/

GARY S. RASMUSSEN" & ASSOCIATES /ENGINEERING GEOLOGY

1906 50. C:OMMl\:RCE:NTE:R EAST, SUITE 207 • SAN BERNARDINO, CA 92408 • C714) 888·2422 • (7141 a:z~"90!:52

September 27, 1979

Camp Teresita P:ines 22801 Big Pines Highway Wrightwood, California 92397

Attention: Ralph Hul lman

Subject: Addendum to Our Report flated August 31, 1979.

Project No. 1551-2

Reference: Engineering Geology Investigation, Dining Hall Addition, Camp Teresita Pines, 22801 Big Pines Highway, Wrigthwood, California, Our Report Dated August 31, 1979, Project No. 1551.

The following modification and additions should be made to the referenced

report in response to questions by Mr. [)avid Popplar, County of Los Angeles,

Engine'ering Geology Section.

Page 6, Linc 6. The fol_lowing sentence should be added, "The fault appears

to be at least 100 feet south of the proposed dining hall addl ti on, based

on the projection of aerial photographic lineaments observed both northwest

and southeast of the site." The last sentence of this paragraph should be

modified to, "It is remotely possible that during a major event on the

San Andreas fault, approximately 800 feet south of the proposed <lining hall .

addition, minor differential settlement or sympathetic movement of the

order of approximately \ inch per 30 feet normal to the fault could occur

along the old fault trace." '

Page 10. Tiie second pa:ragraph under Recommendations should be changed to,

"A slight poss:ibi.lity for sypmathetic movement or differential settlement

along the older, inactive fault which projects approximately l 00 feet

south of the proposed building site is possible. This potential settlement

wi 11 probably not affect the proposed dining hall addition, and the maxiJUum

expected differential settlement along the fault is expected to be of the

order of \ inch per 3_0 feet normal to the fault.-"

OCT O 2197g

Camp Teresita Pines -Addendum September 27, 1979

Project No. 1551-2

Page 10. The following sentence should be "dded to the third paragraph

under Recommendations, "The recommended setback from the steep slopes

will not affect the proposed dining hall addition."

TES:GSR/mt

Respectfully submitted,

GARY S. RASMUSSEN & ASSOCIATES, INC.

~c.S~ Thomas E. Spittler Staff Geologist

Gary S. Rasmussen Engineering Geologist, EG 925

Distribution: Teresita Pines, L.A. (5)

Los Angeles County, Engineering Geology Section (2) Attn: Dave Popplar

-2-G.ARY S. RASMUSSEN & .ASSOCIATES

STATE OF ('.Al!rORNIA-iHE R~50URcrs AGENCV EOMUNO G. Sl?OWN JR,, Ga~ntor

DEF"AR<MENT Of CONSERVATION

DIVISION OF MINES AND GEOLOGY SAN FRANCISCO DISTRICT OFFICE FERRY SUllDING

SAN fJl'ANCfSCO. CA 94111

(Ph.one 4 l!i-557-0633} AfJ-ID37

November 5, 1979

Mr. Poppler Engineering Geology Section 550 South Vermont Avenue Los Angeles, California 90020

Dear Mr. Poppler:

We are placing on open file the following reports, reviewed and approved by the City of Los Angeles in compliance with the Alquist-Priolo Special Studies Zones Act:

//-=--, ··/1.'J-.) Engineering Geology Investigation, Dining Hall Addition, (_~ Camp Teresita Pines, 22801 Big Pines Highway, Wrightwood,

California: Gary S. Rasmussen & Associates, August 31, 1979, -Project No. 1551, 15 p.

2. Geologic Reconnaissance, .39120 Bouquet Canyon Road, Leona Valley, California: Michael V. Smith, Engineering Geologist, File No. 7958-1, October 16, 1979, 7 p.

3. Fault Study, Tax Parcel Number 3052-30-26, Palmdale, California: Michael V. Smith, Engineering Geologist, File No. 78-33, November 13, 1978, 9 p.

4. Fault Study, Tax Parcel Number 3052-18-23, Palmdale, California: Michael V. Smith, Engineering Geologist, File No. 7940-1, July 26, 1979, 8 p.

For your information: Site location maps are missing for reports 2, 3 and 4 listed above.

