gmw.consrv.ca.govgmw.consrv.ca.gov/shp/apsi_siteinvestigationreports_ocr/apsi_001722/apsi_001722...sep...

• •• ST.ATE Of CALlfORNIA~-THE RE$0URC:E5 AGENCY G[QR(;E' pClJKMEJ1AN, Go~rnor ====o============================================---======="====o====o== DE:PARTMENT Of CONSERVATION

DIVISION OF MINES AND BAY AREA REGIONAL OFFICE 380 CIVIC DRIVE, SUITf 100

PLEASANT Hill, CA 94523-1997

!'HONE: (415) 671--4910

Becky Newton Bui 1 cling Department City of Desert Hot Springs 11-711 West Drive Desert Hot Springs, CA 92240

Dear Ms. Newton;

26, 1984

We are placing on open file the following report, reviewed and approved by the City of Desert llot Springs in compliance with the Alquist-Priolo Special Studies Zones Act:

cc:

Engineering geology investigation of Lots 1,2,48 and 49, Block D, Tract 3 immediately southwest of the intersection of Palm Drive ancl Acoma Avenue, Desert !lot Springs, CA; by Rnsmussen & Assoc.; September 28 1 1984.

A-P file V/

Sincerely yours,

EARL W. HART Senior Geologist

,

CITY of DESERT HOT SPRINGS

December 14, 1984

Mr. Earl W. Hart Office of the State Geologist Department of Conservation Division of Mines and Geology San Francisco District Office Ferry Building San Francisco, California 94111

Please place the following Engineering Geology Investigation by Gary S. Rasmussen & Associates on file.

Desert Hot Springs Tract 3, Lots 1, 2, 48 and 49, Block D, immediately southwest of the intersection of Palm Drive and Acoma Avenue.

Also enclosed find a copy of the Geotechnical Report Review by Douglas Moran, Incorporated.

Please send acknowledgement of receipt of these items for filing. If you have any questions, please contact the Building Department.

Sincerely,

~)Lz1Ji1L(/!'~fi/Ji)/\ BECKY NJ$iTON ' Building Department

··· ... _

1 I 711 WcSI UHIVF. DEQcRT HOl SPRING0, CAI lfORNIA ~2240. TFI [PHO NF (619) 32a-6411 THE SPA CITY

DOUGLAS E. MORAN, iNC. ENGINEERING GEOLOGY

CIVIL ENGINEERING

December 10, 1984

Job No.: 84-66

city.of Desert Hot Springs

11-711 West Drive ~~~~ilW!E@ Desert Hot Springs, California 92240 Lt~ C 13 1984

Attention: Ms. Becky Newton CITY OF

DESERT HOT SPRINGS

Subject: Geotechnical Review of Report

by Gary s. Rasmussen and Associates

"Engineering Geology Investigation,

Lots 1, 2, 48 and 49, Block D, Tract 3,

Immediately Southwest of the Intersection of

Palm Drive and Acoma Avenue

Desert Hot Springs, California"

Dated September 28, 1984

Your Purchase Order No. 3234

Dear Ms. Newton:

As requested by your letter of November 16, 1984, we have re

viewed the above-described geotechnical report. The report is

considered satisfactory for its intended purposes, namely: to

satisfy the requirements of the Alquist-Priolo Special Studies

Zone Act, to determine the general ~eismicty of the area, and

to relate general geologic conditions of the site to future

commercial development.

150 S. PROSPECT AVENUE, TUSTIN, CALIFORNIA 92680 * (714) 544-2215

.. City of Desert Hot Springs

Ms. Becky Newton

-2- December 10, 1984

Job No.: 84-66

Evidence of recent rupture of the alluvial sediments that cover

the subject property has been found and related to other evi

dence of active faulting in the vicinity. The evidence has

been described appropriately, and appropriate recommendations

have been made.

A diagrammatic map of the property which was included in the

report (Enclosure 3) illustrated recommendations made regard

ing restricted use. However, the map deserves clarification.

Two lines labeled " ... limits of recommended .restricted use

zone ... " are shown on the map. One is labeled "southwest

limits ... " and the other is labeled "northeast limits ... ".

However, there is no north arrow on the map. The labeling

would have meaning were it shown that Palm Drive runs north

south and that Acoma Avenue runs along the northerly boundary

of the subject property. The text of the report explains that

the two lines shown represent outer limits of separate re

stricted use areas, between which restriction of use is not

recommended.

The consultant has anticipated that ground water levels will

remain stable and so concludes that neither liquefaction nor

subsidence are expected to occur. However, no basis for the

anticipation of stability is provided by the report. It may

be reasonable to anticipate that ground water levels will

remain too low to facilitate liquefaction (in this arid envir

onment). However, it may not be reasonable to anticipate

that ground water levels will not be drawn down.

