Paleoseismology and geomorphology of the eastern Sierra Madre fault: Evidence for a >8ka age of the most recent event

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Content INFORMATION TO USERS This manuscript has been reproduced from the microfilm master. U M I films the text directly from the original or copy submitted. Thus, some thesis and dissertation copies are in typewriter face, while others may be from any type of computer printer. The quality of this reproduction is dependent upon the quality of the copy submitted. Broken or indistinct print, colored or poor quality illustrations and photographs, print bleedthrough, substandard margins, and improper alignment can adversely affect reproduction. In the unlikely event that the author did not send UM I a complete manuscript and there are missing pages, these will be noted. Also, if unauthorized copyright material had to be lemoved, a note will indicate the deletion. Oversize materials (e.g., maps, drawings, charts) are reproduced by sectioning the original, beginning at the upper left-hand comer and continuing from left to right in equal sections with small overlaps. 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PALEOSEISMOLOGY AND GEOMORPHOLOGY OF THE EASTERN SIERRA MADRE FAULT: EVIDENCE FOR A >8KA AGE OF THE MOST RECENT EVENT Copyright 2000 by Allan Zachary Tucker A Thesis Presented to the FACULTY OF THE GRADUATE SCHOOL UNIVERSITY OF SOUTHERN CALIFORNIA In Partial Fulfillment of the Requirements for the Degree MASTER OF SCIENCE (GEOLOGY) AUGUST 2000 Allan Zachary Tucker Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. UMI Number: 1405255 ___ < S ) UMI UM I Microform 1405255 Copyright 2001 by Bell & Howell Information and Learning Company. All rights reserved. This microform edition is protected against unauthorized copying under Title 17, United States Code. Bell & Howell Information and Learning Company 300 North Zeeb Road P.O. Box 1346 Ann Arbor, M l 48106-1346 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. UNIVERSITY O F SOUTHERN CAUFORNIA THC GRAOUATC SCHOOL UNIVERSITY PARK LOS ANGSLCS. CALIFORNIA SOOOT This thesis, •written by Allan Zachary Tucker ________ under the direction of h is . Thesis Committee, and approved by all its members, has been pre sented to and accepted by the Dean of The Graduate School, in partial fulfillm ent of the requirements for the degree of Master of Science (Geology) D tm m Dflif^Jal3LiSjuSSSg. THESIS COMMITTEE Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Acknowledgements We would like to thank Jeff Beard, Shari Christofferson, Ilene Cooper, Robert DeGroot, Ross Hartleb, Marcos Marin, Meredith Robertson, and Kris Weaver for their assistance with field work. We are indebted to the City o f San Dimas, and especially to John Garcia and Khrishna Patel, for allowing us permission to conduct the Horsethief Canyon investigation on city property. We are also indebted to George Dunning and Amelia Ward for allowing us to conduct the investigation at the Shuler Canyon site. We would also like to thank Ned Field. Frank Jordan, Scott Lindvall. Mark Petersen, and Jerry Treiman for helpful discussions. This research was supported by the Southern California Earthquake Center. SCEC is supported by NSF Cooperative Agreement EAR-8920136 and USGS Cooperative Agreements 14-08-0001-A0899 and 1434-HQ-97AG01718. Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Table o f Contents ACKNOWLEDGEMENTS_____________________________________________________________ II LIST OF FIG U R E S _________________________________________________________________ IV ABSTRACT___________________________________________________________________________ V IN TRO D U CTIO N _____________________________________________________________________ 1 REGIONAL GEOLOGY AND RELATIONSHIP TO OTHER FAULTS_________________4 TECTONIC GEOMORPHOLOGY OF THE EASTERN SIERRA MADRE FAULT ZONE 6 PALEOSEISMOLOGY OF THE SIERRA MADRE FAULT____________________________11 PREVIOUS INVESTIGATIONS____________________________________________________________________ 11 THIS STUDY__________________________________________________________________________________ 12 PALEOSEISMOLOGIC INVESTIGATIONS AT THE HORSETHIEF CANYON SITE, SAN DIM AS_________________________________________________________________________ 18 TRENCH AND LARGE-DIAMETER BOREHOLE RESULTS___________________________________________18 STRATIGRAPHY ______________________________________________________________________________ 19 AGE CONTROL_______________________________________________________________________________ 26 EVIDENCE FOR FAULTING_____________________________________________________________________ 28 SHULER CANYON SITE (SD2)_____________________________________________________ 32 SITE DESCRIPTION____________________________________________________________________________ 32 STRATIGRAPHIC UNITS_______________________________________________________________________ 34 AGE CONTROL_______________________________________________________________________________ 40 EVIDENCE FOR FAULTING_____________________________________________________________________ 40 D ISC U SSIO N _______________________________________________________________________ 43 C O N C LU SIO N S_____________________________________________________________________ 51 BIBLIOGRAPHY_____________________________________________________________________ 53 APPENDIX 1: SD-1 BOREHOLE LOGS____________________________________________ 59 APPENDIX 2: FIELD LOGS, SD-1 TRENCH (PHOTOCOPIES)___________________ 7 0 APPENDIX 3: FIELD LOGS, SD-2 TRENCH (PHOTOCOPIES)_____________________80 iii Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. List of Figures FIGURE 1_____________________________________________________________________________ 3 FIGURE 2 _____________________________________________________________________________ 8 FIGURE 3 ____________________________________________________________________________ 14 FIGURE 4 ____________________________________________________________________________15 FIGURE 5 ____________________________________________________________________________ 17 FIGURE 6 ____________________________________________________________________________21 FIGURE 7 ____________________________________________________________________________29 FIGURE 8 ____________________________________________________________________________30 FIGURE 9 ____________________________________________________________________________31 FIGURE 10__________________________________________________________________________ 33 FIGURE 11__________________________________________________________________________ 33 FIGURE 12__________________________________________________________________________ 36 FIGURE 13__________________________________________________________________________ 47 SD-1 BOREHOLE ABBREVIATIONS_______________________________________________ 6 0 S D -H 1 ______________________________________________________________________________ 61 S D -H 2 _______________________________________________________________________________63 S D -H 3 _______________________________________________________________________________64 S D -H 4 ______________________________________________________________________________ 65 S D -H S ______________________________________________________________________________ 