STATE OF CA.UFOf'ir:NIA-THE ReSOURCES AGENCY

DEPARTMENT OF CONSERVATION

DIVISION OF MINES AND GEOLOGY BAY AREA REGIONAL OFFICE 1145 MARKET STR~ET, 3RO fLOOR SAN FRANCISCO, CA 94103-1513 PHONE, (415) 557-11!00

ATSS 597·1500

Sherwin Williams Planner City of Ridgecrest 100 West California Avenue Ridgecrest, CA 93555-4054

Dear Mr. Williams:

' • Pl;TE WILSON, Gow""'r

l

February 3, 1993

We are placing on open file the following report, submitted by the City of Ridgecrest in compliance with the Alquist-Priolo Special Studies Zones Act:

Geologic and seismologic report on Lot 2, Tract 1252 (medical office building), Ridgecrest, Kern County, CA; by Saint-Amand Scientific Services; 3/24/92.

When the review of this report is complete, please send a copy of it, along with any supplemental material, to this. office for file.

EWH:ra cc: A-P filev'

sincerely,

EARL W. HART, CEG 935 Senior Geologist &

Program Manager

February 1, 1993

Dwayne Smith 7201 Fruitvale Extension Bakersfield, CA 93308

Dear Mr. Smith,

As per our conversation on February 1, 1993 I am sending for your review a copy of a geologic & seismologic report prepared for lot 2 of tract 1252 within the City of Ridgecrest. The property owner is planning on constructing a medical off ice building at the subject site.

We thank you for your expeditious reply. Please call me (619) 371'-3721 if you have any questions.

Sincerely, .

~w~ Sherwin Williams Planner

cc. CA Div. Mines & Geology

a:\letters.93\#93-002.geo

100 WEST CALIFORNIA AVENUE• RIDGECREST, CAIJFORNIA 93555-4054 •PHONE (619) 371-3700

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6EOL061C ANO SEISMOLOGIC REPORT ON LOT 2, TARCT 1252

Ridgecrest, Kem County, California .

Pierre Saint-Amand, PhD . David Salnt-Amand, BA.

March 24, 1992

For Calvin Fallgatter

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GEOLOGIC AND SEISMOLOGIC REPORT ON LOT 2 TRACT 1252 RIDGECREST, KERN COUN'IY, CALIFORNIA

Table of Contents

INTRODUCTION .......................................................................................................... 1 Purpose .... ~ ........................................................................................................... 1 Location ............................................................................................................ 1 Method of Investigation ............................. " ............................... "' ............... 1

GID~ ................................................................................... ~ .................... u ................ 1 [)escrlptlon ......................................................................................................... 1

Results of trencllhlg ........................... n ...................................................................... 1 Figure 1. Location of site in Ridgecrest ......................................................... 2 Figure 2. Map of the site showing the locations of trenches ............... .3 Figure 3. Cross-Sections of the trenches ...................................................... .5 01HER GEOIDGIC CONSIDERA TIONS .................................................................. 6

Flooding ............................ n•••n••n••• .. ••·••·• .. •·•·• .. ·•·•·••••tt•••····· ............................. 6 TSunamis and Selches ................................................................................. 6 Bedrock ................................................................................................................ 6 Ground-Water ................................................................................................. 6 Possible Deformation from Plastic Clays ............................................ 7 Liquefaction of Soil During Earthquakes ............................................ 7 Aselsmlc Creep .............................................................................................. 7 landsliding ...................................................................................................... 7 Rolling Rocks .............................. ~ ... u•••••••••uu•••··············· .. ·······•·····••••·•••········ .. 7 Mineral Potentlal .......................................................................................... 7 Agricultural Potential ................................................................................. 7 Setbacks ................................................................................. u •••••••••••••••••••••••••• 7

FAULTS IN INDIAN WELLS VAll.EY ................................................................ 7 SHANGRI LA RANCH FAULT .................................................................... 7

Trajectory of the Shangrl La Ranch Fault .............................. 7 Figure 4. Map showing the trajectory ............................................................ 8

Nature of the Fault in the Region of the Site ........................ 9 Shangrt la Ranch Fault ln the Basement ................................ 9 Extent of the Fault .............................................................................. 9 History- of the Fault ............................................................................ 1 O Level of Actlvl ty' ............................................................................... 10 Name of the Fault ................................................................................. 10

GOlD BUG FAULT .......................................................................................... 10 History of Movement ...................................................................... 11 Ex.tent ·of the Fault ............................................................................ 11

RIIXiECR.ES"T' FAUL T .................................................................. "' ................... 11 sasrvnc GEOIDGY .......................................................... "' ............................................... 11

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FIRST ORDER FAULTS IN THE STATE ................................................... 11 Figure 5. The more Important earthquake producing faults ..•.............. 12

Regional Tectonlcs ........................................................................................ 13 Local vertical movements ......................................................................... 13

LOCAL FAULTS AND EXPECTABLE EARTHQUAKES ..................................... 14 Garlock Fault .......................................................................................... h ......... 14

Figure 6. Cross-section of Indian Wells Valley .......................................... 14 Slerran Fault Zone ........................................................................................ 15 Other Faults ........................................................................................................ 15

TABLE 1. Llst of the More Important Faults ......................... , ..................... 16 Shangrl I.a Ranch Fault and Other Local Faults ............................... 16 EFFECTS OF SEISMIC FLING ...................................................................... 16 AFf'ER.SHOCKS ........ ; ........................................................................................... 16

SEISMOLOGY ......................................................................... h ..................................... 17 ~OF AcnvnY ..................... u .............................................................. 17 IMPORTANT EARTHQJ.JAKES .................................................................... 17

Flgure 7. Earthquake epicenters in the Indian Wells Valley ............... 18 Figure 8. Strain Release fvlap .............................................................................. 19 DESJG N EA.RIBQJ.J.AKES .............................................................................................. 20

FRI:-QUENcY OF OCCURRENCE OF FARlHQJJAKIB ............................... 21 Figure 9. Earthquake recurrence curves ........................................................ 22 Figure 10. Map showin'g the location of the various dlstrlcts ............... 23 CLIMATE .......................................................................................................................... 24

