 6 f t . ) and i n a l l such disturbed areas t h e sewers were destroyed.

x 8

216

4&l 488

8

x

X

1906

A

1906

Schussler, 1906, p. 43.

APPENDIX D. The following are e x t r a c t s from t h e r e p o r t of City Engineer Woodward on t h e breaks i n t h e San Francisco sewer system caused by t h e earthquake as published i n t h e "San Francisco Chronicle" of June 17, 1906: * * r '!On Valencia s t r e e t , between Eighteenth and Nineteenth s t r e e t s , t h e r e was a l a t e r a l mvement t o t h e e a s t , with a maximum of s i x f e e t and a subsidence with a maxirmm of f i v e f e e t . This occurred i n made ground over t h e o l d Willows marsh, one of t h e t r i b u t a r i e s of Mission creek."

8

1906

Derleth, 1906b, p. 551.

The Valencia Hotel, it w i l l be remembered, was s i t u a t e d on Valencia St., near 18th. on f i l l e d ground, where once ran t h e o l d Mission o r I s l a i s Creek. The Valencia Hotel and o t h e r cheap brick and frame buildings i n t h a t region from Valencia t o Howard S t s . very generally collapsed. Many l i v e s were l o s t i n t h e Valencia Hotel.

B

1906

Derleth, 1906c, p. 581.

[Figure caption] STREET SUBSIDENCE IN SIW FRANCISCO. VIEW ON VALENCIA ST., NEAR 18TH ST., OPPOSITE SITE OF VALENCIA HOTEL. ( I t was a t t h i s place t h a t s t r e e t water mains were broken. The st,reet dropped about 4 f t . and moved eastward about 6 f t . a t t h e maximwn point.

e

X

8

-

C

-

X

Quotation

140

HISTORIC GROUND FAILURES IN NORTHERN CALIFORNIA TRIGGERED BY EARTHQUAKES TABLE7.Speeifie descriptions of ground failures in S a n Francisco City a n d County-Continued

Loca- Fig- Fail- Accu- Year of t i o n ure ure a earthNo. quake No. type cy

I

Reference

Quotation

B

1906

Son Francisco .Chronicle, 1906a.

[picture caption] Ruins of t h e Valencia S t r e e t Hotel, showing t h e depression i n t h e s t r e e t . This i s t h e b e s t photograph o f t h e effect of t h e earthquake i t s e l f y e t published.

B

1906

l o s Angetes DniZy Times,

[Picture caption] Valencia Hotel, San Francisco, i n which f o r t y people were k i l l e d .

1906b.

I

B

11106

Los Angetes DniZy Times, 1906b.

A

A

1906

1906

[Picture caption] San Francisco F l a t s Sunk One Story I n t o t h e Ground by Earthquake. Great Fissures i n S t r e e t . photo by H. C. Carr. On t h e corner next t h e Valencia was a new s e t of t h r e e s t o r y f l a t s , j u s t completed, and mast of t h e f l a t s not yet occupied. As though someone had s t r u c k it on top with a giant hammer, t h e e n t i r e building had sunk one s t o r y i n t o the-ground; you could walk r i g h t i n a t t h e second story.

The Evening Wisconsin,

BIG CREVASSE IN STREET. A t Eighteenth and Valencia t h e r e i s a crevasse i n the s t r e e t s i x f e e t wide and e n t i r e sidewalks are torn

1906.

up. The s t r e e t car t r a c k s are badly twisted a l l through t h e southern s e c t i o n o f t h e c i t y and t r a f f i c i s a t a s t a n d s t i l l .

Schussler, 1906, p. 30.

* * r t h e College H i l l Reservoir r * had beem emptied o f its cont e n t s 11,400,000 gallons, which it contained a t 7 A. M. April 18, by i t s main a r t e r i a l pipe, 22-inch diameter, and i t s companion pipe, 16-inch diameter, both an Valencia s t r e e t , having both been torn o f f and destroyed between Eighteenth and Nineteenth s t r e e t s by the sinking of Valcncia s t r e e t o f from one t o f i v e f e e t . VALENCIA STREET SUBSIDENCE. A number o f l e s s e r footmarks of our earthquake are t o be seen i n t h e s t r e e t between Seventeenth and Eighteenth and e a s t and south of Mission. These a l l coincide with the i r r e e u l a r l i m i t s o f our i n d i c a t e d s o e c i a l l v s o f t soots i n rhe former s a l t marsh area, and we follow them around u n t i l we come t o another pronounced case of subsidence and s l i p , which i s noticeable i n Valencia s t r e e t between Eighteenth and Nineteenth, i n Mission between Seventeenth and Eighteenth and i n Howard from Seventeenth and Eighteenth. Valencia s t r e e t shows subsidence of one t o f i v e and a h a l f f e e t and s l i p of one t o s i n f e e t f o r 450 f e e t i n length; Mission shows very s l i g h t subsidence and s l i p of only about one foot f o r about 400 f e e t i n length, while Howard shows a subsidence o f two t o t h r e e f e e t f o r over 500 f e e t i n length and a maximum s l i p o f about four f e e t . The l i m i t s of t h e movement, p l a t t e d on t h e map, exactly o u t l i n e t h e ravine i n which was formerly headed, between Mission and Valencia, "The Willoios," a San Francisco place of r e s o r t . The whole area was i n those days m i s t land, with a l i t t l e stream i n i t f o r a p a r t o f each year, and which has been f i l l e d upon between hard h i l l s i d e s . Being s o f t beneath and on a downgrade i n t h e l i n e o f g r e a t e s t earthquake v i b r a t i o n , t h e temblor found i n it an easy mark f o r a pronounced dermnstration. Again, a t i t s head between Valencia and Guerrero a s i d e ravine came down from t h e south. The s l i p across Nineteenth s t r e e t of about s i n and a h a l f f e e t , as shown by bowing of t h e l i n e o f curbing, o u t l i n e s t h e branch of t h e o l d depression, which was f i l l e d on a steep gradient and q u i t e n a t u r a l l y s l i d e a s i l y . [See l o t . 217.1

~.

.

X

A

1906

Rickard, 1906b, p. 287.

Valencia S t r e e t has sunk 8 t o 10 f e e t * + * Down 18th s t r e e t a l s o , from Valencia t o Howard [now South Van Ness], t h e ground has sunk on t h e north s i d e along t h e c e n t e r of t h e cabble-paved roadway and t h e r e i s a crack 12 t o 15 inches wide along t h e l i n e of rupture. Neighboring houses show t h e e f f e c t s of disturbance. Evidence of a s i m i l a r kind is obtainable elsewhere i n t h i s v i c i n i t y and it is noteworthy t h a t t h e b e l t of deranged buildings and d i s l o c a t e d roadways follows exactly t h e l i n e of the f i l l i n g over t h e o l d creek.

x

A

1906

Schussler, 1906, p. 35.

One a f t h e most serious breaks i n t h e main pipe l i n e s was caused by t h e earthquake shaking and s e t t l i n g down, by from one t o f i v e f e e t , t h e region between Eighteenth and Nineteenth s t r e e t s , on Valencia s t r e e t . Here an o l d swamp had been loosely f i l l e d i n , many years ago, by any and a l l kinds of material and,rubbish obtainable, t h e f i l l being twenty f e e t o r more i n depth.

141

TABLES &9 TABLE 1 . S p e c i f i c descriptions of ground failures in San Frahciseo City and County-Continued Loca- Fig- Fail- Accu- Year of raeartht i o n ure "re No. quake No. type cy 217 50

219

220

1906

Lawson and others, 1908, p. 239, p l a t e 94A.

On land made by f i l l i n g i n , "The Willows," a marshy t r a c t formerly extending up t h e Eighteenth S t r e e t Valley from Mission Lagoon, near t h e corner of Nineteenth and Guerrem S t r e e t s , t h e r e was observed a w n s i d e r a b l e slumping or flaw movement of t h e surface. The photograph ( p l a t e 94A) shows t h e Youth's Directory, a c h a r i t a b l e i n s t i t u t i o n f o r boys, where the s t r e e t and building were moved northward and s l i g h t l y eastward, toward t h e former channel and downstream, fully 6 feet.

B

1906

Lawson and others, 1908, p. 240, p l a t e 900.

Near t h e corner of Waller and Portala S t r e e t s , n o t f a r north o f t h e head of Market S t r e e t , i s a l o c a l i t y , l e s s than a black i n extent, where houses were s h i f t e d s l i g h t l y on t h e i r foundations; t h e i r upper s t o r i e s were moved f a r t h e r eastward (downhill) than t h e foundations r * * Here a t h i n layer of sand reposes upon t h e slopes of a l i t t l e upland v a l l e y between t h e low serpentine h i l l s t o t h e e a s t and t h e high c h e r t h i l l s t o t h e west. The e f f e c t s are such as would be produced by a shaking downhill o f t h i s t h i n sand layer, with t h e s t r u c t u r e s which r e s t upon it.

B

1906

Jordan, 1907, p. 123.

52

.

STREET AND SURFACE DEFORMATIONS Great d i s t o r t i o n of t h e surface was b e s t observed i n the s t r e e t s , and was found on t h e f i l l e d areas

and i n some places, on t h e sand dunes. The b e s t l o c a l i t i e s f o r observation were: * * * (5), Van Ness Avenue a t Eddy S t r e e t ; [Complete quotation under note 3 t a b l e 3.1

A

1906

The A~gonnut, 1906.

[Picture caption] Point a t corner- o f Van Ness and P a c i f i c Avenues, San Francisco where t h e f i r e broke out again, leading t o t h e destruct i o n of North Beach. [Picture shows a crack i n t h e sidewalk w i t h , some subsidence. ]

A

1906

Lawson and others, 1908, p. 231.

A t t h e corner o f Vallejo S t r e e t and Van Ness Avenue, f i s s u r e s were formed i n t h e asphalt paving, sidewalk pavements were t h r u s t over t h e curbing, and water-mains and sewers were broken. Buildings were thmwn out of t h e v e r t i c a l , and foundations and lower s t o r y walls were s h i f t e d and crusht. The w a l l s about t h e foundation of one brick building were a c t u a l l y deformed i n t o undulations with much consequent cracking. This building was $ 0 badly damaged t h a t it had t o be taken down. Surrounding t h i s corner i s a small ovoid d i s t r i c t , about 2 blocks i n extent, i n which t h e i n t e n s i t y rias c l e a r l y of grade B. This was once a sharp ravine and had been f i l l e d t o a depth o f 40 f e e t i n order t o provide a s u i t a b l e grade f o r s t r e e t s and buildings. The f i l l i n g was shaken together and moved s l i g h t l y downhill.

B

1906

Gilbert, Humphrey, Sewell, and Soul6, 1907, p. 118, p l a t e 56.

A t one point on Van Ness avenue (see B, PI. LVI), where I happened t o see t h e mains uncovered, a heavy water pipe, apparently about 20 inches i n diameter, had been broken i n t o pieces not more than 2 feet.long. The t o t a l length o f t h e break, however, was not more than 40 o r 50 f e e t , s o f a r as I could judge from what I saw uncovered.

B

1906

Schussler, 1906, p. 43.

APPENDIX D. The following are e x t r a c t s from t h e r e p o r t of City Engineer Woodward on t h e breaks i n t h e San Francisco sewer system caused by t h e earthquake as published i n t h e "San Francisco Chronicle" of June 17. 1906 ro. 341: "The v i c i n i t y of Van Ness avenue and Vallejo 5 t h is-bne o? t h e prominent p a i n t s of i n t e r e s t . I t was found t h a t Van Ness avenue had been more o r l e s s a f f e c t e d from a point 150 f e e t south of Vallejo s t r e e t t o Union s t r e e t , t h e g r e a t e i t subsidence being two f e e t a t t h e crossing of Vallejo s t r e e t . There was a l s o subsidence of Vallejo s t r e e t f o r 150 f e e t on each s i d e of Van Ness avenue. There was a l a t e r a l movement t o t h e north on Van Ness avenue of about t h r e e f e e t on Vallejo S t r e e t , decreasing t o

x 221

Quotation

A

*

x

Reference

+

HISTORIC GROUND FAILURES IN NORTHERN CALIFORNIA TRIGGERED BY EARTHQUAKES

142

TABLE7 . S p e c i f i c descriptions of ground failures in San Francisco City and County-Continued Loca- Fig- F a i l - Accu- Year of tion No.

ure No.

ure type

racy

Reference

Quotation

earthquake about one foot a t Green s t r e e t , t h e ground and buildings upon i t having been moved bodily so t h a t now t h e buildings encroach upon t h e neighboring l o t s o r upon the s t r e e t . As a r e s u l t of t h e subsidence and l a t e r a l movement t h e seirers extending e a s t , south and west of t h e crossing of Van Ness avenue and Valleja s t r e e t were broken f o r about 150 f e e t . The scene of t h e disturbance was an o l d f i l l of about f o r t y f e e t which had been made years ago i n t h e ravine leading t o t h e northwest t o t h e lagoon formerly c a l l e d Washerwoman's bay." [ ~ l of l t h e information r e l e v a n t t o ground f a i l u r e occurrences i n t h e Chronicle r e p o r t i s contained i n t h i s e x t r a c t by schuss1er.l

* * * VAN NESS AVENUE. In no portion of San Francisco i s t h e vagar i e s o f t h e temblor r e g i s t e r e d as on Van Ness avenue. Do,? towards t h e bay t h e houses facing on t h i s b e a u t i f u l boulevard have been twisted l i k e c&kscrews, and t h e pavement is f i l l e d with gaps several f e e t wide and many f e e t deep.

8

1906

Oakknd Tribune, 1906~.

8

1906

L e s l i e ' s WeekZ.q, 1906e.

A

1906

Lawson and others, 1908, p. 232, p l a t e 888.

A portion of Vnion S t r e e t , between Pierce and S t e i n e r S t r e e t s , not more than a q u a r t e r of a block i n length, where a f i l l i n g had been made t o equalize t h e s t r e e t grade, was shaken down i n t o t h e adjacent b u i l d i n g l o t on t h e north. The n o r t h sidewalk was s h i f t e d about 10 f e e t t o t h e north, and deprest about 10 f e e t below i t s o r i g i n a l l e v e l . The south sidewalk was deprest a few inches and s h i f t e d t o t h e north from 2 t o 3 f e e t . The paving and t h e cable conduit suffered more severe damage than a t any other point i n t h e c i t y . * r * The phenomena have no general significance, however, d e s p i t e t h e i r s t r i k i n g character, being merely a s l i d i n g o f unconsolidated material n o t supported'on t h e sides.

C

1906

Oaklmd Tribune, 1906~.

Near Union S t r e e t t h e bitumen has been converted i n t o a s e r i e s of waves. Closer t o t h e m i l i t a r y reservation t h e e f f e c t of t h e shake upon t h e e a r t h i s even more apparent. Several grades were d i s t i n c t l y changed.

A

1906

Gilbert, Humphrey, Sewell, and Soule, 1907, p. 27.

The group o f buildings comprising t h e p l a n t of t h e San Francisco Gas and E l e c t r i c Light Company, b u i l t on t h e s o f t ground along San Francisco Bay j u s t west of Fort Mason, w a s badly shaken, and none of t h e buildings escaped damage. * * r The ground s e t t l e d very considerably under t h e v i b r a t i o n s o f t h e earthquake, and f u r t h e r destruction was cuased by the unequal s e t t l i n g of t h e building.

224

8

1868

Lawson and others, 1908, p. 438.

On t h e beach a t t h e foot of Webster S t r e e t , below high-water mark, a f i s s u r e opened, extending lengthwise with t h e water.

225

C

1868

222

@ 53

x

Lawson and others, 1908, p. 438.

226

A

---a+

C

1906

1906

Lawson and others, 1908, p. 232.

Lawson and others, 1908, p. 233.

[Picture caption]

A mark of t h e earthquake i n Van Ness Avenue.

A l a r g e f i s s u r e was made i n t h e high bank near Fort Point and t h e shock w a s f e l t severely a t t h e Fort.

On Fulton S t r e e t , between Twelfth and Thirteenth Avenues, t h e r e was m c h slumping of t h e s t r e e t - f i l l i n g down i n t o t h e Park adjacent;

and exactly t h e same s o r t o f damiige occurred on H S t r e e t , between t + They were e s p e c i a l l y susceptible Ninth and Fourteenth Avenues. t o damage from earthquake shock, being p r a c t i c a l l y loose e a r t h embankments. All driveways i n t h e western p a r t o f Golden Gate Park showed s c a t t e r e d narrow f i s s u r e s .

143

TABLES 5 9

TABLE1 . S p e e i f i c descriptions of ground failures Loca- Fig- F a i l - Accu- Year of t i o n "re "re raearthNo. quake No. type cy C

227

1906

Reference

Fallows, 1906, p. 313.

Ln San Francisco City and County-Continued

Quotation

[Picture caption] CRACK I N THE EARTH. This photograph shoios a i n the e a r t h i n Golden Gate Park, San Francisco, caused by the earthquake. CI.BC~

B

1906

Gilbert, H m p h r y , Sewell, and Soule, 1907, p. 30.

At t h e bottom of Strawberry H i l l is a bridge crossing over Stow Lake. This bridge is made of concrete, and showed no signs of cracking, although t h e banks of t h e lake slipped i n t o t h e water.

A

1906

Lawson and o t h e r s , 1908, p. 232 and 233.

Strawberry H i l l , i n Golden Gate Park, is a c h e r t knob r i s i n g abruptly i n t h e sand wastes. * * * The whale periphery of t h e h i l l t o p was broken i n r o a s e r i e s of concentric blocks or s t e p s , and t h e o u t e r ones moved down t h e h i l l from 2 t o 3 f e e t . The a r t i f i c i a l stone work was badly cracked and dislodged. These phenomena i n d i c a t e d t h a t t h e material used i n grading the upper slopes had s e t t l e d somewhat, with consequent rupt u r e of t h e surface and wrecking of t h e building.

A

1906

Gilbert, H m p h r e ~ , Sewell, and Soule, 1907, p. 29 and 30.

The most i n t e r e s t i n g s t r u c t u r e i n Golden Gate Park i s t h e cyclorama (PI. XXIII, A), on t h e top of Strawberry H i l l , b u i l t about f i f t e e n years ago. The top of t h e h i l l had been leveled o f f i n order t o form a foundation. + * * The s e t t l i n g of t h e foundation of f i l l under t h e v i b r a t i o n of t h e earthquake caused t h e s t r u c t u r e t o collapse. 7hc s l i p (PI. XXII, B) occurred p r i n c i p a l l y on t h e northe a s t s i d e , t h e movement being 4 o r 5 f e e t . The p r i n c i p a l crack i n t h e base was about 11 inches wide, with a half-inch horizontal crack leading from it along t h e reenforcement. The f l o o r i s i n good condition, except t h e pavement, which broke i n t o blocks * + *

@

a

0

.

229

A

1906

Gilbert, Humphrey, Sewell, and sou16, 1907, p. 115.

Within the c i t y proper t h e r e s e r v o i r known as Lake Honda was damaged by t h e cracking of i t s concrete lining. It i s reported t h a t t h i s cracking was due t o t h e displacement of a r e t a i n i n g wall by a s l i d i n g bank s e t i n motion by t h e earthquake.

A

1906

Ouryea and others, 1907, p. 249.

The slope, on t h e west s i d e c o n s i s t i n g of very sandy s o i l , was supported by a r e t a i n i n g wall which constituted t h e s i d e of t h e r e s e r v o i r basin. * * * The e f f e c t o f t h e shack was t o rupture t h i s r e t a i n i n g wall, which f a i l e d by shearing near t h e bottom of t h e r e s e r v o i r , although i r r e g u l a r cracks i n one p l a c e extended t o t h e top of t h e wall.