Subsidence attributable to lowering of ground water levels

has caused some damage to structures existing in the vicinity

DOUGLAS E. MORAN, INC. • TUSTIN, CALIFORNIA

,. ' •.

City of Desert Hot Springs

Ms. Becky Newton

-3- December 10, 1984

Job No.: 84-66

of the subject site, and so it is prudent to consider the

potential impact of further subsidence.

A capacity to resist the kind of damage that might be caused

by regional subsidence can be incorporated into the design of

structures to be built on the site. Accordingly, we recommend

that the possibility of subsidence be considered and that

structures be designed to resist damage due to the effects of

subsidence. This should be done in connection with evaluation

of foundation soil conditions on the site and development of

criteria for foundation design.

With this reservation, we recommend acceptance of the report

reviewed and approval of the conclusions and recommendations

incorporated in the report.

It has been our

matter.

call.

If you

/lw

Distribution:

pleasure

have any

to have been of service to you in this

questions concerning this review, please

Very truly yours,

DOUGLAS E. MORAN, INC.

WDi-------

(3) Addressee

(1) Gary S. Rasmussen & Associates

DOUGLAS E. MORAN, INC. • TUSTIN. CALIFORNIA

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

GARY S .. :RASMUSSEN & ASSOCIATES /fl.IVG/NEERING GEOLOGY

1$11 £0. COMMERCl:O.NTE:R W·EST • SAN BCRNARDINO. C:Al.IFORNIA !J.2408 • (714) 800-2422 • (7!4\ 825.90!3~

ENGINEERING GEOLOGY INVESTIGATION OF LOTS l, 2, 48 AND 49, BLOCK D, ·rRACT 3

IMMEDIATELY SOUTHWEST OF THE INTERSECTION OF PALM DRIVE AND ACOM!\ !\VENUE

DESERT HO'r SPRINGS, CALIFORNIA

September 28, 1984

Project No. 2066

Prepared for

The Fisher Associates 3465 Torrance Boulevard, Suite N

Torrance, California 90503


GARY S. RASMUSSEN & ASSOCIATES /ENGINEERING GEOLOGY

H~11 SO. COMMERCE~lTEF\ Wfi',,;1'. SAN BERNAFlr:liNO, CALlrORNIA 9~40a • (7141 888-2422. • <714 1 825-9052

September 28, 1984

The Fisher Associates 3465 Torrance Boulevard, Suite N Torrance, California 90503

Attention: Lawrence Black

Project No, 2066

Subject: Engineering Geology Investigation of Lots 1, 2, 48, 49, Block D, 'l'ract No. 3, Immediately Southwest of the Intersect:ion of Palm Dri.ve and Acoma Avenue, Desert !lot Springs, California.

A subsurface engineering geology investigation of Lots 1, 2, 48, 49, Block D, 'rract No. 3, Desert Hot Springs, California, has been conducted in accordance with your request. The purpose of the investigation was to determine if any active faults have ruptured the upper 10 feet ot natural sediments in ot"der to satisfy the requit"ements of the Alquist-Priolo Special Studies Zones Act, to determine the general seismicity of the area, and to relate general geologic conditions of the site to future commercial development.

No plans were available at the time of our investigation; however, we understand that one- or two-story construction is anticipated on Lots land 2, with Lots 48 and 49 to be utilized as a parking area. Based on the existing topography, maximum cut and fill slope heights are expected to be less than 5 feet, A 200-scale topographic map, prepared by Riverside County Flood Control and water Conservation District, and an assessor's parcel map were used in our investigation.

SIT!:: lNVI::STIGATION

A geologic field reconnaissance of the site and surrounding area was conducted during September 1984. ln addition, our investigation included review of stereoscopic aerial photographs flown in 1939, 1955, 1957, 1970, 1972 and 1974; review of pertinent geologic literature and maps, including reports in our files on projects in the inunediate vicinity of the site; and review of significant seismic information, including recorded, historic earthquakes, A list of references is included as Enclosure 5.

- 1 -

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

/ /

INDEX HAP

The Fisher Associates Alquist-Priolo Spec. Studies Zon

Desert Ho\J'/cflJ'gs, California

Special Studies Zone boundary

Fault; dashed where --···approx., dotted wher

buried

Gary s. Rasmussen & Associates, Inc.

-lA-

) '


The Fisher Associates Lots 1,2,48 & 49 September 28, 1984

Project No. 2066

The site consists of four lots totaling approximately 2/3 of an acre in area. The site is located immediately southwest of the intersection of Palm Drive and Acoma Avenue, Desert Hot Springs, California. The site is bounded on the west by a single-family residence and on the south by vacant lots. A buried, north-south-trending utility line traverses the central portion of this site along the eastern margin of Lot 49. The site slopes to the south at a rate of approximately 3 percent. At the time of our investigation, the site was occupied by a light growth of desert vegetation and by several unpaved roads and footpaths. Minor amounts of trash and construction debris were observed on the site. A minor amount of fill was observed on the northeast corner of the site. This fill is expected to be surficial only and should be addressed by the soils engineer. The site has apparently not been utilized for structures in the past and was J.n a relatively undisturbed state.