PRECIPITATION ............................................................................................. 24 "TEMPERA. TIJRE .................................................................................................... 24 INSOl.A TION ................................................................... u .................................. 25 WINDS ...................................................................................................................... 25 DUST SfORJ\.1S ........................................................................................................ 25

RECO~A TIONS ................................................................................................... 26 CONCLUSIONS ............................................................................................................. 2 7 REFm.ENCES ....................................................................................................................... 28

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GEOLOGIC AND SBSMOLOGIC REPORT ON LOT 2, 1RACT 1252, RlDGECRfST, KERN COUN'IY, CALIFORNIA

INTRODUCTION

Purpose: This report was requested by Calvin Fallgatter of 1275 N. Norma, Ridgecrest, California, 93555, in order to satisfy the requirements of the City of Ridgecrest with respect to geologic and seismic safety. The slte ls on the eastern edge of an Alquist-Priolo Special Studies Zone (Davis 1990) for the Ridgecrest North Quadrangle of the U. S. Geological Survey, figure 1. It Is planned to ask for a land-use and zoning change for the lot.

I.ocat1on: The site ls located on the south-eastern side of the Intersection of North Norma Street and West Moyer Avenue. Lot 2 ls the second lot east of Norma Street, Rgure 2. It is a portion of the south 1/2 of the northeast l/ 4 of Section 28, Township 26 south, Range 40 East, Mount Dlablo Base and Meridian.

.Method of Investigation: The tract was examined on foot, along with the area for about 1/2 mile In all directions. Stereoscopic, colored, aerial photographs at a scale of 1:10,000 were studied. Pertinent literature was reviewed and old reports were reread. TWo trenches were excavated on the property. The locations are in Figure 2.

GEOLOGY

Description: The site Is a flat, featureless, almost level lot, 51.55 feet wide by 129.25 feet long. The wind has scoured several inches of top soil since the site was cleared. No vegetation other than a few weeds are found on the site. The soil exposed at the surface is very hard and difficult to dig. It ls not a suitable home for small animals and none appear to be using the property.

Results oftrenchlna: Trench 1, oriented north-south and 143 feet long, was dug near the western edge of the site. It was started a few feet from the northern edge of an alley on the south side of the site, so as not to dig up any utilities that might be located there. Trench 2, oriented east-west, was dug along the north edge of the site, Just Inside the easement line. We carried carried elevations to the trenches with a dumpy level, using the point of tangency on the curb of the sidewalk on North Norma, at Its intersection with West Moyer,

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Scale: llnch • 2888 feet.

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Figure I • Location of site In Ridgecrest with respect to the Rlqulst-Prlolo Special Studies Zone. The Map Is talcen from the C.D.M.6. Ridgecrest Quadrangle-North, Rlqulst-Prlolo map, Oauls 1990.

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Figure 2. Map of the site showing.site and the locations of trenches 1 and 2. Mapped with tape and compass , March, 1992.

Moyer

Edge of Pauement ~ Concrete Sidewalk

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as a Bench Mark, assuming an altitude of 100.00 feet. We carefully examined and logged the sides of the trenches. Absolutely no evidence of faulting or tectonic distress was present in the trenches. Elsewhere in the valley, the course of the fault ls marked by cracks, elastic dikes, signs of liquefaction, and fault displacements for over 100 feet on either side. Neither trench, revealed any of the above lndlcla. Figure 3 shows the cross-sections for both trenches. ·

Crossection: A thin lag, detrltal from the deflation of the uppermost surface, overlies a well developed paleosol 2 to 3 feet thick. The paleosol is a hard clay-rich paleochrid or paleargld. The paleargld portion being derived from dune sand. It ls coffee or cacao colored with vertical prismatic joints that disappear downward into what might be thought of as the B Horizon. Some of the joint faces are covered with white gypsum skins. Most of the feldspars have been destroyed, but an occasional piece of larger gruss or pebbles of quartz remain. It ls thought that the paleosol ls of mld Pleistocene age, as deduced from old shorelines of Lake China. It was probably formed at a time when a natric ground-water table was near the surface. It bespeaks a protracted, warm wet climate. This rests upon a well developed horizon composed of a dense, cemented, reddish-brown, dry mud. In places this pebble rich mud Iles upon, or contains small lenses of sand.

This paleosol is uncomformable upon a silty layer that contains enough dlatomaceous earth to give it a whitish grey color. At times this soil was near enough to the surface to take on an ochric color, but to no great depth. This in tum rests, ln places, upon a loose, grey, silty sand that appears to contain some volcanic ash. For most of the distance ln both trenches It lies directly upon a layer of very clean gravel mixed with pea gravel and some sand, but containing no silt. This layer has a few unimportant fades changes, some of which are shown in the diagrams of the trenches. It ls continuous under the whole of the property as exposed by the trenching.

The gravel layer flows Into the excavation from the sides making it difficult to dig more than a foot into the gravel. The flowage of the gravel into the ditch undermined the sides and caused a significant piece of the west side of trench one to fall into the trench, We recommend that the sides of all utility trenches be shored In order to protect the workmen.

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South

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95

98 88

South

188

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West

100

95

The origins and locatJons·of the trenches are shown In figure 2.

Please note tbat the horizontal coordinate system for trench 2 runs right-to-left Instead of left-to-right.

Trench 1: Uiew West.

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Trench 1: Uiew West.

8+88 8+98

Trench 2: Uiew North.

Centerline of Trench 1

90 0+58 8+40 8+30

Horizontal and uertical Scale: I inch equals 5 feet.

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1+88 1+18

8+20 8+10

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North

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Centerline of Trench 2

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Key to Geologic Units:

North

188

95

90

~osol: Coffee to Chocolate colored Paleargld and pal eochrfd. U ertJcal prl srri atlc Joi ntlng and SO!lle fragments of gruss mlKed In with the sand from which It was derluecl

l!.rjirl c Sand: D chrlc to G raylsh Ochri c sand, fine grained with silt. MIKed with dlatomaceous earth. Poor to no bedding.

G~y sand; Fine to medium grained sand and uo!canlc ash. Some dlatomaceous earth and wind blown sand. Thinly Bedded In places.

