c -7 -.. 7 · 10/21/1987 · division of mines and geology bay area regional office 380 civic...

STATE OF CALIFORNIA-THE RESOURCES AGENCY

DEPARTMENT OF CONSERVATION

DIVISION OF MINES AND GEOLOGY BAY AREA REGIONAL OFFICE

380 CIVIC DRIVE, SUITE 100 PLEASANT Hill, CA 94523-1997 PHONE, (41 5) 646-5920

ATSS 599-5920

city of Corona Public Works Department 815 West sixth street Corona, CA 91718-0090

Attn: Mehdi Khailaizadeh

c

}' 'I GEORGE DEUKMEJIAN, Governor

-7 . -.. 7 ~-

March 5, 1990

This is to acknowledge the October 21, 1987 geologic fault report of Highland Soils Engineering for Lot 46, Tract 20872, Corona. It will be filed for future reference should we do additional evaluations of the Chino fault.

Enclosed is our Fault Evaluation Report FER-38 as per your request. Please keep this FER on file for future reference.

EWH:hk Enclosure cc: A-P file

Sincerely,

EARL W. HART Senior Geologist &

Program Manager

OFFICE OF: Public Works Department

PW-0299-90 11.03-20872

714/736-2248 714/736-2496 (FAX)

815 WEST SIXTH STREET (P.O. BOX 940), CORONA, CALIFORNIA 91718-0090

March 1, 1990

State of California Department of Conservation

Division of Mines & Geology 380 Civic Drive, Suite 100 Pleasant Hill, CA 94523-1997

ATTENTION: Earl Hart

GEOLOGICAL FAULT INVESTIGATION REPORT - LOT 46 1 TRACT 20872

Per your request and information, attached please find a copy of geological fault investigation report prepared for the subject site.

As we discussed on the phone, please have a copy of "Fault Evaluation Report No. 38 11 (portion pertinent to City of Corona) be sent to this office.

If you have any questions, please call this office.

:;;::;: dov4J MEHDI KHAILAIZADEH civil Engineering Associate

Enclosure as noted.

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October 21, 1987

WSLA Development corporation 3151 Airway Avenue, Suite I-3 Costa Mesa, California 92626

Attention: Mr. Dennis Bushore Project Manager

SUBJECT:

Gentlemen:

GEOLOGIC FAULT INVESTIGATION Parcel 2, Lot 46 Sierra Del Oro Corona, California

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HIGHLAND SOILS ENGINEERING, INC. SOIL ENGINEERING & ENGINEERING GEOLOGY

Job No: 07-3088-027-00-00 Log No: 7-2086

In accordance with your request, we have performed a Geologic Fault

Investigation for Parcel 2, Lot 46, Tentative Tract No. 20872,

located in Corona, California. The purpose of our investigation was

to assess the potential for faulting within the subject site.

For our investigation, we

Site Plan and Topographic These plans were prepared

1.0 INTRODUCTION

were provided with a 100-scale and 40-scale Map of the proposed site, respectively. by Church Engineering.

This report presents the results of our Geologic Fault Investigation for Parcel No. 2, Lot 46, Tentative Tract No. 20872, located along the north side of the Wardlow Wash area,

Corona, California. A SUBSIDIARY OF THE IRVINE CONSULTING GROUP, INC.

1832 S. COMMERCENTER CIRCLE, SUITE A • SAN BERNARDINO, CA 92408 • (714) 884-8828

I I

TABLE OF CONTENTS

I Page No.

I 1.0 INTRODUCTION 1

I 1.1 Proposed Development 2

1.2 Authorization 2

I 1.3 Scope of Services 2

2.0 SITE DESCRIPTION 3

3.0 FIELD EXPLORATION 4

I 4.0 GEOLOGY 5

4.1 Geologic Setting 5

I 4.2 Geologic Units 6

4.2.l Older Alluvium 6

I 4.2.2 Younger Alluvium 6

4.2.3 Artificial Fill 7

I 4.3 Structural Geology/Faulting 7

4.4 Groundwater 8

5.0 GEOLOGY 8

I 5.1 Regional Seismicity 8

5.2 Earthquake Effects 10

I 5.2.l Earthquake Accelerations 10

5.2.2 Soil Settlement 10

I 5.2.3 Liquefaction 11

5.2.4 Ground Rupture 11

I 6.0 THE CHINO FAULT 12

6.1 Summary of Fault Trench Observations 12

6.1.l Trench-1 12

I 6.1.2 Trench-2 13

6.1.3 Trench-3 13

I 6.1.4 Trench-4 14

6.1.5 Trench-5 14

I 6.1.6 Trench-6 14

6.2 Summary of Geologic Mapping 15

I I

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TABLE OF CONTENTS (Continued Page-2)