The entire site lies within an Alquist-Priolo Special Studies Zone. The Alquist-Priolo Special Studies Zone in the vicinity of the site is designated to include suspected traces of active faulting associated with the Mission Creek fault.

Two backhoe trenches approximately 10 feet deep were excavated in a northeast to southwest direction across the site in order to intercept any northwest-trending faults associated with the Mission Creek fault zone, The trenches were entered and logged by an engineering geologist. The excavation of two separate trenches was necessary to avoid rupturing subsurface utility lines at the eastern boundary of Lot 4 9. The sides of the trenches were sloped, and the trenches were approximately 6 to 8 feet wide at the surface, Approximately 269 linear feet of trench was excavated. The on-site sediments were broken into seven generalized units. Classification of the sediments into these soven units was based on lithology, not on relative age. The logs and unit descriptions are included as Enclosure 4. After the trenches were logged, they were backfilled in shallow lifts and flooded with water until they were saturated to aid iri consolidation of tile backfill material. The upper trench backfill was wheel rolled with a backhoe,

- 2 -G·ARY S. RASMUSSJI:N & ASSOCl:..h.'rlCS



SITE GEOLOGY

Project No. 2066

The site lies at the northern end of a northwest-trending basin known as the Salton Trough. The Salton Trough extends from the southern end of San Gorgonio Pass to the Gulf of California. The Salton Trough is characterized by geologically rapid rates of subsidence and sedimentary infilling associated with movement along numerous faults in the San Andreas fault system.

The general area surrounding the site is characterized by a series of relatively young, coalescing alluvial fans emanating from the Little San Bernardino Mountains, approximately one mile northeast of the site. Surficial sediments on the site are considered to be Holocene in age (Proctor, 1968).

Geologic examination of the trench walls revealed the on-site alluvial material to consist of sands and gravels deposited by alluvial streams emanating from the Little San Bernardino Mountains. Although the exact age of sediments at a depth of 10 feet is not known, they are estimated to be on the order of .l, ODO years in age based on the following characteristics: l) stratigraphic position with respect to younger alluvial channels in the area; 2) the geomorphology of the bajada (alluvial apron) beneath the site and surrounding area; 3) the lack of significant soil development and the lack of significant in situ clast weathering; and 4) degree of consolidation of the material. No datable radiocarbon material was found in the trenches.

Evidence of active faulting was found in Trench l in the form of offset beds, caliche-filled fractures, and rotation of prolate clasts within shear zones. Absolute sense of offset was not determined in this study, but is probably primarily right-lateral strike-slip with a minor vertical component. No evidence of active faulting was observed in Trench 2. 'rhe width of the zone of faulting exposed in Trench 1 is approximately 45 feet. It is our opinion that the faulting observed within Trench l represents the northeastern portion of the Mission Creek fault zone. The main trace of the Mission Creek fault is suspected to be located inunediately southwest of the southwest corner of the site, based on the geologic field reconnaissance and the aerial photographs reviewed.

- 3 -GARY S. RAS:M:USS:EDN &, .ASSOCIAtrEB



Project No. 2066

A lath marked "TlB" was placed at the location of the northeasternmost fault (Station 65) and was located with a Brunton compass and a 100-foot fiberglass tape so that the exact location of faulting could be defined and setbacks recommended.

SEISMIC SETTING

The most significant fault to the site from a seismic shaking standpoint is the Mission Creek fault. 'l'hu northwest-trending Mission Creek fault is considered to be the north branch of the San Andreas fault in the Upper Coachella Valley area, This fault has been mapped by Proctor ( 1968) as passing through the southwest portion of the site, The Mission Creek fault can be observed through the southeast portion of the City of Desert Hot Springs on the 1939 aerial photographs as a prominent southwest-facing fault scarp which has been altered by sand dune deposits and erosion, Through the central and northwest portion of the city of Desert Hot Springs, the fault is defined by a prominent vegetation lineament, The Mission Creek fault is believed to be responsible for the Richter magnitude 6.5 earthquake in the Desert Hot Springs area in 1940 (Ricl1ter, et,al., 1958), and is considered to be active. The Mission Creek fault in this area is a right-lateral, strike-slip fault with reverse movement (north side up), The primary movement along the fault is expected to be horizontal with a lesser amount of vertical movement likely during significant earthquakes along this fault. Surface fault rupture is expected along this fault zone in this area within the next 100 years.

