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HomeMy WebLinkAboutFaultstudycounty TERRA GEOSCIENCES SUPPLEMENTARY EVALUATION OF SURFACE FAULT RUPTURE HAZARD LAKE ELSINORE VIEW APARTMENT PROJECT ASSESSOR'S PARCEL NOS. 371-090-001 THROUGH -004, 371-150-001, -002, -009, -010, & -016, AND 371-160-007 LAKE ELSINORE, RIVERSIDE COUNTY, CALIFORNIA Project No. 152772-2 October 20, 2016 Prepared for: Home Front Investments 31938 Temecula Parkway Suite A369 Temecula, CA 92592 Consulting Engineering Geology& Geophysics P.O. Box 1090, Loma Linda,CA 92354 • 909 796-4667 Home Front Investments October 20, 2016 31938 Temecula Parkway Project No. 152772-2 Suite A369 Temecula, CA 92592 Attention: Mr. Steve Galvez Regarding: Supplementary Evaluation of Surface Fault Rupture Hazard Lake Elsinore View Apartment Project Assessor's Parcel Nos. 371-090-001 Through -004 371-150-001, -002, -009, -010, & -016, and 371-160-007 Lake Elsinore, Riverside County, California EXECUTIVE SUMMARY At your request, we have completed a supplementary fault evaluation of the potential for surface fault-rupture hazard within the proposed 55.47±-acre Lake Elsinore View Apartment project as referenced above. This work supplements our previous study on the adjacent parcel to the west (Terra Geosciences, 2015). The purpose for this additional work was to extend the fault zone encountered in our previous study performed along the west (13.59± acres) onto the added parcels to the east (41.88± acres). In summary, it was found that there are active fault zones that traverse through the subject property, which requires establishment of a "Restricted-Use Zone" for "habitable" building purposes. This zone along with the deemed "Buildable Areas" have been determined by subsurface exploration supplemented with survey data for documentation purposes. This report has been prepared utilizing the suggested "Guidelines for Evaluating the Hazard Surface Fault Rupture" (California Division of Mines and Geology, Note 49) in addition to the "Technical Guidelines for Review of Geotechnical and Geologic Reports" prepared by the County of Riverside (2000). 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, SXpNAL G�0 TERRA GEOSCIENCES �S f {' C SCHWAR�, O � CERTIFIED 1 ENGINEERING Donn C. Schwartzkopf GEOLOGIST Certified Engineering Geologist No.1459 CEG 1459 9��GF CALL 0 TERRA GEOSCIENCES TABLE OF CONTENTS Page No. INTRODUCTION 1 SCOPE OF SERVICES 1 PROJECT SUMMARY 2 PHOTOGEOLOGIC SUMMARY 3 FIELD RECONNAISSANCE 4 SUBSURFACE EXPLORATION 4 Exploratory Trench T-5 5 Exploratory Trench T-6 6 Exploratory Trench Summary 7 RELATIVE AGE DATING 8 CONCLUSIONS & RECOMMENDATIONS 8 General 8 Conclusions 8 Recommendations 9 1. Restricted-Use Zone 9 2. Additional Work 10 3. Trench Backfill 10 CLOSURE 10 ILLUSTRATIONS County Fault Zone Map Figure 1 Photolineation Map Figure 2 Property Boundary Map Plate 1 Restricted-Use Zone Map Plate 2 Detailed Fault Zone Map Plate 3 APPENDICES Previous Exploratory Trench Logs (T-1 though T-4) Appendix A Supplementary Exploratory Trench Logs (T-5 & T-6) Appendix B Exploratory Trench Photographs (T-5 & T-6) Appendix C References Appendix D TERRA GEOSCIENCES Project No. 152772-2 Page 1 INTRODUCTION At your request, this firm has performed a supplementary fault evaluation to include additional property to the east that is located adjacent to the study previously performed by this firm (Terra Geosciences, 2015). The revised project now includes a total of 55.47± acres as approximated on Property Boundary Map, Plate 1. However, as requested, this supplementary work only includes a small portion of the southwestern corner of the adjacent parcel to the east as depicted on Plate 1 (rectangle outlined in purple). We understand that the project site use has been revised and is now proposed for development of an apartment complex and associated appurtenances, which includes undetermined amounts of cut and fill grading. No grading or site plans were available at the time this report was prepared. The subject property lies along the southeastern edge of Lake Elsinore in the Lakeland Village area, in the City of Lake Elsinore, Riverside County, California, and contains the following parcels; Assessor's Parcel Nos. 371-150-001, -002, -009, -010, and ; 371-090-001, -002, , and ; and 371- 160-007 (the parcels that were added to this study are shown in red). SCOPE OF SERVICES As authorized by you, the following services were performed during this study: Review of available published and unpublished geologic/geophysical data in our files pertinent to the site, including our previous study on the adjacent parcel to the west. 