TLB/fnl

cc: A-P file ( ~)

Sincerely yours,

TRINDA L. BEDROSSIAN Office of the State Geologist RG 3363

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[~] Plan approved subject to conditions below Submit plans for te-ch~ck

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Remarks:

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I I I I I I I I I I I I I I I I I I I

ENGINEERING GEOLOGY INVESTIGATION DINING HALL ADDITION

CAMP TEREClTA PINES 22801 JUG PINES HIGHWAY WRlGHTl~OOD, CALIFORNIA

August 31, 1979

Project No. 1551

P mp a red for

Camp Terecita Pines 22801 Big Pines Highway Wrightwood, California

I I I I I I

I I I I I I I I I I

•• I

GARY S. RASMUSSEN & ASSOCIATES /ENGINEERING GEOLOGY

1!)06 so. COMME:RCENTER EAST, SUITE 20'7 • SA.N El!::RNARDINO, CA 92408 ~ (714) eee-242.2. • (714) 825·90~.2

August 31, 1979

Camp Tereci ta f'i.nes 22801 Big Pines Highway Wrightwood, California 92397

Att: Ralph Hullman

Project No. 1551

Subject: Dining Hall Addition, Camp Terecita Pines, 22801 Big Pines Highway, Wrightwood, California.

An engineering geology investiga.tion of the proposed dining hall addition for

Camp Terecita Pines has been conducted at your request. The purpose of our

investigation was to determine the geology of the area and to assess any poten­

tial geologic hazards to the proposed rebuilding of the dining hall addition.

We understand the new dining hall will be built on the existing foundation.

The former dining hall, built on the same foundation apparently collapsed in

February 1974 due to snow and wind loads. Camp Tereci ta Pines is located on

the north side of Big Pines Highway, east of Jackson Lake, in the Big Pines

recreation area of the Angeles National Forest. The camp is on the north facing

slope of the San Gabriel Mountains, in the NE \ of Section ·33, T4N, RSW, S. B. B. L.

f,M. The proposed dining hall addition for the camp is approximately 800 feet

north of Big Pines llighway and 1,800 feet east of Jackson Lake. The location

of the proposed dining hall addition is shown on the geologic index map on Page

2.

A geologic field investigation of Camp Terecita Pines was conducted on August

24, 1979. In addition, our invesl:igation included review of black and white

aerial photographs, flown in 1928, and color infrared photographs, flown in

1978; review of pertinent geologic literature; and review of significant seismic

data, including recorded, historic earthquakes. No subsurface exploration was

conducted for this study.

The area near the site was covered with a mature growth of pine, fir, and oak

trees at the time of our investigation. Man-made improvements in the camp in­

clude the cabins, swimming pool, bathing area, chapel, stage, and dining room;

and the entrance and service road for the camp.

I I I I I I I I I I I I I I I I I I I

-2-

GEOLOGIC INDEX MAP Camp Tcrecita Pines

Big Pines Recreational Area Angeles National Forest

Legend

@ Landslide

Qal Qoa be

ps

---

Younger alluvium Older alluvium

Gary S. Rasmussen & Associates, Inc.

I I I I I I I I I I I I I I ,. I I ,I I

Camp Terecita Pines Dining Hall Addition - Wrightwood August 31, 1979

GEOLOGIC SETTING

Project No. 1551

The camp is situated on the north side of a long ,linear valley of the San Andreas

.rift zone. The proposed dining ha.11 addition to Camp Terecita Pines is located

approxi.mately 800 feet north of the most recent break of the active San Andreas

fault as mapped by Ross (1969) and approximately 50 to 100 feet north of the

Alquist-Pri.olo Special Studies Zone as designated by the California Division of

Mines and Geology (Alquist-Priolo Special Studies Zone Map of the Mescal Creek

quadrangle).

In this general region, the area south of the San Andreas fault is characteristi­

cally underlain by white mica, quartz, feldspar, schist, with lesser amounts of

chlorite schist, quartzite, and talc-actinolite rock. North of the San Andreas

fault zone diorite, quartz monzoni te, gneiss and .myloni tic gneiss are the most

common rocks encountered. A thin sliver of the Miocene Punchbowl formation is

mapped along the north side of the San Andreas fault (Noble, 1953) but it was

not encountered during our investigation. Old, inactive faults parallel the San

Andreas fault both north and south of its main trace (Noble, 1953 and Dibblee,

1968a, 1968b, 1970, 1975) in this area,

Large scale landsliding is common within the Pelona Schist, and very Jarge land­

slide-mudflows have caused considerable p.roperty loss within the town of Wrightwood,

approximately 8 miles to the southeast. Small-scale landslides are also quite

common in the vicinity, and Camp Mctaka, which is approximately 1,800 feet south­

east of the site, :is currently being damaged by a landslide along the east fork

of Mescal Creek. The landslides in the area are caused by high levels of p1·eci-

pi tat:ion and/or seismic shaking affecting areas of high relief (Morton and Campbell,

1978, Kojan, 1979).