! :~Z~--~ - - ~ &rauei·' Grauel and fine to course grained sand. No silt.: Loose, not cemented.

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History: The story told by the trenching is a simple one. First there was a lake, with a beach near the site and the gravels were deposited as a near shore sediment. The Jake first grew deeper and then began to dry. Some slits were deposited along with windblown sand. The water became warm and diatoms flourished for a time, mixing their skeletons with the silt. As the lake dried, the upper most slit and diatomaceous earth were oxidized during a short exposure to the air. Following, or during, the drying wind blown sand and fluviatlle material began fllling in the lake. At this time, the water table beneath the sediments was stlll high and the uppermost sediments were weathered to form the paleosol. The paleosol formation ceased as the water table dropped, and the surface became covered with an entisol, which was stripped away in an earlier preparation of the site .

No where in the trenches did we find evidence of tectonic distress, severe shaking, elastic dikes, cracks or abrupt discontinuities in the section. The gravel unit has not been displaced, nor has the paleosol.

The Shangri La Ranch Fault, aka as the Llttle Lake Fault, does not appear at or near the surface anywhere on the Tract. No evidence for other faults or faulting could be found.

OTIIER GEOLOGIC CONSIDERATIONS

Flooding: No evidence of recent flooding could be found on the site .

Tsunamis and Selches: No possibility of either exists because no large body of water is nearby .

BeQr..Qd: Bedrock. as determined hy seismic prospecting, is about 2,000 feet deep, {Zbur, 1963). The Intervening material consists of sands, gravels, slits and clays deposited as slopewash and perhaps as fluviatile and lacustrine sediments. The bedrock ls granodiorlte and granite of upper Cretaceous age.

Ground·Water: Ground-water, of marginal quality, ls about 125 feet deep beneath the property, see Salnt·Amand ( 1986a) and Beren brook and Martin ( 1991, pg 73 ). It may be produced from wells but is unsuitable for domestic use. Good water ls available from the Indian Wells Valley Water District.

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Possible Oefoonatlon [rom Plastic Cla,ys: Because of the depth of the ground·water, there Is no possibility of deformation resulting from flowage of plastic clays beneath the property.

Llquefa,ctlon of Soil During Earthqua,kes: Because of the depth to groundwater, liquefaction of the soil during earthquakes is not to be expected.

Aselsmlc Creep: Hard surfaced roads, sidewalks, driveways and fences In the Immediate area were examined. No evidence for systematic cracking of paved streets could be found.

I andslidlng: No danger exists from landsliding .

Rolling Rocks: No danger exists from rolling rocks .

Mineral Potentla,l: The are no minerals of any economic value.

Agricultural Potential: large scale agriculture ls Impossible. '

Setbacks: In view of the absence of faulting on the property, and the distance to the fault, It Is neither necessary or reasonable to require setbacks. If a set back be required for administrative reasons we recommend a zero setback.

FAULTS IN INDIAN WELLS VALLEY

SHANGRI LA RANCH FAULT: This fault, upon which the Alqulst· Priolo Special Studies Zone is predicated was named after the former Shangri La Ranch, to the east of China lake Boulevard, where it Intersects Bowman Road.

Tra!ectory of the Sba,ngri La Ranch Fa.ult: The trajectory of the Shangri La Ranch Fault near the site is shown on Figure 4. Ample evidence of preHolocene displacement, but no Holocene scarps, are noticeable along its trace In the Ridgecrest area. The scarps are subdued and smoothed over. For most of its trajectory, the fault Is almost Indistinguishable, even on air photos. The topographic expression varies with distance. To the northwest of Trana Road and Ridgecrest Boulevard, the eastern side Is up·thrown, but the fault then passes Into a shallow fold and reappears a few hundred feet to the west as another branch with the west side uplifted. It can be followed topographically from the latitude of East California Street in

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Ridgecrest, as far as the Naval Air Facility where It ls lost in the loose sand and deep sediments of the valley to the north. The fault does not pass within 600 feet of the slte. It has been well located ln several trenches to the south and west of the property (St. Amand, 1981 ) .

Nature of the Fault In the Region of the Site: In Heritage Village, about 1.2 mile to the south of the site, the fault branches, the southern branch dies out and the northern branch takes up to the west thereof, figure 4. It does this several times inits trajectory. The surface expressions of the fault were developed through perhaps 2,000 feet of incompetent sediments at a time when the ground· water was high. It Is not surprising therefore that it should exhibit such behavior near the surface .

Shangrl Ia Ranch Fault in the Basement: Zbur (1963, pg. 38) shows offsets In the crystalline basement of the valley that correlate closely with the surface expression of the fault. He shows another fault sub· parallel to it, about 0.5 miles to the west. The aggregate offset on these two faults is about 500 feet, up on the east side. It ls possible, with imagination, to correlate this system with similar breaks In the basement profiles all the way to Little Lake. Roland von Huene ( 1960) recognized it while doing his thesis on the gravity field of the valley. Dutcher and Moyle ( 1973) do not show it on their map. They do show a ground·water barrier about 0.5 miles to the west, on the north side of Inyokem Road. This barrier is probably associated with the buried, western branch of the fault as shown by Zbur(l 963 ). It is not clearly visible at the surface.

Extent of the Fault: The fault probably crosses the whole of Indian Wells Valley, although this can not be proven at this time (St·Amand, 1958). If so, it emerges on the northwest comer of the valley, where It ls manifested as a 1/2 mile, right·lateral offset In the lava flow to the east of Highway 395 at Little Lake, (Roquemore 1981, p. 10 et seq.). Four miles further north, the fault Joins the frontal fault of the Sierra Nevada. To the south of Ridgecrest, It may cross the Rademacher Hills and curve easterly as it is drag·folded into the regime of the Garlock Fault zone, as Is indicated by Zbur(1963). Our own photo and field work indicate that Wagon Wheel Fault, a major fault with vertical throw, northslde up, is drag folded parallel to the Garlock Fault about where Zbur projects the Shangri·La Ranch Fault. The course of the fault to the south of California Street ls not clear. It may be cut off by any of several north·easterly trending features, or

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It may not have been able to propagate to the surface through the soft sediments. In any case we have not found it south of California street.