@

@

Lake Honda Reservoir, * * * was i n j u r e d by t h e earthquake cracking t h e heavy western wall, t h e shock coming from t h e west and shaking up a sandy mountain, about 100 f e e t high, causing t h e slope t o s l i d e down towards t h e wall. 230

C

1906

Lawson and others, 1908, p. 231.

Ocean Avenue, between Ingleside and t h e sea, tho almost devoid of s t r u c t u r e s , shows by t h e unearthing, bending, and even breaking of drainage and water pipes, and by f i s s u r e s i n t h e road and asphalt paving, a change o f i n t e n s i t y from Grade C t o Grade B.

231

B

1906

Lairson and others, 1908, p. 231.

Near Lakeview, f a i r l y well b u i l t frame buildings on dune sand of unknown thickness were caused t o lurch and s h i f t t h e i r positions.

232

B

1957

Bonilla, 1959,

Landslides occurred a t about a dozen d i f f e r e n t places along t h e shore of Lake Merced, and most, i f n o t a l l , involved a r t i f i c i a l f i l l . The width of t h e s l i d e s ranged from 75 t o 300 f e e t and one s e r i e s of s l i d e s extended along t h e lake shore f o r 800 f e e t . The s l i d e s produced scarps t h a t were about 10 f e e t high. In many o f t h e s l i d e s t h a t a f f e c t e d t h e

>

144

HISTORIC GROUND FAILURES IN NORTHERN CALIFORNIA TRIGGERED BY EARTHQUAKES TABLE7.Specific descriptions of grouna failures in San Francisco City and County-Continued

Loca- Fig- Fail- Aecu- Year of earthrat i o n ure ure No. quake No. type cy

Quotation

Reference

highmy along t h e lake shore t h e pavement was r o t a t e d s o t h a t it dipped away &rn t h e scarp r a t h e r than toward t h e scarp as i s normal i n slumptype landslides. Very l i t t l e d e b r i s from these s l i d e s was v i s i b l e above-the l e v e l of t h e lake a few hours a f t e r t h e earthquake. These two conditions s u m o r t t h e i n t e r o r e t a t i o n t h a t t h e s l i d i n g was i n t h e nature o f a flow 'a;ld t h a t t h e m s e r i a l spread out on t h e Take bottom. The material i n the scarps was mostly uncompacted a r t i f i c i a l f i l l made up o f clean, loose, well-sorted sand which, because it was on t h e shore of t h e lake, must have been saturated. This s l i d i n g probably was of the type c a l l e d sand-flow, which r e s u l t s from spontaneous l i q u e f a c t i o n of sand. 1957

Steinbrugge and others, 1959, p. 103.

At t h e Lake Merced Pump S t a t i o n i n San Francisco, a f i l l e d area s e t t l e d 4 t o 6 inches, severing a 12-inch pipe from t h e s t a t i o n .

1957

Bonilla, 1960, p. 6.

Table 1. Landslide number 11; slump i n s o i l ; 60 f e e t long and 150 f e e t wide.

1957

Bonilla, 1960, P. 6.

Table 1. Landslide number 10; slump i n s o i l ; 100 f e e t long and 100 f e e t wide. Also Landslide number 9; slump i n s o i l ; 60 f e e t long and 125 f e e t wide.

1957

Bonilla, 1960, p. 6.

Table 1. Landslide number 8; slump i n s o i l and sand flow; 100 f e e t long and 800 f e e t wide and consisted o f several coalesced s l i d e s .

1957

Bonilla, 1960, P. 21, f i g . 4.

S l i d e 8, shown on figure 4, probably s t a r t e d as a sand flow, but removal of support by t h e flow r e s u l t e d i n slump f a i l u r e near t h e head of t h e landslide.

1957

Bonilla, 1960, p. 6.

Table 1. Landslide number 7; sand floir and s l m p i n s o i l ; 80 f e e t long and 225 f e e t wide.

1906

Lawson and others, 1908, p. 387.

sudden movement of t h e ground occurred on t h e A + Merced Lake, whereby a l a r g e s e c t i o n of t h e slope sank i n t o t h e lake, and a portion o f t h e bottom of t h e lake above t h e surface by t h e deformations1 r o t a t i o n o f t h e ground.

1906

Lawson and o t h e r s , 1908, p. 251.

J m t south o f the bridge across Lake Merced, a sand-bar was forced up out of t h e lake, from water t h a t was previously 6 or 8 f e e t deep. This b a r i s p a r a l l e l t o t h e west bank o f t h e lake, and has a d i r e c t i o n almost due north and south. This was probably caused by t h e same t h i n g t h a t wrecked t h e bridge; t h a t i s , t h e displacement and s e t t l i n g of t h e west bank o f t h e lake a t t h e time o f t h e earthquake.

..

west side o f toward and was l i f t e d collapsed

Table 1. Landslide number 4; slump i n s o i l ; 110 f e e t long and 200 f e e t wide.

1906

Lawson and others, 1908, p. 251.

Lake Merced.--About 6 miles north o f Mussel Rock, where t h e hlerced beds disappear under aeolian sands, t h e disturbance seems t o have been q u i t e violent. An o l d r a i l r o a d t r e s t l e , t h a t crosses t h e northern end of Lake Merced i n t h e narrowest place, was badly wrecked. This

145

TABLES F-9

TABLE7 . S p e c i f i c descriptions of ground failures in San Francisco City and Comty-Continued Loca- Fig- F a i l - Accu- Year of raeartht i o n u r e ure NO. quake No. type cy

Reference

Quotation

bridge was broken i n two places, and t h e intermediate piece was out of l i n e with both ends. The d i r e c t i o n of t h e o f f s e t s was very nearly due n o r t h and south. A t one bre& t h e west piece was shoved 12 o r 14 f e e t p a s t t h e o t h e r section. The west end o f t h e intermediate piece f a i l e d t o join t h e s e c t i o n a t t h e west bank by 6-ar 7 f e e t . The west s e c t i o n t h a t remained with t h e bank was from 4 t o 5 f e e t lower v e r t i c a l l y than t h e intermediate piece. The t r e s t l e was o l d , b u i l t of heavy timbers on a sharp curve, and not i n use, which w i l l i n p a r t account f o r i t s destruction. The swaying of t h i s bridge destroyed a s e c t i o n of it 50 t o 60 f e e t long. On t h e h i l l s i d e where t h i s t r e s t l e reaches t h e west bank of t h e lake, cracks p a r a l l e l t o t h e shore l i n e Suggest t h e cause of t h e destruction of t h e bridge. The displacements here are l a r g e r than any along t h e main f a u l t l i n e , and it i s apparentl y e n t i r e l y l o c a l , due t o t h e s l i p p i n g and s e t t l i n g of t h e west bank of t h e lake. Table 1. Landslide number 3; slump i n s o i l ; 100 f e e t long and 100 f e e t wide.

1957

Bonilla, 1960, p. 6.

Table 1. Landslide number 2; debris s l i d e ; 100 f e e t long and 150 f e e t wide.

1957

Bonilla, 1960, p. 6.

Table 1. Landslide number 1; d e b r i s s l i d e ; 75 f e e t long and 80 f e e t wide.

In addition t o t h e f a i l u r e s along t h e roadway a t t h e shore of Lake Merced, t h e f a i l u r e of t h e a r t i f i c i a l f i l l a t t h e north end of t h e foot-bridge crossing t h e north arm of t h e lake a l s o was probably caused by sudden l i q u e f a c t i o n of sand. Some of t h e s l i d e s along Lake Merced were of t h e slump-earthflow type and displayed a backward r o t a t i o n of t h e component blocks. These s l i d e s may have been caused by removal of support by sudden liquefaction of sand a t t h e foot of t h e slope.

+

A

1957

Bonilla, 1960,

Table 1. Landslide number 5; sand flow; 70 f e e t long and 80 f e e t wide. Landslide number 6; slump i n s o i l and earthflow; 125 f e e t long and 120 f e e t wide.

A

1957

Bonilla, 1960, p. 21.

S l i d e 5 i s an example of t h i s type o f landslide. I t severed t h e a r t i f i c i a l embankment north o f t h e footbridge t h a t crosses the north arm of Lake Merced, as shown on figure 3. The enact dimensions of t h e s l i d e deposit could not be determined because it was under water but about 80 f e e t of t h e embankment was destroyed. The vegatatian displaced by t h e s l i d e i s v i s i b l e on a i r photos taken four months a f t e r t h e s l i d e . Measurements made on t h e photos show t h a t t h e vegetation on t h e s i d e s of t h e embankment moved a t l e a s t 70 f e e t both eastward and westriard from t h e o r i g i n a l shorel i n e of t h e embankment. The material v i s i b l e i n t h e north end of t h e embankment was a r t i f i c i a l f i l l composed of clean sand, and as a l a r g e deposit of dune sand i s found a short distance north of t h e s i t e , i t is probable t h a t a l l of t h e embankment was clean well-sorted sand obtained from t h e dunes. The slope o f t h e embankment above water was on t h e o r d e r of Zoo, and under water was presumably l e s s . The earthquake v i b r a t i o n s probably l i q u e f i e d t h e s t a u r a r e d sand at t h e base of t h e embankment and t h e unsupported embankment collapsed and spread over t h e lake bottom.

0

~

1906

Lawson and others, 1908, p. 241.