6.3 Evidence of Additional Fault

6.4 Aerial Photograph Review

6.5 Exploratory Borings

6.6 Seismic Refraction

7.0 CONCLUSIONS

e.o RECOMMENDATIONS

Attached and Included Figures:

Appendix A, References Figure 1, Location Map Figure 2, Map of Historic Epicenters Figure 3, Seismicity for Major Faults Plate 1, Geotechnical Map Plates 2-7, Geotechnical Trench Logs

Activity

Page No.

16

17 17

17

19

20

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WSLA Development Corporation

October 21, 1987 Job No: 07-3088-027-oo-oo

Log No: 7-2086

Page 2

1.1 Proposed Development

1.2

1.3

No precise development plans were available for our

review. It is our understanding that the site will be

developed by one-story, reinforced concrete, tilt-up

commercial structures. Conceptual grading was shown for

Lot 2 on the 100-scale site plan and indicates

predominantly fill grading with fills up to 30 feet in

thickness. A realignment and channelization of the

Wardlow Wash will also be performed with fill slopes up

to 35 feet in height.

Authorization

Our proposal for this phase of work is dated September

15, 1987, Proposal Number HSE-7-6755. Written authorization was received from Mr. Dennis Bushore,

Project Manager, dated September 21, 1987. Due to site

conditions, the additional cost of our investigation was

verbally approved by Mr. Dennis Bushore on March 6,

1987.

Scope of Services

The scope of services provided during the course of this

investigation included:

A. Review of previous published and unpublished

geologic and seismological reports and maps pertinent to the subject site {see references);

B. Review of stereographic aerial photographs to

evaluate topography, geomorphic features and geologic structure of the area;


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LOCATION MAP OB NO.: 3088-027-00-00 DATE: OCTOBER 11187

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FIGURE: 1

Highland Soils Engineering, Inc.

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October 21, 1987

Job No: 07-3088-027-00-00

Log No: 7-2086

2.0

c.

D.

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Page 3

Subsurface exploration which included approximately 695 linear feet of geologic trench

at the subject site to depths as great as 21 feet

below the existing ground surface.

Logging of geologic trenches by our Project

Geologist. This work was supervised and on-site observations were performed by a California Registered Geologist;

Geologic analyses of field and office data to provide a basis for our conclusions and recommendations;

F. Performing a geophysical survey utilizing seismic

refraction techniques;

G. Preparation of this report with maps and other graphics, presenting our findings, conclusions and

recommendations.

SITE DESCRIPTION

The project site is an irregularly shaped, 38.6 acre parcel of land which is bound on the north by Palisades Drive, on the east by Serfas Club Drive, on the west by undeveloped land and

on the south by undeveloped property and under-construction

residential property.

Topographically, the site is dominated by the northwest flowing Wardlow Wash. The Wardlow Wash extends entirely across the site and has formed prominent benches and cuts into


WSLA Development Corporation October 21, 1987

Job No: 07-3088-027-00-00 Log No: 7-2086

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the northeast and southwest portions of the project. With the

exception of the benched and channel cut areas at the northeast and southwest portions of the site, this project has

a relatively uniform 3± % gradient to the northwest. Surface

relief between the stream channel and the northeast portions of the site is 30 to 40 feet, and at the southwest portions of

the site, 10 to 15 feet.

The site is currently undeveloped with the exception of two waste hazard disposal areas located at the north portion of the project on Lot 1.

Man-made features on-site were observed to consist of two, fenced, waste hazard areas at the north portion of the site. Concrete spillways are located in the upstream portion of the

wash at Serfas Club Drive and at drainage areas which flow into the wash from the south adjacent properties. The south portion of this site has been zoned a 100-year flood plain by the County of Riverside.

FIELD EXPLORATION

The field exploration program conducted during this

investigation consisted of excavating five (5) geologic exploratory trenches for a total of 695 lineal feet to depths ranging from 12 to 21 feet below the existing ground surface, and performing three (3) seismic refraction traverses

utilizing a Geometrics Model 1210F Seismograph. Our exploratory trenches were excavated with both a Ford, 655 rubber-tired backhoe, and a Caterpillar, Model 225 tracked backhoe.