The geologic map by R.J. Proctor (1968) shows the buried trace of the Miracle Hill fault approximately 1,500 feet northeast of the site. The fault is well exposed within the older sediments of Miracle Hill; however, its position within the alluvium is based on differences in ground-water temperatures measured within widely spaced wells northwest of Miracle Hill. A prominent lineament can be observed on the 1939, 1955 and 1957 aerial photographs, which corresponds to the Miracle !Jill fault within the Pleistocene alluvium of Miracle Hill. Subtle lineaments in the Holocene alluvium can be seen on the 1939, 1955 and 1957 aerial photographs. 'l'he 1 inoaments are subparallel to the extrapolated trace of the Miracle Hill fault and have been interpreted by the State of California to represent a

- 4 -



northwest continuation of the Miracle Hill them are included within the Alguist-Priolo Zone for the Desert Hot Springs area.

Project No, 2066

fault. Some or Special Studies

The Miracle Hill fault has been plotted by Proctor (1968) as passing through Miracle Hill and extending to the northwest, passing approximately 1,500 feet northeast of the site. Proctor's (1968) location of the Miracle Hill fault is only approximate, as it was based on widely sea ttered data on ground-water temperatures. Three subtle northwest-trending lineaments northwest of Miracle Hill that merge with the Mission Creek fault suggest that the Miracle Hill fault may trend significantly more westerly than shown by Proctor (1968), The three lineaments arc visible on the 1939 aerial photographs, One of the lineaments extends from the northeast side of Miracle Hill and passes approximately 200 feet northeast of the northeast corner of the site. Although the lineament is only readily apparent in Pleistocene-age materials, it does exhibit a subtle expression in materials of Holocene age. However, subsurface investigations by our firm (Rasmussen, November 2, 1977; February 22, 1980) did not encounter evidence of active faulting at the location of this lineament approximately one mile southeast of the site. Trench 2 excavated on the site revealed no fault features, and active faulting is not expected on that portion of the site northeast of the faulting encountered in the southwestern portion of the site.

Another significant fault in the area is the north-northwest-trending Blind Canyon fault, located approximately one mile northeast of the site. Not all geologists concur on the state of activity of the Blind Canyon fault; however, based on a subsurface investigation by this firm (Rasmussen, July 10, 1979; May 24, 1977), we conclude that the Blind Canyon fault is probably active.

The Banning fault is located approximately 3 1/2 miles southwest of the site, The Banning fault has been referred to as the south branch of the San Andreas fault. The exact structural relationship between the Banning fault southwest of the site with the true south branch of the San Andreas in the Burro Flats area northwest of Cabazon has not, as yet, been clearly demonstrated or understood. The Banning fault is considered to be an active fault east of Cabazon and is currently included within an Alquist-Priolo Special Studies Zone.

- 5 -0.A'.RY' S. RASMUBS~N & ASSOCIATK:S


The Fisher Associates Lots 1 1 2 1 48 & 49 September 28, 1984

Project No. 2066

The Long Canyon fault, located approximately 3 l/2 miles east of the site, is another prominent north-trending fault within the foothills of the Little San Bernardino Mountains. The Long Canyon fault is probably structurally related to the Blind Canyon fault and may also be an active fault.

A summary of significant faults and their distances from the site is presented in the following table:

FAULT

Mission Creek Miracle Hill Blind Canyon Banning Long Canyon Morongo Valley Pinto Mountain

DISTANCE (MILES)

on-site 1500 feet 1 3 1/2 3 1/2 8 1/2 9 1/2

DI REC'l' l ON

Northeast Northeast Southwest

East North North

Other active or potentially active faults are located within the general region, but because of their greater distance from the site and/or lower expected maximum probable earthquake, they are considered to be less significant to the site.

ON-SITE FAULTING

The location of the Mission Creek fault as plotted by Proctor and as shown on the Special Studies Zones map is based on a veg eta tional lineament which appears on aerial photographs. The 1939 aerial photographs clearly show this vegetational lineament immediately west of the northwest corner of the intersection of Palm Drive and Buena Vista Avenue. 'l'he lineament appears to pass near the southwest corner of the site on the 1939 aerial photographs. Trenches excavated by our firm during previous investigations across this vegetational lineament at five locations have encountered the Mission Creek fault coincident with the vegetational lineament (Rasmussen, August 16, 1977; November 21, 1977; January 15, 1979; January 18, 1979; and April 17, 1979). Subsurface investigations by this firm in the Desert Hot Springs area have shown that the width of the zone of faulting on the Mission Creek fault ranges from 48 feet to 105 feet (Rasmussen, 1979). Faults exposed in Trench l on the site may be coincident with the vegetational lineament

- 6 -O.ArtY 8. RASMUSSliiN &:. ASSOCIATJl:S



Project No, 2066

and probably represent the northeasterly extent of the Mission Creek fault. Trenches excavated on the site did not reveal the main trace of the Mission Creek fault, It is our opinion that the main trace of the Mission Creek fault occurs immediately southwest of the southwest corner of the site.