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 252 lineal feet of exploratory trench, up to 17± feet in depth. Field accompaniment with the project land surveyor (Dennis Janda Inc., Temecula, California) to delineate the necessary survey locations which included the exploratory trench limits and fault locations. y Field meeting with the Riverside County Geologist (Mr. Dan Walsh) 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. 152772-2 Page 2 PROJECT SUMMARY At its nearest point, the project site is located approximately 700± feet to the west of an established Earthquake Fault Zone that is associated with the mapped termination of the Elsinore Fault Zone (Wildomar Fault), as mapped by the California Geological Survey (Bryant and Hart, 2007). The location of this fault zone is shown on Figure 1 below as indicated by the light purple shaded area, with the Wildomar Fault shown as the orange line. Although the site is not included within a State designated Earthquake Fault Zone, the property is however shown to be located within a designated County Fault Zone as also indicated on Figure 1 below (light red shading). The orange shaded regions shown on this map are the fault zone limits that are included within the city limits of Lake Elsinore. COUNTY FAULTZONE ELSINORE FAULT ZONE City of Lake Elsinore 1 Zooft FIGURE 1-County Fault Zone Map(Riverside County Planning Department, 2016) Additionally, this figure shows the 10 individual parcels that comprise the total 55.47± acre project, with the parcels that were studied during our previous investigation (Terra Geosciences, 2015) outlined in green and the new parcels included for the property addition outlined in blue. TERRA GEOSCIENCES Project No. 152772-2 Page 3 PHOTOGEOLOGIC SUMMARY A detailed review of pertinent stereoscopic aerial photographs was performed for this supplemental 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 D 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 along the west and are approximated on the accompanying topographic map, as shown on Figure 2 below. The two lineaments traverse along a northwest-southeast direction along the northern and southern base of the hill within the west-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. Due to the recent sediment deposition from Lake Elsinore and local flooding, the lineations could not be traced farther to the east, wherein the hill becomes topographically submerged. Other than the two delineated lineaments as presented on Figure 2 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 Viila �'� ti • • _ a FIGURE 2- Photolineation Map (base map from U.S.G.S., 1997). Photo lineaments are shown as the purple dotted lines. Previous study boundary is outlined in red,with added property outlined in blue. TERRA GEOSCIENCES Project No. 152772-2 Page 4 Of importance to note is the presence of water that is delineated on the topographic base map that surrounds the west-central elevated portion of the site. The blue hachured symbol indicates submerged areas or lands subject to inundation. This area was evident as being inundated in the 1938 and 1980 photographs reviewed, with the water having a "lagoon-like" appearance south of the hill. The area south and to the east of the hill within the west-central potion of the site clearly verifies that lacustrine earth materials have been deposited in the past within these localities. 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 this supplemental investigation, the water level elevation was around 1232± feet. FIELD RECONNAISSANCE Surficial reconnaissance performed during our field investigation revealed a prominent topographic hill within the west-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 east. 