Histozy of the Fault: This fault is probably the remains of one of a number of old dextral-slip faults that existed In the area prior to the development of the Garlock Fault. The Garlock Fault has moved some 40 or more kilometers, stretching the land on the north of it. Many of the old faults have been cut off from their counterparts to the south of the Garlock Fault and have changed their former pattern of dextral-slip to a variable vertical displacement.

Level of Activity: We have trenched across this fault on six projects, all to the north of Ridgecrest Boulevard (aka as Trana Road). It offsets the paleosol at least 5 times, and shows ample evidence of liquefaction and disturbance of the section. The fault ls active. Many small earthquakes have occurred near or along It in the last fifty · years. If the fault actually joins the Little Lake Fault, and the whole of the fault were to slip, it could produce a magnitude 7 earthquake .

Name of the Fault: Because it appears that the fault does not cross the Shangrl La Ranch site, perhaps we are using the wrong name . Roquemore calls it the Little Lake Fault. This assumes that the fault crosses the whole of the valley, a point not yet in evidence. It is probably wrong to call the part in Ridgecrest by either name. We will continue to use the older name until we can resolve this issue .

GOLP BUG FAULT: The 30 kilometer long Gold Bug Fault was first reported by Moyle (1963). It takes its name from the Gold Bug Mine in the Rademacher Hills. The southernmost end of the fault Iles in Teagle Wash, to the southeast of Ridgecrest, where it joins the Garlock Fault. For about 3 miles, to the west of Jacks Ranch Road, the trace of the fault is marked as a slight depression, probably a mole track produced during some long-ago earthquake. The trace of the fault is almost invisible elsewhere except for a short segment in Section 7, T 27 s. R 39 E. There, the northeast side ls downdropped ten or more feet, cutting off an older land surface and the drainage from the Black Mountain area. The scarp is subdued and almost obliterated by erosion and deposition. Zbur( 1963) shows this fault offsetting the bedrock about 200 feet, up on the southwest side. This fault has not been active for a long time. It has not had much aggregate vertical movement. It has also probably undergone strlke­slip movement, but the amount Is unknown. The fault is so curved,

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where it is drag-folded near the Garlock Fault, that further strike slip motion on it is unlikely .

History of Movement: In Tract 2599-RS, lo the northwest comer of Section 7, the fault was revealed In a series of three trenches (Salnt­Amand, 1984). The fault offsets the paleosol about 4 feet vertically . The fault offsets lake-bed and deltaic sediments, along the face of an old shoreline at an altitude of 2,500 feet. This is 300 feet higher than the Tioga shorelines cxpo:;r·,1 '· · ;;". ,.,,.,:.-,-., ~kk \lfT11di<11·1 \'v'. i;, Valley. Thus lt represents a very early stand of the Pleistocene lakes, probably much older than the Tahoe and possibly at least as old as the Sherwin Glaciation. Movement on the fault is not at all frequent. The fault can not be followed in the "newer" alluvium .

Extent of the Fault:·The Gold Bug fault is about 30 kilometers long. The maximum expectable earthquake that it could produce would be between Magnitude 5 and 6.

RIDGECREST FAULT: Ridgecrest Fault has been predicated to cross Bowman Road near Its intersection with South China Lake Boulevard, about 12 mile west of the tract. This fault first appeared on the map In Bulletin 91-9, (Moyle 1963). Zbur (1963) shows it as a short segment, inferred from questionable evidence. Zbur's sections of the seismic profile along Bowman Road show no faulting in the basement that could be related to the extension of the Ridgecrest Fault. Dr. Roland van Huene, (1960), in his Doctoral Thesis, does not show the fault. Roquemore and Zellmer,( 1986) do not show this fault. Upon examining air photographs, we cannot find the fault in the vicinity of the property, or elsewhere, except for some suggestive features, now destroyed, near the intersection of Bowman Road and China Lake Boulevard. We doubt that the Ridgecrest Fault exists, and have so informed the Ridgecrest City Engineer.

SEISMIC GEOLOGY

FIRST ORDER FAULTS JN THE STATE: Figure 5 shows the site with respect to the important earthquake producing faults in Southern California. The scene Is dominated by the northwesterly trending San Andreas Fault and the northeasterly trending Garlock Fault. The San Andreas Fault Is right-handed, or dextral, the Garlock Fault is left-handed, or sinistral. The land on the ocean.ward of the San Andreas Fault has moved northward several hundred miles. The

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Important Faults in the Southern California Region. Many minor faults 11re not shown. After Hill, 1955.

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block to the south of the Garlock fault has been displaced sinistrally as much as 40 miles (Smith 1962).

Regional Tectonics: The land to the north of the Garlock Fault has been stretched in an east-west direction. The land to the west of the crest of the Sierra has been compressed, and folded, as If the mountain mass had been propelled westward against the coast ranges, bending the San Andreas Fault at Gorman and causing late Tertiary and Pleistocene folding in the coast ranges.

The land to the south of the Garlock Fault, In the Mojave Block, was stretched in early Tertiary time. Since Pliocene, it has been rotated but not stretched (Troxel, Jahns and Wright, 1972).

A zone of intense local compression has resulted in the vicinity of the intersection of the two major faults, causing the development of wide-spread areas of crushing of the rock and the development of several prominent thrust faults, such as the Pastorla and the Frazier Mountain over-thrusts (Hill and Dibblee, 1963).

The degree of faulting and the complexity of the systems mask, to some degree, the basic facts of the matter. The northerly trending faults are In general dextral-strike-sllp and the more westerly trending faults have sinistral-strike-slip. The local area Is being deformed by an east-west extension, combined with the effects of a northerly oriented dextral shear couple. The whole of the area from the Pacific Ocean to the Hurricane Fault in Utah is undergoing this shearing in a consistent manner. Attention is usually focused upon the major faults as being the culprits; but, It is Important to realize that this Is a pervasive phenomenon in which the whole terrain is being deformed.

Inca! vertical movements: The floor of Indian wells Valley Is sinking. Relative vertical movement Is taking place between the valley and the surrounding hllls along high angle faults. The valley Is deepest between Inyokern and Highway 14, where the Crystalline basement is about 5,000 feet below the surface, Figure 6. The basement rock tapers upward to the east and surfaces at B Mountain and in the pass to Trona. That the valley is still a closed basin speaks eloquently for the recency and constancy of the movement.