Job No: 07-3088-027-00-00 Log No: 7-2086 Page 5

4.0 GEOLOGY

4.1 Geologic Setting

The site is located along the northern margin of the Santa Ana Mountains near the eastern edge of the Los Angeles Basin. The site and surrounding terrain are part of the Peninsular Ranges Geomorphic Province of California. The Peninsular Ranges, which extend southward from the Los Angeles Basin through Baja California, are characterized by large Mesozoic Age intrusive rock masses flanked by volcanic,

metasedimentary and sedimentary rocks. The Peninsular Ranges have a general northwest-trending structural

grain that includes such geologic features as faults, bedding and foliation trends and geologic contacts.

Lateral displacement and uplift of the region has

occurred on a series of major, northwest-trending faults which are thought to be related to the regional

tectonic framework. Some of these fault zones have remained active to the present time and includes the

Whittier-Elsinore Fault Zone near the project site.

Locally, the site is underlain by recent alluvial deposits at the central and south portions of the

project and older alluvium at the north portions of the

site. Based on the soil geomorphology coupled with

other geomorphic features, the older alluvium is estimated as Late Pleistocene age. This is in agreement with age assessments by Gray (1961) and Weber (1977). The older alluvium is uncomformably, overlain by the



Job No: 07-3088-027-00-00 Log No: 7-2086

4.2

Page 6

recent alluvium. The older alluvial deposits consisted primarily of unconsolidated gravels and cobbles made up of angular to subrounded fragments of volcanic, granitic, metamorphic and sedimentary rocks set in a reddish-brown to dark gray, sandy matrix. This was interbedded gravels with gray to

light brown silts, sand, gravels and cobbles.

Geologic Units

4.2.l Older Alluvium (Map Symbol: Qalo)

The older alluvium consists of Late Pleistocene age, unconsolidated cobbles and boulders made up of angular to subrounded fragments of volcanic,

granitic, metamorphic and sedimentary rocks set in a dark gray to dark brown, sandy matrix. This was interbedded with gray to light brown silts, sands, gravels, cobbles, and boulders to 10 inches in size. Massive reddish-brown silty sands and silty sand paleosols were also encountered within the

older alluvium.

4.2.2 Younger Alluvium (Map Symbol: Qalr)

The encountered younger alluvium consisted of recent stream channel deposits consisting of gray to light brown, silts, sands, gravels, cobbles and boulders. These deposits are typically

unconsolidated.

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Job No: 07-3088-027-00-00 Log No: 7-2086

4.3

Page 7

4.2.3 Artificial Fill (Map Symbol: af)

Artificial fill was encountered in several of our exploratory trenches which consisted of poorly

consolidated, silty sands with trace amounts of gravels and cobbles. There were some amounts of

asphalt and other debris encountered within the

exposed fill.

Structural Geology/Faulting

The Corona-Santa Ana Narrows Region is comprised of

three major structural blocks. These include the Santa

Ana Mountains Block bound on the northeast by the Elsinore and Whittier Faults, the Puente-Chino Hills

Block bound on the northeast by the Chino Fault and on the southwest by the Elsinore and Whittier Faults; and the Corona-Chino Valley Block located on the northeast side of the Chino Fault.

The dominant structural feature in the general area is the northwest-striking Chino Fault Zone. The Chino Fault Zone branches away from the Elsinore Fault at a

point south of Corona, and extends northwestward along the eastern margin of the Puente Hills. The Chino Fault appears to converge upon or is continuous with segments of the Elsinore Fault. The northern terminus of the fault is unknown and may be as far north as Pomona. The Chino Fault is a northwest trending, reverse fault where the southwest side has been displaced upward relative to

the northeast.



October 21, 1987 Job No: 07-3088-027-00-00

Log No: 7-2086

5.0

4.4

Page 8

Groundwater

Four (4) exploratory borings were excavated to a minimum

depth of 100± feet below the ground surface by O.H. Materials Corporation during October, 1987. These

borings were located at the central and north-central portions of the project (See Plate 1). Static groundwater measurements performed after a minimum of 24

hours following the boring excavation indicated a static

groundwater elevation of 516± feet with a hydraulic gradient of .003 in a north direction. No significant groundwater fluctuations were noted.