~

~~~

On Ocean Avenue and X S t r e e t , near where t h e former o u t l e t of Lake Merced flowed, f i s s u r e s were developed i n the s t r e e t and i n t h e sands on e i t h e r , s i d e , and water was squeezed out so as p a r t l y t o flood t h e roadway. Drain pipes were unearthed and bent o r twisted.

146

HISTORIC GROUND FAILURES IN NORTHERN CALIFORNIA TRIGGERED BY EARTHQUAKES

TABLE? . S p e c i f i c descriptions of ground failures in San Francisco City and County-Continued Ldca- Fig- F a i l - Accu- Year of rat i o n "re ure earthNo. No. type cy quake

1852

Reference

Townley and Allen, 1939, p. 28.

Quotation

1852 November 22. 11 p.m. VIII. Near San Francisco. Severe shock eight miles southeast (?) of San Francisco. Next morning a f i s s u r e h a l f a mile wide and t h r e e hundred yards long was discovered, through which t h e waters of Lake hlerced were flowing t o t h e sea.

1852. Novenber 22 to 24. San Francisco Peninsula. This shock was severe 8 miles southwest o f San Francisco. Apparently, considerable f i s s u r i n g occurred from Lake Merced t o t h e sea. 1852. November 22; 11 p. m.; VIII. Severe shock e i g h t miles southe a s t of San Francisco. Next morning a f i s s u r e h a l f a mile wide and t h r e e hundred yards long was discovered, through which t h e waters of Lake Merced were flowing t o t h e sea. 1852

~ o u l c / , Gihon, and Nisbet, 1854, p. 408.

November 23d.--The waters of Lake La Mercede, i n t h e v i c i n i t y of t h e c i t y , and irhicll cover several hundred acres, sank about t h i r t y f e e t . S h o r t l y before midnight of t h i s day, a shock l i k e t h a t o f an earthquake was f e l t by p a r t i e s r e s i d i n g near t h e place; and t h e following oorning it was discovered t h a t a great channel between t h e lake and t h e sea had been opened, through a broad and high sand bank, during t h e night, by which t h e waters had found a way and been discharged. * * The most probable conjecture i s , t h a t t h e excessive r a i n s o f t h e season had simply forced open a passage through t h e broad and loose sand-bank from t h e lake t o t h e ocean. Formerly t h e lake had no v i s i b l e o u t l e t whatever; and i t s waters had insensibly been kept * about the same l e v e l t

I906

Schusrler, 1906, p. 9.

* * * vest and southwest from Lake Nerced * r r t h e o u t l e t , or ocean end, of o u r b r i c k Lake Merced drainage tunnel was completely covered up and closed by a l a r g e s l i d e .

1906

Lawson and others, 1908, p. 240.

Forty-eight Avenue, between K and N S t r e e t s , i s a d i s t r i c t underlain by deep sand where extensive grading operations were undoubtedly necessary t o convert an area o f sand-dunes i n t o s t r e e t s and building l o t s . Here small, s u b s t a n t i a l frame dwellings were s h i f t e d bodily from 1 t o 2 f e e t out o f p o s i t i o n , and t h e s t r e e t s were s l i g h t l y d i s located.

1906

Lawson and others, 1908, p. 242.

* * * Forty-eight Avenue between K and L S t r e e t s , within a few hundred f e e t of t h e ocean * r * t h e sand i n our basement r a i s e d from 1 f o o t t o 18 inches. A wide and long 3-foot depression wai r a i s e d level. Our l o t , which was 120 f e e t deep, was shorted a t l e a s t a f o o t , which was shown by t h e f o l d i n g of t h e fence. E l e c t r i c - l i g h t poles i n t h e s t r e e t i n f r o n t of us, which were i n t h e sand, were thmwn down north, e a s t , south, and west. There was a f i s s u r e f o r about a block, between Fortyseventh and Forty-eighth Avenues, about 3 f e e t wide and 6 o r 8 inches deep, which was of course i n t h e sand. There were a l s o o t h e r blowholes i n t h e sand, which emitted water and sulfurous odors.

1906

Seattle PostIntelligencer,

There i s one place within p i s t o l s h o t of ruined San Francisco t h a t t h e earthquake did n o t touch, t h a t d i d not lose a chimey o r f e e l a tremor--Alcatraz i s l a n d . Despite t h s f a c t t h a t t h e i s l a n d i s covered with brick buildings, b r i c k f o r t s , and brick chimneys, not a brick was loosened, not crack made, not a quiver f e l t .

1906C.

TABLES &9

TABLE 8 . S p e c i f i c descriptions of ground failures in the,north bay counties region Location number i s assigned t o each reported ground-failure s i t e . Corresponding numbers are found on p l a t e 4. Figure number r e f e r s t o f i g u r e in t h i s report showing damage described under "Quotation" column. F a i l u r e type i s indicated by t h e folloriing symbols. Corresponding symbols are found on p l a t e 4.

@

+

H i l l s i d e landslides including r o t a t i o n a l slumps, block glides, debris avalanches, and r o c k f a l l s

... ... ...

Streambank landslides including r o t a t i o n a l slumps and s o i l f a l l s

0

River s t r e t c h e s with extensively f i s s u r e d flood p l a i n s ; p a t t e r n i n d i c a t e s s t r e t c h e s of r i v e r a f f e c t e d and not width of disturbed zone Sand b o i l s

Lateral spread

Absence of ground f a i l u r e noted

Ground settlement

Miscellaneous e f f e c t s

Ground cracks not c l e a r l y associated with lands l i d e s , l a t e r a l spreads, settlement or primary f a u l t movements

*

Arrows showing extent of area a f f e c t e d . Symbol shows f a i l u r e type

Accuracy with which f a i l u r e s i t e s can be located i s given as follows: A, a s i t e t h a t can be accurately relocated; B, a s i t e t h a t can be r e l o c a t e d t o within a few kilometers and probably could be located more accurately with f u r t h e r invest i g a t i o n ; C, a s i t e where t h e information i s i n s u f f i c i e n t t o allow p r e c i s e location. P l a t e numbers i n t h e "Reference" c o l m r e f e r t o p l a t e s i n t h e o r i g i n a l source material.

Loca- Fig- Fail- Accu- Year of t i o n ure w e raearthNO. No. type cy quake 249

C

1906

C

1906

@

250

x

251

Reference

Jordan, 1907, p. 33.

SaZinas D d l y Indez, 1906~.

B

1906

LawSon and others, 1908, p. 212.

Quotation

A t Sobrante, i n Contra Costa County, e a s t of San Francisco Bay t h e r e are l a r g e slumps o r cracks i n t h e e a r t h .

The Santa Fe's Condition. a t Pinole sank two f e e t .

r r r

The railway bridges and r a i l y a r d s

Mare Island.--The earthquake was much l e s s severe than t h a t of 1898, which wrecked many o f t h e Government buildings i n t h e navy-yard. None of t h e Government buildings was wrecked t h i s time, nor was t h e damage a t a l l serious except i n t h e case o f two or t h r e e new bhildings r e c e n t l y erected on t h e "made" land near t h e water-front. Here t h e ground was thrown i n t o v i o l e n t undulations, and t h e buildings were so twisted t h a t about $2,000 worth of r e p a i r s had t o be made. On t h i s s o f t ground t h e b r i c k walls were cracked * * r In t h e case o f t h e o l d e r buildings r e s t i n g on hard ground, no cracks were formed, nor any i n j u r y reported.

.

252

+

B

1898

Townley and Allen, 1939, p. 105.

B

1906

Lawson and others, 1908, p. 310.

1898 March 30. 11:43 p.m. VIII. Mare Island. San Pablo Bay. This earthquake wrought such damage a t Mare Island Navy Yard t h a t it may properly be known as t h e Mare Island earthquake. + * * Admiral H. W. Lyon, U.S.N., has furnished t h e following information: " r * * The violence of t h e shock was g r e a t e r than any shock previously experienced on t h i s island, as f a r as can be learned from the oldest inhabitants. "A d e t a i l e d account of t h e damages done is s e t f o r t h i n a r e p o r t t o t h e commandant, dated April 5, 1898. The r a i l r o a d t r a c k e a s t o f Martinez, near 8a11'5 Head O i l Works, Many cracks occurred i n t h e embankment on both s i d e s of t h e track. A series of 5 small transverse waves was found i n t h e embankment about 0.5 mile west of Peyton S t a t i o n . The d i s t a n c e between c r e s t s was about 10 t o 15 f e e t ; amplitude estimated a t 3 inches. This embankment l i e s i n f l a t marshy land. A small r a i l m a d bridge near Avo" S t a t i o n was thrown 4 inches toward t h e e a s t abutment, but it had been repaired a t t h e time of t h e v i s i t . was thrown 3 inches out of alignment t o t h e north.

148

HISTORIC GROUND FAILURES IN NORTHERN CALIFORNIA TRIGGERED BY EARTHQUAKES TABLE8.Speeific descriptions of ground failures in the north bay counties region-Continued

Loea- Fig- Fail- Aecu- Year of t i o n ure "re ra- earthNO. quake NO. type cy 253

C

1906

S m Frmzcisco Chronicle,

1906b.

254

X

Stocton, April 30.--It was discovered to-day t h a t i n t h e v i c i n i t y of Woodbridge t h e Mokelumne River has f a l l e n twelve f e e t , t h e bed of t h e r i v e r having dropped from t h e e f f e c t s of t h e recent earthquake. The stream had been c a r m i n e a l o t o f water when it was noticed t h a t t h e r i v e r was s t e a d i i y Falling, contrary t o a l l precedent. The people could hardly believe t h e i r eyes. They watched t h e r i v e r recede f o r a day and made an investigation, with t h e r e s u l t t h a t t h e bed was found t o be almost twelve f e e t lower than before. As t h e water way has been s t e a d i l y f i l l i n g up each year with s i l t from t h e upper portion o f t h e r i v e r , farmers along t h a t stream are highly pleased with t h e change, s i n c e it can carry f a r more water than heretofore, and not endanger t h e i r lands on e i t h e r s i d e of i t . Another incident o f t h e earthquake i s t h e drying up o f Tracy lake, i n t h e northwestern p a r t of San Joaquin county. Ever since t h e earthquake t h e water has been decreasing a t a r a p i d r a t e , and a t present it is almost on a l e v e l with t h e Mokelumne r i v e r . Whether o r n o t t h e r e is a crack i n i t s bed, o r an underground passage connecting t h e lake with t h e r i v e r , i s n o t known, but a t t h e r a t e t h e l a k e has been f a l l i n g it w i l l soon be as low as t h e r i v e r . The b e n e f i t i n both instances w i l l be appreciated by farmers.

C

1857

Sacrmnento Age, 1857.

we have information of severe e f f e c t s of t h e earthquake along t h e l i n e o f t h e lower Srocktan Road. Below Benson's Ferry t h e waters of t h e hlokelumne r i v e r much swelled by recent r a i n s , were thrown over t h e banks, leaving rhe bed of t h e stream almost bare. Houses were shaken v i o l e n t l y , destroying a r t i c l e s of glassware and over turning furniture. Limbs were broken o f f from t r e e s and t h e t r e e s i n some instances s e t t l e d down trio o r t h r e e f e e t i n t o t h e ground. The inhabitants o f t h a t s e c t i o n were t e r m r s t r i c k e n , w h i l s t dwnb brutes appeared t o be paralyzed.

C

1906

Duryea and others, 1907, p. 258.

A t one point on t h e marsh between Benecia and Suisun, on t h e Southern P a c i f i c , t h e settlement was 11 f t . ; a t another point, 5 f t . These were nearly v e r t i c a l .

C

1906

Ransome, 1906, p. 294.

On t h e north shore of Suisun Bay p a r t of t h e t r a c k o f t h e Southern P a c i f i c , l a i d on marsh, subsided several f e e t .

C

1906

Davison, 1906, p. 25416.

Three miles of railway have sunk out of s i g h t between Suisan and Benecia * *

C

1906

X X

Quotation

Reference

Engineering News, 1906.

x

.

Farther e a s t [of Oakland and ~ e r k e l e y ]t h e Southern P a c i f i c Co. s u f f e r e d much disturbance o f i t s railway l i n e s * * A section af t r a c k between Oakland and Sacramento sank several f e e t ; a railway bridge over t h e San Joaquin s e t t l e d some inches [see loc. 1821.

.

C

1906

The Evening Post, 1906e.

Effect of Shock Bezween Susan [ s i c ] City and Benecia. A telegram from Sacramento t o t h e Western Union Telegraph Company's o f f i c e i n t h i s c i t y , r e p o r t s r h a t t h r e e miles of r a i l r o a d sank out of s i g h t as a r e s u l t of t h e earthquake between Suisan [ s i c ] City and Benecia, i n Solano County, and a l l wires were taken with it. * * reported sinking of a three-mile s e c t i o n o f t h e r a i l r o a d company's t r a c k s between Suisun and Benecia, which are on t h e d i r e c t l i n e betireen Sacramento and San Francisco. The road crosses some low land a t t h e point where i t s t r a c k s are reported sunk. The location of t h i s sinking of the e a r t h i s about t h i r t y miles from San Francisco.

C

1906

The Evening Bee, 1906a.

Trains Brought Back. Trains which had been dispatched f o r San Francisco e a r l y t h i s morning had t o be brought back, and they were s e n t t o t h e Bay City by t h e Lathrop route. It was a t t h e spot where t h e t r a c k disappeared t h a t t h e r a i l r o a d company had so much t r o u b l e l a s t Winter, when a loaded passenger t r a i n came near going out of s i g h t . A g r e a t army of men was then s e t a t work t o f i l l up t h e s i n k . The t a s k was a most d i f f i c u l t one,

I

149

TABLES 5-9 TABLE8 , S p e e i f i c descriptions of gfound failures in the north bay counties region-Continued

Loca- Fig- Fail- Accu- Year of t i o n ure ure raearthNo. quake NO. type cy

Reference

Quotation

as enormous timbers which were thrown i n t o t h e hole quickly sank from view, and t h e t r a i n l o a d s o f e a r t h dumped i n disappeared l i k e snow i n a f i e r c e sunshine. But t h e engineers f i n a l l y mastered t h e s i t u a t i o n , and a f t e r a week's time t r a i n s were s e n t over t h e route again. I t i s now feared t h a t i t w i l l take several weeks' time t o r e p a i r t h e present collapse, and i n t h e meantime a l l t r a i n s w i l l be s e n t by t h e s t o c t o n [sic] route. EARTH CRACKED OPEN. There are great crevasses on each s i d e of t h e t r a c k throueh " t h e Suisun marshes and it is r e ~ o r t e dt h a t a m e a t ocean of water has flowed over t h e lowlands between Suisun and Benecia. ENGINE SINKS I N EARTH. A s h o r t d i s t a n c e below Suisun, a Southern P a c i f i c switch engine sank i n t o t h e ground f o r a d i s t a n c e of t h r e e f e e t , not f a r from where t h e t r a c k disappeared. 0

C

1906

B

1906

Los A n g e t e s D a i t y Times, 1906C.

M

Pubtic Ledger, 1906.

X

Sacramento, April 18.--A s h o r t time a f t e r the b i g shock came a message from Suisun, Solano county, saying t h a t a long s e c t i o n of t r a c k had disappeared from view. I t was learned l a t e r t h a t , i n one place between Sprig and Teal s t a t i o n s , i n t h e Suisun marshes, f o r a distance of one mile and a h a l f , t h e t r a c k had sunk down t h r e e t o s i x f e e t , and a t anorher point nearly one thousand f e e t of t r a c k ,rent out. * * * The t r a c k sunk by t h e earthquake is near t h e place where a loaded passenger t r a i n came near going out of Bight. * * * There are great crevices on each s i d e of t h e t r a c k through the Suisun marshes, and it i s reported t h a t a great ocean o f water has flowed over t h e lowlands between Suisun and Benecia. A s h o r t d i s t a n c e below Suisun, a Southern P a c i f i c switch engine sank i n t o t h e ground f o r a distance of t h r e e f e e t , not f a r from where t h e t r a c k s disappeared. Sacramento, April 18.--A s h o r t time a f t e r t h e shock o f t h e earthquake a message came from Suisun, Solano County, saying t h a t a long s e c t i o n of t r a c k had disappeared fmm view. One place between Sprig and Teal s t a t i o n s i n t h e Suisun marshes f o r a distance o f one mile and a h a l f t h e t r a c k had sunk t h r e e t o s i x f e e t , and a t another point near 1000 f e e t o f t r a c k went out. Sacramento, Cal., April 1%- * r * I t was learned t h a r between Sprig and Teal s t a t i o n s f o r a distance o f one mile and a h a l f t h e t r a c k had sunk t h r e e t o s i n f e e t . A t another point nearly a thousand f e e t of track sank from s i g h t .

255

256

c

1906

The E u e n i n g Bee, 1906b.

The Southern P a c i f i c Company repaired i t s t r a c k s beyond Suisun yesterday afternoon and t r a i n s are now running d i r e c t t o San Francisco. The l o c a l o f f i c i a l s s t a t e t h a t tho rumor t o t h e e f f e c t t h a t t h e t r a c k s had gone out of s i g h t was n o t so, and it took but two or t h r e e carloads of d i r t t o l e v e l t h e tracks. This was done by 2:30 yesterday afternoon and l a s t night t r a i n s were running through t o Oakland on schedule time.

C

1892

Holden, 1898. p. 174 and 176.

1892. April 19; Vacaville. places.

Holden, 1898, p. 187.

1892. April 20; Winters. A t Winters t h e r e have been developed a number of f i s s u r e s i n t h e e a r t h , water has been e j e c t e d , gas has escaped, and t h e bed of t h e creek has been f i l l e d up f o r a distance of over 70 yards. Many of t h e wells have been f i l l e d up by t h e collapse of t h e walls.

Holden, 1898, p. 178 and 179.

1892. April 19; \?inters; Zh. 50m. a. m. On Putah Creek, h a l f a mile west of Winters, a phenomenon was witnessed by a young man named Fred Willis, who was r i d i n g p a s t a t t h e time o f t h e big shake. There seemed t o be an explosion, and t h e water was throw? from t h e creek t o a distance of 20 f e e t on e i t h e r bank. Then followed a h i s s i n g sound as o f gas escaping. A t daylight several f i s s u r e s

1892

8 6' C

E]

1892

* * The ground was f i s s u r e d i n many

HISTORIC GROUND FAILURES I N NORTHERN CALIFORNIA TRIGGERED BY EARTHQUAKES

150

TABLE 8.Speeifie Loca- Fig- Fail- Accu- Year of raeartht i o n ure ure No. quake No. type cy

descriptions of ground failures in the north bay counties region-Continued Quotation

Reference

were found i n t h e bed of t h e creek and i n t h e roadway and f i e l d s adjoining. On each s i d e of t h e creek where t h e explosion took place t h e banks caved i n , t h e landslides being 75 f e e t i n length and 12 f e e t deep.

* * near t h e town t h e bank of Putah 1892. April 19; Winters; Creek, t e n f e e t wide, caved i n , and along t h e bottom of t h e creek f o r a great distance r e n t s were made by t h e shocks. West of here about t h r e e miles, an acre of ground s l i d i n t o t h e creek.

6

C

1892

Coffman, 1973, p. 160.

1892. ApriZ 1 9 . * * * Fissures were found i n t h e bed of Putah Creek, 112 mile west of Ivinters, and i n t h e adjoining roadway and f i e l d s ; banks of t h e creek were caved i n .

C

1892

Holden, 1898, p. 195 and 196.

1892. April 21; Winters. * * r The r a i l r o a d t r a c k i s a l l r i g h t , and t e l e g r a p h i c communication has been uninterrupted, but t h e r e are many nasty cracks and f i s s u r e s i n t h e roadways, and d r i v i n g i s dangerous.

C

1892

Holden, 1898, p. 195 and 197.

1892. April 21; Winters. * r The sand bars i n Putah Creek near Winters opened and from t h e f i s s u r e s t h e water spurted high up on t h e banks. In some places t h e creek became dry, i n others i t changed t o a t o r r e n t . The banks caved i n some places and almost dammed t h e stream.

0

0 0

1892. April 19; i * * Up t h e Berryessa road t h e passage i s blocked by immense bowlders [sic], some weighing several t o n s , which were thrown down t h e h i l l s i d e s i n t o t h e road. I t i s near t h i s point where t h e r e n t s i n t h e road were noticed. 258

C

1892

Holden, 1898, p. 195 and 197.

1892. April 21; r * * It was reported t h a t s e v e r a l b o i l i n g springs had b u r s t from t h e f o o t h i l l s on t h e north and west and were flowing steadily. 1892. April 19; Esparto. between here and Capay.

260

A

1906

4

+

The e a r t h opened i n s e v e r a l places

1907, p. 259.

The draw-bridge a t Black Point, over P e t a l m a Creek, on t h e Sonoma Branch of t h e C a l i f o r n i a Northwestern, was open a t t h e time o f t h e earthquake, and was thrown off i t s center 2 f t . t o t h e e a s t and 1 f t . t o t h e north. This i s a s t e e l s t r u c t u r e , 220 f t . long, on four i r o n caissons, f i l l e d with concrete, on p i l e foundations.

Duryea and others,

261

B

1906

Lawson and o t h e r s , 1908, p. 192.

The buildings of t h e Dickson ranch, 2.5 miles south of Olema, are about 0.25 mile e a s t of t h e f a u l t - t r a c e , standing on a h i l l s i d e presumably on firm ground. They n e a r l y a l l s l i d southwest--that i s , downhill and toward t h e f a u l t .

262

C

1906

Lawson and others, 1908, p. 75.

Bedrock cracks occurred a t many p o i n t s within t h e R i f t , usually appearing as branches from t h e f a u l t s . They were seen a l s o a t a number of p o i n t s west of t h e R i f t , t h e i r d i s t r i b u t i o n ,reaching t o t h e ocean i n t h e v i c i n i t y o f Point Reyes, t e n miles from t h e f a u l t t r a c e . A t t h e more remote p o i n t s they were q u i t e small, often barely d i s c e r n i b l e , and no system o f arrangement was discovered. They are p e c u l i a r l v ~ r o m i n e n talone t h e summit of t h e r i d e e c o n s t i t u t i n e t h e ;outhwestkG r i m of t h e miin Bolinas-Tomales t r o i g h . This summit was v i s i t e d on four l i n e s of road [locs. 265, 275; 2761 and a t each l o c a l i t y ccnspicuous cracks were found. On t h e road from Inverness t o Point Reyes Post Office [loc. 2761, about a mile i n a d i r e c t l i n e