67 S D -H 6 ______________________________________________________________________________ 68 S D -II7 ______________________________________________________________________________ 69 iv Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Abstract Paleoseismologic data from the Sierra Madre fault, a major north-dipping reverse fault that extends for 75 km across the northern edge of the Los Angeles metropolitan region, indicate that the most recent surface rupture on the eastern part of the fault occurred more than 8,000 years ago. Coupled with evidence for a minimum reverse-slip rate of 0.6-0.9 mm/yr on the strand that we trenched, these observations suggest that the Sierra Madre fault breaks during very infrequent, but apparently large-magnitude (Mw >7) earthquakes. Events of such large magnitude are much larger than the largest earthquakes that have occurred on any of the Los Angeles-area 'urban' faults during the ~200-year-long historic period (e. g., the 1971 Mw 6.7 San Fernando and 1994 Mw 6.7 Northridge earthquakes), and must be considered in future seismic hazard analyses for southern California. Although more paleoseismologic data are needed to determine whether or not the Sierra Madre fault ruptures together with adjacent faults, available data already show that the Raymond fault, a west-southwest-trending, left-lateral strike-slip fault that intersects the central Sierra Madre fault, has ruptured to the surface at least once, and possibly several times, since the most recent surface rupture on the eastern Sierra Madre fault. Moreover, if the San Andreas fault (SAF) and the Sierra Madre fault ever do rupture together, as has been suggested previously, then such events must be exceedingly rare, with at least 50-100 SAF Mw~8 "Big Ones” occurring between every possible combined SAF-Sierra Madre fault event. Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Introduction Over the past decade ideas about the seismic hazards facing Los Angeles have undergone significant revision and refinement. In particular, most models now focus on the possibility of the recurrence of a great (M~8) 1857-type San Andreas fault rupture (the so-called "Big One"), as well as smaller, moderate-to-large earthquakes on faults directly beneath the metropolitan area (e. g., Wesnousky, 1986; Dolan et al.. 1995; WGCEP, 1995). Because of their proximity to the major population centers, these so- called 'urban faults' can generate earthquakes that could be at least as destructive as a much larger event on the more-distant San Andreas fault (WGCEP. 1995; Dolan et al.. 1995; Heaton et al.. 1995). The metropolitan Los Angeles area is built atop a major tectonic transition. To the south, Pacific-North America plate boundary deformation is accommodated primarily along the north-northwest-trending, right-lateral strike-slip fault o f the San Andreas system. In contrast, in the Transverse Ranges region north of Los Angeles, much of the north-south shortening is accommodated along west-trending reverse faults. The largest of these reverse faults in the metropolitan region is the 75-km-long Sierra Madre fault. Together with the Cucamonga fault to the east and the Santa Susana fault to the west, the Sierra Madre fault forms the central reach of a 140-km-long system of north-dipping reverse faults that extends along the northern edge of the metropolitan region (Figure 1). In this paper we present the first paleoseismologic data from the eastern half of the Sierra Madre fault, and discuss the implications of these data for models of past fault interactions as well as for seismic hazard analysis in the Los Angeles metropolitan region. 1 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Figure 1. Regional neotectonic map for metropolitan southern California showing major active faults. The Sierra Madre fault is a 75-km-long active reverse fault that extends along the northern edge of the metropolitan region. Fault locations from are Ziony and Jones (1989), Vedder and others (1986), Dolan and Sieh (1992), Sorlien (1994), and Dolan and others (1997). Closed teeth denote reverse fault surface trace; open teeth on dashed lines show upper edge of blind thrust fault ramps. Strike-slip fault surface traces shown by double arrows. C-SF=Clamshell-Sawpit fault; ELATB=East Los Angeles blind thrust system; EPT=Elysian park blind thrust fault; Hoi Flt=Hollywood fault; PHT=Puente Hills blind thrust fault; RMF=Red Mountain fault; SCIF=Santa Cruz Island fault; SSF=Santa Susana fault; SJcF=San Jacinto fault; SJF=San Jose fault; VF=Verdugo fault; A=Altadena study site of Rubin et al. (1998); Az=Azusa; LA=Los Angeles; LB=Long Beach; LC=La Crescenta; M=Malibu; NB=Newport Beach; Ox=Oxnard; Pas=Pasadena; PH=Port Hueneme; S=Horsethief Canyon study site in San Dimas; V=Ventura. Dark shading denotes mountains. Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Figure 1 Regional Geology And Relationship To Other Faults The Sierra Madre fault bounds the southern margin o f the San Gabriel Mountains, an 85-km-long, west-trending range composed predominantly of Mesozoic granitic rocks and pre-Mesozoic metamorphic rocks (e. g., Ehlig, 1971; Ehlig, 1975). Reverse slip along the Sierra Madre fault, which has raised the San Gabriel Mountains to peak elevations of 2-3 km, is thought to have begun ~7 million years ago (Blythe et al., 2000). The boundary between the Sierra Madre fault and the Cucamonga fault to the east is marked by a major lateral ramp along a 3-km-wide left step in the frontal reverse fault system at San Antonio Canyon (Figure 1). This lateral ramp is sub-parallel to. and may be coincident with, the left-lateral/reverse(?) San Jose fault, which extends west- southwestward for 15 km from the mountain front (Figure 1). Two small patches of the San Jose fault in the region of the lateral ramp ruptured during the 1988 Ml 4.6 and 1990 Mw 5.3 Upland earthquakes, both of which exhibited left-lateral strike-slip focal mechanisms and steeply west-northwest-dipping faulting planes (Hauksson and Jones, 1991). If the lateral ramp accommodates a component of left-lateral strike-slip, then the reverse-slip rate for the Cucamonga fault is faster than that of the eastern Sierra Madre fault (Dolan et al., 1995; in prep.; Walls et al., 1998; in prep.). Although the reverse-slip rate o f the Cucamonga fault has been determined to be -2-5 mm/yr (Dolan et al., 1995; 1996; in prep.; Walls et al., 1998), no geological slip-rate for the eastern Sierra Madre fault has been published. Fifty kilometers west of the San Antonio Canyon lateral ramp, the east-northeast- trending Raymond fault intersects the Sierra Madre fault (Figure 1). Similar to the San 4 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Jose fault, the Raymond fault is a left-lateral strike-slip fault, as demonstrated by the tectonic geomorphology of the fault zone and the focal mechanism o f the 1988 Mw 4.9 Pasadena earthquake (Jones et al., 1990; Weaver and Dolan, in press). This fault geometry implies that the reverse-slip rate of the Sierra Madre fault may be somewhat faster to the east of the Raymond fault intersection. The Raymond fault may act to transfer slip from the Sierra Madre fault southwestward onto the Verdugo fault, a major northeast-dipping, reverse or oblique right-lateral -reverse fault system that parallels the Sierra Madre fault