SEISMICITY

5.1 Regional Seismicity

The site is located in a region of generally high seismicity as is all of Southern California. During its design life, the site is expected to experience ground

motions from earthquakes on regional and/or local causative faults. Figure 2 shows the geographic

relationship of these faults to the site and the

epicenters for numerous large earthquakes that have occurred in historic time. The table on Figure 3 lists known regionally active faults, their maximum probable earthquake magnitude and seismic parameters for

identified causative faults.

According to Weber, 1977, the Chino Fault traverses the site in a northwest direction, See Plate 1. The Chino Fault is not (at this time) designated as a fault-rupture hazard zone by state or county agencies.

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MAP OF HISTORIC EARTHQUAKE EPICENTERS, MAGNITUDE > 5.0 DATE: FIOURE: JOB NO.: O O 07-3088-027-0 - 0 OCTOBER 1987 2

------------11 SEISMICITY FOR MAJOR FAULTS

ESTIMATED MAXIMUM ESTIMATED REPEATABLE MODIFIED

DISTANCE FROM PROBABLE PEAK GROUND HIGH GROUND MER CALLI FAULTS SITE (MILES) EARTHQUAKE ACCELERATION ACCELERATION INTENSITY

Whittier- 2 SE Elsinore

7.0 .56g .37g IX

San Jacinto 21 NE 7.1 .14g .09g VII

San Andreas 28 NE 7.5 .13g .09g VII

Newport- 26 SW 6.5 .09g .06g VI-VII Inglewood

Chino On-Site 6.5 .60g .39g IX

1. seed and Idriss (1982)

2. Ploessel and Slosson (1974)

3. seismic Design for Nuclear Power Plant (1970)

Job No: 07-3088-027-oo-oo Figure 3



Job No: 07-3088-027-oo-oo Log No: 7-2086

Date

1812

1890

1899 1899 1907

1910 1918 1923 1933

1971 1987

Page 9

The Chino Fault is considered a potentially active fault

and not an active fault by the County of Riverside and State. A potentially active fault is a fault which has shown surface displacement during the Quarternary time

(last 2 million years), but not necessarily during the

last 11,000 years. Normally potentially active faults such as the Chino Fault do not require investigation. However, the County Seismic Safety Element, a portion of

the Riverside County Comprehensive General Plan, 1984, states that, "an active or potentially active fault within 150 feet of a proposed site for a subdivision or

human occupancy structure will require a geologic report to evaluate surface displacement and other seismic hazards".

Earthquake epicenters (exceeding 6.0 on the Richter Scale of Magnitude) within a 65-mile radius of this project are listed below:

Approximate

Distance of Site Richter To Epicenter Miles Fault

6.0+ 28 SW Newport-Inglewood

6.0+ 20 NE San Jacinto 6.0+ 27 N San Andreas 7.0+ 45 SE San Jacinto 6.0+ 35 NE San Andreas 6.0+ 24 SE Elsinore 6.0+ 36 SE San Jacinto 6.0+ 25 NE San Jacinto 6.0+ 27 SW Newport-

Inglewood 6.0+ 55 NW San Fernando 6.1 25 NW Whittier



Job No: 07-3088-027-00-00 Log No: 7-2086

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Earthquake Effects

5.2.l Earthquake Accelerations

We have analyzed the possible earthquake accelerations at the site and determined that, for

the intended use, the most significant event would be an 6.5 Magnitude earthquake occurring on the Chino Fault Zone. The accelerations produced at

the site by such an event would exceed those of events on any other known fault.

A Magnitude 6.5 earthquake occurring on the Chino Fault in close proximity to the site could produce

a peak ground acceleration on the order of 0.60g at the site, (Seed and Idriss, 1982), with the duration of strong motion exceeding 19 seconds (Bolt, 1973). Peak acceleration is not, however, always representative of the accelerations for which structures are actually designed (Ploessel and Slosson, 1974). Repeatable high ground accelerations from an 6.5 Magnitude earthquake on

the Chino Fault are estimated to be on the order

of 0.39g. The design of structures should comply

with the requirements of the governing jurisdictions and standard practices of the

Structural Engineers Association of California.

5.2.2 Soil Settlement

The on-site materials consist generally of loose

to medium-dense, sandy soils. The settlement potential under seismic loading conditions for the on-site materials, in our opinion, is low to

moderate.