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LOCAL FAULTS AND EXPECTABLE EARTHQUAKES

Garlock Fault: The two most likely sources of earthquake trouble in Ridgecrest are the Sierra Nevada Frontal Fault Zone and the Garlock Fault. Although no earthquakes of consequence have occurred on the

WEST

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Figure 6. Cross-section of Indian Wells Dalley taken from St.-Rmand, 1986, Water Supolu of Indian Wells Dalley.

EAST

Garlock Fault in historic time, evidence of Holocene movement on the Garlock Fault ls abundant. This fault ls capable of producing earthquakes of magnitude 8.0. No earthquakes seem to be taking place at present along its length but.some small earthquakes are distrtbuted throughout the surrounding hills. This absence of activity may Indicate that a long time has passed since the last big earthquake. No claims are made that the Garlock Fault is ready to produce an earthquake in the near future, but the possibility should be considered. Movement on the Garlock Fault will result In

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movement on a number of other north-south trending faults and some of these aftershocks may reach magnitude 7.

A magnitude 8 earthquake, or even lesser one, such as a magnitude 7.5 on the Garlock Fault will produce a peak horizontal acceleration of the order of 0.2 to 0.3 gravity at Ridgecrest. The root mean squared shaking will probably exceed 0.1 gravity for 30 seconds to 2 minutes. If an aftershock were to occur in the Ridgecrest area while the main earthquake were going on, the amplitude of motion and the acceleration would be greater. Bigger earthquakes produce lower frequencies of vibration (longer periods) than do smaller earthquakes. The aftershocks produce sharper movement of higher frequency than do the larger main shocks.

Slerran Fault Zone: The Sierran Fault zone is capable of producing an earthquake with which we should be concerned. One might expect that the Slerran Fault would break between the Garlock Fault and Freeman Canyon, or between Indian Wells Canyon and Little Lake. If either segment broke, one could expect an earthquake of magnitude 7 .O to 7.S. If the whole segment from the Garlock to Little Lake broke one could expect a magnitude 7.8 to 8.0.

Because the Sierran Fault is so curved and convoluted, one would not expect much horizontal motion thereon. Hence, horizontal accelerations would not be as large as if the same earthquake were to occur on a strike slip fault of comparable length. On the basis of experience with past earthquakes elsewhere, a Mercalli Intensity IX to X could be reached. This would produce a peak acceleration between 0.2 and 0.9 gravity. See for Instance, Krinltzsky and Chang (197 5). Our personal Impression is that peaks of 0.4 g to 0.6 g could be expected. The duration of shaking would be about 30 seconds. Similar faults in Nevada and in Chile have produced earthquakes with an anomalously long oscll!ational period, probably owing to gravitational dropping of the blocks of land.

Other Faults: The large faults in Owens Valley, Panamint Valley and Death Valley are capable of causing earthquakes up to magnitude 8. These would shake the valley very severely. The shaking from these would contain a higher percentage of low frequency movement than would be expected from smaller local faults. Estimates of the intensity of shaking to be expected from the nearby faults is given in Table 1, (St-Amand et al. 1972).

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TABLE 1. List of the More Important Faults Capable of Producing Earthquakes in the Indian Wells Ualley Area. For more details, see St.-Amand, Engel, Park and Wiiiiams, 1972.

Sierra Nevada Garlock Argus West Frontal Argus East Frontal Panamlnt Valley Panamlnt Frontal Wilson Canyon Several ln Valley Shangri La Ranch Owens Valley

Possible Mainitµde

7-8 7-8+ 7 7+ 8-8+ 7-8 7+ 7+ 7+ St

Distance in Miles

15 13 10 18 20 20-30 12 5-15 0.1 50

Shangrl La Ranch Fault and Other Local Faults: The Shangrl La Ranch Fault appears to cross the entire valley. If lt does, if it ls continuous with the Little Lake Fault, and If it were to move over the whole of Its 35 kms length, we could expect an earthquake of magnitude 7, or slightly more. The frontal faults of the Argus Mountains, the fault running across China Dry Lake to the White Hills, the Wilson Canyon Fault and numerous others in the vicinity could cause earthquakes approaching, or exceeding magnitude 7. All of these faults show signs of Holocene movement.

EFFECIS OF SEISMIC FUNG: If the Shangrl La Ranch Fault were to move, one could expect a horizontal deflection of a foot or less. This movement would take place in about 1 second. Such movement would not present a hazard to the site, but utilities routed over the fault might be damaged. This is not a cause for concern.

AFTERSHOCKS: Following a large earthquake, on any of the faults in the area, at least a month of intense aftershocks could be expected. Of these, the odds are 1/2 that an aftershock will take place that would equal or exceed the magnitude of the main shock. A much larger number will be smaller shocks of no more than nuisance value. It must be pointed out however, that more damage often results from aftershocks than from the original shock. This is

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because buildings, weakened by the main shock, and having the energy adsorbing members damaged, fail during the smaller aftershocks .

SEISMOLOGY

LEYEI. OF ACJJVIIY: Indian Wells Valley Is In one of the more seismically active areas of California. The valley itself has not had a truly destructive earthquake in historic time, but numerous small earthquakes occur throughout the whole valley and the surrounding hills. Between the years 1934 and 1963, energy equivalent to about 20 magnitude 3.0 earthquakes per 100 square kilometers has been released. Figure 7 shows the locations of earthquake epicenters in Indian Wells Valley and vicinity from 1935 until 1980. Figure 8 Is a strain release map for portions of Southern California, Including the Immediate area, (Allen et al. 1963 ).

IMPORTANT EAR1}!0UAKES: The last earthquake of importance that occurred in the vicinity of Indian Wells Valley was one of magnitude 6.3 that took place in Walkers Pass on [\·larch 15, 1946 and was strongly felt in Ridgecrest, but did no damage, (Chakrabarty and Richter, 1949). A few events of about the same size happened in 1980, about 10 kms northwest of Hidgecrest, without notable effect In the town.

