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HomeMy WebLinkAboutTerra Geosciences Fault Study 3-31-2015 TERRA GEOSCIENCES EVALUATION OF SURFACE FAULT RUPTURE HAZARD ELSINORE VIEW MOBILE HOME PARK PROJECT ASSESSOR'S PARCEL NOS. 371-150-001 & -002 (4.51AC & 2.25AC) AND 371-090-001 & -002 (4.55AC & 2.27AC) CITY OF LAKE ELSINORE, RIVERSIDE COUNTY, CALIFORNIA Project No. 152772-1 March 31, 2015 Prepared for: Matrix Geotechnical Consulting P.O. Box 2161 Temecula, California 92593 Consulting Engineering Geology&Geophysics P.O. Box 1090, Loma Linda, CA 92354 • 909 796-4667 Matrix Geotechnical Consulting March 31, 2015 P.O. Box 2161 Project No. 152772-1 Temecula, CA 92593 Attention: Mr. Chris Josef Regarding: Evaluation of Surface Fault Rupture Hazard Elsinore View Mobile Home Park Project Assessor's Parcel Nos. 371-150-001 & -002 (4.51ac & 2.25ac) and 371-090-001 & -002 (4.55ac & 2.27ac) City of Lake Elsinore, Riverside County, California EXECUTIVE SUMMARY At your request, we have completed an evaluation of the potential for surface fault- rupture hazard within the proposed 13.58±-acre mobile home park as referenced above. In summary, it was found that there is an active fault zone that traverses through the central portion of the subject property, which required establishment of a "Restricted- Use Zone" for "habitable" building purposes. Additionally another "Restricted-Use Zone" was also established along the northernmost portion of the site where subsurface exploration was not performed to evaluate faulting potentials within the designated County fault Zone. These Restricted-Use Zones are presented on a topographic base map that was provided by VSL Surveying, Temecula, California, which displays the surveyed fault locations and exploratory trenches along with other pertinent geologic data for documentation purposes. This opportunity to be of service is sincerely appreciated. If you should have any questions regarding this report or do not understand the limitations of this study or the data that is presented, please contact our office. Respectfully submitted, �SS�ONAL Q TERRA GEOSCIENCES of C-SCHWARr2� O� w y CERTIFIED � i�J�f x�� 1 ENGINEERING ^ GEOLOGIST Donn C. Schwartzkopf �� No.1459 �Q Professional Geologist, PG 4094 OF CALIF��� Certified Engineering Geologist, CEG 1459 TERRA GEOSCIENCES TABLE OF CONTENTS Page No. INTRODUCTION 1 SCOPE OF SERVICES 1 GEOLOGIC SETTING 2 LOCAL FAULTING 4 PHOTOGEOLOGIC SUMMARY 5 FIELD RECONNAISSANCE 6 SUBSURFACE EXPLORATION 6 Exploratory Trench T-1 7 Exploratory Trenches T-2 though T-4 9 Exploratory Trench Summary 9 RELATIVE AGE DATING 10 CONCLUSIONS & RECOMMENDATIONS 10 General 10 Conclusions 11 Recommendations 13 1. Restricted-Use Zones 13 2. Additional Work 14 3. Trench Backfill 14 CLOSURE 14 ILLUSTRATIONS Geomorphic Map Figure 1 Regional Geologic Map Figure 2 County Fault Zone Map Figure 3 Topographic Map Figure 4 Comparison Geologic Map Figure 5 Geologic Site Map Plate 1 APPENDICES Exploratory Trench Logs Appendix A Site Photographs Appendix B References Appendix C TERRA GEOSCIENCES Project No. 152772-1 Page 1 INTRODUCTION At your request, this firm has performed an evaluation of the potential for surface fault rupture with respect to the proposed 13.58± acre site. We understand that the site is proposed for development of a mobile home park and associated appurtenances, which includes undetermined amounts of cut and fill grading. No grading plans were available at the time this report was prepared. The subject property lies along the southeastern edge of Lake Elsinore, in the City of Lake Elsinore, Riverside County, California, and geographically lies within the southern half of Section 16, Township 6 South, Range 4 West, SBB&M. and shown on Figure 4. For visual and reference purposes, overall photographic views of the exploratory trenches are presented within Appendix B. The project lies approximately 2,000± feet to the southwest of an established Earthquake Fault Zone that is associated with the Elsinore Fault Zone (Wildomar Fault), as mapped by the California Geological Survey (Bryant and Hart, 2007). However, the site is shown to be located within a designated County Fault Zone as indicated on Figure 3. This report has been prepared utilizing the suggested "Guidelines for Evaluat- ing the Hazard Surface Fault Rupture" (California Division of Mines and Geology, Note 49) in addition to the County of Riverside "Technical Guidelines for Review of Geotechnical and Geologic Reports" (2000). We understand that groundwater, seismic, and other associated pertinent geologic data will be discussed within your geotechnical report, of which this report will be an appendix. SCOPE OF SERVICES As authorized by you, the following services were performed during this study: y Review of available published and unpublished geologic/geophysical data in our files pertinent to the site. Photogeologic analysis of stereoscopic pairs of aerial photographs that were obtained from the Riverside County Flood Control District and other sources. ➢ Geologic field reconnaissance of the site by a State of California licensed Certified Engineering Geologist. Subsurface investigation by means of stratigraphic logging of 1,901 lineal feet of exploratory trench, up to 14± feet in depth. ➢ Field accompaniment with the project land surveyor (VSL Survey) delineating the necessary survey locations which included the exploratory trench limits and fault locations. ➢ Field meeting with the Riverside County Geologist (Mr. David Jones) for the purpose of viewing the exploratory trenching and discussing our findings. ➢ Preparation of this report, which presents the results of our findings, conclusions, and recommendations relating to the potential for surface fault rupture at the site, with respect to the proposed development. TERRA GEOSCIENCES Project No. 152772-1 Page 2 GEOLOGIC SETTING The subject site is situated within a natural geomorphic province in southwestern California known as the Peninsular Ranges, which is characterized by steep, elongated ranges and valleys that trend northwesterly. This province is believed to have begun as a thick accumulation of predominantly marine sedimentary and volcanic rocks during the late Paleozoic and early Mesozoic (pre-batholithic rocks). Following this accumulation, in mid-Cretaceous time, the province underwent a pronounced episode of mountain building. The accumulated rocks were then complexly metamorphosed and intruded by igneous rocks, known locally as the Peninsular Ranges Batholith. A period of erosion followed the mountain building, and during the late Cretaceous and Cenozoic time, sedimentary and subordinate volcanic rocks were deposited upon the eroded surfaces of the batholithic and pre-batholithic rocks (post-batholithic rocks). Most of these post-batholithic rocks occur along the western and northern potion of the province. More specifically, the site lies along the boundary of two sub-structural blocks of the Peninsular Range province, with the Perris Block to the northeast and the Santa Ana Mountain Block to the southwest (see Figure 1 below). These two structural blocks are separated by the Elsinore Fault Zone, of which is one of the major structural features of southern California and can be traced from the Puente Hills to the north to the Mexican Border along the south, a distance of 200± kilometers (Hull and Nicholson, 1992). 