SEISMIC HISTOHY

The accuracy of locating earthquake epicenters is not always sufficient to determine what fault they are associated with, Estimates of magnitude and epicenter location for earthquakes prior to implementation of recording instruments were based on descriptions of the earthquakes by individuals in different areas, Seismic instrumentation did not become available until about 1932, and these earlier instruments were imprecise. The earthquake locations shown on Enclosure 2 are either based on instrument locations or by analysis of isoseismal contouring,

The most significant historic earthquake in the area was the Richter magnitude 6.5 Desert Hot Springs earthquake of December 4, 1948, Although the epicenter for this earthquake was located in the foothills of the Little San Bernardino Mountains, the subsurface movement or focus of the earthquake is believed to have occurred along the Mission Creek fault at depth (Richter et.al., 1958). Therefore, the effective area of energy release at the surface may have been considerably closer to the site than the reported epicenter.

The Imperial Valley earthquake of 1940 has been reported with Richter magnitudes ranging from 6.7 to 7,1. On October 15, 1979, a Richter magnitude 6.6 earthquake (Real et.al., 1979) occurred approximately 12 miles south of the Mexican border and ruptured the ground surface at the same general location that was reported during the 1940 Imperial Valley earthquake. Therefore, at least three earthquakes of Richter magnitude 6. 5 to 7. l have occurred along tne San Andreas fault zone in this region in the last 50 years.

- 7 -0-A.'.Fl-Y $. :A..ASMUSSlCN ~ .A.SSOCIAT:m.S



Project No. 2066

SEISMIC ANALYSIS

The Mission Creek fault, located on the site, is to be an active fault based on seismic geomorphology and previous subsurface investigations. Surface fault rupture through within the next 100 years should be expected.

considered history, geologic

the site

Recurrence intervals for maximum probable earthquakes cannot yet be precisely determined from a statistical standpoint, as recorded information on seismic activity does not encompass a sufficient span of time. However, based on information available at this time, it is our opinion that a maximum probable earthquake of Richter magnitude 7. 5 along the Mission Creek fault should be expected (at least 50 percent chance of occurrence within the next 100 years). Large earthquakes could occur on other faults in the general area, but because of their greater distance and/or lower probability of occurrence, they are considered less significant to the site from a seismic shaking standpoint.

Schnabel and Seed (1973) present data which show" relatively simple relationship between the distance from " causative fault and the ground accelerations in bedrock. Dased on the data of Schnabel and Seed (1973) for a Richter magnitude 7.5 earthquake along the Mission Creek fault, located on-site, a maximum peak acceleration in bedrock under the site would be greater than 0.73g. This corresponds to a maximum repeatable bedrock acceleration of Q,47g (Ploessel µnd Slosson, 1974). These accelerations should not be used as a design value for insertion in the Uniform Building Code formula; rather, they should be considered as an aid in the evaluation of the structural design of the commercial structures to be placed on the site.

GROUND WATER

Based on data from a water well approximately 700 feet northwest of the site (Jim Coats, Desert Hot Springs County Water District, personal communiciltion, September 24 1 1984), the depth to static ground water is estimated to be greater than 80 feet below the existing ground surface. Due to the depth to ground water beneath the site, liquefaction is not considered to be a potential problem. Water well data !n the area of the site (Tom Clem, Riverside County Flood

- 8 -



Project No. 2066

Control, personal communication, September 21, 1984) indicate that water-table elevations have stabilized since the mid-1970 's after a steady decline. Water in the basin beneath the site is relatively warm and is currently subject to only minimal extraction. A significant decrease of ground-water table elevations in the basin beneath the site in the near future is not expected.

SUBSIDENCE

Cracking of many buildings and parking lots in the Desert Hot Springs area may be evidence of regional subsidence of the area due to a general decrease in ground-water table elevations. Subsidence beneath the site in the near future is not expected due to the anticipated stability of ground-water table elevations in the basin beneath the site. If the ground-water table is allowed to decline significantly in the future, subsidence cracking could occur on the site and in the general area northeast of the Mission Creek fault.

FLOODING

The site does not lie within a 100-year flood plain as shown on the Riverside County Safety Element to the General Plan (1976).

The nearest 100-year plain is approximately 3,700 feet northeast of the site. The 1939 aerial photographs reveal a south-trending drainage approximately 300 feet east of the site. Existing flood control measures should at least partially mitigate the potential for flooding of the site. Significant flooding of the site is not expected, assuming existing flood control channels are adequate.