for 30 km (Ziony and Jones, 1989; Wright, 1991; Dolan et al., 1995; Walls et al., 1998). If true, this relationship suggests that the Verdugo fault may accommodate some of the north-south shortening accommodated by the Sierra Madre fault to the east; Dolan et al. (1995) assumed a combined western Sierra Madre-Verdugo fault slip rate of 4 mm/yr. Alternatively, the Raymond fault may be the eastward continuation of the Santa Monica-Hollywood fault system (Weaver and Dolan, in press). The western end of the Sierra Madre fault is marked by another major lateral ramp at a 2.5-km-wide left step in the frontal reverse fault system onto the Santa Susana fault to the west (Figure 1) (USGS Staff, 1971; Allen et al.. 1975; Barrows et al., 1975; Oakeshott, 1975; Heaton, 1982; Yeats, 1987). The 1971 Mw 6.7 San Fernando earthquake, which ruptured the westernmost 20 km of the Sierra Madre fault, terminated against this lateral ramp (Allen et al., 1975; Heaton, 1982; Yeats, 1987). During this oblique, left-lateral-reverse event, two parallel, 45°-50°-north-dipping strands of the Sierra Madre fault ruptured (Heaton, 1982), but along the eastern half o f the rupture, surface rupture occurred only along the southern strand (USGS Staff, 1971; Barrows et 5 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. a l, 1975; Oakeshott, 1975). The area between the two strands is marked by the presence of the Merrick Syncline, a major fold in Tertiary strata (Barrows et al., 1975). Tectonic Geomorphology of the Eastern Sierra Madre Fault Zone The active trace of Sierra Madre fault zone is characterized by several 7- to 15- km-wide, convex-to-the-south 'lobes', in contrast to the relatively linear, east-trending surface trace of the Cucamonga fault to the east (Ehlig, 1975; Crook et al., 1987; Morton and Matti, 1987; Ziony and Jones, 1989; Dolan et a l, in prep.; this study) (Figure 1). As part of a more regional study of the history of interactions between the major faults of the northern Los Angeles metropolitan region (Dolan et a l, 1995; 1997; 2000; in press; in prep.; Rubin et a l, 1998; Walls et a l, 1998; in prep.; Weaver and Dolan, in press; Lindvall et a l, 1995; Fumal et a l, 1996) we conducted an air-photo and field mapping analysis of the tectonic geomorphologic study of the eastern part of the Sierra Madre fault zone in order to find suitable paleoseismologic trench sites for comparison with data from sites on adjacent faults (e. g., the central reach of the Sierra Madre fault, and the Cucamonga and Raymond faults) (Figure 1). Our geomorphologic analysis reveals that, to the east o f Azusa, the active trace of the eastern Sierra Madre fault generally extends along the topographic break-in-slope along the southern edge of the San Gabriel Mountains (Figure 1). The active trace of the fault is defined by intermittent south-facing scarps, faceted spurs, vegetation lineaments, ground water anomalies, and changes in stream gradients and sinuosity (Crook et a l, 1987; this study). These features have allowed us to construct a detailed map of the active trace of the easternmost 20 km of the Sierra Madre fault (Figure 2). In many 6 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Figure 2. Map of the geology of the eastern Sierra Madre fault between Raymond fault lateral ramp and the San Antonio Canyon lateral ramp (location in figure 1). Note that the Sierra Madre fault generally separates Tertiary and older rocks from Quaternary alluvium. Fault location of SMDF from geomorphology of aerial photographs of the region. Fault locations of CCF, SCF, RF, DF, and UDF from Morton and Matti (1987). Geology from Ziony and Jones (1989), Proctor et al. (1970), and Morton and Matti (1987). SMDF=Sierra Madre fault. DF=Duate fault, UDF=Upper Duarte fault, RF=Raymond fault, CCF=Clamshell Canyon fault, SCF=Sawpit Canyon fault. SDCF=San Dimas Canyon fault, CF=Cucamonga fault. Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Reproduced with permission o f the copyright ow ner. Further reproduction prohibited without p erm ission. 34°'°’ 8 to Quaternary - ' □ □ □ □ L n 0 Artilicial (ill Active alluvium in stream channels, Hood plains, and alluvial Ians (Holocene) Stream terrace deposits, abandoned flood plains, and alluvial fans with incipient soils (Holocene) Stream terraces & m oderately dissected alluvial tans with poorly to moderately developed soils (Pleistocene) Terraces or highly dissected or buried Ians with highly developed soils (Pleistocene) =ZJ 10 km Tertiary — Cretaceous — Pre-Cambrian — Undifferentiated rocks Undifferentiated crystalline rocks G neiss m etasedrm entary rocks (uncertain age) oo Figure 2 \\T& wr>&' \\T & S A l7 °5 0 ‘- _ \A7°A°‘ A A 7 ° 4 2 -5 ‘ - A A 7°A5‘ _ a a 7°A7 -5 ‘ E o I in I A A 7 °5 0 ' 4 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Figure 2 (continued) locations, the San Gabriel Mountains front exhibits several strands of the fault, many of which juxtapose bedrock against older alluvium or older alluvium against alluvium (e. g., Pentegoff et al., 1965; Proctor et al.. 1970; 1992; Crook et al., 1987). Many of these bedrock strands, however, do not exhibit topographic expression, and the geomorphologic data indicate that the active fault trace generally lies at, or to the south of the main topographic mountain front. These observations suggest that in many locations the active strand o f the fault has propagated southward from the mountain front. This inference is consistent with several earlier studies of the location of the fault zone to the west, which have revealed common, older, inactive fault strands to the north of the active strand (e. g.. Crook et al.. 1987; Leighton and Associates, 1992). In at least three locations, for example at San Dimas, along the eastern Sierra Madre fault, at Bradbury 20 km to the west, and near the west end of the fault along the Merrick Syncline ("Little Tujunga Syncline" of Ehlig, 1975). the active fault trace appears to have stepped 1 to 4 km southward, generating a 'lobe-shaped' hanging wall block that exposes Tertiary-Quaternary sedimentary and volcanic rocks (Figure 2) (Eaton, 1957; Pentegoff et al., 1965; Proctor et al., 1970; 1992; Ehlig, 1975; Barrows et al., 1975; Crook et al., 1987; Dibblee. 1991a; 1991b). These 'lobes' are bounded to the south by the active fault trace and on the north by a steep, south-facing topographic front of the crystalline. Mesozoic igneous and metamorphic rocks of the main San Gabriel Mountains. The fact that these lobes are cored by Tertiary-Quaternary sedimentary and volcanic rocks indicates that they have experienced much less exhumation than the crystalline core of the high-standing San Gabriel Mountains to the north. This inference is supported by 10 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. relatively old apatite fission-track ages from two localities near the topographic mountain front (Blythe et a l, in press). We interpret the pronounced topographic inflection point at the base of the crystalline rocks at the northern edges of these lobes as the site of an older fault that bounds the crystalline basement (e. g., "Sierra Madre fault" of Pentegoff et al. [1965] and Proctor et al. [1970; 1992] in the San Dimas area and the fault exposed along the northern edge of the Little Tujunga/Merrick Syncline [Ehlig, 1975]). Coupled with geomorphologic evidence for