Only the most sketchy history is available from Indian Wells Valley before 1920 and information is lacking for all the more Important earlier earthquakes that may have been felt in this area. Some episodes are as follows:

1812--"Ano de Los Temblores". Earthquakes were reported to have been continuous for a period of four and a half months for most of Southern California. The activity was most marked in the Santa Inez and San Gabriel Mountains. Damage was widespread from Santa Barbara to San Diego. There ls no evidence that any of these were felt in Indian Wells Valley, but some of them were strong enough to have caused damages to adobe construction, had there been any.

1857--Fort Tejon Earthquake: This earthquake on January 09, 1857, Is thought by some to have been the greatest In California In historic times. The magnitude was probably in

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Scale: I Inch .. 16 miles.

u I cm ... IU Km.

B 16 miles I - -I - - -

B I B 28 kilometers

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rw.tn idw .. •H

.,:. - ~'""""--.....l::cc ."{~· .......

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Magnitude:

0 4.5-6.4

Figure 7. Earthquake epicenters In the lndlan wens Ualley area from 1808 to 1987. Taken from map by Got er, 1988.

0

..... :

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\ \r ·,

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STRRI N RU ERSE I Jan. I !131 ID I J•n. 1963

Num'blm ol oqui..- M ~ 3.0

.......- .... 100 Km2

< 111 D 111-1 [ill

1-4 •

4-lf·. 16-64.

61-256 • >256.

Figure 8. Strain Release Map for Portions of Southern Callfornla, I ncludlng the Immediate Brea (Rllen et al, 1963).

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" ' Ill II

excess of 8.0. Shaking and damage was severe from Cholame to Patton. The San Andreas Fault slipped along most of that dlstance(Wood, 1955 ). This earthquake appears to be repeated about every 130 +/· 30 year's (Sleh, 1989 and 1988).

1872··0wens Valley Earthquake: This may have been the largest earthquake In California history. It happened on March 26, 1872. Faulting occurred between Cartago and Tinemaha The Alabama Hills were displaced some 18 feet vertically and horizontally. Scarps from thls event can stlll be seen from Owens Lake to 11nnemaha. Most of the adobe houses from Owens lake to Bishop were destroyed and 27 people were killed (some ten percent of the local population). Severe damage occurred as far away as Vlsalla and Grass Valley. It was felt In Arizona and Utah. Damage In Indian Wells Valley was severe, as described by j. D. Whitney:

'i'o our party-travelling from Visalia, by way of Walkers Pass, to Owens Valley-­the destructive effects of the earthquake began to be visible at Indian Wells, about 67 miles nearly due south of Lone Pine. Here the walls of the adobe house were badly cracked, and some adobes had been thrown from the north gable to the distance of 15 feet, toward the north. The house, which has walls nearly two feet in thickness, is traversed, in several places, by vertical cracks from top to bottom. Two very heavy shocks were felt here on the morning of the 26th of March."

1952··Kern County Earthquakes: This series of shocks began with a magnitude 7.7 event on July 21, 1952. It caused widespread damage over most of the Tehachapi Mountains and as far away as Bakersfield. Right·obllque·reverse faulting on the White Wolf Fault was responsible. It was strongly felt In Indian Wells Valley, but no consequential damage was noted. More details for these and other earthquakes may be had in Salnt·Amand et al.,(1963, 1972).

DESIGN EARTHQUAKES

The earthquakes associated with movement on any of the faults mentioned in Table 1, would give an extreme set of design criteria. Several acceleration peaks In excess of gravity could occur with a period of 0.1 seconds or less, with a root mean squared shaking of about 0.3 to 0.4 gravity for 10 to 30 seconds. The short, high frequency pulses in excess of gravity usually do no damage to structures, because not enough time is available to couple the energy to the structures. They do upset articles and cause cosmetic damage. The more protracted shaking Is what causes damage to buildings.

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Structures in the valley should be capable of withstanding two sets of shaking criteria, one for distant earthquakes on the San Andreas, Garlock, Sierran, Owens Valley or Panamint Faults. The other would be for a local earthquake occurring right under the valley itself. The worst case would be the happening of an aftershock within the valley while a major earthquake was still going on.

FREQUENCY OF OCCURRENCE OF EAfilliOlJAKES: At present, we can estimate the recur:rence rate of earth4uakes; but, predlctlon ls not possible. A predlction is not important because any project In Californla of any degree of permanence is eventually golng to be subjected to an earthquake of some consequence. It behooves us to build for the deslgn earthquake without worrying about when It will happen. Some use may be made of the recurrence interval of earthquakes as we will illustrate.

A key to the selsmic future is through the past. Figure 9 shows the past occurrences of earthquakes in six regions of California. One notes that the activity has been higher in Kern county than along Owens Valley. The Ridgecrest area lies outside both regions, see Figure 10, but it is very close to the boundary of the chart for Kern County.

If we use the seismic behavior of Kern County as an example, we can expect that there will be, within a ten mile radius of Ridgecrest, one magnitude 6 earth4uake every 30 years, one magnitude 7 earthquake every ZOO years and a magnitude 8 earthquake every 1,000 years. ll1is procedure, although the only one available to us here, Is not to he taken at face value because one does not know when, in that time interval, the earthquake might occur or if it will occur at all. furthermore, the San Andreas Fault Zone, by way of caution, does not show nearly as much activity as do other regions of the state, and yet we know full well that it has had the biggest earthquakes in the state in historic time.

Some Idea of the possibility of an earthquake on the Garlock Fault in the vicinity of Christmas canyon may be had from the work of G. I. Smith as reported in U.S.G.S. Prof. Paper 975, pg. 202. Near Christmas canyon, at the southeast end of Searles Valley, lt appears as if two horizontal displacements, totalling 24 feet have occurred in the last 10,000 years. The older of the two displacements cuts lake bed gravels estimated to be 10,000 years old or older. This

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\\ \\ ! \Ul,,soutf.erh Colilornhi region

\ \ z~;;1qo •m• I 10, /26 ~r;ulhtfiJO/(IJ

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\ " \ u ' \ \\ \\ I , I \· \ \ \\

\ \ \ \\ Son B~rn~l"dlno Mtsj "

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\ V /mp~nal Voll~r.