No large water storage reservoirs are located in the vicinity of the site topographically higher than the site; therefore, seismically induced flooding is not considered to bE.' a hazard to the proposed development at this time,

- 9 -0-A-.;A.Y S. RASMU6Sll:N & ASSOCIA-rES



CONCLUSIONS

Project No. 2066

The active Mission Creek fault zone passes through the southwest portion of the site as shown on tho index map on page lA and on Enclosure numbers 1, 3 and 4. This fault is considered to be active and surface rupture within the fault zone is expected in the next 100 years.

Severe seismic shaking of the next 100 years from Creek or Banning faults.

the site can an earthquake

be expected within along the Mission

Liquefaction and other shallow ground-water related hazards are not expected, as the ground-water table is estimated to be greater than 80 feet below the surface.

Earthquake induced flooding of the site is not expected to be a potential hazard, as there are no large bodies of water at higher elevations than the site in the immediate area.

This area is subject to occasional wind-blown sand.

Due to the anticipated stability of the ground-water table elevations in the basin beneath the site, subsidence beneath the site is not expected in the near future.

The trenches were flooded during backfilling to aid in the consolidation of the trench backfill. No compaction testing was conducted on the trench backfill.

RECOMMENDATIONS

Human occupancy structures should not be placed within the recommended restricted use zones as shown on Enclosure 3. The northeast limit of the southwestern zone trends N36W and is located 50 feet along a line trending N54E from Lath TlB, Lath TlB is located 100 feet south of the centerline of Acoma Avenue and 241 feet west of the centerline of Palm Drive. The southwest limit of the northeastern recommended restricted use zone trends N36W and is located 2 feet along a line trending S54E from Lath 2B. Lath 2B is located 10 feet south of the northern property boundary and 11 feet west of the eastern property. The area northeast of the southwest limits of the restricted use zone as shown on Enclosure 3 includes the portion of the site not covered by

- 10 -0-.A::A.'Y" S. RASMUSSEN & ASSOCIATES



Project No. 2066

trenching. The recommended setback zones are parallel to the trend of the Mission Creek fault on the site.

A Richter magnitude 7.5 earthquake is expected along the Mission Creek fault zone located within the southwest portion of the site; therefore, we recommend human occupancy structures be designed accordingly.

Positive drainage of the site should be provided, and runoff should not be allowed to flow over cut or fill slopes in such a way as to cause erosion.

All cut and fill slopes should be planted as soon as possible to minimize erosion by wind and water.

The maximum inclination of all horizontal to l vertical, unless the soils engineer.

cut slopes should be 2 otherwise recommended by

All on-site fill, including the trench backfill, should be evaluated by the soils engineer.

JJM:GSR/mt

Enclosure 1: Enclosure 2: Enclosure 3: Enclosure 4: Enclosure 5:

Respectfully submitted,

GARY S, RASMUSSEN & ASSOCIATES, INC.

f; j)-h1~ Jay J, Martin Staff Geologist

G1~~en . Engineering Geologist, EG 925

Geologic Index Map Earthquake Epicenter Map 40-Scale Map Trench Logs References

Distribution: The Fisher Associates (8)

- 11 -GARY s. :Ft.ASMUSSEN & ASSOCIArr:ms

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

nd ~:li> I

I I 'j

./··- ......... ---.._. -·

ENCLOSURE 1 GEOLOGIC INDEX !·IAP

GARY S. RAS~IUSSEN & ASSOCIATES, l'<C. The Fisher Associates

A-P Zone-Desert Hot Springs, CA. Base Map:ceolor;ic map of

Desert Hot Springs, Proctor, 1968

ScaJel:62,500 Project No. 2066

6 d ..., 0 1 2 miles

Qs Qal Qt l)c Qo Sg

Legend

Geologic contact

Fault; dashed where approx., dotted where burled

Superficial Alluvium

sand

Terrace deposits Cabezon Fanglomcrate _ NOcotillo Conglomerate ~ San Gorgonio c.on1plex

Well location



ENCLOSURE 2 Eanhqllal<e Epicenter Map

GARY S. RAS'·IUSSl:N & ASSOCIATES, JNC. The Fisher Associates

A-P Zone- Desert Hot Springs, California

\_

". , . •

\ e

/

5 :·loximum r~portcd int.,nsity (prior to 1930's)

" ', L 1.

R!CHfER l·L~GNITUDE

C).

C)

4.0 5.0 60

TO 4.9 TO 59 i TO 6.9 ~

Bose: Real, ~.!.·'!..!.·, 1978 [artllqllal<e Epi co:nt er ~lap of California; 1900-1974

Scale l"-~)l!HOX. 16 mi_les

. N

Project Na.2066 ~

. .



----+-----

.,.., "'

Q) 0

"' " N

" Q)

.g: u-'

~ 0 u «:

~ a

""

50'

30'

100'

130.00'

ENCLOSURE 3

.,. ______ Palm Drive

fi.