1. emna..y sp oaf NN/ " 2 pbton 6an6 ll d. bped Peaetr _ '(l � H � m.uy �ac,orelea �/y �1 y �11 PYmonh rat. O � \ H 2 u c r . ■ � iM us rp ,, San'J i SITE + P rns Block Santa 7/; N P �tle.ilrmwr T 1 O YP ——— — ——---- FIGURE 1- Geomorphic map of a portion of the north-central Peninsular Ranges (modified from Morton and Weber, 2003). Red band shows age contour offsets (right lateral)across Elsinore Fault Zone. TERRA GEOSCIENCES Project No. 152772-1 Page 3 Along its length, the Elsinore Fault Zone forms numerous complex series of pull-apart basins, with the most distinct closed basin forming La Laguna, which is partly filled by Lake Elsinore, of which the site is partially located near its southeastern margin. Locally this basin, which is bounded by active faults, is essentially a graben, where a block or portion of the earth's crust has been down-dropped along faults relative to the surrounding areas that have been uplifted. Locally, as mapped by Morton and Weber (2003), indicated on Figure 2 below, the central elevated hillier portion of the site is shown to consist of Pleistocene sedimentary bedrock locally referred to as the Pauba Formation, which is generally described as a moderately well-indurated channeled and filled siltstone, sandstone, and conglomerate facies. Locally, the Pauba Formation has been further subdivided into a sandstone member (Qpfs) that is generally comprised of moderately well-indurated, cross-bedded sandstone, containing sparse cobble- to boulder-conglomerate beds. Northeast of this hill, the site is shown to be mantled by late Holocene age lacustrine deposits (QI), generally described as clayey, silty and fine-grained sediments. The surficial sediments southwest of the hill have been mapped as Holocene and late Pleistocene fluvial deposits derived as alluvial valley outwash (Qyv), consisting of unconsolidated sand, silt, and clay. This more recent published mapping generally coincides with previous mapping prepared by Webber (1977). >� • QI .. nd Village - --- -- ,. •• �• •• ; �`-- i ice._ _->, h YV Or FIGURE 2- Partial geologic map of the Elsinore 7.5' Quadrangle (Morton and Weber, 2003). Symbol "QI" represents lacustrine deposits (late Holocene), "Qyv" indicates alluvial-valley deposits (Holocene and late Pleistocene), with "Qpfs" denoting bedrock of the Pauba Formation (Pleistocene). Dashed/dotted lines depict faults while thin solid lines depict geologic contacts. The property boundary is outlined in red. TERRA GEOSCIENCES Project No. 152772-1 Page 4 Based on our subsurface exploration and as discussed further in this report, these geologic units are generally consistent with our findings. However, the actual mapped earth materials and fault locations shown on Figure 2 vary somewhat across the site. LOCAL FAULTING According to the State of California (C.D.M.G., 1980), the site is shown to be located just to the west of a designated Alquist-Priolo Earthquake Fault Zone (see Figure 3 below). This fault is locally referred to as the Wildomar Fault, which is one of the central strands of the Elsinore Fault Zone System (part of the Temecula Segment), which runs from the Los Angeles Basin to the north, into Mexico to the south. The Wildomar Fault is a right-lateral, strike-slip fault, being approximately 42 kilometers in length. Weber (1977), the County of Riverside (2000), and Morton and Weber (2003), indicate two discontinuous unnamed fault branches to traverse through the site as shown Figure 2 and on Figure 3 below. The red-shaded fault zone as indicated on Figure 3 below was the basis for this surface fault hazard report. City'bf Lake Elsinore �1•. c 1F R8 DR r�0 9 , FIGURE 3- Partial map the County Fault Zone Map (County of Riverside, 2000). Faults are indicated by solid red lines with the fault zones defined by the red shading. The northeast-southwest trending blue line is the approximate trench location. The purple shaded zone east of the site is the Wildomar Fault as zoned by the C.D.M.G. (1980). Site is outlined in black. TERRA GEOSCIENCES Project No. 152772-1 Page 5 PHOTOGEOLOGIC SUMMARY A detailed review of pertinent stereoscopic aerial photographs was performed for this study for the purposes of evaluating the geomorphology of the site, specifically for the presence of photogeologic features (e.g. linear topography, tonal contrasts, etc.) that may traverse through the subject property. Eight sets of photographs at various scales were reviewed between the years 1938 to 2010 (see references in Appendix C for a listing), that were obtained from the Riverside County Flood Control Department and U.S. Department of Agriculture. In addition, the historical imagery database of Google Earth (GoogleTm Earth, 2013) was also utilized. Review of these photographs revealed two linear geomorphic features that traverse through the subject property and are depicted on the accompanying topographic map, as shown on Figure 4 below. The two lineaments traverse along a northwest-southeast direction along the northern and southern base of the hill within the central potion of the site. This feature is expressed as linear topography that forms a fairly sharp geomorphic boundary delineated by a scarp on the south side of the hill, with a subdued expression on the north, due to lake sediment deposition. Numerous water level stands were observed parallel with the fault zone trend in the north which masked any possible lineations that could be present north of the central hill. Other than the two delineated lineaments as presented on Figure 4 below, no photogeologic features unrelated to flooding and/or historic lake levels were observed to traverse through the site, based on the aerial photographs reviewed. eland Villa }` ` : 4 ` A% • +� hh FIGURE 4- Partial topographic map the Lake Elsinore 7.5' Quadrangle (U.S.G.S., 1997). Photo lineaments are shown as the purple dotted lines. Site boundary is outlined in red. TERRA GEOSCIENCES Project No. 152772-1 Page 6 Of importance to note is the presence of water that is delineated on the topographic map that surrounds the central hillier portion of the site. This high water elevation was evident in the 1938 and 1980 photographs reviewed, with the water having a "lagoon- like" appearance south of the hill. Lake Elsinore is supplied by inflow from the San Jacinto River and local watershed runoff which eventually can increase the water elevation in the lake until the outflow channel elevation of 1255 feet is reached, thus resulting in discharge of lake flows to Temescal Creek. During significant storm events, if the inflow to Lake Elsinore is greater than the outlet channel capacity, the surface water elevation of the lake will continue to rise until it reaches 1262 feet, resulting in the potential to reach the lake levee top elevation of 1265 feet (E.V.M.W.D., 2015). During our investigation, the water level elevation was around 1238± feet. FIELD RECONNAISSANCE Surficial reconnaissance