active reverse faults along the southern edge of these lobes, we interpret these relationships as evidence for relatively young southward propagation of the Sierra Madre fault outward from the trace of the mountain-front fault. Paleoseismology Of The Sierra Madre Fault Previous Investigations A trench excavated across a hanging wall strand of the western Sierra Madre fault along the 1971 San Fernando rupture at Oak Hill revealed evidence for a pre-1971 surface rupture in the form of a colluvial wedge interpreted to have developed by collapse of a scarp (Bonilla, 1973). This pre-1971 colluvial wedge contained a single wood fragment that yielded a radiocarbon date of 200±100 years (Bonilla, 1973), suggesting the possibility that the penultimate event on the western Sierra Madre fault may have occurred during the past several hundred years. Trenches excavated at two sites along the 1971 rupture trace by Fumal et al. (1996; pers. comm., 2000) yielded tentative evidence in support of this interpretation, but further age dating is required to confirm this result. As part of a comprehensive seismic hazard analysis of the fault zone, Crook et al. (1987) excavated more than a dozen paleoseismologic trenches across the central and 11 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. western parts of the Sierra Madre fault. They found evidence for the fault at numerous sites, but were unable to determine the precise ages of any past surface ruptures, because of the absence of datable material in their trenches. The accelerator mass spectrometer (AMS) 1 4 C dating technique, which facilitates age determinations of very small carbon samples, was not available to these researchers, and may explain the absence of datable material. Although they were not able to directly date any past events. Crook et al. (1987) suggested, on the basis of soil development and geomorphologic observations, that the central reach of the fault (east of La Canada; Figure 1) has not ruptured for at least for several thousand years, and perhaps as long as 11,000 years (the oldest soil age estimate that they tentatively assigned to their oldest unfaulted fan deposit [their unit 2]). This basic result was at least partially supported by paleoseismologic observations from a trench in Altadena, along the central reach of the fault, where Rubin et al. (1998) saw evidence for only two surface ruptures during the past 15,000 years. Together, these two events produced -10.5 m of reverse slip, yielding an average slip/event of -5 m at this site; the most recent event produced at least 4.2 m of reverse slip. However, the presence of abundant reworked detrital charcoal fragments of widely different ages in their trench prevented Rubin et al. (1998) from determining the age of the most recent event. This Study We concentrated our search for paleoseismologic trench sites in the San Dimas area, along one of several geomorphically defined 'lobes' where the fault has propagated southward from the crystalline mountain front. In this region the hanging wall of the main 12 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. active trace consists predominantly of Miocene-aged, pale yellow-gray mudstone of the Puente Formation mudstone and purple-to-dark gray basalt and associated rocks of the Glendora Volcanics, also of Miocene age (Eaton, 1957; Pentegoff et al., 1965; Proctor et al., 1970; 1992). The active strand of the fault separates these rocks from Pleistocene- Holocene alluvium to the south. Our air photo and field analysis revealed the presence of several closely spaced strands that generally extend along, or just to the south of, the topographic mountain front. This narrow zone of faults is traceable continuously both to the east and west of the study area (Figure 3). We located our trench site along what our geomorphologic analysis suggests is the main active strand of the fault in this reach (Figure 3). This trace is marked by south- facing scarps and a generally linear mountain front that exhibits triangular facets at the southern terminations of many ridges. In addition, the fault crossings o f several canyons, including the small canyon along which we excavated our trench, are marked by vegetation lineaments, suggestive of either springs or ponding of groundwater along the fault. Vegetation lineaments and a linear alignment of several springs suggest the presence of at least two fault strands to the north of the main, active strand. Neither o f these apparent fault strands, however, have any topographic expression, suggesting that they are either no longer active, or are much less active than the topographically well-expressed main strand that we trenched. Several small, surficial landslides have locally obscured the active fault trace (Figure 5). Our study site is located 150 m southwest of a major water-diversion tunnel (Figure 3). Geotechnical investigations for this tunnel project involved a series of deep 13 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. lission o f the copyright ow ner. Further reproduction prohibited without perm issio n . CD wind gaps springs / } 1 3 G \ •• \ MQ A u i scarp at edge ot drainage Faceted Spurs Fig. 5 '/V -1 SHULER CANYON SITE . VL HORSETHIEF CANYON SITE Q> R D BASELINE 1-210 8i 0.5 contours in teet 1.5 km Figure 3. Map of Horsethief Canyon study site. Shaded box shows location of figures 5 and 6. Note location of geotechnical bore holes (gray-filled circles) used to construct cross section shown in figure 4 along route of water diversion tunnel (Pentegoff et al., 1965; Proctor et al., 1970; 1992). ShC=Shuler Canyon; SC=Shay Canyon; SyC=Sycamore canyon; WC=Wildwood Canyon. Reproduced with permission o f the copyright ow ner. Further reproduction prohibited without perm issio n . G lendora V olcanics P ro p o sed Landslide Pentegoff e t al. (1965) 400 m < D I o' 3 S 300- 200- Fault in d e e p b o reh o les projects to su rface at scarp /tren ch ex p o su re SD-1 ( Figure 6 -Projection of SD-1 Trench Puente Formation TUNNEL GLENDORA THRUST FAULTS? Topanga Formation , j Tunnel bearing N39W Sycam ore Canyon Topographic Profile 0 100 200 50 150 _ NOTE: Boreholes D-16G and D-18G 250 m are Pr°jectecl onto section westward from Sycam ore Canyon. Figure 4. N40W cross section across major active strand of Sierra Madre fault at Horsethief Canyon in S an Dimas ("Cucamonga fault" strand of Pentegoff et al., 1965; Proctor et al., 1970; 1992). Note location of figure 6. S ee text for discussion. Figure 5. Detailed topographic map (kindly provided by City of San Dimas) of our Horsethief Canyon study site showing location of trench SD-1 and transect of large- diameter boreholes. Note pronounced change in slope at fault trace. Also note approximate borehole locations from earlier studies of Pentegoff et al. (1965) and Proctor et al. (1970; 1992); "D" borehole prefix is for smal 1-diameter boreholes drilled with a diamond bit, whereas "A" prefix denotes large-diameter bucket-auger boreholes. Contour interval is 5 feet (1.5 m) in steep terrain; and 1 foot (0.30 m) in flatter areas. 