Southwest lin11ts of --------recommended restricted

use ?.one for human occupancy structures

N36°W

0 0

0 0 ,..;

Northeast limits c1f recommended restricted use zone for human oc.c.upanc.y struc..:ture8

N3li 0 W

.Leg en<!_

o Lath location TlB

GARY S. RASMUSSEN & ASSOCIATES, INC. The Fisher As$oc.iates

Project No. 2066 Scale: 1 11 ~40'

0 20 40 80'

I Sc.ale.:_ --~-r_=;j_ 1

I TREXCH 1

I I I

5

I 10

I I I

N52E

I I I

70 80 90

I I

5

I I 10

I N47E

I I

110

5

10

1.

2.

3.

4.

5.

6.

7.

N47E

/

70 0

5

10

ENCLOSURE 4 GARY S. RASMUSSEN & ASSOCIATES, INC. The Fisher Associates -Desert Hot Springs, CA., Project No. 2066

Lithologic Descriptions

Gravel, lt. brown, about 65% medium to very coarse silty sand matrix, about 35% coarser framework material (boulders, cobbles, pebbles), occasional small channels and fine to medium silty sand lenses.

. rown, occasiona Medium to coarse silty sand with pebbles, lt b 1 cobbles.

~edium to coarse silty sand, lt. ~ediu~ brovm, a few low angle cross beds. Fine to coarse silty sand, gray brown, biotite rich.

Same as 1 but with 50% matrix, 50% framework.

Same as 2 but lacking cobbles.

Fill


0

5

10

5

140 0

5

TRE:ICH 2 10

80

150

5

10 N56.5E

20 30 40 50

:<56.5E

90 100 110 120

N56.5E

60 70

5

10

130 140

5

10

ENCLOSURE 4 GARY S. RAS:1\JSSE:< & ASSOCIATES, INC. The Fisher Assoeiates -Desert Hot Springs, California Project No. 2066


HEFERENCES

Allen, C.R., Saint Amand, P., Richter, C.P., 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.

Biehler, S., Kovach, R. L., and Allen, Geophysical framework of northern end of Gulf structural province, Marine geology of California, Memoir 3: American Association Geologists publication.

C.R., 1964, of California

the Gulf of of Petroleum

Dibblee, T.W., Jr., 1975, Late Quaternary uplift of the San Be.rnardino Mountains on the San Andreas and related faults, in Crowell, J,C., ed., 1975, San Andreas fault in southern California, a guide to San Andreas fault from Mexico to Carrizo Plain: California Division of Mines and Geology Special report 118, p. 127-135.

Fairchild Camera, September 29, 1939, Black and white aerial photographs, Plight C-6060, Photo No.'s 247 and 248, Scale: !"=approx, 1500',

Hileman, J.A., Allen, C.R., Nordquist, J.M., 1973, Seismicity of the southern California region l January 1932 to 31 December 1972: Seismological Laboratory, California Institute of Technology, Pasadena, California, p. 404.

Hope, R.A., 1969, Maps showing recently active breaks along the San Andreas and related faults between Cajon Pass and Salton Sea, California: U.S. Geological Survey Open-file report, 1:24,000,

Jennings, C.W., 1975, Fault map of California with locations of volcanoes, thermal springs, and thermal wells: California Division of Mines and Geology, 1:750,000,

Ploessel, Repeatable California

M.R., and Slosson, J.E., September 1974, high ground accelerations from earthquakes:

Geology, v. 27, no. 9, p. 195-199,

Proctor, H.J., 1968, Geology of the Desert Hot Springs, Upper Coachella valley area, California: California Division of Mines and Geology Special Report 94.

Rasmussen, Gary s., April 1979, Width of fault rupture in late Holocene alluvium in San Bernardino and Riverside Counties, California: in Abstracts with programs, Cordilleran Section, Geological Society of America, 75th Annual Meeting, v. 11, no. 3, p. 123.

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0-.A..RY a. RASMU$81IlN & AeaocxA':I':a:iS


Rasmussen, Gary S., April 1981, San Andreas fault geometry and maximum probable earthquakes in southern California: in Abstracts with programs, Cordilleran Section, Geological Society of America, 77th Annual Meeting, v. 13, no. 2, p. 102.

Rasmussen, Gary S. & Associates, Inc., llay 24, 1977, Engineering geology investigation of an approximately 6-acre parcel, Angel View Crippled Children's Foundation, northeast of Casa Grande Drive and Vista del Valle, Desert Hot Springs, California, Project No. 1202.

Rasmussen, Gary S. & Associates, Inc., August 16, 1977, Engineering geology investigation, Lots 14-17, Pierson Boulevard, West of Palm Drive, Desert Hot Springs, California, Project No. 1230.