5.2.3 Liquefaction

Job No: 07-3088-027-00-00 Log No: 7-2086 Page 11

The alluvial soils underlying the site have a low

potential for liquefaction due to the absence of shallow groundwater within 50 feet of the ground surface. During this investigation, four (4) exploratory borings revealed a static groundwater elevation of 516± feet. This is in excess of 75 feet below the ground surface.

5.2.4 Ground Rupture

Breaking of the ground due to active faulting is

considered low to moderate at this site, due to the presence of the potentially active Chino

Fault. The recurrence interval for a 6.5 Magnitude event occurring on the Chino Fault is approximately 20,000 to 40,000 years. This

recurrence interval is based on a strain rate (.02 to .06 millimeters per year, Clark and others, 1984 Prado Dam area of the Chino Fault) and

Earthquake Magnitude Relationships presented in

Slemmons, dated May, (1977).

The potential for ground rupture was also addressed by our subsurface work on both the

subject site and the adoining site to the south

(Highland Soils, 1987). In our trenches, an older alluvial unit estimated at over 15,000 years in age was unbroken indicating no movement within a minimum of 15,000 years. This is in agreement with the recurrence interval discussed above.



October 21, 1987

6.0 THE CHINO FAULT

Job No: 07-3088-027-00-00 Log No: 7-2086 Page 12

6.1 Summary of Fault Trench Observations

6.1.l Trench-1

Fault Trench-1 was located within the Wardlow Wash at the east portion of the site. This trench was approximately 300 lineal feet in length and varied in depth from 15 to 21 feet below the existing

ground surface. The exposed stratigraphy from

Station o to 115 consisted of older alluvium at depths below 15± feet of the existing grade. This was unconformably overlain by recent stream channel deposited silts, sands, gravels, cobbles and boulders.

The older alluvium consisted of reddish-brown to dark gray, slightly bedded, unconsolidated silts, sands, gravels, cobbles and boulders to eight (8) inches in size with occasional laminations of

sands and silts. From Station 115 to 125 and again from 225 to 230, the older alluvium had been

scoured and filled with recent channel deposits. Recent channel deposits consisting of gray to



October 21, 1987 Job No: 07-3088-027-00-00

Log No: 7-2086 Page 13

light brown, silts, sands, gravels, cobbles and

boulders overlie the older alluvium from Station o to 260. The older alluvium was exposed nearly

continuously throughout the lower portions of our geologic trench. No fractures or evidence of faulting was observed within the limits of this trench.

6.1.2 Trench-2

Trench-2 exposed older alluvial deposited silts,

sands, gravels, and cobbles which were overlain by reddish-brown, duricrust paleosols. No fractures or evidence of faulting was observed within the limits of this trench.

6.1.3 Trench-3

Trench-3 consisted of fluvial, point bar type depositional sediments. These sediments consisted of thin laminations to interbedded one-foot beds of silt, sands, and gravels. There was no evidence of faulting observed within this trench. There was good soil stratigraphic control.

However, this trench lacked the older alluvium necessary to provide relative dating. The sediments are estimated to be less than 1000 years in age and provide evidence only that no faulting

has occurred in the last 1000 years within the trench exposures.



6.1.4 Trench-4

Job No: 07-3088-027-oo-oo Log No: 7-2086 Page 14

Trench-4 was located at the northwest portion of

the project. This trench was approximately 95 lineal feet in length and 12 to 20 feet deep. The

exposed soils consisted of up to four (4) feet of artificial fill which was underlain by older

alluvium deposited as reddish, light-brown to gray silts, sands, gravels, and cobbles. At Station 55 to 95, the older alluvium was observed to be scoured, then overlain by recent deposits of silts, sands, and gravels. No fractures or evidence of faulting was observed within the limits of this trench.

6.1.5 Trench-5

Trench-5 was located adjacent to Trench-3. The purpose of this trench was to extend the depth of our observations at this location. It was

observed that several scours and stream channels occurred within the recent point bar deposits. No

evidence of faulting was observed within our trench.

6.l.6 Trench-6

Fault Trench-6 was excavated in conjunction with the investigation for the adjoining property.