16 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. t- 0 ) © c tfl w 3 O c o u in w © © E m r^ o in in £ 3 05 in C M O 17 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. boreholes, as well as examination of the tunnel bore itself (Pentegoff et al., 1965; Proctor et al., 1970; 1992). Several o f these boreholes and the tunnel penetrated the main strand of the Sierra Madre fault (their "Cucamonga fault"), which dips northward at ~11° north to a depth of 135 m. Projection of two boreholes (D-16G and D-18G) westward onto the cross section suggests that the fault steepens below 135 m depth to a dip of -25° north (Figure 4). The main fault strand projects to the surface at the topographic base of slope at our trench site. Correlation of the upper contact of rocks interpreted by Pentegoff et al (1965) and Proctor et al. (1970; 1992) to be of Miocene age in the footwall of the fault with those exposed in our trench at the tip of the hanging wall (discussed below) indicate a minimum of -260 m of reverse slip on this fault (Figure 4). We note, however, that it is possible that Pentegoff et al.'s (1965) and Proctor et al.'s (1970; 1992) "basal conglomerate of [Miocene] Puente Formation or Topanga Formation", which forms the basis for this reconstruction, might be easily confused with much younger alluvium in a core. In this case, rocks of Miocene age would lie deeper than interpreted by Pentegoff et al. (1965) and Proctor et al. (1970; 1992), and total post-Miocene slip on this strand of the main, active strand of the Sierra Madre fault at the study site may be much greater than the 260 m minimum value we derive. Paleoseismologic Investigations at the Horsethief Canyon Site, San Dimas Trench and Large-Diameter Borehole Results We excavated a 62 m long, 5 m-deep trench across the geomorphically defined main strand at Horsethief Canyon Park, a San Dimas city park that is still largely undeveloped (Figures 2 and 4). The main active strand in this reach of the fault 18 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. extends along the topographic base of the southern edge o f the San Gabriel Mountains foothills, where it is locally obscured by small landslides (Figure 4). Our N20°-35°W- trending trench was excavated along the eastern margin of a small canyon that has incised into the mountain front, creating a re-entrant that allowed us to cross the entire width of the main active fault zone (Figure 5). Following mapping of the trench walls, we backfilled the trench and then excavated a transect of eight large-diameter (70 cm) boreholes (commonly known as "bucket-auger" holes) along the length of the trench in order to define the geometry of the fault and deformed strata below trench depth. The walls of boreholes HI, H3, and H7 were examined directly by lowering a geologist downhole. whereas the descriptions o f the strata in the remaining boreholes are based on examination of cuttings taken every 25-50 cm of borehole depth. Stratigraphy We encountered 13 distinct stratigraphic units in the trench and large-diameter boreholes (Figure 5). We refer to these as units 1 through 13, from youngest to oldest. Six of these units were exposed in the trench. The upper four units extend most of the length of the trench, but the deeper units are truncated by a prominent fault (discussed below). The fault separates the lower part of the trench and the borehole transect into two distinct lithologic sections, with alluvial units exposed below and to the south of the fault and bedrock overlain by alluvium exposed above the fault. All colors mentioned in text are from the Munsell Soil Color Chart (1994), and all locations are listed in meters to the north of the south end of the trench. 19 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. The southern half of the trench, south of the projected topographic base of slope along the scarp to the east, is capped by a 0- to 2-m-thick section of historic fill that contains numerous man-made objects (e. g., barbed wire), as well as several >70-cm- diameter, 3-m-long buried tree trunks. The basal contact of the fill sequence with Unit 1 is sharp. Unit 1 is the A horizon of the active surface soil. In the northern part of the trench Unit 1 extends to the surface, whereas in the southern half of the trench it underlies, and is locally cut out by, the historical fill. Unit 1 consists of a medium- to dark gray-brown, organic-rich silty fine- to medium-grained sand that locally contains disseminated small pebbles o f Puente Formation mudstone. The unit ranges in thickness from 70 to 130 cm over most of the trench, but locally reaches -300 cm at the north end of the trench. Unit 1 overlies Unit 2 along a gradational contact that is locally marked by discontinuous stringers of pebble gravel consisting of Puente Formation mudstone clasts. In the southern part of the trench, where Unit 1 is locally cut out by the historic fill, the contact between the fill and Unit 2 is sharp. Unit 2 is a pale yellow-brown, clayey silty sand that contains sparse, disseminated Puente Formation mudstone pebbles and granules. In the northern 15 m of the trench, the lower part of Unit 2 contains several pockets and lenses of pale grayish yellow-brown pebble to cobble gravels consisting of Puente Formation mudstone clasts. Several of these gravels exhibit oblique channel cross sections. Unit 2 overlies Unit 3 along a sharp, undulating contact marked by local small pebble gravel lags along the base of Unit 2 (Figure 6). 20 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. - - f f i o f f i c e ' • - East Wall of Trench SD-1 Sierra Madre Fault Horse Thief Canyon Park, San Dimas, CA Ground BC 3 9 8 0 1 9 2 Surface RfJ *54fi7+?Q'' * BC 6252179 UNIT 2 UNIT 11 ’ sheared UNIT 12 2 0 9 1 0 + /- 7 0 B P UNIT 7 SD -H 2 UNIT 8 UNIT 13 SD - SD -H 6 SD -H 7 SD -H 4 \ S heared clay in Sierra M adre fault SD-H1 meters Figure 6. C ross section showing ea st wall of trench SD1 and large-diam eter borehole results from the Horsethief ~ Canyon site. Note location of 14C sam ple SD-H3, recovered in situ from borehole SD-H3. No vertical exaggeration. Unit 3 is a yellow-brown silty clay with -20% pebble-sized Puente Formation mudstone clasts. Most o f Unit 3 is massive, but it locally exhibits horizontal to gently south-dipping sandy silt layers. Unit 3 extends from the southern end o f the trench northward for 45 m, where it pinches out to the north. At the southern end of the trench, the unit is -4 m thick, gradually thinning northward to ~2 m at m 34. At m 34, Unit 3 abruptly thins to - 1 m thickness along an irregular, interfingering contact. We examined this contact in some detail in order to determine whether or not it is a fault. Our investigations, however, showed that it was a purely sedimentary feature. Unit 3B is a cohesive, yellow-brown sandy clay with 5-10% pebbles. It is distinguished from overlying Unit 3 by having fewer clasts and a higher clay content. The base of Unit 3B is marked by a pebble-cobble gravel between meters 10 and 15. South of ~m 6, Unit 3B cannot be distinguished from overlying Unit 3. The part of Unit 4 that is exposed in the trench is a cohesive, red-brown (8.5YR 5/6) silty clay with 5-15% pebble-sized Puente Formation mudstone clasts. In the northern part of the trench. Unit 4 contains several pebble- to cobble-gravel channels consisting of Puente Formation mudstone clasts. Farther south, in boreholes HI and H3. Unit 4 contains more gravel (15-30%) and is a pale yellow-brown. Unit 4 overlies Unit 5 along a sharp to locally gradational (over <15 cm) contact. Unit 5 is a moderately well-indurated, pale purplish-brown, clast-supported