Rasmussen, Gary S, & Associates, Inc., November 2, 1977, Engineering geology investigation of a 5-acre parcel, located at the southwest corner of La Salle Road and Hacienda Avenue, Desert Hot Springs, California, Project No. 1263.

Rasmussen, Gary s. & Associates, Inc., November 21, 1977, Engineering geology investigation of a 40-acre parcel at the northwest corner of 19th Avenue and Palm View (Langlois Road), Desert Hot Springs, California, Project No. 1255.

Rasmussen, Gary S. & Associates, Inc., Engineering geology investigation of 190-acre parcel, portions of Section Section 5, 'r3s, R5E, 'l'wo Bunch Palms, California, Project No. 1256-2.

January 30, 1978, an approximately

32, T2S, R5E, and Desert Hot Springs,

Rasmussen, Gary s. & Associates, Inc., January 15, 1979, Subsurface engineering geology investigation of a 2 l/2-acre site, 1,063 feet south of Dillon Road and 2,350 feet west of Corkhill Road, Desert Hot Springs, California , Project No. 1412-2.

January 18, 1979, 100-acre parcel, Road, Desert Hot

Rasmussen, Gary S. & Associates, Inc,, Engineering geology investigation of a north of Dillon Road, east of Long Canyon Springs, California, Project No. 1430.

Rasmussen, Gary s. & Associates, Inc., February 1, Addendum to our report dated November 2, 1977, our dated January 12, 1979, Project No. 1263-3.

1979, letter

Rasmussen, Gary s. & Associates, Inc., April 17, 1979, Engineering geology investigation of an approximately 30-acre parcel, Dillon Road, 1,341 feet west of Corkhill Road, N 1/2, NW 1/4, SE 1/4 and N 1/2, S 1/2, NW 1/4, SE 1/4

ii 0-.AztY S. RASMUSSEN&, ASSOCIATE:iS


of Section 10 1 T3S, R5E, E:xcept the N 4 O feet, Desert !Jot Springs, California, Project No. 1473.

Rasmussen, Gary S. & Associates, Inc., July 10, 1979, Subsurface engineering geology investigation of Tentative Tract 11851, 11851-1 1 11851-2, 65 total proposed lots, north of Pierson Boulevard, 125 feet east of Ambrosio Drive, Desert Hot Springs, Riverside County, California, Project: No. 1390.

Rasmussen, Gary S. & Associates, Inc., February 22, 1980, Engineering geology investigation, W 1/2 of the NE 1/2 of the NW 1/4 of the SW 1/4 1 Section 32, T2S, R5E, southwest ot the intersection of Hacienda Avenue and Foxdale Drive, Desert Hot Springs, California, Project No. 1545.

'l'.R. 1 and Parke, D.L., 1978, map of California, 1900-1974:

Real, C.R. , 'roppozada 1

Earthquake epicenter California Division of Mines and Geology Map Sheet 39.

Real, C.R., McJunkin, R.D., Leivas, E., 1979, Effects of Imperial Valley earthquake, 15 October 1979, Imperial County, California: California Geology, v. 32 1 no. 12, p. 259-265.

Richter, C.F., Allen, C.R., and Nordquist, J.M., 1958 1 The Desert Hot Springs earthquakes and their tectonic environment: Seismological Society of America Bulletin, v. 48, p. 315-337.

Riverside County Flood Control and Water Conservation District, October 20, 1955, Aerial photograph numbers 8-2, 8-3, Scale: 1"•1000'.

Riverside County Flood Control and Water Conservation District, February 26, 1957, Aerial photograph numbers 48 and 49, Scale: 1"•1000'.

Riverside County District, February 25, 26, 36 and 37,

Flood Control and Water Conservation 14, 1970, Aerial photograph numbers 24,

Scale: 1"•1000'.

Riverside County Flood Control and Water Conservation District, May 24, 197 4, Aerial photograph numbers 125, 126 and 127, Scale: 1"•2000'.

Rockwell, T., and Sylvester, A.G., 1979, Neotectonics of the Salton Trough, in Crowell, J.C. and Sylvester, A.G., Tectonics of the----")uncture between the San Andreas fault system and the Salton Trough, southeastern California: A guidebook, Annual Meeting Geological Society of America, San Diego, CA.

Schnabel, P.B., and Seed, H.G., 1973, Accelerations in rock

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for earthquakes in the western United States: Seismological Society of America Bulletin, v. 63, no. 2.

Toppozada, Seismicity California

'11• R. , Rea 1 , C.R. , and

of California, January Geology, July 1979.

Pierzinski, D.C., 1979, 1975 through March 1979:

U.S. Geological Survey, January 18, 1972, Black and white aerial photographs, VCWE, Numbers 1-229 and l-230, Scale: l"•approx, 3000'.

Wood, H.O., Snismological 47-67.

1955, The 1857 earthquake in Society of America Bulletin,

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California: v. 45, p.

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