performed during our field investigation revealed a prominent topographically higher hill within the central portion of the site. Based on the known local faulting, this hill is suspected of being a localized pressure ridge, such as Rome Hill, located just to the southeast. Pressure ridges can form where lateral motions on a typically curving fault will force rocks into a smaller space, resulting in pushing them upward, of which has formed the small hill situated within the central portion of the site. These ridges, or hills, are then bounded on both sides by a fault. The remainder northern and southern portions of the site are relatively flat-lying and are covered by a growth of annual weeds and grasses. These areas did not provide any geomorphic or visual indications suggestive of fault-related features. SUBSURFACE EXPLORATION One 1,716-foot long exploratory trench (T-1) was excavated ranging in depth from 8± to 14± feet. This trench was excavated in a general northeast to southwest direction, being near normal to the general trend of the Elsinore Fault Zone. It should be noted that the total length of this trench as indicated on the log presented within Appendix A is shown to be 1,736 feet in length. This is due to a sewer easement that traverses through the site where a 20-foot wide zone was left undisturbed that could not be trenched across. Based on the initial findings in this trench, three small check trenches were also excavated west of and parallel to Exploratory Trench T-1, with these being 60, 50, and 75 feet in length (Exploratory Trenches T-2, T-3, and T-4, respectively). The surveyed locations of all the exploratory trenches are presented on the Geologic Site Map, included as Plate 1. Graphic logs of the exploratory trenches (7 sheets) are provided within Appendix A, which were prepared at a scale of one inch equals eight feet (horizontal and vertical) and depict the structure and Iithologic nature of the earth materials encountered locally. This scale was deemed appropriate for this project due to the generally uniform and continuous Iithologic features exposed along the trench walls. The southeastern trench side-wall was continuously logged for this study. TERRA GEOSCIENCES Project No. 152772-1 Page 7 In general, the earth materials that were encountered within these trenches consisted of Holocene to late Pleistocene age Iacustrine and fluvial deposits, and Pleistocene age sedimentary bedrock of the Pauba Formation, and are described in more detail below. In addition, localized historical deposits of artificial fill mantle a large portion of the site on both sides of the hill. These materials were placed sometime between the years 1980 and 1990 based on our photogeologic review. It is believed that these materials were placed in an attempt to elevate the land surface to above historic flood level limits locally, to prevent any local future flooding. These deposits appear on the trench log but have been omitted from the Geologic Site Map (see Plate 1) in order to better illustrate the natural geologic units that comprise the site. A description of each earth material unit encountered is provided in Appendix A (see Lithologic Descriptions, Page A-2) that describe their main physical characteristics (i.e. color, grain size, soil structure, density/induration, etc.). These Iithologic descriptions should be referred to when reading the trench summaries given below. Also included within Appendix A is a legend, which groups the earth materials together based on their depositional origins and estimated ages, and a key to the symbols used on the trench logs (see Legend, Page A-1). Exploratory Trench T-1 This exploratory trench was excavated within an area that is encompassed by the designated County Fault Zone, as shown on Figure 3, along a near-perpendicular direction to the fault zone trend. This trench extended just beyond the southern fault zone limit, with the end of the trench in the north extending approximately 75 feet north of the proposed development limits as delineated by the client. Although the trench was not extended across the zone boundary in the north, sufficient coverage was maintained with respect to the project development limits. Initially encountered at the beginning of the exploratory trench in the north, are Iacustrine sediments (QI) that have originated as lake deposits from Lake Elsinore. These deposits extend from Station 0+00 to Station 4+37 and consist of Units "A" through "G." The surface is mantled by an unconsolidated sand unit that averages just one-foot in thickness (Unit "A") being very recent (modern deposits). Directly below this layer are progressively older (late- to mid-Holocene) moderately indurated to very firm/indurated sediments, herein in termed Units "B", "D", and "C." None of these Iacustrine units displayed visible signs of fracturing, faulting, or deformation. Around Stations 2+75 to 3+15, these deposits are in turn underlain by well-indurated late Pleistocene age Iacustrine deposits separated by an unconformable erosional contact. These deposits (Units "E", "F", and "G") are distinctly well-stratified and tilted at an angle of between 20 to 25 degrees to the northeast. It is believed that this tilting is a direct result of tectonic uplift and deformation from local faulting, likely associated with the northernmost fault encountered in this trench, at Station 4+37. At this location, the Iacustrine deposits are juxtaposed against Pleistocene age sedimentary bedrock of the Pauba Formation (Qpfs), which forms the north boundary of the fault zone. TERRA GEOSCIENCES Project No. 152772-1 Page 8 This fault locally has a relatively low-angle dip towards the northeast, trending in an overall N50W direction (when connected to T-4). Due to previous grading that had occurred to place the overlying artificial fill materials across the fault, potential Holocene disruption or offsets could not be observed or verified. Although not mapped as a geologic unit on the Geologic Site Map (Plate 1), the artificial fill materials (af) become visible beginning around Station 4+00 and extend to Station 11+85, generally near the terminus of the lacustrine deposits along the south. The thickness of this unit varies locally up to 5± feet deep and it contains an abundance of asphalt chunks, numerous large boulders (up to 5± feet in diameter), miscellaneous debris, and assorted trash, with a fine- to coarse grained silty sand matrix in a loose condition. Between Stations 4+37 to 5+55, the Pauba Formation, which consists of interbedded sandstone and silty sandstone (Units "R" through "U"), is somewhat disturbed and fractured, containing numerous faults that offset different sedimentary beds. At Station 5+55, a significant fault was encountered which completely separates the local bedrock structure and lithology. Additionally, within Unit "V," direct evidence was observed that this fault displaces recent age channel sands (very late Holocene) by up to 10± vertical inches, with thin radial fractures extending into the sands overlying the visible upward terminus of the fault. South of this fault zone extending to Station 7+57, the Pauba