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 west-central portion of the site. These ridges, or hills, are then bounded on both sides by a fault. The predominance of the added property for this supplemental study is relatively flat-lying and is covered by a growth of annual weeds and grasses. These areas did not provide any geomorphic or visual indications suggestive of fault-related features. Only a very small portion of the hill is exposed within the supplemental study area, which then becomes buried by lake sediments farther to the east. SUBSURFACE EXPLORATION Two supplementary exploratory trenches (T-5 and T-6) were excavated ranging in depth from 14± to 17± feet. These trenches were excavated in a general northeast to southwest direction, being near normal to the general trend of the Elsinore Fault Zone. The surveyed locations of all the exploratory trenches are presented on the Restricted- Use Zone Map and the Detailed Fault Zone Map, included as Plates 2 and 3, respectively. Graphic logs of the previous exploratory trenches excavated on this property (T-1 through T-4, seven sheets) are provided for continuity and comparative purposes within Appendix A. The supplementary Exploratory Trenches T-5 and T-6 excavated for this study were logged at a scale of one inch equals four and five feet TERRA GEOSCIENCES Project No. 152772-2 Page 5 (horizontal and vertical), respectively, and appear within Appendix B, and depict the structure and lithologic nature of the earth materials encountered locally. The southeastern trench side-wall was continuously logged for all of the trenches. In general, the earth materials that were encountered within all of the trenches excavated for both studies consisted of Holocene to late Pleistocene age Iacustrine and fluvial deposits, along with Pleistocene age sedimentary bedrock of the Pauba Formation, and are described in more detail below. In addition, localized historical deposits of artificial fill mantle portions of the site on both sides of the hill along the west but were not locally encountered within the supplemental trenches excavated for this study. These fill materials were placed sometime between the years 1980 and 1990 based on our photogeologic review. A description of each earth material unit encountered in our previous investigation (Trenches T-1 through T-4) 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.) along with an accompanying legend (Page A-1). The detailed summary of these trenches has not been reproduced for this supplemental report but can be reviewed in our previous report (Terra Geosciences, 2015) if necessary. The lithologic descriptions for the two current trenches excavated for this supplemental study (Exploratory Trenches T-5 and T-6) are provided in Appendix B on Page B-2. These lithologic descriptions should be referred to when reading the trench summaries for T-5 and T-6 given below. Also included within Appendix B is a legend, which groups the earth materials based on their depositional origins and estimated ages, and a key to the symbols used on the trench logs (see Legend, Page B-1). Exploratory Trench T-5 Exploratory Trench T-5 was excavated along a near-perpendicular direction to the fault zone trend, totaling 128± feet in length. The intent of this trench was to further trace out the fault zone encountered within the trenches along the west (Exploratory Trenches T- 1 and T-4), toward the added property to the east. The earth materials encountered from Station 0+00 to Station 0+28 (and at depth to Station 0+39) consist of interbedded sedimentary bedrock deposits of the Pauba Formation (late Pleistocene), being units "A" through "D." These materials are generally comprised of generally massive and indurated fine- to coarse-grained sandstone with thin interbeds of silty sandstone and conglomerate, overlain by a mantle of indurated clayey silty sand (paleosol). Surficially beginning at Station 0+28 and extending to the end of the trench (Station 1+28) are unconsolidated fine- to coarse-grained silty sand Iacustrine earth materials originating from deposition within Lake Elsinore, and are considered to be late Holocene in age (Unit "E"). Directly