SITE GEOLOGY

The proposed dining hall addition for Camp Terecita P:ines lies on a relatively

planar surface which slopes downward to the north, approximately 10 degrees. In

a relatively undisturbed area south of the proposed dining hall addition, the

-3-0-ARY S. RASMUBSE:N' &. ASSOCIATES

I I I I I I I I ·I I I I I I I I I I I

Camp Terecita Pines Dining Hall Addition - Wrightwood August 31, 1979

Project No. 1551

surface clasts include a majority of white mica-quartz-feldspar Pelona Schist,

with lesser amounts of chlorite bearing schist, retrograde Pelona Schist mylonite,

quartzite, diorite, amphiboli te gneiss, and rare quartz monzoni te. The majority

of Pelona Schist clasts have well developed planar foliation, however, a few

clasts were observed which exhibit kink banding. Within the canyon along the

east side of the camp, tabular clasts of the Pclona Schist were observed near

the top portion of the formation where they lie parallel to the ground surface.

Most of the clasts are angular to subangular, however, a minor amount of rounding

has apparently occurred. Based on these observations, we infer that the material

on which the proposed din.i ng hall addition to Camp Tereci ta Pines is to be con­

structed is of alluvial and not mud flow orig.in.

The material within the mudflows emanating from Heath Canyon and Sheep Canyon rn

the Wrightwood area is almost exclus.ively composed of Pelona Schist detritus

which is angular, unsorted, and randomly arranged as to orientation of tabular

clasts. The landslide-mudflows in the Wrightwood area are three-stage cyclic

events (Morton & Campbell, 1978). The first stage is large-scale landslidi.ng at

the head of major canyons (Sheep and Heath Canyons). The second stage is smaller­

scale landsliding of the first stt•ge landslide mass. The third stage is the mud­

flow. Mudflows arc the most destructive and costly to the Wrightwood area of all

three stages of the failures. They occur when the broken up material of the second

phase slides become saturated with water during the spring thaw following periods

of high precipitation, thereby resulting in a cohesionless mass. Although numerous

small -scale landslides were observed on the aerial photographs on the steep slopes

south of Camp Terecita Pines, none were of the scale of the first-cycle landslide

within Heath Canyon and Sheep Canyon. The landslides, as opposed to mudflows,

within the Pelona Schist are generally moved only short distances at low velocities

(Morton and Campbell, 1978). The closest steep sloping mass of Pelona Schist

to the proposed dining hall addition to Camp Tereci ta Pines is located approxi­

mately 1,000 feet to the south. Based on the above and on field observations

landsliding does not appear to be a significant hazard to the proposed addition.

One small-scale debris slide was observed on the camp property approximately 600

feet north of the proposed dining hall addition. At this location, the very steep

-4-GARY S. RASMUSSE:N & ASSOCIATES

I I I I I I I '

I I I I I I I I I I I I

Camp Terecita Pines Dining Hall Addition, Wrightwood August 31, 1979

Project No. 1551

north facing stream bank is failing by intermittent shallow debris slides. This

slide, located adjacent to the chapel and stage, will probably some day affect

those two structures. The rate of advance of this slide should be monitored by

camp personnel.

A faint, west-northwest trending l.ineament was observed on aerial photographs

projecting toward the site. This lineament was not observed across the alluvium

under the site, docs not affect the surface grading of the alluvial material, nor

was it observed affecting very old, dissected landslide masses to the southeast

of the site. There is no evidence that the geomorphology of the camp has been

affected by the fault. Field investigation revealed that this lineament is a

fault affecting the bedrock southeast and northwest of the camp. Although no

subsurface investigation was undertaken for this study, the west bank of the

stream, which is incised approximately 30 to 35 feet into both the alluvium on

the west and the bedrock on the east, was examined for fault related features.

Al though much of the bank exposing alluvium was covered with slope wash and

colluvium, no indications of a fault or fault related features were observed

along the projection of the bedrock fault, where it was observed to the south-

east.