Formation consists predominantly of a highly fractured and faulted massive silty sandstone overlain by an argillic clayey silty sandstone (Units "W" and "X" respectively). Another significant fault was observed at Station 7+29, where again major sedimentary bedrock units are juxtaposed. These materials (Unit "Y") consist of a well-stratified silty sandstone with numerous thin sand lenses dipping a various low angles. At Station 7+57 a major fault was encountered that separates the Pauba formation on the north, with fluvial and lacustrine deposits to the south. This fault forms the southern margin of the central hill and is coincident with the aerial photo lineation as shown on Figure 4. This fault is accompanied by a highly sheared zone (Unit "Z") that is variegated and intensely fractured/faulted. This fault also offsets recent age lacustrine sediments (late Holocene) which are comprised of unconsolidated, loose, well-stratified sands (Unit "M"). Locally where exposed, there may be as much as 30± inches of apparent vertical offset between the Pauba Formation and these sediments. Beyond Station 7+57 the site is mantled (directly beneath the overlying fill) by lacustrine sediments (Units "H" through "M") that were deposited during periods of very high lake water elevations that forms the intermittent "lagoon" on the south side of the central hill, which are in turn underlain by fluvial deposits at depth. These relatively shallow lake deposits extend southward to Station 11+94, generally where the overlying artificial fill materials end. As discussed earlier, it would appear that this coincides to the original topographically lower elevation of the site, which would correlate to the limits of the historic high-water lake edge as marked by the southern limits of the lake deposits. Based on the firmness, presence of disseminated CaCO3 and nodules, and localized clay films along the ped faces, these deposits (with the exception of Unit "M") appear to be at least middle Holocene to possible late Pleistocene in age. TERRA GEOSCIENCES Project No. 152772-1 Page 9 The fluvial sequence of earth materials along the south side of the hill are first exposed at Station 7+57, juxtaposed against the Pauba Formation. Here Unit "N" was observed to be entrenched by the overlying lacustrine deposits and extends to Station 8+14 where they have been eroded to a depth below the bottom of the trench. The fluvial deposits then reappear around Station 10+05 at depth below the lacustrine deposits. For reference, the boundary between the fluvial and lacustrine deposits has been denoted as a "facies contact" as depicted on the Exploratory Trench Log (Sheets 3 and 4, Pages A-5 & A-6). Around Station 11+32, the earth materials mantling the site are fluvial deposits (Unit "Q") which are relatively young unconsolidated silty sands (late Holocene). By Station 11+94, only fluvial deposits were observed to the end of the trench at Station 17+36. The fluvial units underlying the youthful Unit "Q" have been estimated to have an age ranging from middle Holocene to late Pleistocene based on relative induration, great abundance of CaCO3 in the form of blebs and stringers, and the grussification of the occasional felsic gravel-sized clasts observed. These deposits (Units "N through "P") did not show direct evidence of soil cracking, fracturing, or other deformation, that could be related to faulting. It should again be mentioned that due to the presence of a high-pressure sewer line (located in the field by a representative of the Elsinore Valley Municipal Water District), the exploratory trench between Stations 14+80 to 15+00 could not be excavated. However, the sequence of the underlying fluvial deposits was noted to be consistent across the untrenched gap and the Iithologic contacts appear to be continuous at depth through this area (see Exploratory Trench Log T-1, Sheet 5 of 6). The exploratory trench was then terminated at Station 17+36, which is located just beyond the limit of the designated County Fault Zone, as depicted on Figure 3. Exploratory Trenches T-2 through T-4 Three short check trenches were excavated to the west of Exploratory Trench T-1 for the purposes of locating the three main fault splays that were initially encountered and determining their trend across the property. These trenches all had similar lithology that matches the Iithology exposed in Exploratory Trench T-1. Each major fault was clearly identified that provided a means to trace the local fault trend across the property. Exploratory Trench T-2 and T-3 displayed somewhat subdued faulting structures directly as a result of previous earthwork and/or shoreline erosion. Exploratory Trench T-4, however, provided an exceptional exposure of the southern fault zone splay. Here the fault (consisting of a zone of closely spaced faults) displays very recent activity noted by the overlying offset sand channel (Unit "M"), which has an apparent cumulative vertical offset of up to 30± inches and closely resembles the faulting observed in Exploratory Trench T-1. Numerous radial fractures clearly extend into the overlying sand channel deposits. It is believed that this sand channel could have an age estimated to be less than 1,000 years based on the friable and loose nature of the sediments. The fault zone that was encountered in Exploratory Trench T- 4 was also logged in greater detail (1 inch = 2 feet) for illustrative purposes, and appears on Exploratory Trench Log T-4 found within Appendix A (see Page A-9). TERRA GEOSCIENCES Project No. 152772-1 Page 10 Exploratory Trenching Summary The central, hillier portion of the site (between Stations 4+37 to Station 7+57), was found to consist of well-indurated sedimentary bedrock of the Pauba Formation that is highly faulted, sheared, and fractured, which is contained within the fault zone that traverses through the site. Outside of this designated fault zone (areas comprising Stations 0+00 to 4+37 and Stations 7+57 to 17+36), it was found that there were continuous and unbroken lithologic lacustrine and fluvial strata across the bottom of the Exploratory Trench T-1, which consisted of at least mid-Holocene to late Pleistocene age sediments. Along the southern portion of the site, there was a 20-foot wide section of land was unable to be trenched due to a sewer line easement (Stations 14+80 to 15+00, Sheet 5 of 6, Appendix A), but the subsurface lithologic contacts across this untrenched span are consistent. After all of the exploratory trenches were cleaned, examined, and logged, Mr. David Jones (Riverside County Chief Engineering Geologist) was invited to view the trenches and discuss our findings in the field (March 25, 2015). Additionally, prior to backfilling, the limits of each exploratory trench excavation, along with the major fault locations, were surveyed in our presence and under our direction by VSL Surveying, Temecula California, for location and permanent documentation purposes. This survey data was provided for our use in preparing the Geologic Site Map, as presented on Plate 1. RELATIVE AGE DATING The lacustrine deposits, primarily located within the northern portion of the site