pebble to cobble conglomerate. More than 95% of the clasts consist o f purple-gray volcanic rocks derived from outcrops o f the Miocene Glendora Volcanics to the north and northeast of the trench. The matrix consists o f a pale purplish-gray-brown silty sand. 22 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. This unit can be traced southward as a southward-thinning wedge from its exposure at the base of the trench through boreholes H6, H7, H2, and HI (Figure 5). Unit 5 is not exposed in borehole H3, and appears to pinch out to the south o f borehole HI. Unit 5 overlies Unit 6 along a gradational contact. Unit 6 consists o f medium brown to medium purplish-brown silty clay to silty sand that is generally similar to overlying Unit 5 except for a much lower gravel content (<10-40% clasts) and a less purplish color. Unit 6 can be traced laterally for -20 m in boreholes H6, H7, H2, and HI. Unit 6 overlies Unit 7 along a relatively sharp contact (gradational over <5 cm). Unit 7 is a medium- to dark-brown clay to clayey sand that contains <5% clasts larger than sand size. The dark color and abundant clay in this unit lead us to interpret it as a buried soil horizon. This unit, which can be correlated across all five southern boreholes, dips southward at 10°, sub-parallel to the ground surface. Unit 8 consists of pale brown to locally dark brown clay, clayey sand, and fine grained sand with a southward decreasing amount of gravel. Pebbles and cobbles within Unit 8 were derived from both the Puente Formation mudstone and Glendora Volcanics. In boreholes H6 and H7, the unit contains -60% pebbles and cobbles, whereas in more southerly borehole HI and H3, the unit contains <20% clasts. Unit 9 is a southward-thickening wedge composed of clast-poor, dark brown clay with 5-20% pebbles and cobbles derived from the Puente Formation, Glendora Volcanics, and granitic rocks. 23 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Unit 10 is made up o f highly deformed Puente Formation mudstone that is exposed only in the hanging wall of the prominent fault described below. Unit 10 comprises several 25- to 50-cm-thick blocks of intact, well-bedded mudstone, as well as more brecciated 'pods' of altered, iron-oxide-stained mudstone. Bedding in the intact blocks dips 35° north, parallel to the underlying fault plane. Several prominent shear zones, some of them marked by 5- to 35-cm-thick white to purple-gray clay gouge zones, cut through Unit 10. Units 11 and 12 were encountered only in boreholes H4 and H5 (Figure 5). These two boreholes were not logged directly due to unsafe borehole conditions (water in boreholes). Thus, these units, unlike the other stratigraphic units we encountered, are known only from cuttings obtained every 25 to 50 cm. These cuttings indicate that Unit 11 is a 2- to 5-m-thick, orangish yellow-brown (7.5YR 4/6) to yellow-brown (10YR 5/8) sand with abundant angular fragments of granitic rock: it is unclear if these are individual clasts in a gravel or whether they are more intact pieces of a 'pod' or lens of granitic rock interleaved with the Puente Formation mudstone of Unit 10 to the south. There is a notable absence of Puente Formation mudstone clasts in Unit 11. We suspect that the sand observed in the cuttings is actually the remains of an intact granitic body that was ground to sand by the bucket-auger cutting teeth during drilling. The presence of intact granitic rock in the borehole could not be confirmed because, as noted above, neither borehole in which Unit 11 was encountered was logged downhole. Unit 12 is a friable, blue-gray (Gley 2 colors) sand with angular granodiorite clasts (ground-up bedrock?) and sparse Glendora Volcanics pebbles and cobbles. 24 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Directly below Unit 12, beneath the fault gouge discussed below, is alluvial Unit 13. This unit is a purple to brown sand and clay that locally contains pebbles derived from the Puente Formation mudstone facies and Glendora Volcanics. In general, this unit is quite similar to several of the shallower units exposed in the footwall of the fault. The 4 m of Unit 13 that was exposed in borehole H5 consists of a medium- to dark-brown silty sand matrix with 30-50% petroleum-stained Puente Formation mudstone clasts. Below the oil-stained gravel is a pebble to cobble gravel containing 30-50% clasts in a purple-brown sand matrix. In borehole H4 Unit 13 is a pale yellow-brown to dark brown clay with 5-10% pebble gravel and local sand stringers and thin beds with<10% pebble sized clasts. Below Unit 9 in boreholes H6, and H7, Unit 13 consists o f a pale yellow- brown sand with 10-20% Puente Formation mudstone and Glendora Volcanics pebbles. Further south, in borehole HI, Unit 13 is a brown silt to fine-grained sand matrix with 25- 60% Glendora Volcanics, Puente Formation, and granitic pebbles and small cobbles. On the basis of their borehole results from between our trench site and the water- diversion tunnel 125 m east, Pentegoff et al. (1965) and Proctor et al. (1970; 1992), suggested the presence of large, deep-seated landslides beneath the southern mountain front (Figure 4). In their large-diameter boreholes located along, and just south of the mountain front (e. g., A-4G in figure 3), geologists lowered down the boreholes noted the presence of a gently north-dipping shear plane, which they interpreted as the basal landslide thrust fault near the toe of the slide (Pentegoff et al., 1965; Proctor et al., 1970; 1992; R. Proctor, pers. comm., 2000). Along the tunnel route, this slide surface would project to the ground surface >50 m south of the topographic mountain front (Figure 4). 25 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. In our study area just to the west, however, the presence o f an undeformed, well-defined alluvial section >20 m thick in the footwall of the fault rules out the presence of large, deep-seated landslides that extend south of the topographic mountain front. Although the shear surface noted in the water-diversion tunnel boreholes may be the basal detachment of a large, old landslide, the lack of any geomorphic expression of this feature to the south of the mountain front suggests that it is no longer active. Age Control We recovered four detrital charcoal samples from our excavations, three from the trench and one from borehole H-3, for Accelerator Mass Spectrometer (AMS) radiocarbon dating (Figures 6 and 7; Table 1). Samples SD-14, SD-26, and SD-41 were collected from unfaulted strata directly above the main fault zone exposed in the trench (discussed below). These samples yielded calibrated, calendric AMS ages of B. C. 3980±92, B. C. 5467 ±29 yr, B. C 6252±79, respectively (Table 1). The ages of the samples indicate that they are in correct stratigraphic order, suggesting that they have not been reworked. All three of these samples were small, and consequently received only a acid wash in pre-treatment, rather than acid-alkali-acid washes. The samples were recovered from 3-4 m depth, however, and we therefore do not think that they have been significantly contaminated by young illuviated carbon. We also recovered a detrital charcoal fragment (SD-H3) from the drill rig cutting teeth when borehole H3 had reached a depth of 12.4 m. We are quite certain that the detrital charcoal fragment was from Unit 7, as we were careful to clean the cutting teeth after each drill run, and the sample was taken from a freshly broken face of a coherent 26 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Table I. Radiocarbon Ages for trench SD-I Sample H Bela Lab it Wall Trench Coordinate (m, horizontal) Trench Coordinate (m, vertical) Conventional M C Age (years BPH o) Calcndric **C Age (year BCi2o)* Age II P. (2cr) SD-14 Beta-123849 East 43.9 5.3 6380140 5467129 7417129 SD-26 Bela-12S076 West 38.2 4.6 5140150 3980192 5930192 SD-41 Bela-123831 East 40.0 4.0 7330140 6252179 8202179 SD-H3 Bela-123852 borehole dcpth- 12.4m 20930170 ♦Culendric ages using CALIB 3.03 (Stuiver and Reiiner. 