No absolute method of dating the alluvium under the site was available for this

study. The alluvium is interpreted as being Pleistocene in age, based on the

following evidence. The closest material south of the San Andreas fault which

has a geomorphic expression similar to that of the older alluvium under the site

is located approximately 2,000 to 3,000 feet to the northwest, within the drainage

on the west side of Jackson Lake. This suggests that the older alluvium has

been offset, in a right-lateral manner a minimum of approximately 2,000 to 3,000

feet since its deposition. Sieh (1978) suggests an offset rate for this portion

of the San Andre"s fault of 3. 7 cm per year based on his investigation of this

porti,on of the San Andreas fault (Sieh, 1971). Using the 3. 7 cm per year offset

rate, the suggested offset equivalents across the San Andreas fault would indicat:e

an age of between 16,SOO years and 24,700 years for the deposition of the alluvium

under Camp Terecita Pines. It is, however, possible that the source of the alluvium

under the site was from a canyon farther to the northwest, which would indicate

-S-O.AR¥ $,RASMUSSEN & ASSOCIATES

I I I I I I I I I I I I I I I I I I I

Camp Terecita Pines Dining Hall Addition, Wrightwood August 31, 1979

Project No. 1551

an even older age for the material. Based on the evidence that the fault in the

bedrock apparently does not offset the alluvial material under the camp, the

old dissected landslides to the southeast of the camp have not been offset by

the fault, and the fault does not exhibit a geomorphic expression through the

older alluvium, it appears that the fault is inactive, presenting minimal hazard

to the site from a surface rupture standpoint. It is remotely possible that during

a major event on the San Andreas fault, approximately 800 feet south of the pro­

posed dining hall addition, minor differential settlement or sympathetic movement

could occur along the old fault plane, therefore, we suggest that the addition

be designed to w.ithstand minor tensional cracking.

SEISMIC SETTING

The west-northwest trending San Andreas fault zone, located approximately 800 feet

south of the proposed ·dining hall addition for Camp Terecita Pines, is the most

significant tectonic feature in the area. Other active faults of significance

in the area are the San Jacinto fault and the Cucamonga fault.

Other active faults are located in the general region, hut they are considered less

significant to the site. than the above mentioned faults because of their greater

distance and/or lower probability of having a significant earthquake occur along

them which m:ight affoct the proposed dining hall addition. A summary of the major

faults and their distances from the site is shown in the following table;

FAULT

San Andreas

San Jac.i.nto

Cucamonga

SEISMIC HISTORY

DISTANCE FROM SITE (MILES)

800 feet SSW

6 SE

15 s

The San Andreas, San Jacinto, and Cucamonga fault zones are all considered to be

active faults. The San Andreas fault has been seismically quiet along its south

central reach ln southern Cali fomia in recent times. The last significant earth-

-6-GARY$. RASMUSSEN & ..ASSOCIATES

I I I I I I I I I I I I I I I I I I I

Camp Terecita Pines Dining Ilall Addition, Wrightwood August 31, 1979

Project No. 1551

quake along it was the great Port Tejon earthquake of 1857, centered near Port

Tejon, north of Gorman, which ruptured the ground surface along the fault 800

feet southwest of the dining hall. The San Andreas fault in this area has a

pattern of almost no movement for long periods of time (160± years, Sieh, 1977)

followed by a sudden release of large amounts of energy and related surface

rupture. The Port Tejon earthquake had an estimated Richter magnitude of 8\+

(Sieh, 1978) which is comparable to the 1906 San Francisco earthquake. A minor

earthquake on 28 August, 1979 with a Richter magnitude of 3.5 was centered within

approximately 5 miles of the site. No ground rupture was associated with this

earthquake.

Numerous earthquakes between Richter magnitude 6.0 to 7.0 have occurred along the

length of the San Jacinto fault zone between the San Gabriel Mountains and Mexico

during historic times. Since 1890, an earthquake within this magnitude range

has occurred somewhere along the fault a.t least once every 5 to 6 years (Lamar,

et.al., 1973). Several of these earthquakes were centered in the Lytle Creek

area, approximately 8 miles from the site.

Documented evidence for large earthquakes along the Cucamonga fault has not yet

been found. However, this fault is pat·t of the Sierra Madre-Cucamonga fault

system which did move in the 1971 San Fernando earthquake of Richter magnitude

6.4. A subsurface investigation in progress by the U.S. Geological Survey has

uncovered evidence of Holocene activity along the Cucamonga fault (personal

communication, Morton, Tinsley, and McFadden, .June, 1979).