and to a lesser extent just south of the central hill, range in age from recent to late Pleistocene in age. The relatively thin surficial sand deposits are very recent and are underlain by increasingly older lake deposits. These deposits are generally moderately well- indurated to well-indurated and have formed localized disseminated CaCO3 blebs and stringers, with occasional carbonate nodules. The fluvial deposits within the southern portion of the site are also capped by a late Holocene silty sand deposit, again with increasingly older deposits found at depth. These underlying deposits are somewhat indurated and also have localized to very abundant disseminated CaCO3 blebs and stringers and are estimated to range from the late Holocene to possible late Pleistocene. These ages are also supported by the abundance of grussified clasts, most all of them felsic in composition. The underlying sedimentary bedrock materials exposed in the hilly central portion of the site have been mapped as the Pauba Formation (Qpfs), which are Pleistocene in age (Morton and Weber, 2003). It should be noted that an exhaustive search for datable materials (such as organic rich sediments and/or charcoal) was performed in both the lacustrine and fluvial deposits. However, none were found within the excavated trench limits that could be used for radio-carbon age-dating purposes. TERRA GEOSCIENCES Project No. 152772-1 Page 11 CONCLUSIONS AND RECOMMENDATIONS GENERAL: Based on our study and review of available pertinent literature, development of the subject site for the proposed mobile home park appears to be feasible from a surface fault rupture hazard standpoint, provided that our conclusions and recommendations are considered and adhered to as outlined below. CONCLUSIONS: Based on review of published geologic data, field reconnaissance, photogeologic analysis, and our subsurface exploration, faulting was observed within the limits of the subject property as indicated on the Geologic Site Map as presented on Plate 1. The faulting that was encountered has been assessed to be active in nature (surface ground rupture during the past 11,000± years) based on varying localized features such as juxtaposed Quaternary sediments against Pleistocene sedimentary bedrock of the Pauba Formation, geomorphic expression, and the association with the active San Elsinore Fault Zone located just to the east of the site. This activity was clearly evident based on the offset of recent sand channel deposits (less than 1,000 years) along the southern and central fault sections. Due to the location of the northern fault farther towards the lake, there has been numerous erosion and depositional sequences during high water events that have eroded sufficient evidence of recent offset sediments. Based on our photogeologic review and our subsurface exploration, it appears that the hill within the central portion of the site is a transpressional ridge, created by the active movement of faults on both sides of the hill. This pressure ridge is internally highly faulted and fractured wherein each fault splay and/or fracture, could and/or has, moved sympathetically during previous ground rupture events that have occurred along the major bounding faults in the relatively recent geologic past. This is evidenced by the presence of abundant faults and fractures within the bedrock between the north and south fault zones. Additionally, due to the lack of any overlying datable soils across the hill (due to previous grading), the activity potentials of any of these internal faults could not be ascertained properly. The exploratory trench depth of 8 to 14± feet beyond the limits of the fault zones to the north and south, was deemed appropriate for this project based on the lack of suggestive photolineaments, soil fracturing, and/or deformation. Additionally, based on the degree of induration, abundant accumulation of carbonate (as stringers, blebs, and nodules), formation of clay along ped faces, and the grussified felsic clasts observed within the sediments along the bottom of Exploratory Trench T-1, the age of these materials may range from middle Holocene to late Pleistocene. No datable organic materials or charcoal was found during our subsurface exploration which could yield absolute age dates. Based on the recurrence interval of the Elsinore Fault Zone of 450 to 750 years (Treiman, 1998), there should be numerous surface TERRA GEOSCIENCES Project No. 152772-1 Page 12 faulting events within these Quaternary deposits that would have occurred since they were deposited. This suggests that there are no active faults underlying the fluvial and lacustrine deposits, where locally explored, that are beyond the limits of the actively faulted pressure ridge within the central portion of the subject property. Based on our photogeologic review, it appears that the fault mapped within the southern portion of the site by Weber (1977), County of Riverside (2000), and Morton and Weber (2003), such as shown on Figures 2 and 3, is fairly coincident of the boundary of where the high water lake edge has been historically located, which created a distinct vegetation and tonal lineament. However, this lineament was not observable prior to the more recent lake flooding event of 1980 within the 1938, 1960, and 1974 aerial photographs reviewed. It is possible that the base geologic map prepared by Morton and Webber, as shown on Figure 2, has been shifted around 150± feet to the north. If the base map is shifted slightly to the south, then there is some general similarity between this map and our findings with respect to the mapped faults and Pauba Formation (Qpfs). The data transfer onto the base map was accomplished using map overlays on Google Earth (2013). For illustrative purposes, Figure 5 below depicts this observation. dp ` e _ � • �ffi93�� o�a � ``�� FIGURE 5- Comparison Geologic Map; from Morton and Weber (2003). The green northeast-southwest line is the approximate trench location. The red lines are the northern and southern faults forming the boundaries of the hill (Pauba Formation). The blue east-west trending line in the south is the vegetation/lake edge lineament. Site outlined in purple. TERRA GEOSCIENCES Project No. 152772-1 Page 13 Based on the suggested misalignment of the geologic base map, of which Weber (1977), County of Riverside (2000), and Morton and Weber (2003) used, and the surmised lake edge lineament within the southern portion of the site, the geologic data shown on Figure 2 does not appear to be representative of actual site conditions. The only active faulting within the subject property where confirmed by subsurface exploration is confined to the northern and southern margins of the central hill. This hill appears to be a direct result of transpressional movement from motion along the northern and south fault zone branches. In summary, due to the lack of suggestive photolineaments, related geomorphic features, and the absence of deformed and/or fractured Quaternary fluvial and Iacustrine sediments, no active faulting to the north and south of the designated fault zone (as shown on Plate 1) was observed within the limits