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\ \\ \ \ ' \ \\ \ \\

' \' \ Y. Ott1~11s Voll~y I -

StJA And,.as faul'.,v Los Angele!/ /Jos1n 1 \Y\\\

I

:J,O 4,0

' ' ' ' ' ' " ' ' ' ' ' " \ ' ' \ \\\' \ \

\ $.O

Mognilude

\ \~ 6.0

\ \ l.O 8.0

Figure 9. Earthquake recurrence curues for different parts of southern California. Taken from Allen et al., 1964.

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Figure 1 o. Map showing the location of the uarious districts shown In Figure 9. Taken from Hllen et al., 1964 •

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displacement was covered by alluvial gravels, estimated to have ceased deposition some 6,000 lo 8.000 years ago. The younger of the two displacements cuts both deposits and itself is covered by, but does not cut, deposits that are a few hundred to no more than 2,000 years old,

In Pilot Knob Valley, opposite the end of the Panamint Valley, the last displacement cut a thin alluvial unit estimated to be about 2,000 years old. The sum of the two displacements ls 24 feet. The rate of strain accumulation therefore appears to be about one millimeter per year. If so, then about 2 meters of strain may have aecumulated and the fault still has a while to go, maybe.

More recent work by McGill and Sieh,( 1991) indicate that along the 90 kilometer length of fault, that offsets of 2 to 4 meters are commonly observed, whereas south of the El Paso Mountains, two sllps, one of 7 meters and another ol' ..+ meters were observed. The recurrence rate Is estimated at between 600 and 1200 years In that area. This coincides with earlier estimates based on appearance of scarps that the Garlock is about one tenth as active as the San Andreas fault. ·

CL! fvl /\TE

PRECIPITATION: The climate is ariJ. The annual rainfall averages about 2 to S inches per year. In some years it may not rain but in other years ten inches or more may fall. Summertime thunder showers, usually in August, occasionally yield up to l or 2 inches per hour in a localized area. Snow falls once or twice a winter, every four or five years. It rarely lasts more than a day. Most of the precipitation falls from October to April, see Ouimette (197 4) and the weather summaries put out by the Oceanographic Detachment at the Naval Air Facility. See for example Miller( 1962).

TEMPERAilJRE: The temperature varies from soo C ( 1200 F) during a few summer days to as low as -1so C (60 F) during some winter nights. Temperatures drop below freezing on a few nights almost every winter, with some cold snaps lasting for several days. Temperatures vary from place to place in the valley, depending upon altitude and shelter from the wind. Surface temperatures on asphalt may reach 6So C ( 1 soo F) or more on windless days. Temperatures in closed cars may reach even higher.

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INSOlAJ]ON: This area has one of the highest lnsolatlon levels In the United States. In June and July the daily total reaches 8 kilowatt-hours-per-square-meter on a south facing surface. This gives ample opportunity to take advantage of solar heating In the design of buildings.

WINDS: Winds are the principal mechanical hazards to any construction in the area. The danger from winds exceeds that from earthquakes. The highest recorded gust at the Naval Air Facility was 130 km/hr (70 knots). Winds at the Inyokern Airport, 13 kms to the west, have exceeded 160 kms/hr on several occasions. The strongest winds are commonly from the west, but sustained strong winds are frequently from the southwest and are the prevaillng winds during most of the year. An easterly wind drift during summer months ls largely responsible for the extremely hot weather In July and August.

DUST STORMS: During several days each year, usually In the spring and/or fall, local sand storms occur with a strong west wind. These are especially serious when a rotor cloud from the Sierra touches the earth near Ridgecrest. They usually last only a few hours but can do considerable damage to paint, windows and windshields.

During five to seven days a year, usually in late winter and spring, dust is carried from Owens Valley on the north wind. This dust an Impalpable powder consisting of sodium carbonate, sodium sulphate and clay. These event can last for up to two days, (Salnt­Amand et al., 1986b) .

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RECOMMENDATIONS

The permanent structures on the property will not require any special design considerations except for adherence to the uniform building code. The use of plywood shear walls will go a long way to ensure survival of the structures and to prevent even cosmetic damage. Heavy roofs should be avoided. Attention should be given to securing loose articles and heavy objects, such as water heaters and bookcases within the structures. Special attention to making the structures fireproof Is advisable because a large fire during a heavy wind following an earthquake would be almost uncontrollable.

If relocatable buildings, or prefabricated units, are used, they should be well secured to their footings and foundations. The usual spindly pyramidal supports made of strap iron fail miserably in earthquakes.

If the recreational vehicles or large trucks are to be left for any length of time, they should be secured to the extent of having their wheels chocked to prevent their movement, either in earthquakes or high winds.

No setback of construction from any of the indicated "faults" is necessary. If a set back is required for administrative reasons we recommend a zero setback.

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CONCLUSIONS

The Shangrl La Ranch Fault does not appear to cross the property. No evidence for faulting can be found on the property . No danger from flooding exists on the property . No danger from liquefaction of the soil during earthquakes exists. No evidence for aseismic creep could be found . The sol! Is adequately firm for foundations . No other geologic hazards were found . No setback is necessary to ensure safety of construction .

Pierre Salnt-Amand, PhD Registered Geologist, #2919 Registered Geophyslclst,#GP27 4

David C.H. Saint-Amand, BA Geologist

24 March 1992 1748 Las Flores Ridgecrest, California, 93555 619-375-0481

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REFERENCES

Allen, C. R., Pierre Saint-Amand, C. F. Richter and J.M. Nordqulst.1963, Relationship Between Selsmiclty and Geologic Structure In the Southern California Region. Seismological Society of America Bullctin,Volume 55. pp 753-797.

Berenbrok, Charles and Peter Martin, 1991, The Ground-water Flow System in Indian Wells Valley, Kern, Inyo and San Bernardino Counties, California. U.S.Geoiogical Smvey Water Resources Investigations Report 89-4191. 81 pp.

Chakrabarty, S. K. and C. F. Richter, 1949, The Walkers Pass Earthquake and Structures of the Southern Sierra Nevada. Seismological Society of America, Bulletin, Vol. 77, No.2, pp 163-182 .