1993; method A) IO -J mass o f distinctive Unit 7 clay. We emphasize that the color and grain size of Unit 7 are very distinctive, as demonstrated by direct downhole observations. This charcoal sample yielded an uncalibrated AMS date of 20,930±70 years B. P. Although this sample is beyond the maximum calendric calibration age of C ALIB 4.1.2 (Stuiver and Reimer, 1993), we can use the l4C production rate curves of Voelker et al. (1998) to estimate the approximate calendric age of this sample at ~B. C. 22,000. Error bars are difficult to determine for this crude calendric age estimate, but they are probably on the order of ~± 1,000 years. Evidence for Faulting A prominent fault zone was exposed in the base of the trench and in the northernmost two boreholes (Figure 6). The fault, where it is exposed in the trench, consists of a 10- to 30-cm-thick, intensely sheared pale gray clay gouge. The clay gouge thickens downward, and it is 75-120 cm thick in boreholes H4 and H5. The fault separates completely different stratigraphic sections, with sheared and brecciated, pale yellow-brown Puente Formation mudstone of Miocene age exposed in the hanging wall and late Pleistocene to early Holocene(?) alluvium of units 5-10 exposed in the footwall. The fault strikes N40°E and dips northward at 22° in the uppermost 18 m. The near surface part of the fault exposed in the trench and boreholes projects downdip directly to the gently north-dipping main strand of the fault observed in the water-diversion tunnel boreholes adjacent to our trench site (Figure 3) (Pentegoff et al., 1965; Proctor et al., 1970; 1992). 28 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Unit 2 BC 5467 ± 2 9 Unit 4 -41 BC 6252 ± 79 Unit 10 Unit5 Fault G o u g e silty clay silty line-coarse grained sand Altered Puente Fm S heared Clay | ^ r j Coherent Puente Fm f f c f ] Conglomerate/Gravel to v O Figure 7. Detail of northern part of e ast wall of trench SD-1 showing locations and corrected, calendric ag es of three detrital charcoal sam ples recovered from unfaulted alluvium in trench SD-1. Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. SD-1 East Wall N Gravel Channels 0 5 Unit 4 Fill U nits Unit 10 Unit 3b Unit5 ■ > 'i« « Coherent Puente Formation 0 i i i i i i i i i i i 1 t I I I I I T 1 I I I I 1 I 1 I I I I I I I I I I I I I I I I I I I I I I I I 1 I I I I 10 5 0 4 0 3 0 M eters N o V ertical E xaggeration 2 o 10 Figure 8. Cross section showing east wall of trench SD-1. U > O Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. SD-1 West Wall Gravel Chan n e l ^ ' . 0 S D 1 M Unit 3 S O I - 3 J 5 e S S Unit 3 F ill i D U f f f a — — 5? Unit 3b S O I - 3 9 § 0 1 - 5 Unit 10 Unit 5 S O I - 4 , . - 0 i | i i i i i i i i i | i i i i i i i i i | i i i i i i i i i p i T _r'i i i i i i | l i i i i i l i i | i i i i i i i l i | i 10 10 20 30 40 50 60 M eters No Vertical Exaggeration Figure 9. Cross section showing west wall of trench SD-1. U > In the base of the trench, the clay gouge is truncated along a sharply defined, erosional unconformity at the base of unit 4, which is not faulted. The shallowest part of the fault juxtaposes sheared, pale yellow-brown Puente Formation mudstone in the hanging wall against purple-gray gravel of Unit 5 (Figure 7). Several of the faulted alluvial units in the footwall, including the dark brown clay of unit 7, can be traced northward through several boreholes to within 10 m of the fault (Figure 6). Any strata correlative with these units in the footwall must have been deposited above the Miocene bedrock currently exposed in the hanging at the base of the trench. Thus, projection of the base of unit 7 to its pre-faulting position requires at least 14 m of reverse slip. This reverse-slip estimate is a minimum because any strata that were correlative with unit 7 have been eroded off the hanging wall prior to deposition of unit 4. The fault locally controls the depth of near-surface groundwater. Groundwater was encountered immediately above the fault in hanging-wall boreholes H4 and H5. We interpret this as evidence for groundwater flowing along and/or as ponded against the impermeable clay of the fault gouge. In contrast, the only groundwater encountered in the footwall of the fault was in borehole H6. where the gravels at the base of Unit 5 were wet. We interpret this as evidence for groundwater flowing southward from the fault zone through the permeable Unit 5 gravels along the top of the impermeable clay of Unit 6. Shuler Canyon Site (SD2) Site Description The second study site (SD2) was located just east of the mouth of Shuler Canyon at the north end of Cataract Way in the City of San Dimas, California (Figures 3 and 10). The Shuler Canyon site is ~1 km west of the Horsethief Canyon site (SD-1). The two 32 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. h-335- 320 h 314 \ \ m 10 20 30 40 50m Elevation in M.S.L Contour Interval = 1.5m u > U ) Figure 10. Detailed topographic m ap of Shuler Canyon study site showing Icoation of trench SD-2. Bend in trench at southw est end is ramp out of the trench. Contour interval 1,5m. sites lie along the same geomorphically defined fault strand. The surface trace of the Sierra Madre fault in the Shuler Canyon area is defined by local south-facing scarps, faceted spurs along the southern edges of several ridges, vegetation lineaments, and aligned springs. The active fault trace is obscured in the active part of the Shuler Canyon drainage. Stratigraphic Units The trench contains eight discemable stratigraphic units that are capped by a ~1 m-thick sequence of artificial fill in the southern part of the trench. We refer to these units as Units 1-8, from youngest to oldest (Figures 11 and 12). All units except the brecciated bedrock of Unit 8 (discussed below) appear to be either alluvial or colluvial in origin. The alluvial sediments were derived from exposures of the Miocene Glendora Volcanics and Miocene Puente Formation mudstones to the northeast of the site, whereas the colluvial units were derived from exposures of Puente Formation mudstone located directly upslope from the trench. All horizontal distances noted are in meters south of an arbitrary horizontal datum designated as 'meter zero'; vertical elevations within the trench are relative to an arbitrary zero datum. The sediment colors listed are taken from the Munsell Soil Color Chart (1994). The historic fill that covers the alluvium in the southern half of the trench consists of several layers of dark reddish brown (5YR 3/4) to gray (10YR 3/2) pebbly clay. Small chunks of asphalt are distributed throughout these layers. The youngest alluvial unit (Unit 1) is a dark gray-brown (10YR 