151

TABLES &9

TABLE8 . S p e c i f i c descriptions of ground failures in the north bay counties region-Continued Laca- Fig- Fail- Accu- Year of t i o n ure ure racarthNo. quake No. type cy

Reference

Quotation

from Tomales Bay, a crack was t r a c e d f o r more than 800 f e e t . I t s general t r e n d is e a s t and west, but i t s course i s not s t r a i g h t a d Along t h i s crack t h e r e i s a horiit has a branch diverging a t 45'. zontal throw of from 2 t o 6 inches, t h e south s i d e having moved westward with reference t o t h e north s i d e . C

264

1906

Lawson and o t h e r s , 1908, p. 195.

In t h i s region [Bear valley] I saw only a fen. cracks other than road-cracks, and t h e road-cracks were unimportant.

Lawscn and others 1908, p. 192.

Mr. Payne J. S h a f t e r ' s place i s near t h e v i l l a g e of Olema. The f a u l t - t r a c e i s close t o t h e house and o t h e r buildings. These stand on a bed of alluvium which i s probably supported by bedrock a t a s h o r t d i s t a n c e below the surface. In t h e barnyard men were milking, and were thrown v i o l e n t l y t o t h e ground, along with t h e c a t t l e . The buildings were much damaged. During t h e earthquake a cow f e l l i n t o t h e fault-crack and t h e e a r t h closed i n o n h e r , so t h a t only t h e t a i l remained v i s i b l e . At t h e time of my v i s i t t h e t a i l had disappeared, being eaten by dogs, but t h e r e was abundant testimony t o s u b s t a n t i a t e t h e statement. As t h e f a u l t - t r a c e i n t h a t neighborhood showed no cracks large enough t o receive a cow, i t would appear t h a t during t h e production o f t h e f a u l t t h e r e was a temporary p a r t i n g of t h e ioalls. [Some have d i s c r e d i t e d t h i s r e p o r t . See Earthquake Engineering Research I n s t i t u t e Newsletter, v . 9, no. 1, p. 103.1 0Lema.--The v i l l a g e of Olema i s about 0.5 mile e a s t of t h e f a u l t t r a c e and a t t h e edge of t h e R i f t b e l t , t h e g r e a t e r p a r t being included within t h e R i f t . The residence o f Mr. Pease, stand'ing on alluvium, was s h i f t e d south about 2 f e e t , f a l l i n g from i t s supports. r r + A neighboring piece o f a l l u v i a l land bordering Olema Creek sank about 2 f e e t .

B

1906

Lairson and others, 1908, p. 193.

B

1906

Lawson and others, 1908, p. 75.

I 265

266

58

C

1906

Lawsan and others, 1908, p. 74.

p l a t e 498

C

59

1906

Lawson and others, 1908, p l a t e 50B.

On Mount \%ittenberg t h e r e are two bedrock cracks.

One of these

crosses t h e northeastern spur of the peak near i t s junction with t h e main c r e s t . I t s t r e n d i s approximately northwest and southeast and a t one point it margins a fault-sag. As i t assumes i n one place t h e r i d g e phase o f t h e fault-crop, I i n f e r t h a t it has horizontal displacement. On t h e opposite s i d e of t h e main c r e s t is a crack which was t r a c e d f o r about 1,000 f e e t . I t s general course i s northwestsoutheast, but i t i s not s t r a i g h t and exhibits a v e r t i c a l throw of 1 or 2 f e e t t o t h e southwest. A t one point it touches a fault-sag. Between these two long cracks a group of s h o r t cracks occurred, with s i m i l a r trend, on a knob c o n s t i t u t i n g a portion of t h e main divide. [These cracks may have been caused by secondary faulting.] They [cracks i n alluvium] were seen from t h e t r a i n i n t h e bottomland o f P a p e m i l l [Lagunitas] Creek within a mile o f Point Reyes Station. They were a l s o seen i n t h e d e l t a o f Papermill Creek, i n t h e bottom-land of Olema Creek near Olema, and i n t h e d e l t a of Pine Gulch Creek. They were seen i n t h e bottom-lands and d e l t a s of a number of small creeks e n t e r i n g Tomales Bay from t h e west between Inverness and t h e head of t h e bay. Other l o c a l i t i e s were t i d a l marshes a t t h e head o f Bolinas Lagoon ( p l a t e 4981, a t the head of Tomales Bay, and i n small e s t u a r i e s ncar Inverness. They irere seen i n t h e marsh of Bear Valley Creek near where t h e stream j o i n s P a p e m i l l Creek; and a road embankment crossing t h a t marsh was elaborately cracked and f a u l t e d t h r u much of i t s extent. [Picture caption] Faults i n road embankment, southwest of Point Reyes S t a t i o n . Fault-trace i s beyond fence. Ground lurched toward marsh of Bear Valley Creek. G. K. G.

152

HISTORIC GROUND FAILURES IN NORTHERN CALIFORNIA TRIGGERED BY EARTHQUAKES

TABLE8.Specific descriptions of ground failures in the north bay counties region-Continued Loca- Fig- F a i l - Accu- Year of earthrat i o n ure ure NO. quake NO. t s e cy A

1906

Jordan, 1907, p. 19.

] p a s t t h e same v i l l a g e [Point Reyes Paper M i l l Creek [ ~ a ~ u n i t a sruns The two banks of t h e stream were forced toward each Station], * * * o t h e r s o t h a t t h e length of t h e bridge was shortened by about s i n f e e t and t h e bridge was correspondingly humped a t i t s n o r t h end, an arch about s i x f e e t high being forced up.

B

1906

Duryea and others, 1907, p. 270, p l a t e 54.

* r * a highway bridge across a creek t r i b u t a r y t o Tomales Bay, near Point Reyes S t a t i o n on t h e North Shore Railway, i n Marin County, and within l e s s than 2 miles of t h e f a u l t l i n e . * * * The bridge, o r i g i n a l l y , had e i g h t panels, i t s t o t a l length being appmximately 120 f t . It i s located i n a d i r e c t i o n nearly north and south. The abutments are of p i l e s and timber. The e f f e c t of t h e earthquake was t o s e t t l e t h e north abutment some 2 o r 3 f t . , and move it southivard s o much t h a t , i n patching up t h e s t r u c t u r e temporarily, t h e north end panel was n o t u t i l i z e d as p a r t of t h e span * * r

+

X +

.

.

B

1906

Duryea and o t h e r s , 1907, p. 258.

Portions of t h e t r e s t l e over Lagunitas Creek, about a mile from Point Reyes, were throrm e n t i r e l y o f f t h e p i l e s , t h e p i l e s themselves being moved down stream.

C

1906

Lawson and others, 1908, p. 196.

Beyond Garcia t h e creek has several reaches of a l l u v i a l bottom, and 5 0 badly shaken t h a t t h e railway embankments and t r e s t l e s had t o be repaired. Railiray t r a f f i c t o Point Reyes [from Sausalita] was interrupted f o r about 10 days.

1906

Lawsan and others, 1908, p l a t e SOA.

[Picture caption] Road embankment broken by shaking of s o f t ground beneath. Southwest o f Point Reyes S t a t i o n and 10 rods from f a u l t t r a c e . G. X. G.

1906

Lawson and others, 1908, p. 71.

The road running southwest from Point Reyes S t a t i o n and crossing t h e valley a t t h e head of Papermill Creek [Lagunitas] d e l t a was o f f s e t 20 f e e t [by faulting]. r t The embankment of t h e road r e s t e d on marshy ground s o s o f t t h a t a portion o f t h e embankment sank i n t o it, and material o f t h i s character was i n o t h e r l o c a l i t i e s demonstrably s h i f t e d .

1906

Lawson and others, 1908, p. 196.

+

267

Quotat ion

Reference

C 60

some of these were

I dmve a few miles n o r t h and e a s t from t h e [Point Reyes] s t a t i o n ,

over a high t e r r a c e separating t h e upland from t h e bay a t t h e e a s t . * A few cracks were seen i n t h e ground, but they were much smaller and l e s s numerous than a t a s i m i l a r d i s t a n c e on t h e appos i t e side of the fault.

1906

Lawson and others, 1908, p. 197.

The "fills" across t h e arms o f Tamales Bay generally sank from 2 t o 8 f e e t . The 1,000-yard f i l l about 2 miles north of Point Reyes S t a t i o n sank from 6 t o 8 f e e t ; as did t h e next f i l l , which i s some 500 f e e t long. In one o r two instances t h e pile-supported bridge The bottom i n t h e middle o f t h e f i l l remained a t grade. * * of t h e bay i n these arms i s usually sand.

1906

Duryea and others, 1907, P. 258.

On t h e North Shore, about 2 m i l e s north of Point Reyes, t h e road, o r i g i n a l l y , had been constructed with p i l e t r e s t l e s across several arms of Tornales Bar: these t r e s t l e s had been f i l l e d about 15 years ago, t h e road-bed being about 8 f t . above ordinary high tide.. Two of these embankments, 2 200 f t . and 900 f t . long, r e s p e c t i v e l y , sank u n t i l t h e water a t high t i d e washed over t h e r a i l s .

1906

lveatherbe, 1906, p. 402.

Along t h e coast, t h e railway was g r e a t l y disturbed, invariably sinking i n t h e low swampy land except where b u i l t on p i l i n g .

1906

Lauson and others, 1908, p. 78 and 79.

A l a r g e portion of t h e d e l t a was throim by t h e earthquake i n t o gentle undulations, t h e difference i n height between t h e swells and hol1ou.s being usually l e s s than a foot. The chief evidence

TABLES 5 9

TABLE8 . S p e e i f i c descriptions of ground failures in +e north bay counties region-Continued Loca- Fig- Fail- Accu- Year of raeartht i o n w e "re No. NO. type cy quake

Reference

p l a t e 548, p l a t e 558, p l a t e 56A.

61 62

A

1906

Lawsan and others, 1908. p. 79 and 80, p l a t e 558, p l a t e 57A, p l a t e 578, p l a t e 58.

Quotation

of t h i s i s found i n t h e d i s t r i b u t i o n of pools a t low t i d e , and where vegetation i s present t h e evidence from pools is supplemented by t h a t from t h e condition o f t h e p l a n t s . The undulations were not elongate and were not found t o have a systematic r e l a t i o n t o t h e fault. Men t h e t i d a l mud was f i r s t seen a f t e r t h e earthquake, it was observed t o be covered with r i d g e s and troughs. ( P l a t e 548.) This corrugation was gradually smooti;ed out by tho a c t i o n of t h e waves ( p l a t e s 5 5 8 and 56A). so t h a t a t t h e expiration of a year i t s enpression was l a r g e l y l o s t , tho a few of t h e l a r g e r ridges could s t i l l be traced. and much of t h e ~ l a i nr e t a i n e d a o a t t e r n imorest on it bv t h e ridging. It is probable t h a t t h e e n t i r e t r a c t of t i d a l mud was thus affected, a l t h o t h e ridges were not seen on t h e area lying nearest t o t h e e a s t shore. That area did not come under observation u n t i l a f t e r t h e s p r i n g floods o f 1907, and i t was then overspread by a f r e s h deposit brought by P a p e m i l l Creek [Lagunitas Creek]. The r i d g e s varied somewhat i n height, t h e amplitude from c r e s t t o trough ranging from 1 t o 3 f e e t and possibly more. Their general t r e n d was p a r a l l e l t o t h e f a u l t - t r a c e , but t h e r e were notable encept i a n s , and aver small t r a c t s t h e d i r e c t i o n was even a t r i g h t angles t o i t . In some cases, where t h e minor ridges were p a r a l l e l , t h e r e were l a r g e r r i d g e s t r a v e r s i n g them obliquely. Fig. 25 reproduces a sketch map o f t h e l o c a l i t y showing t h e g r e a t e s t complexity. [See f i g . 25 a t end of tables.] So f a r as t h e broad undulation o f t h e t i d e lands were seen i n conjunction with t h e ridging, t h e g r e a t e r r i d g e s were on t h e sirells and not i n t h e holloxrs. [see t e n t , "North bay counties region," paragraph 5, f o r additional discussion of f a i l u r e mechanism and d i r e c t i o n o f movement.] There was a l s o a horizontal s h i f t i n g of mud aver a considerable area. Residents f a m i l i a r with depths of water i n t h e v i c i n i t y o f Inverness s t a t e d t h a t t h e earthquake caused a decided shoaling along the coast, but t h a t t h e r e l a t i o n of water l e v e l s t o firm ground was unchanged. I t was a l s o s t a t e d t h a t a channel which had e x i s t e d p a r a l l e l t o t h e west share of t h e bay, and t o irhich p i e r s had been run, was a b l i t e r a t e d by t h e earthquake. The shoaling might have been caused e i t h e r by an u p l i f t of t h e bottom o r by a s h i f t i n g of t h e mud of which it i s composed toward t h e shore. That t h e second of t h e s e explanations is c o r r e c t seems t o be s h a m by t h e following f a c t s . At various places along t h e shore, from Inverness t o a point 1.5 miles southirard, the t i d a l mud seemed t o be crowded against t h e firmer ground a t t h e shore, being pushed up i n a ridge, as shown i n Two p i e r s a t Inverness, t h e accompanying photograph. (Plate 558.) l i g h t wooden s t r u c t u r e s , r e s t i n g on p i l e s and extending out several hundred f e e t from t h e shore, were telescoped. (Figs. 26 and 27.) In the case of M a r t i n e l l i ' s [See f i g s . 26 and 27 a t end of t a b l e s . ] p i e r t h e telescoping was sho!un by t h e i n c l i n a t i o n given t o p i l e s a t t h e landward and bayward ends, from which i t appears t h a t t h e ground i n which t h e p i l e s were s e t was crowded together, s o t h a t t h e foundat i o n of t h e p i e r was shorrened, while t h e superstructure r e s i s t e d shortening. The r e s i s t a n c e was temporary only, f o r before t h e agit a t i o n ceased t h e p i e r was bmken i n two; and t h e i n c l i n a t i o n of the p i l e s i s supposed t o have been given during the e a r l y stages of t h e tremor. Coincident with t h e movement of t h e ground toward t h e share, t h e r e was a movement p a r a l l e l t o t h e shore irhich had t h e e f f e c t of o f f s e t t i n g t h e outer knd of t h e p i e r about 25 f e e t toward t h e northThe r e s u l t a n t of the two movements, o r t h e west. ( P l a t e 57A.) a c t u a l d i r e c t i o n of s h i f t i n g of t h e mud, was westward, or a l i t t l e t o t h e north of vest: and t h e maximum s h i f t i n r i n t h a t d i r e c t i o n was not l e s s than 30'feet. Rather more than h a l f t h e p i e r , t h e p a r t nearer t h e shore, remained s t r a i g h t and suffered c h i e f l y from t h e s l a n t i n g of i t s supporting p i l e s . This p a r t stands on t h e submerged d e l t a o f a small creek, and i t s foundation appears not t o have s h i f t e d . The outer p a r t suffered most violence near t h e junction o f t h e s h i f t i n g mud with t h e firmer gmund, being t h e r e 50 completely wrecked t h a t its platform f e l l . The photograph and map represent it a f t e r r e p a i r s had been made.

HISTORIC GROUND FAILURES IN NORTHERN CALIFORNIA TRIGGERED BY EARTHQUAKES

154

TABLE8.Speeifie descriptions of ground foilures in the north bay counties region-Continued Loca- Fig- Fail- Accu- Year of raeartht i o n "re "re No.

No.

type

cy

Reference

Quotation

quake In the case o f Bailey's p i e r , which i s beyond t h e d e l t a , t h e most important telescoping, as shown by t h e s l a n t i n g of p i l e s ( f i g . 27), was close t o t h e shorc, and n e a r l y the whole s t r u c t u r e was t r a n s ported by t h e s h i f t i n g mud. I t a l s o sagged more than a foot j u s t beyond t h e middle, and t h e a t t i t u d e s o f t h e associated p i l e s suggest t h a t t h e sag corresponds t o a holloir made i n t h e surface of t h e mud. The p i e r was so badly broken as t o r e q u i r e extensive r e p a i r s , and i n making these r e p a i r s Mr. Bailey used t h e o l d material f o r flooring, but found t h a t he had enough lumber remaining f o r 12 f e e t of flooring, so t h a t he i n f e r r e d a shortening of 12 f e e t . The whole p i e r was s h i f t e d t o t h e northwest, being given a curved form ( p l a t e s 578 and 58), and t h e maximum amount of s h i f t i n g i n t h a t d i r e c t i o n was a t l e a s t 25 f e e t , a l t h o t h e circumstances did not admit of accurate measurement. Combining t h e movement toward t h e shore with t h e o f f s e t p a r a l l e l t o t h e shore, it i s probable t h a t t h e d i r e c t i o n and the maximum amount o f s h i f t i n g were about t h e same a s i n t h e case of the M a r t i n e l l i p i e r . I t i s a notable f e a t u r e of t h i s displacement t h a t t h e disturbed material moved uo t h e s h o e instead of dom. so t h a t the t r a n s f e r was not only independent o f gravity but opposed t o it. The phenomenon, therefore, does not f a l l i n t h e same category with landslides, and i f properly i n t e r p r e t e d it may throw l i g h t on the mechanics of the earthq;ake pulses. The area t h r u which t h e s h i f t i n g o f t h e mud took place is i n d e t e r minate. I t a f f e c t e d a shoal o a r a l l e l t o t h e irest shore of t h e bay and more than a mile long. A; t h e p i e r s t h e width of t h e affected region was a t l e a s t 400 f e e t and may have been much more. The reported c l o s i n g of t h e chnnel suggests 700 or 800 f e e t as a minimum estimate, but t h e o u t e r margin o f t h e a f f e c t e d area was probably beneath t h e water of t h e bay and outside t h e range of observation. The firmer p a r t of t h e P a p e m i l l [ ~ a g u n i t a s ]d e l t a appeared n o t t a be included i n t h e movement. A l l of t h e area know t o be affected l i e s southwest of t h e f a u l t - t r a c e , which i n t h a t neighborhood i s about 2,000 f e e t from t h e shore.

e

A

1906

Gilbert, Humphrey, Sewell, and Soulk, 1908, p. 8 and 9, p l a t e 7A, p l a t e 8A.

[BY the same author as t h e above quotation.1 r r- * an extensive s h i f t i n g of mud on t h e bottom o f Tomales Bay. At t h e head of tho bay and thence f o r a d i s t a n c e o f several miles northwestward t h e s o f t mud was moved bodily westward. I t n o t only descended from t h e northeast shore, 5 0 as t o cause deeper water, but ascended toward t h e southwest shore, c r e a t i n g a broad s h o d (PI. VII). The horizontal change o f p o s i t i o n near t h e southwest shore was i n places more than 25 f e e t , and t h e v e r t i c a l change as much as 2 f e e t . As t h e ascending movement can n o t be ascribed t o gravity, it must be r e f e r r e d t o t h e earthquake, even though t h e way i n which t h e e a r t h waves produced t h e e f f e c t i s not evident. The l o c a l i t y i s adjacent t o the f a u l t t r a c e , t h e p o s i t i o n o f which i s along t h e bottom of t h e bay, e a s t of t h e shoal. The i l l u s t r a t i o n s may r e q u i r e a few words of explanation. The upper view of P1. V I I looks northward from t h e southwest shore of t h e bay. Tide being low, t h e newly formed shoal or mud bank is broadly exposed, but the receeding t i d e has l e f t a lane o f water t o mark t h e separat i o n of t h e mud bank from t h e firmer ground t h a t withstood t h e quaking. Immediately a f t e r t h e earthqu&e t h e mud was r i g i d , as i n t h e t r a c t shorn i n PI. V I I , A; but before t h e view of PI. VII, A, was taken (April 28, 1906) t h e surface had been l a r g e l y smoothed by t h e a c t i o n of wind waves. A s i n g l e ridge which escaped t h a t a c t i o n appears a t t h e l e f t i n t h e upper view o f PI. VII and i n t h e foreground of t h e lower view.

B

1906

Lawson and others, 1908, p. 194, p l a t e 458.

Inverness i s a v i l l a g e of s m e r residences on and near t h e southwest shore o f Tomales Bay. The upland o f t h e peninsula t h e r e c l o s e l y approaches t h e bay. The v i l l a g e occupies two narrow v a l l e y s normal t o the shore, and a mesa between them. I t s s i t e i s within t h e R i f t , and both v a l l e y s and mesa were traversed by many cracks, of which some had the character of branch f a u l t s . A l l t h e houses were of wood. About h a l f o f them were s h i f t e d on t h e i r foundations. To a c e r t a i n

62 61

155

TABLES 5 9

TABLE 8 . S p e c i f i e descriptions of ground failures in the north bay counties region-Continued Loca- Fig- Fail- Accu- Year of t i o n "re "re raearthNo. NO. type cy quake

Reference

Quotation

extent the d i r e c t i o n of s h i f i i n g was determined by t h e slopes of t h e ground, t h e houses moving downhill; but where t h a t f a c t o r did not control, t h e movement was toward t h e west o r southwest. In one Instance I noted a southwestward movement of several f e e t uphill. Lawson and others, 1908, p l a t e SIB.

[picture caption] G. K. G.

Lawson and others, 1908, P. 195.

Sunshine Ranch and Vicinity.--I drove t o t h e s u m i t of t h e ridge southwest of the head of Tomales Bay, f i n d i n g abundant and s t r o n g road-cracks a l l t h e way t o t h e c r e s t , which i s about 1.5 mile* from the f a u l t - t r a c e . There were a l s o a number of landslides i n t h i s region, and a considerable number of t r e e s were broken o r uprooted.

Lawson and others, 1908, p. 77.