of our exploratory trenching. RECOMMENDATIONS: 1. Restricted-Use Zones Restricted-Use Zones have been established within the northern and central portion of the site, as presented on the Geologic Site Map, Plate 1. No "habitable" structures for human occupancy (defined as 2,000 person hours per year, or as determined by local agencies) should be constructed within the delineated "Restricted-Use Zones." These setbacks are necessary due to the active nature of faulting encountered during our subsurface exploration and also presumed to be present where not trenched within the designated County Fault Zone in the north. The central Restricted-Use Zone and associated building setback lines were established by measuring 50 feet outward from the fault zone along a parallel direction to the observed fault zone trend as shown on Plate 1. The northern Restricted-Use Zone was established since the exploratory trench did not completely traverse across the County Fault Zone boundary. Therefore, it is assumed that there may be an active fault located just beyond the end of the trench (Station 0+00), thus requiring a 50-foot setback. The setback line was established by measuring 50 feet southwest from the beginning of the trench (Station 0+00), parallel to the northern fault trend. To reduce the amount of trenching necessary towards the north portion of the site, the client provided a conceptual map showing the project development limits. Exploratory Trench T-1 was then excavated a conservative distance of 75 feet beyond the proposed northern development limits to insure that the Restricted-Use Zone would not impact any structures. The limits of the exploratory trenches, established fault zones, and the associated Restricted-Use Zones are considered accurate based on the provided survey data form VSL Surveying as previously discussed. TERRA GEOSCIENCES Project No. 152772-1 Page 14 2. Additional Work If any future development is proposed to encroach within the northern Restricted- Use Zone, additional subsurface exploration would be required. 3. Trench Backfill We understand that the exploratory trenches were backfilled in an uncompactive and/or unsupervised manner. Periodic settling of the trenching area may occur over time. If settlement is of concern, such as for the placement of roadways, structures, etc., then removal and replacement of these soils as compacted fill is recommended. Such services should be supervised by a qualified geotechnical engineer. The limits of these trenches have been properly surveyed and can be obtained from VSL Surveying, Temecula, California. CLOSURE Our conclusions and recommendations are based on a surficial field reconnaissance limited subsurface exploration, photogeologic analysis, and an interpretation of available existing geologic/seismic data. We make no warranty, either express or implied. Should conditions be encountered at a later date or more information becomes available that appear to be different than those indicated in this report, we reserve the right to reevaluate our conclusions and recommendations and provide appropriate mitigation measures, if warranted. However remote, it is important to note that the potential for "new faulting" exists in the region, due to its location to a seismically-active and complex geologic region. Collins (1990) has described the process of "new faulting" and indicates that it is a normal process where stress is applied to earth masses of any size. He notes that during an earthquake, new faults can develop in several ways, such as by vertical extension (or growth) of a pre-existing fault or fault zone; by horizontal extension of a pre-existing fault or fault zone; by branching from a pre-existing fault or fault zone; and by faulting related to, but not an extension or branch of, a nearby fault (e.g., faulting created within a block of near-surface material subjected to coupling actions from nearby faults). It is therefore prudent to assume that there is at least a remote probability that fault rupture could occur at the site during a large nearby seismic event and that there is no way of predicting actual possibilities and/or probable locations. Such potential occurrences of "new faulting" should be made aware to the property owners so that they may decide on acceptable risk levels, based on the locations of their property in relation to seismically active areas. It is assumed that all the conclusions and recommendations outlined in this report are understood and followed. If any portion of this report is not understood, it is considered to be the responsibility of the owner/contractor/engineer/governmental agency, etc., to contact this office for further clarification. TERRA GEOSCIENCES GEOLOGIC SITE MAP South 720 East T-4 f f T ' QICount Fault Zone Limit io QaI T-3 QIV— REESTRICTED-USE ZONE — Y I �7+31i Ai'N-371-:50-0�1 � QI f { � illl ?_ I n=y 3a�-�5:,-�0. Q� ( Qpf$ APN.321-29C-D02 - See Detail Below LEGEND F I Qal FLUVIAL DEPOSITS NOTE: Photolineations are coincident with fault/geologic contact j QI LACUSTRINE DEPOSITS - T,4 - QpfS PAUBA FORMATION T 2 ,I �; �Q (�1 QpfS T-3 �� �' — APP. GEOLOGIC CONTACT FAULT (SURVEYED) S' �'o50, RESTRICTED- ZONE I � I_ EXPLORATORY TRENCH QI , t Qp fs QI RESTRICTED-USE ZONE PROJECT NO. 152772-1 PLATE 1 i APPENDIX A EXPLORATORY TRENCH LOGS LEGEND UNIT EARTH MATERIAL ESTIMATED AGE (Epoch) of Artificial Fill -Recent (Holocene) LACUSTRINE DEPOSITS (QI) A Silty Sand - Recent (Holocene) M Sand - Recent (Holocene) V Sand - Recent (Holocene) Silt - Late Holocene B Silty Sand C Sandy Silt �- Late - Mid Holocene D Clayey Silt H Clayey Silty Sand J Clayey Silty Sand Mid Holocene — Late Pleistocene K Clayey Silty Sand J L Clayey Silty Sand J E Sand / Silty Sand F Sandy Silt �- Late Pleistocene G Silty Sand FLUVIAL DEPOSITS (Qal) Q Silty Sand - Late Holocene N Silty Sand O Silty Sand �- Mid Holocene — Late Pleistocene P Clayey Silty Sand PAUBA FORMATION (Qpfs) R Sandstone S Silty Sandstone T Silty Sandstone U Silty Sandstone Pleistocene W Silty Sandstone X Clayey Sandstone Y Silty Sandstone J Z Silty Sandstone J SYMBOLS Z Lithologic Unit 17+36 Distance Stationing (100x feet + 1x feet) N45W/85S Fault/ Fracture / Bedding Attitude 1 Survey Point A-1 LITHOLOGIC DESCRIPTIONS A- SILTY SAND: Gray (2.5Y 5/1), fine- to coarse-grained with trace of gravel, loose N- SILTY SAND: Olive Brown (2.5Y 4/3), fine- to coarse-grained with minor clay, massive, dry, slightly stratified, non cohesive, rootlets present, recent lake bottom sediments. very dense, moist, cohesive, occasional caliche blebs (<'/8") B- SILTY SAND: Brown (10YR 5/3), fine-coarse grained, trace of fine gravel, moderately indurated, O- SILTY SAND: Olive Brown (2.5Y 4/3), fine- to coarse-grained, moist, cohesive, massive, abundant caliche, moist, slightly cohesive, slightly blocky soil structure. dense/indurated, abundant as stringers. C- SANDY SILT: Olive Brown (2.5Y 4/3, fine- grained with minor clay, very moist, cohesive, massive, P- CLAYEY SILTY SAND: Dark Olive Brown (2.5Y 3/3), fine-grained, moist, cohesive, massive, very firm/indurated, upper24± inches has CaCO3 stringers, clay along ped faces. firm/indurated, abundant