SEISMIC ANALYSIS

The most signific;mt earthquake affecting the site is likely to occur on the San

Andreas fault during the life of the proposed dining hall addition. Significant

earthquakes affecting the site are also likely to occur on both the San .Jacinto

and Cucamonga faults. A recurrence interval of approximately 160:!: years for

major earthquakes along the Sun Andreas fault is suggested by Sieh (1977) based

on his investigation of sediments along Pallet Creek, approximately 10 miles

northwest of the site. The last significant earthquake along the San Andreas

affecting thi.s site occurred on January 9, 1857. Recurrence intervals for maximum

-7-GARY $. R..ASM'U'SSEN & .ASSOCIAT~S

I I I I I I I I I I I I I I I I I I I

Camp Terecita Pines Dining Hall Addition, Wrightwood August 31, 1979

Project No. 1551

probable earthquakes along the San Jacinto and Cucamonga faults cannot yet be

determined from a statistical standpoint as recorded information on seismic

activity does not encompass a sufficient span of time, and no detailed analyses

of sediments along either of these two faults, sililar to that undertaken at

Pallet Creek by Sioh (1977), have been reported. Based on the information

available at this time, it is our opinion that a probable earthquake of Richter

magnitude S.O+ shot1ld be expected (at least 50 percent chance of occurrence

wi.thi.n the next 100 years) along the San Andreas foul t 800 feet south-southwest

of the proposed dining hall. Larger earthquakes could possibly occur on any

of these foul ts, but their probability of occurrence for that time period is

low. A Richter magnitude 8.0 earthquake along the San Andreas fault zone should

be expected to produce a maximum peak ground acceleration Jn bedrock under the

site of approximately 0.7Sg+ (Schnabel & Seed, 1973). This corresponds to a

maximum repeatab_le bedrock acceleration of 0.49g+ (Ploessel & Slosson, 1974).

These accelerations should not be used as a design value as they are maximum

accelerations in bedrock, estimated to he at least 30 to SO feet beneath the site;

rather, they should be regarded us an aid in the structural evaluation of the

proposed building.

Large earthquakes may occur on other faults in the area, but are considered less

significant to the site because of their greater distance or lower probability

of occurrence than the above.

HYDROLOGY

Streams were observed fl owing in the drainages east, north and west of the site.

These streams are currently flowing approximately 30 feet below the surface of

the alluvium on the site. No springs were observed issuing from the alluvium

within the incised drainages bounding the site. The streams within the drainages

are interpreted as being zones of infiltration of ground water, as opposed to

zones of exfUtration, because of the close proximity of the effective ground

water barrier, the San Andreas fault, above (south of) the site. Ground water

is therefore, probably at least 30 feet beneath the ground surface under the

site.

-8-GARY S. RASMUSSJi;:N &; A$$0Cl.A'I'ES

I I I I I I I I I I I I I I I I I I I

Camp Terecita Pines Dining Hall Addition, Wrightwood August 31, 1979

FLOODING

Project No. 1551

The drainages wh:i ch currently flow east, south and west of the site are somewhat

prone to flooding. However, because of the deep entrenchment of these stream

courses, flood:i ng of the building site is highly unlikely. This is further

substantiated by the occurrence of large (4 to 5-foot diameter) fir trees, esti­

mated to be of the order of 300 to 500 years old, growing on terraces, approxi­

mately 15 to 20 feet below the surface of the building site. Seismically induced

flooding of the drainage on the west s:i de of the camp is possible as the dam for

Jackson Lake is built directly upon the main, active trace of the San Andreas

fault. Because of the small volume of water within Jackson Lake, and the size

of the incised drainage on the west side of the site, any flooding probably

would not affect the proposed building itself.

CONCLUSIONS

Severe seismic shaking of the proposed dining hall addition can be expected

within the next 100 years. This shaking is expected to be no more severe for

this site than for other sites in the vicini tY.

A photo lineament projecting through the site was observed in the field to be

a bedrock fault, and does not affect the Pleistocene alluvium under the proposed

dining hall. This fault is considered to be inactive, presenting minimal hazard

to the site from a fu.ult rupture standpoint. However, it is possible that sym­

pethetic movement or differential settlement could occur along the fault. This

apparently did not occur during the 1857 earthquake.