below this layer (from Station 0+39 to 1+26) is Unit "F" which is also Iacustrine in origin and is comprised of a fine- to coarse-grained silty sand that is slightly-loose to medium-dense (density gradually increasing with depth), characterized by an abundance of calcium carbonate in the form of blebs and stringers (Holocene). These materials were deposited during periods of TERRA GEOSCIENCES Project No. 152772-2 Page 6 very high lake water elevations that form the intermittent "lagoon" on the south side of the west-central hill, which are in turn underlain by fluvial deposits at depth. These fluvial deposits begin at Station 0+39 (juxtaposed along the fault zone) and are fine- to medium- and fine- to coarse-grained silty sand earth materials (Units "G" through "J") of late- to mid-Holocene age. The bedrock of the Pauba Formation was noted to be somewhat disturbed and fractured, containing numerous faults that offset different sedimentary beds. At Station 0+39, a significant fault was observed, which separates the sedimentary bedrock from the lacustrine and fluvial (alluvial) deposits. This fault is believed to be the same fault that was encountered within Trenches T-1 and T-4 to the west, where the sedimentary bedrock was offset against alluvial materials. This fault was traced to extend up through Unit "F" (Holocene) to the contact between the very recent (late Holocene) surficially mantling Unit "E." This fault forms the southern margin of the west-central hill (as encountered to the west) and is coincident with the aerial photo lineation as shown on Figure 2. This fault is accompanied by a sheared alluvial zone (Unit "G") that is variegated and fractured/faulted, which offsets recent age lacustrine sediments (late Holocene) and fluvial deposits (Holocene), which extends to Station 0+52. Locally where exposed, there may be as much as 26± inches of apparent vertical offset between the Pauba Formation and these sediments. Additionally, another fault zone was encountered between Stations 0+94 to 0+98 that disrupts Holocene age lacustrine and fluvial deposits and was also traced to extend upwards to the very recent surficial deposits (contact between Units "E" and "F"). Up to 48±-inches of relative offset was observed within the thick lacustrine deposits (Unit "F"). Neither fault was observed to disrupt the very recent age surficial silty sand deposit (Unit "E"). This fault zone was not encountered within our previous Trench T-1 to the west. Exploratory Trench T-6 Exploratory Trench T-6 was also excavated along a near-perpendicular direction to the fault zone trend, totaling 124± feet in length. The intent of this trench was to further trace out the fault zone towards the east that was encountered within Exploratory Trench T-5 excavated for this study, so that a proper fault zone trend and location could be established. Additionally, the trench depth was extended to insure that the sedimentary bedrock would be exposed so that proper stratigraphic and structural correlation between Exploratory Trenches T-5 and T-6 could be established. Extending across the entire trench length is Unit "F" which is lacustrine in origin and is comprised of a fine- to coarse-grained silty sand that is slightly-loose to medium-dense (density gradually increasing with depth), characterized by an abundance of calcium carbonate in the form of blebs and stringers (Holocene). These deposits are the same near surface materials encountered within Exploratory Trench T-5 and was found to be up to 12± feet in thickness. Below this surficial mantling Unit "F" from Station 0+14 to TERRA GEOSCIENCES Project No. 152772-2 Page 7 0+60 are Holocene age silty sand fluvial deposits (Unit "K"), in turn underlain by late Pleistocene age sedimentary bedrock of the Pauba Formation (Unit "L"). At Station 0+60 a significant fault zone was encountered which separates the sedimentary bedrock from the alluvial materials as found within Exploratory Trenches T-1, T-4, and T-5. This fault offsets the overlying Holocene age lacustrine deposits by up to 12± inches locally were observed. South of this fault zone (Station 0+60 to 1+24) are lacustrine deposits (Units "F" through "M") underlain at depth by various fluvial deposits (Units "N", "I", and "J"). However, within these alluvial deposits, another fault zone was encountered between Stations 0+80 to 0+84 that disrupts both Holocene age lacustrine and fluvial deposits and was also traced to extend upwards to approximately four feet from the ground surface. There was no evidence that the rupture extends to the ground surface locally. This fault zone appears to correlate structurally and Iithologically to the fault zone encountered within Exploratory Trench T-5 (Stations 0+94 to 0+98). This fault zone appears to have disrupted the overlying lacustrine deposits (Unit "F") by up to 18±- inches locally. Exploratory Trenching Summary The structure and lithology of the faults encountered in Trenches T-1 and T-4 and the newly excavated Trenches T-5 and T-6 excavated for this supplementary study are all similar and direct correlation between these trenches was possible. The west-central, hillier portion of the site (between Stations 4+37 to Station 7+57, Exploratory Trench T-1), 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. These deposits were also encountered at depth within the supplementary trenches T-5 and T-6. Beyond the sedimentary bedrock materials both to the north and south directions (where explored), it was found that there were both lacustrine and fluvial strata which consisted of a wide time range of late Holocene to late Pleistocene age sediments. After Exploratory Trenches T-1 though T-4 were cleaned, examined, and logged for, 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, the supplementary trenches performed for this study (Exploratory Trenches T-5 and T-6) were observed by Mr. Dan Walsh (Riverside County Associate Engineering Geologist) on September 22, 2016. 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 Dennis Janda, Inc., Temecula California, for location and permanent documentation purposes. This survey data was provided for our use in preparing the Restricted-use Zone Map and Detailed Fault Zone Map, as presented on Plate 2 and 3, respectively. TERRA GEOSCIENCES Project No. 152772-2 Page 8 RELATIVE AGE DATING The lacustrine deposits encountered range in age from recent to late Pleistocene in age, with the more recent deposits located primarily south of the west-central hill. This encompasses the entirety of the supplementary excavations for this study (Exploratory Trenches T-5 and T-6). The relatively thin surficial sand deposits (Unit "E," Trench T-5) are very recent and are underlain by increasingly older lake deposits (Units "F" and "M"). These deposits are generally moderately dense and have formed localized disseminated CaCO3 blebs and stringers, with occasional carbonate nodules. The fluvial deposits are somewhat indurated and also have localized to very abundant disseminated CaCO3 blebs and stringers (Exploratory Trench T-1) 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 fluvial deposits observed within Exploratory Trenches T-5 and T-6 did not expose CaCO3 deposits or grussified clasts, and are believed to be locally younger (late Holocene). The underlying sedimentary bedrock materials encountered in the exploratory excavations and as exposed in the hilly west-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. CONCLUSIONS AND RECOMMENDATIONS GENERAL: Based on our study and review of available pertinent literature, development of the subject site for the proposed apartment complex 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 Restricted-use Zone Map and Detailed Fault Zone Map, as presented on Plate 2 and 3, respectively. 