On the west s i d e of t h e main ridge west o f t h e head of Tomales Bay t h e r e occurred two wet s l i d e s . In one case a h i l l s i d e bog was loosened from t h e slope on which i t rosted and descended as a flow of m d t o a canyon bottom 100 or 200 f e e t below. I n Llre o i h c r case t h e e a r t h beneath a wet meadow i n a r a t h e r s t e e p canyon flowed down t h e canyon f o r about 0.5 mile, overpowering t r e e s on i t s way and leaving a deposit 15 or 20 f e e t deep i n places. This was t h e l a r g e s t individual s l i d e observed. In a l l the cases mentioned t h e conditions were such t h a t s l i d e s would have taken place a t some time had t h e earthquake not occurred.

Lawson and others, 1908, p. 75.

Roadside crack a mile southeast of Inverness.

On t h e next road t o t h e southward [from loc. 2761 a group of cracks These cracks occur on a c r e s t trending northwest and southeast, and t h e i r t r e n d makes a small angle with t h a t of t h e c r e s t . The arrangement of t h e cracks suggests horizontal shear, but no d e f i n i t e observation was made on t h i s point. They extend f o r s e v e r a l hundred f e e t a t l e a s t , but were not t r a c e d out. llas seen a t a point a mile from t h e shore o f Tomales Bay.

Lawson and o t h e r s , 1908, p. 194.

Inverness to Point Reyes Ligkt-house.--For t h e f i r s t 2 miles of t r a v e l , covering a r i g h t - l i n e d i s t a n c e o f about 1.5 miles, roadcracks were numerous and often large. There were a l s o numerous small f a l l s o f e a r t h from t h e road c l i f f s . Beyond t h a t point t h e r e was a rapid f a l l i n g o f f of such evidence, and tho road-cracks were frequently seen they were a i l small. [See loc. 262.1 [Some of these cracks may have been caused by secondary f a u l t i n g . ]

Lawson and others, 1908, p l a t e 51A.

[picture caption] Roadside crack 2 miles west of f a u l t , between Inverness and Point Reyes P. 0. G. K. G.

Lawson and o t h e r s , 1908, p l a t e 538.

[picture caption] Landslide from r o a d - c l i f f about two miles west of Inverness. S l i d e occurred a t time o f earthquake. G. K. G.

Lawson and others, 1908, p. 195.

A t t h e U. S . Life Saving Station, on t h e coast 3 or 4 miles from t h e light-house * * * t h e f i l l e d ground about t h e house s e t t l e d several inches.

Lawson and others, 1908, p. 197.

A t Marshall's a h o t e l and a s t a b l e b u i l t oq t h e r e s t s i d e of t h e track and on underpinning, r e s t i n g i n t h e t i d a l f l a t , vent e a s i l y and gently i n t o t h e bay. The occupants o f t h e h o t e l did not r e a l i z e t h a t the h o t e l had f a l l e n . but a t f i r s t thoueht t h e water had risen. [Photographic evidence i n ' t h e Branner ~01lee;ion a t Stanford suggests this'lnay have been s t r u c t u r a l f a i l u r e , t h a t t h e building simply s l i d o f f its p i l e s . ]

156

HISTORIC GROUND FAILURES IN NORTHERN CALIFORNIA TRIGGERED BY EARTHQUAKES

TABLEi - S p e c i f i c descriptions of ground failures in the north bay counties region-Continued Loca- Fig- Fail- Accu- Year of raeartht i o n ure ure quake No. No. Type cy

279

X

1906

Lawson and others, 1908,

J u s t above Hamlet a trestle-work which had been f i l l e d i n s e t t l e d , leaving t h e trestle-work some 2 f e e t above. The bottom of t h e bay in these arms i s usually sand. At Hamlet q u i t e an extensive l a n d s l i d e has s t a r t e d i n t h e h i l l s i d e above t h e track. The r a i l m a d c u t is i n o l d rock, and t h e arch of t h e head of t h e s l i d e is some 70 f e e t above t h e track. The country wagon road has been c a r r i e d away by t h e s l i d e f o r possibly 100 yards.

C

1906

Lawson and others, 1908, P. 65, p l a t e 1428.

At t h e mouth of Tomales Bay t h e r e are two points p r o j e c t i n g westward from t h e e a s t shore, and both of these, according t o t h e observations of Prof .R. S. Holway, are c r o s t by t h e fault-trace. * * On each s i d e of t h e crack [ f a u l t ] are c r a t e r - l i k e depressions, some of them being double or overlapping. M r . Keegan, t h e ommer of Oillon's Beach, reported t h a t these c r a t e r l e t s were numerous and d i s t i n c t . In some instances a great deal of sand and water had been ejected. Others are reported on t h e southwest s i d e of t h e f a u l t t r a c e , from which t h e b e l t containing t h e n extends some 70 f e e t . The c r a t e r l e t s vary i n s i z e up t o 6 f e e t i n diameter and i t i s reported t h a t on t h e day a f t e r t h e earthquake t h e water trhich stood i n them could not be bottomed by a f i s h i n g pole.

B

1906

Lawson and others, 1908, p. 191, p l a t e 142A.

la ear Salmon Creek] + * a small mud-flat extends f m n t h e sea up t o t h e road. Curious mounds o f mud, shaped l i k e truncated cones, were thrown up by t h e earthquake. Subsequent examination showed t h a t t h e l i n e of t h e earthquake f i s s u r e must have p a s t near t h i s spot.

C

1906

Lawson and others, 1908, p. 199.

There are q u i t e a number of cracks i n t h e f l a t valley-bottom adjacent [to Valley Ford, Sonama Comty]. A landslide of several hundred' yards i n length but of very s l i g h t movement is found on t h e s i d e of t h e valley d i r e c t l y e a s t of town. The s l i d e has moved j u s t enough t o make a furmw-like ridge on t h e lower s i d e and has developed cracks on t h e upper side. Other small s l i d e s occur i n t h e v i c i n i t y .

B

1906

Duryea and others, 1907, p. 258.

Trest2es.--Trestles over marshes suffered more o r l e s s from t h e movement of t h e s o f t material i n t o which t h e p i l e s were driven. The most serious damage was a t Fallons, on t h e North Shore, where a t r e s t l e , 600 f t . long and 70 f t . high, was thrown down. This t r e s t l e was constructed of framed bents on p i l e s .

B

1906

Duryea and others, 1907, p. 214 and 215.

Trest2es.--The damage t o t r e s t l e s was small, except on t h e North Shore Railroad, where a t r e s t l e of framed bents on p i l e s , 600 f t . long and 70 f t . high, was thrown down, and portions of another t r e s t l e were thrown e n t i r e l y o f f t h e p i l e s , t h e p i l e s themselves being moved down stream. These t r e s t l e s were across s o f t ground, and near t h e f a u l t - l i n e .

B

1906

Larison and others, 1908, p. 198, p l a t e 129A.

Tomtes, Mmin County. * * Cracks were reported i n t h e s t r e e t and near t h e depot. J u s t north of t h e depot t h e r e was an extensive landslide along t h e r a i l r o a d , which threw one t r a c k over t h e other. (Plate 129A.)

B

1906

Weatherbe, 1906, p. 402.

A t Tomales, about e i g h t miles inland, t h e [ r a i l r o a d ] l i n e f a r over 1,000 f t . was c a r r i e d down a g e n t l e slope t o t h e e a s t f o r a d i s t a n c e of 50 f t . A l l these disturbances are e x a c t l y along t h e f a u l t e d l i n e , now well defined, though t h e movement and a c t i o n i n each of t h e cases above noted has been e n t i r e l y l o c a l and following t h e configuration of t h e ground. L i t t l e evidence, therefore, can be deduced pointing t o a d e f i n i t e regional movement i n any c e r t a i n d i r e c t i o n . Buildings an ground r e s t i n g on long p i l e s seem undisturbed and t h e worst e f f e c t s are noted on or toward swampy grolmd.

+

283

+

0

284

+ +

Quotation

B

0

282

Reference

157

TABLES 5-9

TABLE8 . S p e c i f i c descriptions of ground failures in the north bay counties region-Continued Loca- Fig- Fail- Aecu- Year of t i o n ure ure raearthNo. No. type cy quake 1906

1906

Reference

Lawson and others, 1908, p. 198, p l a t e 1298.

Lawson and others, 1908, p. 199.

1906

Lawson and others, 1908, p. 206.

1906

Lawson and o t h e r s , 1908, D. 206.

Quotation

At Freeman's, 3 miles northeast of Tomales, a l a r g e landslide was caused by t h e shock. ( P l a t e 129B.)

No cracks are reported i n t h e low a l l u v i a l land around t h e lagoons

nor i n Chileno Valley.

A t J u r ' s ranch, about 2.5 miles northwest [of petalma], 3 cracks with a very s l i g h t dropping of small blocks between them, are reported. A temporary flow o f water was reported from a crack by t h e road.

Small cracks were reported on t h e road about 4 miles [north] from Petalma.

1906

Lawson and o t h e r s , 1908, p. 203.

A t r i p was made out on t h e P e t a l m a road t o t h e Copeland d i s t r i c t ~ c h 0 0 1 ,then t o Cotate, t o t h e Durham d i s t r i c t school, and back t o Santa Rosa. I could hear o f no cracks i n t h e ground i n t h e v a l l e y ; and i n only one place, about 2 miles from Santa Rosa, on t h e Petalroad, could I hear of any increase o r change i n t h e flow of springs.

1906

Lawson and o t h e r s , 1908, p. 206.

Near Stony Point school-house, about 9 miles out [north fmm Petalma], 19 cracks across t h e road were reported by t h e teacher.

1906

Lawson and o t h e r s , 1908, p. 206.

A t Nason's ranch t h e r e i s s l a n d s l i d e of t h e bank of t h e lagoon 100 yards o r more i n length. Four miles [south] from Scbastopol is another l a n d s l i d e a t Davis' ranch, where a house was thrown from i t s underpinning.

1906

Lawson and o t h e r s , 1908, p. 206.

Cracks were reported a t Hansen's and several places. There i s a d i s t i n c t increase i n cracks and landslides i n t h e approach t o Sebastopol [from Petalma].

1906

Lawson and others, 1908, 0. 205.

[G. X. Gilbert] On t h e Burbank farm a small landslide occurred, a l a y e r o f moist s a i l only a few f e e t i n thickness moving down t h e slooe. introducing bends i n various l i n e s of c u l t i v a t e d e l a n t s . I s a i a n o t h e r feat"& o f t h i s s o r t on an adjacent farm, a& was t o l d of others which I did not v i s i t .

1906

Lawson and o t h e r s , 1908, p. 204.

[David S t a r r Jordan] A t Burbank's farm, 0.5 mile west o f Sebastopol, I noted these things: In t h e l o t adjoining, t o t h e south, tho s o i l being clayey, t h e r e i s a l a r g e crack running northwest znd southeast, o r nearly so, and, according t o Burbank, 0.25 mile long. It runs t h r u t h e f i e l d s and weeds, and was very d i s t i n c t on Augcst 6. The end of t h i s crack comes up against the sandy h i l l occupied by Mr. Burbank's orchard. The crack does not show i r s e l f i n t h e h i l l , but an t h e e a s t s i d e of t h e l i n e o f t h e crack t h e raws of t r e e s and p l a n t s were s h i f t e d toward t h e south--or, i f you p r e f e r it, those on t h e west s i d e toivard t h e north--2 or 3 f e e t . A well of W . Burbmk's, sunk i n t h e sandy ground, i s bodily shifted, without being injured, along with t h e raws of p l a n t s between which i t i s place=. No crack appears a t t h e surface i n Burbank's ground, but on t h e o t h e r s i d e of t h e h i l l s , t o t h e north o f it, I was t o l d t h e crack reappears.

..

HISTORIC GROUND FAILURES IN NORTHERN CALIFORNIA TRIGGERED BY EARTHQUAKES

158

TABLE8.Specific descriptions of ground failures in the north bay counties region-Continued Loca- Fig- Fail- Accu- Year of tion No.

ure ure NO.

type

racy

eanhquake

B

1906

C

1906

+

294

Reference

Jordan, 1907, p. 32 and 33.

Larison and others, 1908, P. 203.

La~vsonand others, 1908, p. 201.

Jordan, 1907, p. 188.

B

1969

Quotation

There are d i s t i n c t t r a c e s of great disturbance across Burbank's famous orchard a t Sebastapol, but i t i s not c l e a r t h a t i n any of these t h e underlying rock i s r e a l l y broken. Here on a slope l i n e s of f r u i t t r e e s were s h i f t e d , a ricll was moved bodily t h r e e or four f e e t , and a crack about one fourth mile long extended acmss a neighboring f i e l d , i t s d i r e c t i o n p a r a l l e l with t h a t o f t h e Tomales rift. Other s i r n ~ l a rcracks open a t i n t e r v a l s on t h e road toward Point Delgada. Near t h e top of Taylor H i l l , i n a marshy place, t h e r e was s l i d e , t h e e a r t h having s l i d on a clayey bottom.

a land-

The most marked physiographic e f f e c t s i n t h e v i c i n i t y of S m t a Rosa were found near t h i s [main Santa Rosa] cemetery. J u s t north of t h e cemetery h i l l i s a swampy depression. Part of t h i s s e t t l e d 2 o r 3 f e e t with t h e formation of a crack along t h e s i d e , extending f o r some 200 f e e t . The cemetery is on a low h i l l which t h e sexton r e p o r t s as being sand, gravel, and clay, but which shows a rocky outcrop, on t h e e a s t e r n s i d e , near t h e base. A crack an inch or more wide was found on t h e northern end o f t h e h i l l near t h e swamp mentioned above. This crack could n o t be followed f o r more than 100 f e e t , a l t h o t h e sexton r e p o r t s t h a t a t f i r s t i t extended 2 o r 3 times t h a t distance. A small r a t e r - p i p e on t h e southern p a r t of t h e h i l l , running north and south, was pulled a p a r t . A pipe on t h e northern p a r t of t h e h i l l , running e a s t and west, i s reported by Mr. Weaver as pulled a p a r t abbut 4 inches. On t h e southwest of t h e cemetery h i l l , M r . John Livsey r e p o r t s t h a t s e v e r a l f i n e cracks formed acmss t h e road running north and south, and t h a t t h e dust was blown away near t h e edges of t h e tracks. San J o s e ' s water works, l i k e t h a t o f Santa Rosa, was not i n j u r e d ;

i t s sewers a l s o were l e f t i n t a c t , showing t h a t t h e r e was no unequal displacement of t h e ground.

Lawson and others, 1908, p. 201.

A teamster working i n t h e creek j u s t south o f t h e tannery [F and 2nd St5.1 says t h a t he noticed cracks an inch wide and s e v e r a l rods long a few days a f t e r t h e shock. He "thinks t h e cracks were n o t t h e r e before."

Moore, 1906, p. 527.

About 1 112 miles from t h e water tower i n t h a t c i t y [Santa Rosa] t h e r e i s a crack i n t h e ground about 3 f t . wide a t t h e top and about 20 f t . deep. A few hundred f e e t from t h e tower a man driving across t h e f i e l d i n a buggy yesterday (April 28) s t r u c k an impassable morass, where before he had driven many times, and before discovering it had driven s o f a r i n t o it t h a t t h e horse was with d i f f i c u l t y got out.

Cloud and others, 1970, p. 54.

The e a r t h - f i l l approaches t o t h e Highway 12 bridge over Highway 101 subsided several inches i n response t o t h e shaking. 'The only orher known bridge damage was repeated pounding a t t h e construction j o i n t 3 i n t h e sidewalks over t h e abutments of t h e Brookwoad Avenue bridge a t Matanzas Creek. No major landslides were t r i g g e r e d by t h e shock. A few minor rock f a l l s were found along steep road cuts and s e v e r a l f i s s u r e s were formed i n a marshy area and on steep slopes. Some of these cracks may have been generated by l a n d s l i d e a c t i o n (see a r t i c l e on Surface Breaks, page 60).

Cloud and others, 1970, p. 60 and 61.

Adjacent t o such p r i n c i p a l drainage courses as t h e Santa Rosa and Matanzas Creeks, ground shaking and r e s u l t a n t cracking was p a r t i c u l a r l y apparent. * * On t h e c r e s t o f "moving mountain" n o r t h of t h e c i t y along De Vera Way, a crack developed which passed through a house; t h e crack showed evidence o f v e r t i c a l movement. This crack appeared t o be r e l a t e d t o t h e l a n d s l i d e scarps immediately adjacent where s e v e r a l houses were destroyed a few years ago.

159

TABLES %9

TABLE8 . S p e c i f i c descriptions of ground failures in the north bay counties region-Continued Loca- Fig- F a i l - Accu- Year of t i o n "re "re raearthNO. quake NO. type cy

Reference

Quotation

~p

A search f o r f r e s h ground ruptures along the Radgers Creek f a u l t was made but none Here found. * * A few boulders from s t e e p m a d cuts i n t h i s area [of Crane Canyon Road] were dislodged but no s i g n of f r e s h landslides were detected o t h e r than a small slump beneath a p a r t of t h e road bounded by a s t e e p embankment. The most widespread cracking was found in t h e IOOF Cemetery on t h e north s i d e of town. [See Lawson and o t h e r s , 1908, p. 201 above, f o r 1906 comparison.] Here, along Poppy Drive, t h e asphalt paving was crossed by several dozen fresh cracks oriented both northwest across t h e road and a l s o northeast, p a r a l l e l t o t h e road. The area l i e s i n a low depression c l o s e to a swamp. The adjacent ground immediately t o t h e north ires a l s o observed t o be cracked, but t h e o r i e n t a t i o n of t h e cracks appeared t o be random. The cracks i n Poppy Drive, which opened from 1/16 t o 114 inch, were pulled a p a r t perpendicular t o t h e crack faces. There was no apparent l a t e r a l m r i o n component or v e r t i c a l component, n o r did t h e cracks form any en echelon o r o t h e r r e g u l a r pattern. The cracks appeared i n a zone o f f i l l e d ground adjacent t o t h e swamp; thus they appeared t o be t h e r e s u l t o f heavy shaking of marshy s u b s t r a t a . * * * The day following t h e October 1 quake, f r e s h i r r e g u l a r cracks 118 t o 114 inch wide were noted i n t h e hard-packed dry d i r t roads i n t h e c e n t r a l p a r t o f t h e Rural Cemetery; however, these were n o t o r i e n t e d along any preferred trend. S t r s e t s i n t h e immediate v i c i n i t y north and south of t h e cemetery area were c a r e f u l l y examined f o r cracks bur no fresh cracks i n t h e asphalt were found. 296

B

1906

B

1906

x 0

297

298

a

Laivson and others, 1908, p. 201.

Lawson and others,

The only o t h e r physiogrsphic e f f e c t s folmd were a t t h e County Hospital, a l i t t l e more than a mile north of t h e cemetery. Here low ground a t t h e f o o t of a small h i l l sank f o r some 2 f e e t and springs were formed. These springs were reported as s t i l l running t h e l a s t o f July.

1908, p. 203.

I n t h e v i c i n i t y o f t h e Sonoma County Hospital, t h e s o i l i s very r a t t h e h o s p i t a l a marshy place along l i k e t h e Santa Rosa s o i l * t h e creek s l i p t toward t h e creek and t h e flow o f springs was g r e a t l y increased.

C

1906

Lawsan and others, 1908.

A few l o c a l s l i d e s on t h e south s i d e o f Mount St. Helena loere confined t o t h e alluvium.

A

1906

Lawson and others, 1908, p. 184 and 185, p l a t e 124A, p l a t e 1248.

MmcSZide, 6 m i t e s easter7.g from HeaZdsburg (R. S. Holiray) This s l i d e i s an t h e north s i d e of a ridge t h a t runs i n an e a s t e r l y d i r e c t i o n and t h a t i s a t t h i s point from 225 t o 300 f e e t above t h e bed of Maacama Creek, which runs along tho f o o t o f t h e north slope. Mr. Hugh Simpson, whose house i s j u s t beyond t h e f o o t of t h e s l i d e , s t a t e s t h a t t h e e n t i r e s l i d e took place a t t h e i n s t a n t o f t h e earthquake. The s l i d e i s about 0.125 mile wide a t t h e top and about 0.5 mile long. The rock i s a very l i g h t , porous, volcanic t u f f and seems t o be f r e e from water. A slicken-sided wall on t h e e a s t shows a very smooth surface i n s p i t e o f t h e s o f t rack. S t r l a e near t h e top The s l i d e seems t o have run N. 13' W. with a p i t c h o f about 24'. taken o f f some of t h e t o p of t h e r i d g e ; t h a t i s , it s t a r t e d a few f e e t down t h e south slope of t h e ridge, cut i t s way t h r u a f i r f o r e s t and dammed btaacama Creek with rocks and t r e e s . Either two successive s l i d e s occurred o r e l s e t h e upper p a r t of t h e moving mass was a r r e s t e d p a r t way down, f o r a bank with t h e vegetation of t h e top r e s t s across t h e s l i d e about one-third o f t h e way dom. (See p l a t e 124A. B.) This s l i d e was subsequently v i s i t e d by M r . G. K. Gilbert, who cont r i b u t e s t h e following supplementary note:

A t Maacarna schoolhouse, I saw t h e l a r g e landslide aescribed by Professor Holway. The rocks involved are i n l a y e r s , with a dip of about 30' i n t h e d i r e c t i o n of t h e s l i d e . It i s therefore

HISTORIC GROUND FAILURES IN NORTHERN CALIFORNIA TRIGGERED BY EARTHQUAKES

160

TABLE8 . S p e c i f i c descriptions of ground failures in the north bay counties region-Continued Loca- Fig- Fail- Accu- Year of raeartht i o n ure u r e No, quake No. type cy

Reference

quotation

probable t h a t t h e s l i d e was p a r t l y determined by t h e dip, tho it seems t o have been f u r t h e r determined by t h e erosion of t h e v a l l e y of hlaacama Creek. * * * [Mr. Stimson] and o t h e r s mentioned numerous cracks i n t h e bottom lands a mile t o t h e north, and e s p e c i a l l y i n t h e bottom lands of t h e Russian River a t i t s neighboring l a r g e bend.

299

A

1906

Lawson and others, 1908, p. 390.

Maacama s l i d e , 6 miles e a s t of Healdsburg. ( p i a t e 124A, 8.1 The s l i d e i s about 0.125 mile wide a t t h e top, and 0.5 mile long. The r o c k i s a s t r a t i f i e d volcanic t u f f , and t h e slip was down t h e dip of t h e beds. The avalanche cut i t s way t h r u a f i r f o r e s t and dammed Maacama Creek.