Trench-6 provides additional control for the subject site and is included on Plate I. This trench was approximately 280 lineal feet in length and exposed from Station o to 83, primarily


WSIA Development Corporation

October 21, 1987 Job No: 07-3088-027-oo-oo Log No: 7-2086

6.2

Page 15

older alluvium which was overlain by significant amounts of artificial fill. This older alluvium

consists of unconsolidated cobbles and boulders made up of angular to subrounded fragments of volcanic, granitic, metamorphic, and sedimentary rocks set in a dark gray to light brown sandy matrix. Massive reddish, light brown, silty sands

were also encountered within these deposits. As in similar exposures of older alluvium in the

other trenches, the rubification of arkosic, gravelly sands and the clast weathering rinds are

indicative of a deposit in excess of 15,000 years

(Birkeland, 1984).

From Station 83 to 280, recently deposited stream channel alluvium overlain by artificial fill was encountered. The recent alluvium consisted of gray to light brown, poorly consolidated, silts, sands, gravels, cobbles and boulders which was overlain by significant amounts of artificial fill. This fill consists of silty sands, gravels, and cobbles with trace amounts of debris. No

fractures or evidence of faulting was observed throughout the trench.

summary of Geologic Mapping

The observed surf icial geology consists of recent stream channel alluviums within the Wardlow Wash which unconformably overlies the older alluvium on the northeast. The recent alluvium derived from the hills to the west grades into the stream alluvium to the southwest.



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Evidence of Additional Fault Activity

A Geologic Fault Investigation was performed on the Elsinore-Chino Fault Zone 4± Miles southeast of the site by Highland Geotechnical Consultants, dated July, 1987. The findings of this investigation indicated that the

portion of the Chino Fault crossing the Main Ranch site

was not active by definition - less than 11,000 years in age. The date of the most recent offset was found to be 15,000 - 20,000 years in age.

According to Weber (1977), relative youthfulness of

activity along the Chino Fault Zone in the Puente Hills area, 3.5± miles northwest of the project site, is revealed by right deflected drainages and apparent offset of older alluvium suggesting maximum age of faulting as Pleistocene. Weber also observed several

scarps and other geomorphic features from aerial photos of the Chino Fault within the Pleistocene age sediments. In our opinion, there was no direct geologic evidence presented by Weber (1977) which would indicate Holocene age faulting.

According to Durham and Yerkes (1964), the youngest strata cut by the Chino Fault in the eastern Puente Hills area are assigned to the Sycamore Canyon member of the Puente Formation of late Miocene Age, although the uppermost part of this unit may include strata of Pliocene Age. Durham and Yerkes (1964), also suggests that movement along the Chino Fault probably followed formation of the Mahala Anticline and probably coincided with or followed the middle Pleistocene deformation of the Los Angeles basin.



Job No: 07-3088-027-00-00 Log No: 7-2086 Page 17

6.4 Aerial Photograph Review

6.5

From our aerial photograph review, there were no significant geomorphic features observed within the site bounds. Subtle scarps and minor lineaments were

observed 2 to 3 miles southeast of the site within the

late Pleistocene age deposits (Weber, 1977). No features which indicated or suggested Holocene faulting was observed.

Exploratory Borings

During this investigation, four (4) exploratory borings were performed by O.H. Materials Corporation. The

locations of these borings are shown on Plate 1. The following data was provided by an O.H. Materials representative:

"!,oring Number

Depth of

Boring Groundwater Elevation Comments

1

2

3

4

6.6

140 1 515.90 1 No Refusal 99 1 514.61 1 No Refusal

120' 514.39' No Refusal 111' 517.47 1 No Refusal

Seismic Refraction

Three (3) seismic refraction traverses were performed utilizing a Geometrics Model 1210F Seismograph with a 12-geophone spread. Geophone spacing was 20 feet in the 100 to 320- foot spread. A 12-pound sledgehammer and



Job No: 07-3088-027-00-00 Log No: 7-2086 Page 18

metal striker plate was used to generate the P-Wave energy. A permanent electrostatic tract was made of the

field data; time-distance curves were then plotted at

our office for calculations of critical values.

The approximate locations of the seismic traverses are indicated on the Site Plan, Plate 1. No conclusiv,e

evidence was obtained from our seismic traverses that indicated or reflected the existance of faulting.



October 21, 1987

Job No: 07-3088-027-00-00

Log No: 7-2086 Page 19

7.0 CONCLUSIONS

Based on our observations of physical evidence and evaluation of our geologic trenches, the referenced aerial photographs

and review of previous published and unpublished geologic and seismological reports and maps pertinent to the subject site

(see references), it is our opinon that the Chino Fault, crossing the subject property, is not active by definition -

less than 11,000 years in age.