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 TERRA GEOSCIENCES Project No. 152772-2 Page 9 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. No datable organic materials or charcoal was found during our subsurface exploration in either the previous or current study 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 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 west-central portion of the subject property. Since the purpose of this investigation was to trace the southern-most fault that was encountered within our previous study farther towards the east, supplemental exploratory Trenches T-5 and T-6 were strategically placed along the extrapolated fault zone orientation. Both trenches encountered the same fault structure where the Pleistocene age sedimentary bedrock of the Pauba Formation is juxtaposed against Holocene age alluvial deposits and was coincident with the same local direction. This fault zone is the continuation of the faulting that was encountered within Exploratory Trenches T-1 and T-4 to the west. However, the southern-most fault zone encountered within Exploratory Trenches T-5 and T-6 does not appear to traverse through Exploratory Trench T-1 that was excavated and logged during our previous study (see Exploratory Trench T-1, Appendix A). It was noted that the appearance of the fault zone becomes somewhat weaker towards the west and it is most likely that the fault terminates before our previous trenching. Therefore, we have elected to terminate the fault along the original property boundary between our previous study and the added parcel to the east as shown on Plates 2 and 3. This fault appears to be en-echelon in nature. RECOMMENDATIONS: 1. Restricted-Use Zone A Restricted-Use Zone has been established within the northern and central portion of the site ("orange" shaded regions), as presented on the Restricted-use Zone Map and Detailed Fault Zone map, as presented on Plate 2 and 3, respectively. 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. Conversely, all of the "green" shaded regions, as shown on Plates 2 and 3, are areas where structures for human-occupancy can be built and is termed the "Buildable Area." TERRA GEOSCIENCES Project No. 152772-2 Page 10 The west-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 Plates 2 and 3. The northern Restricted-Use Zone was established since Exploratory Trench T-1 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 County Fault Zone trend (South 72' East). Since trenching was not performed in the northern portion of the added parcels, the isolated "Buildable Area" that was established in our previous study along the northwest, could not be extended eastward and was terminated along the property line between the old and new property boundaries. 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 Dennis Janda Inc., as previously discussed. 2. Additional Work If any future development is proposed to encroach within any portion of the Restricted-Use Zone as delineated on Plates 2 and 3, additional subsurface exploration and evaluation 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 Dennis Janda, Inc., 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. TERRA GEOSCIENCES Project No. 152772-2 Page 11 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 PROJECT BOUNDARY MAP 0MEW e — \4k - - 111 11 111 I I Blue shading previous study (Terra Geosciences, 2015); green shading additional property; purple shading current study area. PROJECT NO. 152772-2 PLATE 1 RESTRICTED-USE ZONE MAP I I ! ! ! ! ! ! ! ! ! ! Inset detail, see Plate 3 I I LEGEND - 0 EXPLORATORY TRENCH FAULT - ----- BUILDING SETBACK LINE -- OLD PROPERTY BOUNDARY RESTRICTED-USE ZONE I ! BUILDABLE AREA +-`---------------------------------------------- I PROJECT NO. 152772-2 PLATE 2 DETAILED FAULT ZONE MAP T-4 T-3 T-2 50' T-1 50• •J •J T-5 LEGEND 50, O EXPLORATORY TRENCH T-6 FAULT BUILDING SETBACK LINE OLD PROPERTY BOUNDARY T4 RESTRICTED-USE ZONE li 1OW e •J BUILDABLE AREA PROJECT NO. 152772-2 PLATE 3 i APPENDIX A PREVIOUS EXPLORATORY TRENCH LOGS T-lthrough T-4 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 J- Late - Mid Holocene D Clayey Silt J 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 • % ' C' F. N66W/33N . ' 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 X F. N44W/72N W X 7+00 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 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 MEN MEN I l 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 -- -- -- S q -- - 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 0+50 !' Y of 0+75 M Silt Lens Y Y M Sand Lens � �II 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 SUPPLEMENTARY EXPLORATORY TRENCH LOGS T-5 & T-G LEGEND EXPLORATORY TRENCHES T-5 & T-6 