C

1906

Lawson and others, 1908, p. 184, p l a t e 13% p l a t e 1398.

Cracks i n t h e Russian R i v e r Ftood-ptain (R. S. Holriay1.--Cracks have been observed a t i n t e r v a l s i n t h e a l l u v i a l banks of t h e Russian River from near i t s mouth t o Alexander Valley, 5 o r 6 miles northeast of Healdsburg. These cracks are sometimes 100 yards i n length and from a few inches t o 2 f e e t i n width. Sometimes near t h e bank t h e r e w i l l be a deep f a u l t 5 t o 6 f e e t i n width and 100 f e e t long, as shown i n t h e photograph of t h e crack a t Monte Rio. The d i r e c t i o n of t h e cracks i s usually p a r a l l e l t o t h e bank of t h e r i v e r o r t h e bank of some small t r i b u t a r y . A t Duncan Mills t h e cracks ran north and south above t h e bridge and n e a r l y e a s t and west j u s t below t h e bend of t h e r i v e r . A t Monte Rio they are e a s t and west. In,Alenander Valley they run north and south, while a mile o r two below some are found nearly e a s t and west running up a small t r i b u t a r y .

C

1906

Lawson and others, 1908,

Heatdsburg, Sorvrm County. * * * Along t h e bottom-land of t h e ~ u s s i a n~ i v e r ,cracks from an inch t o a foot i n width opened a t s e v e r a l places. * r Fissures i n t h e creek bed near t h e t o m [ ~ e a l d s b u r g ] are i n evidence. Water was t h r o w out and continued t o flow f o r s e v e r a l hours, a t f i r s t with some considerable force; then it gradually diminished and f i n a l l y disappeared.

C

1906

Lawson and others, 1908, p. 184.

Along t h e creek and r i v e r bottoms t h e e a r t h was f i s s u r e d and water ivas forced up which, i n some instances, flooded t h e orchards.

B

1906

Duryea and others, 1907, p. 259.

The bridges over t h e Russian River, a t Healdsburg, and a t Bohemia, an t h e C a l i f o r n i a Northwestern, were both s h i f t e d s l i g h t l y on t h e p i e r s a t one end.

B

1906

Lawson and others, 1908, p. 184.

Alexander Valley i s p a r t o f t h e Russian River Valley l y i n g e a s t of Lytton Springs. The main bridge across t h e Russian River was wrecked, t h e trestle-work p a r t g o ~ n gdown. The bridge was old and was t o have been r e b u i l t t h i s year. At t h e e a s t end of t h e bridge cracks cross t h e road, northwest t o southeast, p a r a l l e l t o t h e r i v e r bank. These cracks appear a t i n t e r v a l s northwesterly, a t l e a s t as f a r as t h e ranch o f Rev. E. 8. Ifare, about a mile up t h e r i v e r . The cracks vary from a few inches t o aver a foot i n width, and are sometimes 200 t o 300 f e e t long, roughly p a r a l l e l t o t h e r i v e r . Mr. Ware s t a t e s t h a t t h e shock threw t h e r i v e r water upon t h e sandbars t o such an extent t h a t he found f i s h t h e r e during t h e day., Other cracks are reported a mile o r two northward. Subsidence frequently occurs where t h e cracks are near t h e bank.

C

1906

Lawson and others, 1908, p. 191.

mincm's M Z Z s (J. Parmeter).--On t h e Russian River, when fisherman t r i e d t o seine f i s h a f t e r t h e earthquake o f April 18, t h e i r n e t s were torn t o pieces by snags, e t c . , where t h e r e had formerly been no obstruction. Large t r e e s t h a t had been buried i n t h e bed of t h e r i v e r were l i f t e d up by t h e convulsion, while o t h e r t r e e s vanished t h a t had been i n s i g h t . Low places i n t h e r i v e r bed were made high and vice verso. The bottom o f t h e r i v e r appears t o have dropt 2 f e e t a l l along by Duncan's Mills f o r 2 miles; and a t t h e mouth of t h e r i v e r , where t h e r e used t o be water 12 o r 14 f e e t deep, t h e r e i s now only 2 f e e t , and a r i f f l e till boats can hardly cross, f o r a length of almost a mile. For over a mile t h e r e i s now a s t r o n g current, where t h e r e

.... .. .. .

0

+

n

161

TABLES 5 9 TABLE8.Specific descriptions of ground failures in the north bay counties region-Continued Loca- Fig- F a i l - Accu-. Year of t i o n ure ure raearthNo. No, type cy quake

Refarenee

-

used t o be quiet water with very l i t t l e c u r r e n t . A man who was by t h e r i v e r , near Monte Rio, when t h e earthquake occurred, t o l d t h e Parmeters t h a t he saw t h e muddy bottom of t h e r i v e r r i s e t o t h e surface, and t h e water ran off over t h e banks. The bottom was t h e highest where t h e ivater had been 8 o r 10 f e e t deep; then it s e t t l e d back. A road and fence moved 10 f e e t . On t h e a t h e r s i d e of Russian River from Duncan's Mills, 200 o r 250 f e e t back from t h e stream, t h e earthquake made many holes t h r u which black sand and water blew up.' Such blow-holes were made a l l along t h i s r i v e r . Between t h e r i v e r and t h e ruined h o t e l a t Duncan's is an i r r e g u l a r crack abbut 20 f e e t wide, 80 f e e t long, and 1.5 t o 4 f e e t deep, with a blow-hole 4.5 f e e t wide and 2 f e e t deep where coarse r i v e r gravel came up. (R. S. Ho1way.)-* * [ A t Duncan's Mills] Along t h e r i v e r t h e r e !?as several cracks i n t h e alluvium.

0

300

-a+

301

303

C

1906

Lawson and others, 1908, p. 387.

From Paint Arena southward t o Fort Rosg, t h e c l i f f s are.low, being f o r t h e most p a r t not i n excess o f 100 f e e t . Earth-avalanches were nevertheless o f common occurrence along t h i s s t r e t c h of coast. South of Fort Ross t o Bodega Head t h e c l i f f s are again, as f a r as t h e mouth of t h e Russian River, several hundred f e e t high and very steep. Here again earth-avalanches were extensive. The rocks along t h i s e n t i r e s t r e t c h o f coast from Cape Mendocino t o Bodega Head are p r e v a i l i n g l y sandstones and shales.

C

1906

Lawson and others, 1908, p. 190 and 191.

Several s l i d e s were seen about 3 miles south o f t h e Fort [ ~ o r tROSS]. One of these was of g r e a t s i z e , being between 300 and 400 f e e t i n height. These are evidently old s l i d e s , and t h e amount of material brought down by t h e recent earthquake, though l a r g e , is i n s i g n i f i c a n t compared ivith t h e s i z e of t h e scar.

A

1906

Lawson and others, 1908, p. 180 and 181, f i g . 14.

GunZnZo VaZZeq.--At Casey's ranch * * The ranch stands on t h e e a s t edge of t h e r i d g e , west of t h e Gualala River, and t h e f a u l t runs along t h e mountain s i d e several hundred f e e t below it. The slope i s a steel, . one.. densely timbered exceot f o r i t s u n e r oortion. Landslides were found over a l a r g e p a r t o f i t s surface, but only i n a few i s o l a t e d spots had they r e s u l t e d i n t h e complete removal o f t h e o r i g i n a l surface, and t h e f o r e s t growing thereon; so t h a t a view from across t h e r i v e r revealed no appreciable changes i n t h e landscape. The slopes e a s t of t h e r i v e r were s i m i l a r l y a f f e c t e d and t h e f a l l e n timber produced a tangle not unlike t h a t o f extensive windfalls. In a t l e a s t two places t h e r i v e r was temporarily dammed up by s l i d e s from both slopes meeting i n t h e stream bed, but none of these dams was of noteworthy s i z e . [See f i g . 14 a t end of tables.]

Lawson and others, 1908, p. 180, p l a t e 690.

East of Stewart's Point t h e bridge aver t h e South Fork of t h e Gualala River ( p l a t e 6901 was damaged by t h e slumping of t h e r i v e r t e r r a c e on which i t s south end r e s t s . I t was subjected t o a strong longitudinal, compressive s t r e s s , which r e s u l t e d i n a s l i g h t upward buckling of t h e bridge f l o o r near t h e southern end, and mafked bending and t w i s t i n g of t h e tension rods i n t h e 2 s o u t h e r n m s t panels. The supports a t t h e south end furthermore appear t o have s e t t l e d 13 inches, causing t h e f l o o r and t h e l a s t panel t o assume a marked i n c l i n a t i o n . A hundred yards e a s t o f t h e wagon bridge is an older, d i l a p i d a t e d one, whose f l o o r has been removed f o r some time. I t s r i c k e t y aspect and crookedness render it an u n s a t i s f a c t o r y object f o r study i n t h i s connection. There i s , however, clear evidence of t h e slumping o f t h e t e r r a c e a t i t s south end, i n a manner s i m i l a r t o t h a t a t t h e new bridge; y e t t h e old bridge appears t o have stood t h e compressive s t r e s s b e t t e r than t h e new, and i t s south end has merely overridden [sic] t h e displaced masses of t h e t e r r a c e . On both s i d e s o f t h e sharp bend o f t h e r i v e r e a s t of t h e two bridges are extensive landslides, making a clean sweep down t h e mountain s i d e . The s l i d e on tho north s i d e completely blocked t h e iragon road and was being removed a t t h e time of t h e v i s i t (May 12). It i s of such height and steepness as t o menace t h e road a t t h i s point with renewed s l i d i n g i n f u t u r e , e s p e c i a l l y during wet weather.

A

0

x.

Quotation

1906

.

.. .

162

HISTORIC GROUND FAILURES IN NORTHERN CALIFORNIA TRIGGERED BY EARTHQUAKES

TABLE8 , S p e c i f i c descriptions of ground failures in the north bay counties region-Continued Loca- Fig- Fail- Accu- Year of raeartht i o n ure ure quake No. No. type cy

Reference

Quotation

C

1906

Lawson and others, 1908, p. 180.

Annapolis, S o m m County (G. W. Fiscus).--Buildings were destroyed and bridges wrecked i n t h i s neighborhmd; landslides occurred and t h e waters of t h e Gualala River were thrown out 50 and 60 f e e t on a m a v e l bar. The r i v e r rose 12 o r 14 inches i n a few hours a f t e r th; shock. * * * In several places along t h e l i n e o f t h e f a u l t f i s s u r e , t h e e a r t h has opened $0 as t o allow gravel t o f a l l i n t o t h e cracks. I n o t h e r cases water and sand were s h o t out o f t h e openings, t h e sang remaining.

305

B

1906

Lawson and others, 1908, p. 179, p l a t e 68C.

GunlaZa, Mendocino County.--The wagon bridge over t h e Gualala River, south of t h e town, was s e r i o u s l y damaged. I t c o n s i s t s of a t r u s s e d three-span s t r u c t u r e 500 f e e t long, with a wooden appraoch of s i m i l a r length b u i l t on t r e s t l e s 20 f e e t high t h r u t h e svampy bottam-lands on t h e south side. This approach collapsed completely, t h e t r e s t l e s being thrown f l a t and carrying with them t h e south end of t h e main span. The l a t t e r , hoirever, did n o t leave i t s n o r t h e m abutments and appears otherwise undamaged. It i s considered safe t o t r a v e l over, a l t h o t h e bridge i s now s t e e p l y i n c l i n e d t o t h e south. (See p l a t e 68C.)

306

C

1906

Larison and others, 1908, p. 180.

A number of landslides blocked t h e wagon road and r a i l r o a d t r a c k north of t h e r i v e r . A p a r t i c u l a r l y extensive one occurred n o r t h of t h e j ~ m c t i a nof t h e branches of t h e G w l a l a , burying t h e tracks under many tons of rock and loose dkbris.

B

1906

La!uson and o t h e r s , 1908, p. 177.

Farther up, between t h e l m b e r camp and Hutton's ranch, extensive landslides occurred, c h i e f l y on the e a s t s i d e , wiping out t h e wagon m a d which was graded along t h e mountain slopes. Immediately north of Huttan's ranch, a l a r g e l a n d s l i d e plowed i n t o a grain f i e l d , producing a s e r i e s o f billolry wrinkles i n t h e s o f t a l l u v i a l material. The outermost ridge has a steep front about 8 f e e t high and seems t o have been t h r u s t h o r i z o n t a l l y over t h e l e v e l surface o f t h e f i e l d . The frontage of t h e s l i d e is f u l l y 400 f e e t .

C

1906

Lawson and others, 1908, p. 177.

On the south s i d e o f Point Arena harbor, l a r g e masses of rock s l i d down t o t h e beach. Small rock s l i d e s took place a l l along t h e coast i n t h i s neighborhwd.

C

1906

304

•

307

66

!a

308

Lawsan and others, 1908, p. 179.

0 309

B

1906

310

B

1906

Lawson and others, 1908, p. 188.

Lawson and others, 1908, p. 188.

[Point ~ r e n a ] In many cases houses d r i f t e d away and l e l t p a r c h e s standing i n t h e i r o l d location. On t h e creek-bottoms many small cracks or f i s s u r e s appear, t h r u which f i n e slate-colored sand has been forced t o t h e surface, forming cones.

One mile south of Kelseyville and half a mile t o t h e west, a t t h e place of Mr. McLauglilin on t h e Lower Lake county road, a crack was found i n t h e alluvium out of which gas escaped, burning upon i g n l tion. About one mile north are gas wells i n t h e same kind of rock, t h e gas being obtained by boring t o a depth of 165 f e e t . About 3.75 miles south of Kelseyville on t h e road t o Lower Lake, a t t h e ranch of Mr. M. E. D. Bates, i s a crack varying i n width from 1 t o 6 inches. I t cmsses t h e road about 200 f e e t below t h e house. A t t h e r i e h t of t h e road m i n e south it crosses t h e creek and can be seen no f i r t h e r . At rhe ; e f t o f t h e road it parses up t h e h i l l

163

TABLES C-9

TABLE8.4'pecific descriptions of ground failures in the north bay counties region--Continued Loca- Fig- Fail- Accu- Year of raeartht i o n "re "re No. quake No. type cy

Reference

quotation

toward Uncle Sam Mountain [~t. ~ a n o c t i lf o r about a mile, but is not .continuous. Near t h e road two small t r e e s standing on t h e crack have been p a r t l y uprooted and a fence post has been t h m m out e n t i r e l y . The rock t h r u which t h e crack passes is alluvium and a loose, uncons o l i d a t e d conglomerate. I t apparently does not pass t h r u t h e hard Franciscan rocks. In places t h e r e are as many as 10 p a r a l l e l cracks, separated by i n t e r v a l s of 5 t o 10 f e e t , which could be traced f o r only s h o r t distances. On t h e r i g h t s i d e of t h e road, about 100 f e e t south o f t h e cracks, stands a schoolhouse. I t has been s l i g h t l y t i l t e d t o t h e south. C

1962

Coffman, 1973, p. 180 and 181.

1962. June 6. Near Lakeport. * * * About 2 miles r e s t of Lakeport, S c o t t Creek rose 1 1/2 f e e t and flowed s t e a d i l y f o r 11 days a f t e r being nearly dly before t h e shock. Several wells i n Scott Valley rose 7 t o 10 f e e t , and t h e water was milky white f o r 3 t o 5 days. Four-inch-high undulating movement of f i l l s o i l was observed. About 10 miles southwest o f Lakeport, a geyserlike spout of water i n Clear Lake was reported by t h e press.

C

1906

Lawson and o t h e r s , 1908, p. 188.

On t h e s i d e of Mount Konocti, several large loose boulders were caused t o r o l l down, but no landslides nor cracks were observed.

@ 0 311

164

HISTORIC GROUND FAILURES IN NORTHERN CALIFORNIA TRIGGERED BY EARTHQUAKES TABLE9 . S p e e i f i e descriptions of ground failures in the north coast counties region

Location number i s assigned t o each reported ground-failure s i t e . Corresponding numbers are found on p l a t e 5. Figure number r e f e r s t o figure i n t h i s report showing damage described under "Quotation" column. Failure type i s indicated by t h e following symbols. Corresponding symbols are found on p l a t e 5.

... . ..

H i l l s i d e landslides including r o t a t i o n a l slumps, block glides, d e b r i s avalanches, and r o c k f a l l s

...

River s t r e t c h e s with extensively f i s s u r e d flood lai ins; p a t t e r n i n d i c a t e s s t r e t c h e s of r i v e r affected and not width of disturbed zone

0

Sand b a i l s

@

Streambank landslides including r o t a t i o n a l slumps and s o i l f a l l s

+

Lateral spread

Absence of ground f a i l u r e noted

Ground settlement

Miscellaneous e f f e c t s

Ground cracks n o t c l e a r l y associated with lands l i d e s , l a t e r a l spreads, settlement or primary f a u l t mvements

+ U - + A r r o i r s showing extent of area affected. shows f a i l u r e type

Symbol

Accuracy with which f a i l u r e s i t e s can be located is given as follows: A, a s i t e t h a t can be accurately relocated; 8, a s i t e t h a t can be r e l o c a t e d t o within a few kilometers and probably could be located more accurately with f u r t h e r invest i g a t i o n ; C, a s i t e where t h e information i s i n s u f f i c i e n t t o all019 p r e c i s e location. P l a t e numbers i n t h e "Reference" c o l m r e f e r t o p l a t e s i n t h e o r i g i n a l source material.

Laca- Fig- F a i l - Accu- Year of earthrat i o n "re ure NO. quake NO. type cy

Reference

Lawson and others, 1908, p. 175.

Quotation

The road between Point Arena and Mendocino was cut off by numerous s l i d e s (report of t o u r i s t ) .

1908, p. 176.

Bridgeport, Mendocino County.--An extensive landslide came dotm i n t o t h e c u l t i v a t e d f i e l d s on t h e f l a t , wave-cut t e r r a c e e a s t of t h e road.

Lawson and o t h e r s , 1908, p. 175.

were numerous cracks i n t h e gmund. c l i f f s took place, some very large.

Lawson and o t h e r s ,

Mendocim, Mendocim Cowzty.--

*

.

* The day a f t e r t h e shock t h e r e * * * numerous s l i d e s on t h e

Mountain roads e a s t of Mendocino were 1898. April, 14. * * rendered impassable by landslides and f a l l e n t r e e s .

Lairson and o t h e r s , 1908, p. 187 and 188, p l a t e 738.

WiZZets, Mendocim County * r * Small cracks across some of t h e s t r e e t s were reported, but they are n o t nari v i s i b l e . * * * The Calley i s an old lake bed with ground water within 3 t o 4 f e e t of t h e surface i n April. (See p l a t e 738.)

Lawsan and o t h e r s , 1908, p. 174.

(W. T. Fitch.1--There were several small cracks across t h e roads a few miles south o f Fort Bragg; and back i n t h e h i l l s t h e r e were more and l a r g e r ones.

Lawson and others, 1908, p. 174.

There are a number of f i s s u r e s i n t h e mud f l a t s i n and near t h e Noyo River and Puddin Creek. The boys say t h e r e are cracks i n t h e streams. There are cracks i n t h e l e s s s o l i d rocks along t h e ocean shore l i n e .

La!uson and others, 1908, p. 174.

(Eri Higgins.)--My house faces west. The e a s t p a r t was moved 6 inches south, breaking water and sewer connections. The west end o f t h e house did not move. Goods on shelves were thrown from t h e north s i d e , but not from t h e south s i d e . A l l brick buildings i n town went down except two, and these were damaged.

165

TABLES 6 9

TABLE9 . S p e c i f i c descriptions of ground failures in the north coast counties region-Continued Loca- Fig- F a i l - Accu- Year of t i o n "re "re raearthNo. quake No. type cy 317

Quotation

B

1906

Lawson and others, 1908, p. 172.

Cteone, Mendocino County. * * * A l l svay-braces on t h e wharf had t o be replaced, and the r a i l r o a d t r a c k was buckled i n many places. The bridge across t h e lagoon sank 3 f e e t i n some places, and was thrown out of l i n e l a t e r a l l y , a l l t h e p i l i n g supporting the bridge being l i s t e d t o t h e south.

B

1906

Lawson and others, 1908, p. 172.

Inglenook, Mendocin0 County * * On t h e banks of a small lake i n t h e s a n d h i l l s between t h e town and t h e ocean, some a l d e r s and irillaws f e l l owing t o a slumping o f t h e banks.

C

1906

Lawson and others, 1908, p. 174 and 175.

In t h e bed o f t h e Ten-Mile River, 10 miles north of Fort Bragg, where l e v e l surfaces occurred before, t h e r e were noted a f t e r t h e earthquake funnel-shaped depressions resembling e x t i n c t volcanoes i n miniature. These were only a few f e e t i n diameter.

C

1906

Lawson and others, 1908, p. 172.

Westport + * * Large cracks were made i n t h e ground, and a f t e r t h e heavy r a i n s of t h i s winter (March, 1907), l a r g e landslides occurred.

C

1906

Lawson and others, 1908, p. 172.

Hardy r * * The e a r t h cracked, both upon the mountains and near t h e creek, where t h e e a r t h was broken away from t h e banks.

C

1906

Lawson and others, 1908, p. 172.

Monroe, Mendocino County r Fissures opened i n t h e mountain s i d e s , and during t h e present winter (March, 1907) many large lands l i d e s have r e s u l t e d from these openings. [Located 7 m i . northeast of Rockport according t o Board a f Geographic Names, Washington D.C.]

C

1906

Lawson and others, 1908, p. 170.

On t h e e a s t bank o f t h e main Eel River, t o t h e e a s t of Laytonville (A. S . Eakle), t h e ground was cracked f o r a distance of 300 yards, t h e t r e n d of t h e crack falloriing t h e course o f t h e r i v e r . The crack was merely l o c a l i n t h e a l l u v i a l bank of t h e stream, perhaps 100 yards from t h e water. A long bridge crossing t h e stream a t t h i s place showed no e f f e c t s o f t h e shock * * *

x + 0

0

0

Reference

.

.

.

B

1906

Lairson and others, 1908, p. 171 and 172.