The following is a summary of our findings and other pertinent data relative to the site:

a)

b)

c)

d)

No evidence of faulting was observed within our geologic trenches. These trenches exposed the older alluvium of Pleistocene age approximately 15,000 to 20,000 years in age.

From our aerial photograph evaluation, there were no

significant geomorphic features observed which would suggest Holocene faulting along the Chino Fault through

or near the site.

Fault trenching along the same fault trace 4± miles southeast of the project site, produced physical geologic evidence that the most recent offset of the Chino Fault in that area was 15,000 to 20,000 years in age. This offset was found in older alluvium similar to that encountered in our geologic trenches.

Within the Prado Dam area, 1± miles northwest of the site, the recurrence interval for a 6.5 magnitude event occurring on the Chino Fault is approximately 20,000 to


WSLA Development Corporation Job No: 07-3088-027-00-00 October 21, 1987 Log No: 7-2086

Page 20

8.0

e)

40,000 years. This.recurrence interval is based on a strain rate of .02 to .06 millimeters per year and an earthquake magnitude relationship.

From our review of previous published and unpublished geologic and seismological reports, there is no direct geological evidence suggesting Holocene faulting through

or near the site.

It is our opinion, that the portion of the Chino Fault which crosses the subject site is not active. Therefore, it should be considered as a Quaternary or a potentially active fault as it is presently classified by state and county agencies.

RECOMMENDATIONS

No setback requirement for human occupancy structures is necessary for the Chino Fault at the site.

This opportunity to be of service is appreciated. If you have any questions, please call.

Very truly yours,

HIGHLAND SOIL.S ENGINEERING, INC.

A-i-J.. c. ~ . Robert Manning ~ Project Geologist

Reviewed by:

Warren L. Sherling, C.E.G. 1182 Chief Geologist Registration Expires 6-20-88

RM:WL.S:WTA:vdp

£1 4 q 4rd'- T.Cl 4 C,?t CJ'" ..... William T. Altmeyer, R.C.E. 929 Director of Geotechnical Services Registration Expires 12-31-88


REFERENCES

Durham, D.L., Yerkes, R.F., 1964, Geology and Oil Resources of the Eastern Puente Hills Area, Southern California, U.S. Geological Survey Professional Paper 420-B, pp 32-35.

Gray, C.H., 1961, "Geology of the Corona south Quadrangel and the Santa Ana Narrows Areas, Riverside, Orange, and San Bernardino Counties, California", California Division of Mines and Geology Bulletin 178:

Highland Soils Engineering, July 1987, Geologic Fault Investigation, Main Ranch, Corona, California; Job Number 07-6750-003-00-01, Log Number 7-1901.

Ploessel, M.R., Slosson, J.E., September, 1974, Repeatable High Ground Accelerations from Earthquakes, California Geology;

Ral, C.R., et. al., 1978, Earthquake Epicenter Map of California, 1900-1974; California Division of Mines and Geology Map Sheet 39;

Seed, H.B., Murarka, R., Lysmer, J., and Idriss, I.M., 1975, Relationships Between Maximum Accelerations, Maximum Velocity, Distance from Source and Local Site Conditions for Moderately Strong Earthquakes: Earthquake Engineering Research Center Report No. 75-17;

Seed, H.B., Idriss, I.M., 1982, Ground Motion and soil Liquefaction During Earthquakes, Earthquake Engineering Research Institute Nomograph;

Slemmons, D.B., 1977, Faults and Earthquake Magnitude: Miscellaneous Paper 5-73-1, State-of-The-Art for Assessing Earthquake Hazards in the United States, Report 6, U.S. Army Corps of Engineers, Washington, D.C.

Weber, H.F., 1977, Seismic Hazards Related to Geologic Factors, Elsinore and Chino Fault Zones, Northwestern Riverside County, California.

I I I I I County

I County

county

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

Flight, 1959

Flight, 1974

Flight, 1984

REFERENCES

AERIAL PHOTOGRAPHS

Photos: AXM-18W-163-l66 AXM-18W-117-123

Photo: 292

Photos: 1318-1320

c -7 -.. 7 · 10/21/1987 · division of mines and geology bay area regional office 380 civic...

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