UNIT EARTH MATERIAL ESTIMATED AGE(Epoch) LACUSTRINE DEPOSITS (QI) E Silty Sand - Recent (Holocene) F Silty Sand - Late Holocene M Silt - Late Holocene FLUVIAL DEPOSITS (Qal) G Silty Sand H Silty Sand Clayey Silty Sand J Silty Sand Late Holocene — Middle Holocene K Silty Sand N Silty Sand PAUBA FORMATION (Qpfs) A Silty Sandstone B Sandstone C Conglomerate Pleistocene D Silty Sandstone L Silty Sandstone O Silty Sand (Soil infill within fault zone) -Late Holocene SYMBOLS M Lithologic Unit 1+28 Distance Stationing (100x feet + 1x feet) N45W/85S Fault/ Fracture / Bedding Attitude 1 Survey Point B-1 LITHOLOGIC DESCRIPTIONS EXPLORATORY TRENCHES T-5 & T-6 A- SILTY SANDSTONE: Olive Brown (2.5Y 4/3), fine- to coarse-grained, blocky soil structure, indurated, abundant CaCO3 disseminated throughout, minor clay, moist, cohesive. B- SANDSTONE: Brown (10YR 5/3), fine- to coarse-grained, massive, fractured, very crude bedding, occasional small pebbles, moderately-well indurated. C- CONGLOMERATE: Brown (7.5YR 4/4), fine- to coarse-grained, indurated, massive, moist gravel and cobbles to 40%, mod-indurated, clasts are grussified, non cohesive. D- SILTY SANDSTONE: Reddish Brown (5Y 4/4), fine- to coarse-grained, moderately stratified, indurated, moist, non cohesive, trace of gravel. E- SILTY SAND: Dark Grayish Brown (2.5Y 5/2), fine- to coarse-grained, crudely stratified, loose, damp, non cohesive, abundant roots. F- SILTY SAND: Grayish Brown (2.5Y 4/2), fine- to coarse-grained, damp, non cohesive, massive loose to medium dense (increases with depth), abundant CaCO3 disseminated throughout. G- SILTY SAND: Variegated to Brown (10YR 4/3), fine-coarse grained, dense, moist, massive, minor gravel, non cohesive, sheared throughout. H- SILTY SAND: Brown (10YR 4/3), fine- to coarse-grained, moist, non cohesive, medium dense, massive structure. I- CLAYEY SILTY SAND: Dark Brown (10YR 3/3), fine- to coarse grained, moist, cohesive, minor rootlets, firm. J- SILTY SAND: Light Olive Brown (2.5Y 5/3), fine- to medium-grained, minor coarse, moderately dense, crudely stratified, moist, cohesive. K- SILTY SAND: Dark Grayish Brown (10YR 4/2), fine- to coarse-grained, massive, medium dense, trace of gravel, massive to crudely stratified with occasional discontinuous sand lenses. L- SILTY SANDSTONE: Dark Yellowish Brown (10YR 4/6), fine- to coarse-grained, trace of gravel, indurated, moist, moderately cohesive. M- SILT: Light Yellowish Brown (2.5Y 6/3), fine-grained, moderately firm, damp, slightly cohesive, minor CaCO3 disseminated throughout, slight prismatic soil structure. N- SILTY SAND: Light Olive Brown (2.5Y 5/3), fine- to coarse-grained, massive soil structure, medium dense, moist, non cohesive. O- SILTY SAND: Variegated to Grayish Brown (10YR 5/2), fine- to coarse-grained, moist, cohesive, highly sheared zone, forms infill within narrow fault zone. B-2 EXPLORATORY TRENCH T-5 < Northeast - Southwest > ele. 1257' WELL 0+00 0+10 0+20 0+30 0+40 0+50 0+64 A `� - E A - ---- B % ii —- - B C C F B B F C D ii B F. N70E/75S / C' F. N52W/80N H ll F. N65W/81 S F. N49W/82N � Fault Zone I 0+64 0+70 0+80 0+90 1+00 1+10 ele. 1262' 1 i1 1+20 1+28 E E F F --�---- ---- - ---------n- -------� Facies Contact H J F. N62W/85S/ SCALE 1" = 4' (Horizontal & Vertical) B-3 EXPLORATORY TRENCH T-6 < Northeast - Southwest > 0+00 0+10 0+20 0+30 0+40 0+50 1 0 62 ele. 1256' F F K a K L o a M � Fault Zone I L 0+64 0+70 0+90 1+00 F. N45w/90 1+10 1+24 ele. 1256' F F I Facies Contact 0 M ------------ J F. N65W/78S SCALE 1" = 5' (Horizontal & Vertical) B-4 i APPENDIX C EXPLORATORY TRENCH PHOTOGRAPHS T-5 & T-6 EXPLORATORY TRENCH PHOTOGRAPHS e- �. �.. � I r ` View looking southwest along Exploratory Trench T-5. F a� rk View looking northeast along Exploratory Trench T-6. i APPENDIX D 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. Riverside County Planning Department, 2016, Map My County V4 — Riverside County, Web Site, http://mmc.rivcoit.org/MMC Public/Viewer.html?Viewer=MMC Public. 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. Terra Geosciences, 2015, 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, dated March 31, 2015. 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.