J u s t n o r t h of W. Geforth's house i s a crack 1,000 f e e t long, trending N. 55' E . , and following roughly a low ridge running out from t h e main h i l l s . I t c u t s almost a t r i g h t angles t o t h e main h i l l s and is i n s o f t material which has l i t t l e s l o w . I t could hardly be an ordinary s l i d e . On t h e t a p o f t h e ridge [Poonkinney ridge?], where t h e s o f t s t r e a k crosses t h e h i l l s a t an elevation of about 1,000 f e e t above the r i v e r , is a crack about SO f e e t long j u s t below a 1059 sandstone knob. trendine northwest o a r t l v across t h e draw a t a considerable a w l ; with t h e c r e s t of t h e h i i l s . I t i s i r r e g u l a r and shows no i slide. diiplacement of any kind. I t could hardly be . S t i l l f a r t h e r north, j u s t beyond E. Gevire's house [not p l o t t e d on ma01 and about 5 miles from Rabbins. i s another crack trendine northeast. It i s probably a s l i d e . ' Mr. Gevirc s t a t e d t h a t &ere were several s l i d e s i n t h e h i l l s on a l l s i d e s of h i s house, but no o t h e r cracks were reported t o t h e north. To t h e south t h e cracks extended t o t h e r i v e r , but none were known south of t h e r i v e r . About a mile f a r t h e r west, a t Poon Kenney, s e v e r a l more s h o r t cracks were reported trending n o r t h e r l y but varying i n d i r e c t i o n , and n o t connecting along t h e i r t r e n d , but I could not f i n d any of these. About 6 miles north of t h e bridge on t h e Eel River, a t a sheep camp c a l l e d Hole-in-the-Ground [not p l o t t e d on t h e map], t h e r e are s a i d t o be a great many cracks running i n various d i r e c t i o n s , but I did not v i s i t them. On t h e whole, I believe t h a t these cracks were a l l due t o t h e earthquake, but t h a t they are nothing mare than surface cracks due t o t h e j a r . They occur only i n t h e s o f t s t r i p s of weathered sandstone and where they seem t o be r e l a t e d i n trend they a l s o seem t o follow t h e s t r i k e o f t h e racks.

.-

166

HISTORIC GROUND FAILURES IN NORTHERN CALIFORNIA TRIGGERED BY EARTHQUAKES

TABLE9,Specific descriptions of ground failures in the north coast counties region-Continued Loca- Fig- Fail- Accu- Year of earthrat i a n "re "re No. quake No. type cy

Reference

325

C

1906

Lawson and o t h e r s ,

326

C

1906

Lawson and o t h e r s , 1908, p. 171.

Several cracks were reported crossing t h e road from Cavelo t o Laytonville near t h e t a p of t h e h i l l t o t h e north of Middle Eel River. They are s a i d t o continue a t i r r e g u l a r i n t e r v a l s f o r a mile o r more t o t h e north o r s l i g h t l y n a r t h of west. They g e n e r a l l y ' trend north t o n o r t h r c s t , but vary considerably.

327

C

1906

Lawson and others, 1908, p. 170.

There were a great many e a r t h cracks farmed i n the Round Valley region. Some were examined, but many had been obscured by t h e winter r a i n s , while o t h e r s were not v i s i t e d on account of t h e heavy r a i n which s e t i n and made it impossible t o cross t h e streams or get about i n t h e h i l l s .

328

C

1906

Lawsan and o t h e r s ,

One mile f a r t h e r west toward t h e Eel River, a crack c r o s t t h e road toward t h e north. There i s a s t r i p o f s o f t sandstones and shales t h r u here resembling t h a t found a t t h e Horse Ranch [loc. 3301 and s t r i k i n e t o t h e northwest. In t h i s s t r i o numerous cracks were found. o f t e n trending northwest but varying considerably. Four of these cracks were v i s i b l e , but o t h e r s could not be found as t h e r a i n s had healed them. I t was s a i d t h a t t h e do!mhill o r southwest s i d e was sometimes higher than t h e n o r t h e a s t side. Only one of these cracks could be ascribed t o a s l i d e . The o t h e r t h r e e might very well have been due t o t h e shock.

No cracks !rere found between Dobbins and Covelo.

1908, p. 171.

330

B

1906

Lawson and o t h e r s , 1908, p. 171.

The extension [of loc. 3301 should pass f a i r l y close t a the road from Covelo, but none o f t h e ranchers along t h e road knew of any cracks i n t h e h i l l s u n t i l Dobbins' p l a c e was reached, 10 miles southwest, on s e c t i o n 14, township 23 N., range 13 W. Here a crack 600 f e e t long, trending N . 25' W., occurs an a bench 150 f e e t wide, made up of s o f t alluvium gravel, e t c . , bounded on t h e northeast by a s t e e p h i l l of serpentine; i n t h e southwest by a s t e e p slope t o t h e creek 200 f e e t below, and on t h e northwest and southeast by bedrock ridges. The crack occurs near t h e o u t e r edge of t h e bench and t h e creek (southwest) s i d e i s a few inches higher than the h i l l side. I t does not continue i n t o t h e hard rocks a t e i t h e r end. Between t h e creek and t h e h i l l t h e g m m d i s s o f t , miry, and f u l l of springs, while a t t h e edge of t h e h i l l i r r e g u l a r cracks are sametimes seen, showing t h a t t h e muddy f l a t had likewise s e t t l e d r e l a t i v e t o t h e h i l l and i n d i c a t i n g t h a t t h e s o f t c e n t r a l area had s e t t l e d r e l a t i v e t o t h e hard, dry slope toward t h e creek and t h e bedrock of t h e h i l l . The crack runs under t h e cabin where t h e r e was t h e g r e a t e s t movement, but tho t h e cabin i s on four pegs, i t was n o t disturbed.

A

1906

Lawson and others, 1908, p. 170 and 171.

About 20 miles north of Covela, about s e c t i o n 2, townsl~ip24 N. range 14 W . , on t h e Horse Ranch, and about 700 f e e t above t h e north fork o f t h e Eel River, i s a crack about 40 f e e t acmss and 600 f e e t long. A t t h e southeast end a r i d g e of massive sandstone makes t h a t p a r t o f t h e t e r r a c e somewhat wider. A t e i t h e r end are small g u l l i e s . At t h e back, t o t h e n o r t h e a s t , a r a t h e r steep h i l l of sandstone r i s e s abruptly from t h e t e r r a c e . Below, t o t h e southwest, t h e t e r r a c e ends i n a s t e e p slope which shows evidence of repeated s l i d i n g and has several springs near i t s base. There are no t r e e s on t h i s slope, but t h e h i l l back of t h e t e r r a c e i s covered with t r e e s and t h e r e are some t r e e s on t h e t e r r a c e , mostly on t h e h i l l s i d e of t h e crack, a l t h o several oaks 8 inches i n diameter are on t h e s i d e toward t h e r i v e r . The main crack i s about 400 f e e t long. I t is i n d i s t i n c t and disconnected a t t h e northwest end, but gradually becomes more prominent t i l l it reaches a point j u s t beyond t h e c e n t e r where t h e r i v e r , o r sourhwest s i d e , i s 6 inches higher than t h e h i l l s i d e , and t h e r e i s an open gap of about 8 inches. I t then begins t o d i e out and upon reaching

167

TABLES 6 9

TABLE9 . S p e c i f i c descriptions of ground failures in the north coast counties region-Continued Loca- Fig- F a i l - Accu- Year o f t i o n ure ure raearthNo. quake No. type cy

Reference

Quotation

t h e sandstone r i d g e t u r n s about t h e edge o f t h e r i d g e and c o n t i n u e s about 100 f e e t more i n t h e shape of i r r e g u l a r cracks along t h e r i d g e . * r r The h i l l s f a r a c o n s i d e r a b l e d i s t a n c c on a l l s i d e s o f t h i s crack are covered w i t h o l d s l i d e s . 1906

California Department o f Water Resources, 1971, p. 41.

An unpublished r e p o r t i n t h e f i l e s o f t h e Northwestern P a c i f i c R a i l r o a d r e f e r s t o a l a r g e s l i d e on t h e Eel River near I s l a n d Mountain which blocked i t s flow i n A p r i l 1906. The s l i d e rias a t t r i b u t e d t o t h e San Francisco earthquake, b u t t h e e x a c t d a t e o f t h e s l i d i n g i n A p r i l i s unknown. According t o an a r t i c l e i n a Eureka newspaper, t h e Humboldt Standard of A p r i l 26, 1906, t h e earthquake was d i s t i n c t l y f e l t i n t h e Alderpoint-Fort Seward area and reportedly "stopped t h e water i n t h e r i v e r " . T h i s may be i n r e f e r e n c e t o a temporary blockage upstream, perhaps t h e s l i d e a t I s l a n d hlountain referred t o i n the railroad report.

1906

Lawson and o t h e r s , 1908, p . 387.

The most n o t a b l e o f t h e earth-avalanches occurred where t h e seac l i f f s are lhighest and s t e e p e s t . T h i s happens an t h e c o a s t of Humboldt County, between Cape Mendocino and P o i n t Delgada. Not only are t h e c l i f f s h e r e p a r t i c u l a r l y f a v o r a b l e f o r l a r g e e a r t h avalanches, but t h e c o a s t h e r e i s c l o s e t o t h e l i n e o f t h e f a u l t which caused t h e earthquake, and s o r e c e i v e d an e x c e p t i o n a l l y severe shaking. For many m i l e s o f c o a s t t h e r e was a g e n e r a l s l i p p i n g of rock and e a r t h i n t o t h e sea, doim very p r e c i p i t o u s s e a - c l i f f s ranging up t o over 2,000 f e e t i n h e i g h t . Between S h e l t e r Cove and P o i n t Arena, t h e s e a - c l i f f s are n o t so high n o r so continuous, but t h e r e was n e v e r t h e l e s s a very g e n e r a l , and l o c a l l y l a r g e , shedding of m a t e r i a l from t h e i r f a c e ; and t h e sea was muddy f o r many days a f t e r t h e earthquake i n consequence o f t h e d e j e c t i o n b f t h e d 6 b r i s upon t h e s h o r e , w i t h i n range o f t h e a t t a c k o f t h e waves.

1906

Lawson and o t h e r s , 1908, p. 58.

On t h e south s i d e o f t h e cove [ S h e l t e r Cove] t h e r e are t h r e e p a r a l l e l deep gorges which extend a s h o r t d i s t a n c e i n t o t h e h i l l s ; and t h e i r c o n t i n u a t i o n over t h e h i l l s i s shown by s l i g h t d e p r e s s i o n s which appear t o have been c l e f t s which have become almost f i l l e d with t h e wash o f t h e h i l l s . Along a l l t h e s e l i n e s o f weakness f i s s u r e s were opened and t h e ground subsided 2 t o 3 f e e t . Cross f i s s u r e s running from one d e p r e s s i o n t o a n o t h e r are a l s o p r e s e n t . The t r e n d o f t h e main f i s s u r e s [ f a u l t ? ] followed t h e c o a s t , which i s northwest-southe a s t . On t h e h i g h c r e s t s o f t h e Cooskie and King Mountains, [see l o c . 3321 which b o r d e r t h e c o a s t n o r t h o f t h e town, f i s s u r e s and l a n d s l i d e s were r e p o r t e d by r a n c h e r s looking f o r c a t t l e , but t h i s r e g i o n was n o t v i s i t e d . In t h e range s o u t h of t h e cove l a n d s l i d e s were a l s o r e p o r t e d and a photograph o f a l a r g e one was taken.

1906

Lawson and o t h e r s , 1908, P. 56, f i g . 10.

1906

Weekly Hwnboldt rimes, 1906a.

At S h e l t e r Cove + + * r h e severe shock a t 5 o ' c l o c k , w i t h t h e h e l p o f t h e ocean waves, washed about twenty acres o f land near t h e wharf i n t o t h e sea, l e a v i n g a deep depression. The wharf r o a d from t h e t o p a f t h e b l u f f t o t h e warehouse i s completely d e s t r o y e d by a huge s l i d e , making i t impossible t o reach t h e wharf even an f o o t . * * * a chasm aver a f o o t wide was made w i t h i n a few f e e t o f t h e h o t e l . The r o a d s are blocked w i t h f a l l e n t r e e s e v e r w h e r e o u t t h i s !ray.

1961

Coffman, 1973, p. 180.

1961. April 5. Off c o a s t of n o r t h e r n C a l i f o r n i a . F e l t p r i n c i p a l l y i n Humboldt County. At t h e Bear Harbor Ranch, about 10 m i l e s s o u t h of E t t e r s b u r g , a 50-yard s l i d e occurred. Magnitude 5.0.

[See f i g . 10 a t end of t a b l e s . ]

168

HISTORIC GROUND FAILURES IN NORTHERN CALIFORNIA TRIGGERED BY EARTHQUAKES TABLE9 . S p e c i f i c descriptions of ground failures in the north coast counties region-Continued

Loca- Fig- Fail- Accu- Year of tion No.

ure No.

"re type

racy

Reference

Quotation

earthquake Briceland was more badly shaken up than t h i s place [Garberville]. J. W. Bowden's s t o r e and Ben Harris' h o t e l were both moved from t h e i r foundations, and t h e s t o r e was badly t w i s t e d and shaken on one side. A f i s s u r e some inches wide runs t h e length of one of t h e streets.

336

C

1906

WeekZy HmboZdt Times, 1906a.

Miranda. The r i v e r became very muddy and t h e ground was cracked i n places as much a s two f e e t across and f o r s e v e r a l hundred yards i n length.

337

B

1906

Lawson and o t h e r s , 1908, p. 58.

South f ~ a mHadley's ranch a t Big Flat, t h e precipitous mountain slopes have been destroyed by extensive and high landslides, t h e dislocated materials o f which have frequently advanced out upon the beach i n t h e form o f g l a c i e r - l i k e tongues. The waves a t high t i d e have s i n c e n i p t these protruding masses and truncated them a t t h e i r ends. Many of t h e s l i d e s occurred apparently on t h e s i t e s of o l d e r ones. Their c o n t i n u i t y and extent made t h e discovery of the f a u l t i n t h i s neighborhood impracticable. The prevalence of great s l i d e s along t h e coast, back inland, seems t o suggest t h e p o s s i b i l i t y of * t h e f a u l t curving along t h e coast

.

B

338

1906

Lawson and others, 1908, p. 169.

.

Petrolin, HwnboZdt County. * * Cracking of t h e land occurred r along t h e edge of t h e r i v e r i n close proximity t o t h e h o t e l * A note from M r . Blackbum regarding t h i s same town says t h a t t h e only place which is reporred f o ha"; s u f f e r i d r e l a t i v e l y more than Ferndale i s t h e l i t t l e town o f P e t r o l i a , on t h e Mattole River; * * * t h e e a r t h cracked very much and made wide f i s s u r e s ; many s l i d e s occurred and t h e shock was heavier. P e t r o l i a Badly H i t . The ground from t h e North Forks t o t h e edge o f town i s furrowed, j u s t as though it had been plowed. On t h e r i v e r bar near town t h e ground opened and water shot high t o t h e North Fork bridge has i n t h e a i r . One end of t h e amroach .. s e t t l e d one foot. The s t e e l bridge across Cook's gulch [near Upper Mattale] s e t t l e d a t one end a foot and a h a l f . Bath bridges are passable.

B

1906

The Ferndale Enterprise, 1956.

A t P e t r o l i a . * * * Cracks i n t h e e a r t h are noticeable i n many places. * * * The bridge near Levant Cook's place sunk a t one end about 18 o r 20 inches. Acmss t h e r i v e r from P e t r o l i a a huge s l i d e occurred, t h e mountain s i d e p a r t l y going i n t o t h e water and throwing a dam h a l f way across t h e stream.

C

1923

IVood, Allen, and Heck, 1939, p. 19.

1923 January 22. I X . Upper Mattole and P e t r o l i a , where most of t h e chimneys f e l l and t h e r e were many aftershocks. Bad s l i d e s on nearby roads.

C

1906

WeekZy HwnboZdt Times, 1906a.

Upper Mattole. * * + The waters of t h e Mattole r i v e r were splashed two o r t h r e e rods each s i d e of t h e natural channel along t h e valley. The roads are cracked and contain many p i l e s of rubbish and gravel. Thousands of t a n s of d i r t and rocks have s l i d over precipices.

X

1968. June 25. Petrolia-Honeydew area. * * ,A t P e t r o l i a , minor landslides were noted and t h e press reported l a r g e ground cracks along t h e Mattole River.

339

67A 67B

0

A

1906

Lawsan and others, 1908, p. 390 and 391, p l a t e 127A, p l a t e 1278.

Cape Fortirnas [ ~ a l s ecape] earth-slump (F. E. Matthe*).--This l a n d s l i d e , immediately south o f Cape Fortunas, i s by f a r t h e mast In May, extensive one on t h e northern coast. (See p l a t e 127A, B.) 1906, it projected i n t o t h e ocean f o r about 0.25 mile, l i k e a hummocky headland of i r r e g u l a r o u t l i n e ; indeed, it formed a new cape on t h e coast-line, but w i l l doubtless r a p i d l y be cut back by

TABLES 5-9 TABLE9 . S p e c i F c descriptions of ground failures in the north coast counties region-Continued Loca- Fig- F a i l - Accu- Year of t i o n "re "re raearthNO. quake No. t w e cy

Reference

Quotation

t h e a c t i o n o f t h e waves. I t s length, i n t h e d i r e c t i o n of i t s movement toward t h e ocean, i s estimated a t l i t t l e short of a mile; i t s width v a r i e s from 0.25 mile t o 0.5 mile. I t s t o t a l descent, from t h e summit of the higher scalps a t i t s head t o t h e l e v e l of t h e sea, i s probably l e s s than 500 f e e t . I t s s u r f a c e i s encoodingly i r r e g u l a r , with many large humps and hollowr. Over large areas the sod i s more o r l e s s rhythmically broken by deep cracks extending a t r i g h t angles t o t h e d i r e c t i o n of movement. These cracks are only a few f e e t a p a r t , and t h e sad-blocks between them l i e mostly i n t i l t e d a t t i t u d e s , making t h e area exceedingly d i f f i c u l t t o traverse. The general aspect i s not unlike t h a t of a much crevassed g l a c i e r . In some places, however, t h e mass seems t o have been t o m a p a r t s o completely t h a t the sod i s not merely broken but almost swallowed up o r buried, the bmwns and yellows o f t h e under s o i l being t h e p r e v a i l i n g t i n t s . Around i t s head are a number of steep scarps, from 100 t o 200 f e e t high. They are e s p e c i a l l y prominent on t h e north s i d e , and again toward t h e southeast; but over considerable s t r e t c h e s between these two s e t s , t h e broken surface of t h e s l i d e joins t h e unbroken h i l l s i d e s t o t h e e a s t without s i g n i f i c a n t o f f s e t . Owing t o t h i s , t h e s l i d e i s e a s i l y approached from the ragon road (from C e n t e r v i l l e t o Cape Town), which passes close by i t s head. The longitudinal p r o f i l e of t h e landslide is one of gentle slopes f o r t h e mast p a r t ; i t s d e c l i v i t y i s n o t a t a l l g r e a t , and i n a few places even reversed slopes occur. I t s noteworthy fearure i s not i t s v e r t i c a l drop but its great forward movement. In a sense it has flowed l i k e a p a r t i a l l y p l a s t i c mars, expanding and advancing 0.25 mile beyond t h e coast-line. but descendinn.only a feu hundred feet. In i t s general aspect, as well a s i n t h e nature of i t s movement, t h e Cam Fortunes landslide -is - altowether d i f f e r e n t from those observed f a r t h e r south, p a r t i c u l a r l y along t h e mountainous coast both north and south of Point Delgada, which, i n e f f e c t , did l i t t l e e l s e than revive a s e r i e s o f old l a n d s l i d e facets. This may not be apparent t o an observer on t h e beach, but i s q u i t e s t r i k i n g when s e- n t-i r e t v from a vessel off-shore. These t h e coast i s viewed i n -i t ~ f a c e t s e x i s t e d before t h i s earthquake, and had been recognized as such. They are conspicuously o u t l i n e d against t h e dark timbered slopes behind them, r i s i n g from 1,000 t o 2,000 f e e t above t h e shore, and affording an important s e r i e s of landmarks f o r t h e mariner. In strong c o n t r a s t with these bold mountain forms i s t h e region i n lihich t h e Cape Fortunas landslide took place. The land here can scarcely be c a l l e d mountainous; and while i t breaks o f f i n c l i f f s a t t h e coast and i s traversed by many f a i r l y deep d r a w , i t is e s s e n t i a l l y a region of subdued r e l i e f . Great d e c l i v i t i e s are notably absent, except i n t h e s e a - c l i f f s , and even these are only a few hundred f e e t high. A t t h e same time, evidences of former landslides may be seen on every hand. They are not extensive, as a r u l e , and arc as l i k e l y t o occur on gentle slopes as on steep ones. In a few cases only i s a marked do3unslip noticeable, r e s u l t i n g i n t h e uncovering of a stecp scarp; i n nearly every instance t h e d i s l o c a t e d mass appears not s o much t o have sheared off and dropt from i t s former p o s i t i o n , as t o have expanded o r slumped, with an accompanying subsidence of i t s surface. The billowy and irregul a r l y p i t t e d appearance of these areas, together ivith the rank veget a t i o n t h a t covers them, afford t h e p r i n c i p a l marks of i d e n t i f i c a t i o n . o f p l a s t i c flow, and Both from t h e i r c h a r a c t e r i s t i c form,. sugnestive . . from t h e i r mode of occurrence, i t seems reasonable t o i n f e r t h a t ground-water plays an important =^ole i n t h e i r genesis. They are apparently masses which have changed t h e i r shape i n obedience t o a lessenine" of cohesion i n t h e i r i n t e r i o r . through s a t u r a t i o n with water. Whether t h e movement be i n i t i a t e d by an earth-tremor o r nor, i t i s i n every case e s s e n t i a l l y an adjustment t o a more s t a b l e posit i o n , rendered necessary by a change i n t h e physical c o n s t i t u t i o n of t h e mass. I t is t o t h i s category of landslides t h a t tho one a t Cape Fortunas belongs. While t h e r e are scarps i n various places a t i t s upper end, these are r e a l l y i n s i g n i f i c a n t f e a t u r e s alongside of t h e extensive ~