disseminated CaCO3 (small blebs and as stringers). D- CLAYEY SILT: Olive (5Y 4/3), fine- grained, very moist, cohesive, occasional roots, prismatic Q- SILTY SAND: Very Dark Grayish Brown (2.5Y 4/3), fine- to coarse-grained, moist, rootlets structure, very firm/indurated, minor disseminated CaCO3 (small blebs and as stringers). present, loose, non cohesive, massive structure, porous. E- SAND & SILTY SAND: Grayish Brown (2.5Y 5/2), fine-coarse grained, dense/moderately indurated, R- SANDSTONE: Yellowish Brown (10YR 5/4), fine- to coarse-grained, indurated, interbeds of well stratified, thinly layered, damp, non-cohesive, occasional orange-stained fine sand lenses. silty sandstone, well stratified, relatively thinly layered. F- SANDY SILT: Olive Gray (5Y 5/2), fine- grained, damp, non cohesive, very firm/indurated, S- SILTY SANDSTONE: Light Olive Brown (2.5Y 5/3), fine- to coarse-grained, generally massive, well stratified, thinly layered. trace of fine gravel, well indurated, minor CaCO3. G- SILTY SAND: Light Olive Brown (2.5Y 5/3), fine-coarse grained, abundant fine gravel, damp, massive, T- SILTY SANDSTONE: Yellowish Brown (10YR 5/4), fine- to coarse-grained, trace of clay, occasional grussified clasts, non cohesive, very dense/indurated, slight mottling with minor CaCO3. slightly indurated, massive structure. H- CLAYEY SILTY SAND: Very Dark Grayish Brown (2.5Y 5/2), fine-coarse grained, moist, cohesive, U- SILTY SANDSTONE: Yellowish Brown (10YR 5/4), fine- to coarse-grained, minor gravel, abundant caliche blebs (to '/4"), massive structure, very firm/indurated. slightly stratified, thinly layered, occasional fine-medium grained sand lenses. I- SILT: Dark Grayish Brown (2.5Y 4/2), fine- grained, moist, moderately cohesive, rootlets present, V- SAND: Brown (10YR 5/3), fine- to coarse-grained with minor gravel, dry, loose, non cohesive, massive to slightly prismatic soil structure, slightly firm. minor gravel, well stratified, thinly layered, minor silt. J- CLAYEY SILTY SAND: Olive Brown (2.5Y 4/3), fine grained, trace of caliche blebs (to '/4"), moist, W- SILTY SANDSTONE: Brown (10YR 5/3), fine- to coarse-grained, massive, highly fractured, cohesive, very firm/indurated, occasional carbonate nodules, clay along ped faces. occasional small pebbles, moderately-well indurated. K- CLAYEY SILTY SAND: Olive Brown (2.5Y 4/4), fine-grained, moist, cohesive, minor caliche blebs, X- CLAYEY SANDSTONE: Brown (7.5YR 5/4), fine- to coarse-grained, indurated, massive, Slightly blocky structure, firm/indurated, occasional carbonate nodules, clay along ped faces. roots present from adjacent trees, forms argillic horizon. L- CLAYEY SILTY SAND: Olive Gray (2.5Y 5/2), fine-grained, moist, cohesive, massive structure, Y- SILTY SANDSTONE: Light Olive Brown (2.5Y 5/3), fine- to coarse-grained, well stratified, with firm/indurated, abundant disseminated CaCO3 (small blebs and as stringers). numerous thin sandstone lenses, slightly-indurated, thinly layered, occasional grussified gravels. M- SAND: Grayish Brown (2.5Y 5/2), fine- to coarse-grained, well stratified, thinly layered, dry, loose Z- SILTY SANDSTONE: Variegated, fine- to coarse-grained, forms a highly sheared zone with non cohesive, occasional gravel, bedding is nearly horizontal. numerous vertical closely-spaced fractures, slightly friable, overall mottled appearance. A-2 EXPLORATORY TRENCH T-1 < Northeast - Southwest > 0+00 ele. 1241' 1+20 / 0+20 0+40 0+60 0+80 1+00 A B B 1+40 1+60 1+80 2+00 2+20 2+40 1+20 r777 A B B 3+00 3+20 3+40 3+60 2+40 2+60 2+80 • . A • ' . • Sand Lens G B. N50W/23N B. N53W/25N SCALE 1" = 8' (Horizontal & Vertical) A-3 SHEET 1 of 6 EXPLORATORY TRENCH T-1 < Northeast - Southwest > IFault Zone 00 4+80 4+20 e1e. 1257'� 4+40 4+60 I 4+00 of T 3+60 3+80 R R S ---------- A . G G I Silt Lens F. N60W/85N do goo ' C' F. N66W/33N 60 do do Fine Sand Lens B. N54W/28N 6+00 5+80 X W 5+60 ele. 1270', of W 5+40 5+20 V F. N58W/84S 4+80 5+00 U of S S F. N57W/90S F. N58W/80S F. N55W/86S Sandy Silt Lens SCALE 1" = 8' (Horizontal & Vertical) A-4 SHEET 2 of 6 EXPLORATORY TRENCH T-1 < Northeast - Southwest > 6+00 6+20 6+40 6+60 ele. 1281' of X 6+80 w W X 7+00 F. N44W/72N X F. N39W/85N F. N40W/59N of 7+20 w X F. N43W/85N X 7+20 Fault Zone I 7+40 ele. 1265'\1 7+60 7+80 8+00 8+20 8+40 X of of w X w M I I � -•� H Y N J F. N46W/75S •• Y 1 N F. N25W/75N F. N44W/85S F. N68W/83S Facies Contact SCALE 1" = 8' (Horizontal & Vertical) A-5 SHEET 3 of 6 EXPLORATORY TRENCH T-1 < Northeast - Southwest > 8+40 8+60 8+80 9+00 9+20 9+40 9+60 of of I I J L J 9+60 9+80 10+00 10+20 10+40 10+60 10+80 of of I I P p Facies Contact 10+80 11+00 11+20 11+40 11+60 11+80 12+00 of Q I I O P P Facies Contact SCALE 1" = 8' (Horizontal & Vertical) A-6 SHEET 4 of 6 EXPLORATORY TRENCH T-1 < Northeast - Southwest > NOTE: Upper 8" - 12" Ground Disturbed 12+00 12+20 12+40 12+60 12+80 13+00 13+20 Q Q O O P P NOTE: Upper 8" - 12" Ground Disturbed 13+20 13+40 13+60 13+80 14+00 14+20 14+40 Q Q O P 14+80 15+00 NOTE: Upper 8" - 12" Ground Disturbed 14+40 14+60 Sewer Easement ele. 1266' 15+20 15+40 15+60 Q Q SEWER O • O P P SCALE 1" = 8' (Horizontal & Vertical) A-7 SHEET 5 of 6 EXPLORATORY TRENCH T-1 < Northeast - Southwest > NOTE: Upper 8" - 12" Ground Disturbed 16+20 16+40 16+60 16+80 15+80 16+00 15+60 Q Q O O NOTE: Upper 8" - 12" Ground Disturbed 17+36 +00 17+20 ele. 1271' 16+80 171 Q O SCALE 1" = 8' (Horizontal & Vertical) A-8 SHEET 6 of 6 EXPLORATORY TRENCHES T-2 through T-4 < Northeast - Southwest > 0+50 T-2 0+60 T-3 0+00 0+20 0+40 0+25 of of A 0+00 -- - G I R -- W Silt Layer F. N52W/75S F. N46W/68N Sand Lens F. N61W/81S DETAIL: TRENCH T-4 0+48 0+55 of 0+00 T-4 0+25 I Y 0+75 M of Silt Lens M Y Sand Lens N Z See Detail SCALE 1" =2' (Horizontal &Vertical) N Colluvial Backfill \ F. N65W/81 S SCALE 1" = 8' (Horizontal & Vertical) A-9 SHEET 1 of 1 i APPENDIX B SITE PHOTOGRAPHS SITE PHOTOGRAPHS y. t - View looking southwesterly along Exploratory Trench T-1 i • S k • y .` R. 4Z `� y . View looking northeasterly along Exploratory Trench T-1 B-1 SITE PHOTOGRAPHS +3 ii 03/18/2015 t - ` View looking northeasterly(from Station 6+00)along Exploratory Trench T-1 t. t - .,,.� � � c _ /._ .