Because of its position, the proposed building is not prone to being inundated

by landslides or debris flows. A small-scale debris slide is located in the far

northern portion of the site, along the steep stream bank, near the chapel a.nd

the stage.

Liquefaction is not expected to be a problem because of the coarse, poorly sorted

natore of the sediments, their probable Pleistocene age and high density, and

-9-G.ARY $. RASMUSSEN &. ASSOClA'I'ES

I I I I I I I I I I I I I I I I I I I

Camp Terecita Pines Dining Hall, Wrightwood August 31, 1979

Project No. 1551

the estimated minimum depth to ground water of at least 30 feet.

Flooding and se·i smically Jnduccd flooding is not expected to be a hazard to the

building because of the deeply incised drainages on the cast, north and west.

RECOMMENDATIONS

A Richter magnitude 8 .. 0 earthquake is expected along the San A:nd.reas fault zone

(800 feet south-southwest of the proposed dining hall addition); therefore, we

recommend human occupancy structures be designed accordingly.

A slight possibility for syinpethetic movement or d.i fferential settlement along

the older, inactive fault which projects near the building is possible; there-

fore, we suggest this be taken into consideration during the design of the proposed

addition,

Because of the debris slide fai.lure along the northern margin of the camp, we

recommend a minimum setback for human occupancy structures from the top of

slopes above existing incised drainages should be the greater distance calculated

from the following two methods: 1) A 2: 1 (horizontal to vertical) plane,

extending upward from the toe of the steep slopes, If several oversteepened

slopes exist on any one slope, the setback shoul cl be the farthest from the

top of tho slope (see Enclosure l); 2) A horizontal distance equal to J, the

vertical height (distance from tho top edge of the steep slope to bottom of

drainage). The Soils Engineer may impose greater restrictions and recommended

setbacks based on slope stability analysis using actual shear parameters, how­

ever, the recommended setback (greater of the two possibilities) is considered

to be a minimum from a geologic st<>ndpoint.

Much of Camp Tcrcci ta Pines south of the proposed dining hall add:i tion lies

within an A:lqui st-Priolo Special Studies Zone as illustrated on the index map

on page 2; therefore, we recommend that no human occupancy structures be planned

for that portion of the site unless a detailed subsurface investigation is under­

taken by an engineering geologist in accordance with the Alquist-Priolo Special

-10-GARY $. R.A$:t.!!t,;T$SEN & A$$0C.t.ATE$

I I I I I I I I I I I I I I I I I I I

camp Terecita Pines Dining Hall Addition, Wrightwood August 31, 1979

Studios Zones Act.

Project No. 1551

Please feel free to contact us if you have any questions regarding this report.

TES:GSR/rc

Respectfully submitted,

GARY S. RASMUSSEN & ASSOCIATES

~c.S~ Thomas E. Spittler Staff Geologist

Gary S. Rasmussen Engineering Geologist, EG 925

Enclosures; 1: Slope Setback Illustration 2: References

Distribution: John Fortune and Associates (5) Tcrecita Pines, Inc. (1)

-11-GARY$. E.1\.SWUSSEN &. ASSOCIATES

I I I I I I I :1 I I I I I I I I I I I

------

Slope Setback Illustrations

ground surface~

ground surf;lcc-......._

2;1

f'NCLOSlJRE l

J1.iini1num rcconuncnded set buck

GARY S. R~SMUSSEN & ASSOCIATES, INC. Project No. 1551

I I I I I I

I I I I I I I I I I I I

REFERENCES

Allen, C.R., Saint Amand, P., Richter, C.F., and Nordquist, J.M., 1965, Relationship between seismicity and geologic structure in the southern California region: Seismological Society of America Bulletin, V. 55, No. 4, p. 753-797.

Bennett, .J.H., and Rodgers, P.A., 1975, Crustal Movement Investigations along the San Andreas fault in southern California, in COMG Special Report 118, p. 53-60.

Bolt, B. A., 1970, Causes of earthquakes, Earthquake Engineering, Prentice­llall, Englewood Cliffs, Ch. 3, pp. 21-47.-

Bonilla, M.G., 1970, Surface fault.ing and related effects in earthquake engineering, .!Jarthqmike l!ngin.cering, Prentice-Hall, Englewood Cliffs, Ch. 3, pp 47-74.

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