~~~

~

~

-

~

~

-

170

HISTORIC GROUND FAILURES IN NORTHERN CALIFORNIA TRIGGERED BY EARTHQUAKES

TABLE9.Speeifie descriptions of ground failures in the north coast counties region-Continued Laca- Pig- F a i l - Accu- Year of raeartht i o n ure ure No. quake No. type cy

Reference

Quotation

t r a c t of t h e s l i d e i t s e l f . lYhat downslipping occurred on these scarps was merely an incident i n t h e e n t i r e movement. Both i n t h e large r a t i o between i t s horizontal advance and its v e r t i c a l drop, and i n i t s general appearance, t h e Cape Fortunas l a n d s l i d e i s closely ar~alogoust o tile )numerous l e s s e r s l i d e s referred t o ; and t h e r e is good reason f o r t h e b e l i e f t h a t , l i k e them, i t consisted e s s e n t i a l l y of an adjustment of e q u i l i b r i a " i n a p a r t i a l l y water-saturated mass. I t probably had long been i m i n e n t before the earthquake s t a r t e d it. A

1906

Lawsan and others, 1908.

Near t h e False Cape it threw t h e old h i l l , on which t h e O i l Creek coast road ran. out i n t o t h e ocean for 0.5 mile. I t i s estimated t h a t 200 acres were thrown i n t o t h e ocean. Q u i t e a number of c a t t l e went with t h e h i l l . The s l i d e i s s a i d t o have obscured t h e view of Cape Mendocin0 l i g h t from Trinidad heads.

A

1906

Jordan, 1907, p. 296 and 299.

11. Landslips, etc. In t h e meisoseismal area, t h e r e were a g r e a t many cases of mountain s l i d e s . The most remarkable among these was t h a t which occurred near Cape Fortuna (False Cape), where an enornous quantity of debris was detached fmm a m u n t a i n s i d e and was pushed i n t o t h e ocean, c r e a t i n g a new promontory of about 314 mile length. [The name Cape Fortunas was o f f i c i a l l y changed t o False Cape on Oec. 14, 1939, Board on Geographic Names, Washington O.C.]

A

1906

TheFerndote Enterprise,

A t t h e Woodland Echo d a i r y ranch, j u s t t h i s s i d e of O i l creek on t h e C e n t e r v i l l e beach, a l a r g e mountain s l i d i n t o t h e ocean and now extends i n t o t h e water f o r a distance of probably a h a l f mile, comp l e t e l y obstructing t h e view o f t h e Cape Mendocino and Table Bluff l i g h t s , which before t h e upheaval were p l a i n l y v i s i b l e t o each s t a t i o n . On t h i s mountain a t t h e time o f t h e quake were four o r f i v e head o f c a t t l e , and they are reported t o have been wiped out of existence. The road leading from t h e Woodland Echo rancli t o Ferndale has been completely o b l i t e r a t e d near t h e s l i d e .

0

1956.

1906

The Ferndaze Enterprise, 1956.

1906

The HwnboZdt Times,

At t h e rear of A. Boyd's residence a t Port Kenyon a large f i e l d bordering S a l t r i v e r was spread open i n many p l a c e r , several acres of t h e land s e t t l i n g a couple of f e e t . From its appearance it would seem t h a t water spurted i n l a r g e q u a n t i t i e s from t h e ground. On t h e north bank of S a l t r i v e r a t t h e latrer bridge t h e land has s l i d i n and cracked f o r a d i s t a n c e o f s e v e r a l hundred f e e t and t o a width of t h i r t y o r f o r t y f e e t . The bridge i t s e l f does n o t seem t o have been damaged any and i s presumably i n as good condition f o r t r a v e l as before t h e shack. A l l along S a l t r i v e r , on e i t h e r s i d e , but more e s p e c i a l l y on t h e south s i d e , f i s s u r e s can be noticed, and i n some instances of s e v e r a l f e e t i n width, and we are t o l d by those who have t r i e d probing t h e gaps t h a t they appear t o be p r a c t i c a l l y bottomless. A t Fort Kenyon a vegetable garden turned i n t o a lake, t h e water being a depth of about two f e e t .

1906. 1954

1906

The HwnboZdt Times, 1954b.

[Ferndale] S t r u c t u r a l damage was reported a t Rings Pharmacy, where t h e building s e t t l e d . t * across t h e s t r e e t a s i m i l a r s t r u c t u r a l damage occurred t o t h e Martin and Betriga fountain.

Fle/eekZv H d o Z d t Times,

was f i l l e d i n by

On t h e Wildcat road, one and a h a l f miles from Ferndale, t h e road a b i g s l i d e , but w i l l be opened f o r t r a v e l today.

1906~. 1906

Lawson and others, 1908, p. 167.

At Dungan's Ferry, on t h e north bank of t h e Eel River, t h e ground Every bar on t h e r i v e r had been opened by f i s s u r e s , and t h e gravel toppled over leaving b i g ditches, some 6 f e e t deep and over 500 f e e t long. Coming up on t h e mainland t h e mad had dropt about 2 f e e t i n one p l a c e and was f u l l o f small

was f u l l of f i s s u r e s .

171

TABLES 6 9 TABLE 9 . S p e e i f i e descriptions of ground failures in the north coast counties region-Continued Laca- Fig- Fail- Accu- Year of t i a n ure "re raearthNo. quake No. type cy

Reference

f i s s u r e s . A 40-acre f i e l d was e n t i r e l y ruined. I t was heavily f i s s u r e d , having dropt down i n s t r i p s from 2 t o 6 f e e t wide, from 4 t o 6 f e e t deep, and from 5 t o 500 f e e t long, t h e f i s s u r e s pointing between' south and southwest. A l l t h e f i e l d s were f u l l o f quicksand volcanoes, some 1 t o 3 cubic yards i n s i z e . They were perfect miniature volcanoes, every one having a c r a t e r . I t i s s a i d they extended 30 miles up t h e r i v e r .

* 0

... ... C

1906

Lawson and others, 1908, p. 168, p l a t e 138A, p l a t e 1388.

On t h e flood p l a i n of t h e Eel River t o t h e north of Ferndale, Professor Eakle r e p o r t s t h a t t h e ground was cracked f o r a distance of 0.25 mile on t h e west bank of t h e r i v e r . The cracks were i n close v i c i n i t y t o t h e r i v e r , and seemed t o be on t h e l i n e o f an old channel. A s e r i e s of p a r a l l e l cracks, some having a v e r t i c a l displacement o f 2 f e e t , t h e surface being u p l i f t e d and deprest, followed t h e trend of t h e r i v e r and were evidently l o c a l i n t h e s o f t alluvium. A t t h e time of t h e earthquake water and sand spouted up i n several places t h r u openings which were i n some cases 4 inches wide. Mr. Blackburn r e p o r t s t h a t t h i s water remained on t h e s u r f a c e of t h e f i e l d s f o r some time a f t e r t h e earthquake. In t h i s same connection, Mr. J. A. Shaw r e p o r t s t h a t "a f i e l d on a high bar near t h e Eel River was l i t e r a l l y shaken t o pieces, and water f i l l e d with quicksand was ejected several f e e t high. The r e n t s run from north and south i n a curve t o e a s t and west. Some p a r t s are a c t u a l l y cut i n t o squares. The jump v e r t i c a l l y w i l l reach 2.5 f e e t . There were no such l a r g e r e n t s t h r u t h e valley generally, as t h e upper s o i l r e s t s an a clay foundation which seemed t o stand it a l l r i g h t . , '

C

1906

WeekZy Hmbotdt Times,

The S c o t i a [ r a i l r o a d ] l i n e went out of c o m i s s i o n by reason o f a s l i d e a t t h e b l u f f s and t h e breaking of two of t h e heavy l a t e r a l rods on t h e Van Duzen Bridge.

Y 0

+

343

1906b. 344

Quotation

C

1906

The Ferndate Enterprise,

Cock Robin Island cams i n f o r i t s share of t h e shake, chimneys being t o r n down and many holes and cracks i n t h e ground made. The same destruction v i s i t e d Cannibal Island, it being s a i d t h a t t h e land t h e r e t h a t was q u i t e high before t h e shake-up i s now lowered from one t o ten f e e t , while low places have been f i l l e d up. In many instances where t h e ground opened a kind o f black sand or sediment oozed f o r t h , showing t h a t i t must have been tlirown from t h e very bowels of t h e earth. On t h e Hamner ranch on t h e Island, under l e a s e t o Rasmus Nielsen, we are t o l d t h a t t h i s sand o r sediment was very warm and t h a t snake arose from it f o r s e v e r a l hours a f t e r t h e convulsion.

The H d o Z d t Times,

On Cannibal i s l a n d t h e e a r t h trembled and cracked but t h e r e p o r t t h a t mud and water issued fmm t h e f i s s u r e s and rose i n t h e a i r 100 f e e t could not be v e r i f i e d .

1956.

0

C

1906

0

1906.

1932. June 6 . Hwnbotdt C o m t y . r * * a t Eureka Slough [loc. 3491, a r a i l r o a d drawbridge was put out of commission; a t Loleta. small cracks appeared i n t h e gmund and a brick wall f e l l . Cracks 28 inches wide and s e v e r a l hundred f e e t long were observed on Cock Robin Island [loc. 3441.

346

B

r(

1906

Lawsan and others, 1908, p. 166.

South of E w e h ( H . H. Buhne).--A few days a f t e r t h e quake everything laokt a l l r i g h t along t h e road, excepting chimneys, u n t i l I reached F i e l d ' s Landing, a t South Bay. Here t h e shock opened a f i s s u r e over 100 f e e t long i n t h e middle of t h e road, which 6 teams spent one day i n f i l l i n g . Pelican Island, as it i s conmanly c a l l e d , opposite Field's Landing, dropt 3 f e e t a t t h e p a i n t where t h e United S t a t e s p i l e beacon stands. I t l e f t t h e beacon landing a t an angle of 45' from t h e southwest.

172

HISTORIC GROUND FAILURES IN NORTHERN CALIFORNIA TRIGGERED BY EARTHQUAKES

TABLE9,Specific descriptions of ground failures in the north eoost counties region-Continued Loca- Fig- F a i l - Aceu- Year of raeartht i o n ure ure No. quake No. type cy 1906

The X d o t d t Times, 1906.

1906

Quotation

Reference

The HwnboZdt Times, 1906.

A t F i e l d ' s Landing around t h e home of John Johnson, small cracks i n t h e e a r t h became geysers throwing out warm water f o r s e v e r a l hours, t h e flow f i n a l l y abating about noontime. In front o f t h e h o t e l an t h e county road many cracks were i n evidence but they f i n a l l y closed up. A l i t t l e beyond t h e Landing i n t h e county road was a crack about 18 inches wide and twelve t o fourteen f e e t long. A nine-foot s t i c k f a i l e d t o touch bottom and teams were busy a l l day t o f i l l up t h e gulch.

Many are t h e r e p o r t s o f sinking i n various s e c t i o n s but out the Elk r i v e r way it heaved up, breaking t h e water mains of t h e Eureka Water Company running thmugh t h e Feckelstein place and t h e Russ claim.

1908

Coffman, 1973, p. 162 and 163.

1908. August 18. Eureka. * + * A t Freshwater, a few miles north of Eureka, walls cracked, chimneys f e l l , and s o f t ground fissured.

1908

Townley and Allen, 1939, p. 150.

1908 August 18. * * * VIII. Humboldt Bay. * r * Reports from t h e Seazy ranch, n e a r Freshwater, s i x miles north of Eureka, s t a t e t h a t t h e earthquake caused a b i g f i s s u r e i n t h e e a r t h f o r about one-half mile.

1906

Weekly H d o Z d t Times,

across t h e slough had been bmken, and i n many places t h e road was

1906.

cracked.

Holden, 1898, p. 41.

1853. October 23; VIII. Gal.--J. B. T. A t Eureka

1865

Townley and Allen, 1939, p. 45 and 46.

1865. October I . 7 a.m. IX. Eureka. Heavy Shock. * * r "Fort Humboldt, a few miles below Eureka on t h e Bay, rras even more roughly handled; a l l f o r t buildings were i n j u r e d and t h e r e was a f i s s u r e along t h e edge of t h e parade ground." [Also i n Coffman, 1973, p. 157.1

1906

Weekly HmboZdt Times,

GREAT GAPS IN THE EARTH. A t t h e home of R. L. Haughey, t h e shingle manufacturer, was a scone of havoc a f t e r t h e earthquake had passed. A recent addition t o t h e residence was t o r n loose and moved a f o o t t o t h e southward, and a t t h e same time sank about four inches. Another p a r t o f t h e dwelling a l s o shrunk away from t h e main s t r u c t u r e and took a l i t t l e drop. Cracks were i n evidence i n t h e e a r t h a l l around t h e property when t h e gentlemen got out of t h e house, and water was spouting up through them. The cracks were about ten inches wide. but durine" t h e day they closed up, and l a s t evening were only about four inches across. AT THE EUREKA FOUNDRY. * * * t h e ground surrounding t h e p l a n t was cracked by t h e tremor o f yesterday morning. The ground sank mater i a l l y a l s o i n places.

1853

1906b.

1906

WeekZy Hmboldt Times,

Damage a t Sweasey Ranch.

* *

q u i t e a good deal of water pipe

Three heavy shocks a t Humboldt Bay, * t h e wharf sank 4 f e e t .

t t

The large water mains of t h e Eureka Water Company are badly twisted

* * * .

1906b. 1954

Coffman, 1973, p. 176.

1 0 5 4 . December 21 and 30. Eureka-Arcata areas. * * * In t h e poorly consolidated ground areas n o r t h and e a s t of Eureka t h e r e were some p i p e l i n e f a i l u r e s , and Eureka's main water r e s e r v o i r was cracked. A large s e c t i o n o f t h e older, downtown f i l l e d area of Eureka s e t t l e d from 2 t o 6 inches.

[Picture caption] * * t h e b i g shaker l e f t t h i s giant-sized f r a c t u r e i n t h e c i t y ' s surface on Hairthollie s t r e e t near Broadway. The crack's depth was unrecorded, but i t measured up t o 12 inches wide.

174

HISTORIC GROUND FAILURES IN NORTHERN CALIFORNIA TRIGGERED BY EARTHQUAKES

The following figures are those referred to in the preceding tables:

Table 6, location 179

Table 6, location 118

APPROX. SCALE 100

200FEET

w 0

25

50 METERS

0 0

50

100 FEET 25

50ME

FIGURE68.-Map

of landslide caused by the earthquake east of San Pablo (Lawson and others, 1908, p. 392).

FIGURE7.-Dam

at Crystal Springs Lake showing cracks formed by the displacement (Taber, 1906, p. 310).

Table 6. location 179

FIGURE6 9 . S e c t i o n of landslide shown in fig. 68, along the line A-A' (Lawson and others, 1908, p. 392).

175

FIGURES CITED IN TABLES

Table 8, location 270

Table 8, location 271

Table 8, location 271

FIGURE27.-Diagrams with exaggeration of vertical scale, to illustrate deformation of Inverness piers by shifting of mud toward the shore. Bailey's pier above; Martinelli's below (Lawson and others, 1908, p. 791.

FIGURE 25.-Arrangement of ridges on tidal flat near Inverness. Map. (Lawson and others, 1908, p. 79). FIGURE2 6 . S k e t c h of Inverness piers. Full lines show positions of piers after earthquake; broken lines show positions before earthquake, Dotted line shows shoreward limit of the shifting of bottom (Lawson and others, 1908, p. 79).

Table 8, location 302 I

I

I

FIGURE14.-Profile of southwest side of South Fork of Gualala River, showing relation of fault to geomorphic features (Lawson and others, 1908, p. 62).

HISTORIC GROUND FAILURES IN NORTHERN CALIFORNIA TRIGGERED BY EARTHQUAKES

Table 8, location 303

FIGURE13.-Map

of valley of South Fork of Gualala River, showing relation of fault-trace t o geomorphic features (Lawson and others, 1908, p. 61).

FIGURES CITED IN TABLES

Table 9, location 333

FIGURE10.-Map of country traversed by fault to north of Shelter Cove, Humboldt County (Lawson and others, 1908, p. 56).