�•5-Jj Ifl(yJ chi t View looking southwesterly (from Station 6+25) along Exploratory Trench T-1 B-2 SITE PHOTOGRAPHS d.. a � w View looking southwesterly along Exploratory Trench T-2 b' F 4j a f View looking southwesterly along Exploratory Trench T-3 B-3 SITE PHOTOGRAPHS ti. i F t View looking northeasterly along Exploratory Trench T-4 B-4 i APPENDIX C REFERENCES REFERENCES Avery, T.E., and Graydon, L.B., 1985, Interpretation of Aerial Photographs, MacMillan Publishing Co., New York, Fourth Edition, 554 pp. Bryant, W.A. and Hart, E.W., 2007, "Fault Rupture Hazard Zones in California," California Division of Mines & Geology Special Publication 42, Interim Revision 2007. California Division of Mines & Geology (C.D.M.G.), 1978, Fault Evaluation Report FER- 72, 94pp. California Division of Mines & Geology (C.D.M.G.), 1979, Supplement No. 1 to Fault Evaluation Report FER-72, 16pp. California Division of Mines & Geology (C.D.M.G.), 1986, "Guidelines to Geo- logic/Seismic Reports," Note No. 42. California Geological Survey (C.G.S.), 2008, Guidelines for Evaluating and Mitigating Seismic Hazards, in California C.D.M.G. Special Publication 117. Cao, T., Bryant, W.A., Rowshandel, B., Branum, D., and Wills, C.J., 2003, The Revised 2002 California Probabilistic Seismic Hazard Maps, June 2003, California Geological Collins, T.K., 1990, New Faulting and the Attenuation of Fault Displacement, in Bulletin of the Association of Engineering Geologists, Volume XXVII, Number 1, pp. 11-22. County of Riverside, 2000, Technical Guidelines for Review of Geotechnical and Geologic Reports, Transportation and Land Management Agency, 66 pp. Dudley, Paul H., 1936, Physiographic History of a Portion of the Perris Block, Southern California, from "Journal of Geology," 1936, Volume 44, pp. 358-378. Engel, R., 1959, Geology and Mineral Deposits of the Lake Elsinore Quadrangle, California, C.D.M.G. Bulletin 146. Elsinore Valley Municipal Water District (E.V.M.W.D.), 2015, Lake Levels, http://www.evmwd.com/depts/admin/public_affairs/lake levels/default.asp. Harden, J.W., 1982, A Quantitative Index of Soil Development from Field Descriptions: Examples from a Chronosequence in Central California: Geoderma, v. 28, pp. 1- 28.fornia, in, Bulletin of the Seismological Society of America, Vol. 82, No. 2, pp. 800- 818, April 1992. Hathaway, Allen W., and Leighton, F. Beach, 1979, Trenching as an Exploratory Method, Geologic Society of America, Reviews in Engineering Geology, Volume II, Pages 169-195. Holden, Richard, and Real, Charles, 1990, Seismic Hazards Information Needs of the Insurance Industry, Local Government, and Property Owners in California; An Analysis, C.D.M.G. Special Publication 108. Hull, A.G. and Nicholson, C., 1992, Seismotectonics of the Northern Elsinore Fault Zone, Southern Cali Survey. Kennedy, Michael P., 1977, Recency and Character of Faulting Along the Elsinore Fault Zone in Southern Riverside County, California, C.D.M.G. Special Report 131. Knecht, A.A., 1971, Soil Survey of Western Riverside Area, California, Sheet Number 126. Lamar, D.L. and Swanson, S.C., 1981, Study of Seismic Activity by Selective Trenching along the Elsinore Fault Zone, Southern California, U.S.G.S. Open-File Report 81-0882. Larson, R., and Slosson, J., 1992, The Role of Seismic Hazard Evaluation in Engineer- ing Reports, in Engineering Geology Practice in Southern California, AEG Special Pub- lication No. 4, pp. 191-194. Mann, John, F.J., 1955, Geology of a Portion of the Elsinore Fault Zone, California, C.D.M.G. Special Report 43. Rockwell, T.K., and Lamar, D.L., 1986, Neotectonics of the Elsinore Fault, Southern California, in Geological Society of America Guidebook, Neotectonics and Faulting in Southern California, March 1986, pp. 149-208. Ron, H., Beroza, G., and Nur, A., 2001, Simple Model Explains Complex Faulting, in EOS, Transaction, American Geophysical Union, Volume 82, Number 10, March 6, 2001, pp. 125-129. Shlemon, R.J., 1985, Application of Soil Stratigraphic Techniques to Engineering Geol- ogy, in Bulletin of the Association of Engineering Geologists, Volume XXII, No. 2, 1985, pp. 129-142. Treiman, J., compiler, 1998, Fault number 126d, Elsinore Fault Zone, Temecula Section, in Quaternary Fault and Fold database of the United States: U.S. Geological Survey Website, http://earthquakes.usgs.gov/hazards/gfauIts. U.S. Department of the Interior, Bureau of Reclamation, "Engineering Geology Field Manual," undated, distributed 1989, 598 pp. Weber, F. Harold, 1977, Seismic Hazards Related to Geologic Factors, Elsinore and Chino Fault Zones, Northwestern Riverside County, California, C.D.M.G. Open File Re- port 77-4 LA, 96 pp. Woodford, A., Shelton, J., Doehring, D., and Morton, R., 1971, Pliocene-Pleistocene History of the Perris Block, Southern California, Geological Society of America Bulletin, V. 82, pp. 3421-3448, 18 Figures, December, 1971. Ziony, J.I., and Yerkes, R.F., 1985, Evaluating Earthquake and Surface Faulting Poten- tial, in Evaluating Earthquake Hazards in the Los Angeles Region, U.S.G.S. Profes- sional Paper 1360. MAPS UTILIZED California Geological Survey, 2010, Geologic Compilation of Quaternary Surficial Deposits in Southern California, Santa Ana 30' X 60' Quadrangle, CGS Special Report 217, Plate 16, Scale 1:100,000. California Division of Mines and Geology, 1980, Elsinore 7.5' Earthquake Fault Zone Map, Scale 1" = 2,000'. GoogleTm Earth, 2013, http://earth.google.com/, Version 7.1.2.2041. Gray, C.H. Jr., 1954, Geology of the Corona-Elsinore-Murrieta Area, Riverside County, Map Sheet No. 21, C.D.M.G. Bulletin 170, Vol. 1 & 2, Scale 1" = 3 miles. Greenwood, R.B., and Morton, D.M., 1991, Geologic Map of the Santa Ana 1:100,000 Quadrangle, California, and C.D.M.G. Open File Report 91-17. Jennings, C.W., 1992, Preliminary Fault Activity Map of California, Scale 1:750,000, C.D.M.G. Open File Report 92-03. Jennings, C.W. and Bryant, W.A., 2010, 2010 Fault Activity Map of California, California Geological Survey Geologic Data Map No. 6, Scale 1:750,000 Morton, D.M. and Weber, F.H. Jr., 1990, Geologic Map of the Elsinore Quadrangle, Riverside Count, California, U.S.G.S. Open-File Report 90-0700, Scale 1:24,000. Morton, D.M., 1999, Preliminary Digital Geologic Map of the Santa Ana 30' x 60' Quadrangle, Southern California, Version 1.0, U.S.G.S. Open-File Report OFR 99-172, Scale 1:100,000. Morton, D.M. and Weber, F.H. Jr., 2003, Preliminary Geologic Map of the Elsinore Quadrangle, Riverside County, California, U.S.G.S. Open-File Report 03-281, Scale 1:24,000. Morton, D.M. and Miller, F.K., 2006, Geologic Map of the San Bernardino and Santa Ana 30' x 60' Quadrangles, California, U.S.G.S. Open-File Report 2006-1217, Scale 1:1000,000. Jennings, C.W., 1992, Preliminary Fault Activity Map of California, Scale 1:750,000, C.D.M.G. Open File Report 92-03. Rodgers, T.H., 1966, Geologic Map of California, Santa Ana Sheet, Scale 1:250,000 (Second Printing 1973). United States Geological Survey (U.S.G.S.), 1997, Lake Elsinore 7.5' Quadrangle, Riverside County, California, Scale 1:24,000. Ziony, J.I., and Jones, L.M., 1989, Map Showing Late Quaternary Faults and 1978-1984 Seismicity of the Los Angeles Region, California, U.S.G.S. Miscellaneous Field Studies Map MF-1964. AERIAL PHOTOGRAPHS Riverside County Flood Control District, 1960, Photo Numbers 45 through 47, Scale 1"=1,000', dated September 6, 1960. Riverside County Flood Control District, 1974, Photo Numbers 724 and 725, Scale 1"=2,000', dated June 20, 1974. Riverside County Flood Control District, 1980, Photo Numbers 754 through and 756, Scale 1"=2,000', dated May 4, 1980. Riverside County Flood Control District, 1990, Photo Numbers 14-10 and 14-11, Scale 1"=1,600', dated January 22, 1990. Riverside County Flood Control District, 2000, Photo Numbers 14-9 through 14-11, Scale 1"=1,600', dated March 18, 2000. Riverside County Flood Control District, 2005, Photo Numbers 14-9 through 14-11, Scale 1"=1,600', dated April 13, 2005. Riverside County Flood Control District, 2010, Photo Numbers 14-9 and 14-10, Scale 1"=1,600', color, dated April 2, 2010. U.S.D.A., 1938, Photo Nos. AXM-31-20 and AXM-31-218, Scale 1" = 1,667', dated May 24, 1938.