Davis, J.F., 1990, State of California Special Studies Zones, Ridgecrest North Quadrangle. Callfornla Division of Mines and Geology, official map. This document was largely based on Roquemore and Zellmer, 1987 and on Wills, 1988 .

Dutcher, LC. and W. R. Moyle, Jr. 1973, Geologic and Hydrologlc Features of Indian Wells Valley, California. United States Geological Survey Water Supply Paper 2007, 30 pp., 6 plates, 3 figures and 3 tables .

Hill, Mason Land Diblee, T.W. Jr. 1963, San Andreas, Garlock and Big Pine Faults, Callfomla. Geological Society of America, Bulletin, Volume 64, pp. 443-458, 7 Figures, 4 Plates.

Goter, Susan K., 1988, Seismiclty of California, 1808-1987. National Earthquake Information Center. Map .

McGlll, Sally F. and Kerry Sieh, 1991, Surflclal Offsets on the Central and Eastern Garlock Fault Associated with Prehistoric Earthquakes. Journal of Geophysical Research, Vol. 96, No. B 13, Pp 21,597-21,621.

Miller, Paul H., 1962, A Cllmatological Summary of the Surface and ·Upper Alr Weather at NOTS, [1946-1962). Naval Ordnance Test

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Station Technical Publication TP3003. 74pp, numerous tables and references.

Moyle, W. R. Jr., 1963, Data on Water Wells in Indian Wells Valley Area, Inyo, Kem and San Bernardino Counties, California. Agency of califomia, pp. 243, 6 illustrations, 5 tables and a large map.

Ouimette, James R. 1974, Survey and Evaluation of the Environmental Impact of the Naval Weapons Center Activities, Naval Weapons Center, Technical Memorandum 2426. Naval Weapons Center, China Lake, California. 248 pp.

Park, William H., 1981, Geologic Hazards Investigation Tract No. 43(}-4, October 1981. Signed by Duane R. Smith and Dayne L Frary. Typewritten, 17 pp and maps.

Roquemore, Glenn R., 1981, Active Faults and Associated Tectonic Stress in the Coso Range, California, Naval Weapons Center Technical Publication, 6270. 101 pp.

Roquemore, G. R. and Zellmer, J. T. ,1987, Naval Weapons Center, Active Fault Map Series, Naval Weapons Center Technical Publication, TP 6828, 16 pp, 14 maps. This map series was based on aerial photographs. Some field checking was done, but the enormous area precluded careful checking of all the faults.

Saint-Amand, Pierre, 1958, Circum Pacific Orogeny. Publication of the Dominion Observatory, vol. 20, No. 2, pp. 403-411.

Salnt-Amand, Pierre, O.W. l.Dmbardi, and H. Schuler 1963. Earthquake of the Western United States: Chapter tn Estudlos Sohre La Slsmkldad de la Costa Occidental del Contlente Americana, Primera Parte: Americas del Norte y Central. Boletin Bibllographico de Geoflslca y Oceanografta Americana, Volume III, Parte Geoflsica 1960-1962, pp. 1-144, 63 Figures . Mexico D.F., Mexico 1963 pp 41-105.

Saint-Amand, Pierre, Rene Engel, William Park, and Bradley F. Willlams, 1972, Geology and Eanhquake Hazards-Planning Gulde to the Seismic Safety Elements of Kern County, California,

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June 1972. Available from Kem County Council of Governments, 11106-26th St., Bakersfield, Califomia,93301.

Saint-Amand, Pierre, July 1981. Geologic and Seismologic Conditions in the Heritage Village Site. Trench logs and maps.

Saint-Amand, Pierre, February 1984, Geologic and Seismic Report for Tract 2599-RS. For Wilbur Stark and Associates. Trench logs in pocket.

Salnt-Amand, Pierre, 1986a, Water Supply of Indian Wells Valley Technlcal Publication 6404, Naval Weapons Center, China Lake Calif., 71 pp, 34 Figs, 9 Tables .

Saint-Amand, Pierre, Mathews, Larry A.,1986b, Camille Gaines, and Roger Reinking. Dust Storms from Owens and Mono Valleys, Callfornla Technical Publication 6731, Naval Weapons Center, China Lake California, November 1986. 79 pp.

Sieh, Kerry, 1978, Slip Along the San Andreas Fault Associated with the Great 1857 ~arthquake Seismological Society of America, Bulletin, Volume 68, No 1, 5 pp. 1421-1448. '

Sieh, Kerry, Minze Stuiver and David Brilllnger, 1989, A More Precise Chronology of Earthquakes Produced by the San Andreas Fault in Southern California. Journal of Geophysical Research, Vol. 94, No. Bl, Pages 602- 623, January 10, 19&9.

Smith, George Ira, 1962, Large Lateral Displacement on Garlock Fault, California, as Measured from Offiiet Dike Swarms. American Association of Petroleum Geologists, Bulletin, Volume 46, No. 11, pp 85-104

Troxel, B.W., LA. Wright and R.H. Jahns, 1972, Evidence for Differential Displacement Along the Garlock Fault Zone, Callfomia. Geological Society of America, Bulletin. Abstracts, Volume 4, No. 3, p 250.

van Huene, Roland Ernst, 1960, Structural Geology and Gravlmetry of Indian Wells Valley, Southeastern California. Doctoral 1hesls, University of California at Los Angeles, 138 pp, 4 maps, 7 figures, 2 tables.

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Whitney, J. D. 1872, The Owens Valley Earthquake Overland Monthly, Volume IX, No. 8, August, pp. 13-140 and No. 9, September, pp. 266-278.

Wills, C.J., 1988, Uttle Lake and Airport Lake Fault Zones, Inyo and Kem counties, California, California Division of Mines and Geology; Fault Evaluation Report, FER-199. This document ls unpublished.

Wood, H.O., 1955. The 1857 Earthquake ln California, Bulletin of the Seismological Society of America, Volume 45, pp. 47-68.

Zbur, Richard T., 1963, A Geophysical Investigation of Indian Wells Valley, California. Naval Ordnance Test Station, Technical Publlcatlon, 1P 2795, Naval Ordnance Test Station, China Lake, California, 98 pp, 4 plates, 24 Figures.

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