4/2) organic-rich silty clay in the central and southern portions o f the trench, and grades northward into a 34 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Unit 3 SD2 East Wail 5 U nit Artificial Fill SD2-8 Unit 1 0 SD2-16 SD 210«V ^\ Unit 2 Unit 4 3 0 Unit 6 I Faults Unit 5 i ' 5 i 0 5 10 15 2 0 2 5 3 0 M e te rs N o V ertical E x a g g e ra tio n Figure 11. Cross section showing east wall of trench SD-2 at Shuler Canyon site (see figure 8 for location). U t Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. SD2 W est Wall Artificial Fill \ Faults Meters No Vertical Exaggeration Figure 12. Cross section showing west wall of trench SD-2 at Shuler Canyon site (see figure 8 for location). U ) O s dark brown (10YR 3/3) silty clay that contains small to large pebbles of Puente Formation mudstone. The clay content of Unit 1 gradually increases southward. We interpret Unit 1 as the A-horizon of the surface soil. This unit is 25-40-cm thick in the northernmost part of the trench, but thickens abruptly at ~m6, reaching a maximum thickness of 4 m at mlO (Figures 11 and 12). South of mlO, Unit 1 gradually thins southward to 1 m thickness in the southern part of the trench. The lower part of Unit 1 exhibits minor white carbonate micro-veining and mottling. In the central portion of the trench, Unit 2 is a dark brown (10YR 3.5/3), locally sandy, clayey silt. Sand content gradually increases southward, and in the southern part of the trench Unit 2 is a dark yellow-brown (10YR 4/4) clayey sand. The contact between Units 1 and 2 is gradational and difficult to define precisely between m5 and m8. To the south, this contact is gradational over 15-25 cm. South of ml 1.5, the upper 15-50 cm of Unit 2 is characterized by an absence of white carbonate veining and mottling. Below this carbonate-free zone, Unit 2 exhibits common white micro-veining and mottling suggestive o f a Bk horizon. Unit 3 is a gravel that consists of pebbles and cobbles composed exclusively of Puente Formation mudstone that are set in a clayey sand matrix. In the northern 6 m of the trench, Unit 3 directly underlies Unit 1 along a sharp contact; to the south, Unit 3 underlies Unit 2 along a contact that is gradational over 2-20 cm. Unit 3 varies markedly in thickness and geometry along the length of the trench. It is only ~10 cm thick in the northern 3 m of the trench, but thickens abruptly to 1.5 m between ml and m3.5. To the south of m3.5 Unit 3 is 30-60 cm thick. Unit 3 pinches out to the south o f m l 7.75, although isolated pebbles at the same stratigraphic level extend southward as far as 37 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. m22. To the north of m 3.5, the upper and lower contacts of Unit 3 dip generally parallel to the ground surface. Between m3.5 and m5, however, the bed dips steeply to the south. Most of the clasts within Unit 3 are platy in shape, and in general their long axes are oriented parallel to the basal contact of Unit 3, mimicking the southward transition from gentle to steep dips between ml and m5. The northern part of the deposit is clasts supported, whereas the southern part is matrix supported, reflecting a pronounced southward decrease in both the clast size and the total percentage of gravel. In contrast to other gravels in the trench (e. g., Unit 6), which contain sub-rounded to rounded clasts, the clasts in Unit 3 are subangular to angular. Given the softness of these clasts, their angularity indicates that they have experienced very little transport. These observations, coupled with outcrops of Puente Formation mudstone located only a few meters directly upslope from the trench, leads us to interpret Unit 3 as a locally derived colluvial deposit, which was probably deposited as a rockslide. Unit 4 directly underlies Unit 3 along a sharp contact. Unit 4 is a massive, dark yellow-brown (10YR 4/4) sandy silty clay that contains <5 % o f small to large Puente Formation mudstone pebbles. The unit varies markedly in thickness along the trench. North of m5, Unit 4 is 75-130 cm thick, whereas to the south of m5 the unit thins southward from 35 cm to zero at m l7. Unit 5 is a very dark brown (10YR 2/2) silty clay, which we interpret as a buried A horizon. The unit contains less than 5% pebbles and is between 50 and 75cm thick. The upper contact with Unit 4 is gradational over -1 0 cm. Unit 5 is gently south dipping in the central to southern portions of the fault. 38 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. The contact is sharp between Unit 5 and 6. Unit 6 is an orange-brown clay that contains pebbles and small cobbles derived from the Glendora Volcanics; in contrast to all shallower deposits, this bed contains no Puente Formation mudstone clasts. Unit 7 is a massive, dark yellowish-brown (10YR 4/4) sandy silty clay. The unit contains abundant small to large Puente Formation mudstone pebbles near the ground surface, but clast content decreases downwards to -1% small pebbles at the bottom of the unit. Unit 8 consists of brecciated pale grayish yellow-brown ( to 2.5Y 6/4), Puente Formation mudstone. On freshly broken faces, the bedrock in the upper part of the unit is pale grayish yellow-brown (2.5Y 6/4 to 2.5Y 6/6). but on weathered fracture surfaces the rock is commonly coated with white carbonate, giving the unit an overall pale grayish yellow-brown color (2.5Y 8/2). 39 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Age Control Table 2: Age Control in trench SD-2 Charcoal Sample Horizontal Location (m) Vertical Location (m) Wall Unit SD2-1 4.9 -1.2 E Unit 5 SD2-2 5.4 -1.15 E Unit 5 SD2-3 1.5 0.4 W Unit 7 SD2-4 7.65 • O 00 J W Unit 2 SD2-5 -0.8 1 00 o 1 E *In shear zone SD2-6 4.15 -1.25 E Unit 5 SD2-7 15.2 -0.6 W A-horizon SD2-8 1.3 2.7 E Unit 6 SD2-8a 15.1 -0.4 W A-horizon SD2-9 1.4 3.1 W Unit 3 SD2-10 5.2 o I E Unit 4 SD2-15 5.3 -1.05 W Unit 5 SD2-16 18.3 0.1 E A-horizon We recovered 13 detrital charcoal fragments from trench SD-2. Table 1 shows the locations and units from which each of these samples was obtained. Charcoal samples SD2-1, 2. 3,4,6, 7. 9. 10. and 15 have been sent to the NSF-University of Arizona AMS Radiocarbon Lab for analysis. However, no radiocarbon dates have been received as of this writing. Evidence for Faulting A prominent 2.5-m-thick fault zone was exposed at the base of the trench to the north of m8.5 (Figures 11 and 12). This fault zone, which comprises three discrete fault strands, has thrust the brecciated bedrock of Unit 8 over alluvium, including the buried A horizon. The fault planes dip gently north (<20°), although at the north end of the trench the shallowest fault strand is near-horizontal, and dips a few degrees southward north of m0.5. 40 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. In the lower part of the trench, most of these faults are marked by thin, sharply defined dark brown to dark gray clay-filled shear zones. The faults exhibit abundant evidence for brittle slip. For example, the shallowest fault strand juxtaposes the sheared bedrock of Unit 8 with a sheared mix of pale yellow- brown bedrock and alluvium, including several thin, fault-bounded slivers of dark brown A horizon material. Another example of brittle faulting occurs at zero meters depth on the west wall, where Unit 3 exhibits a marked change in character. Above that depth, Unit 3 contains abundant cobbles and small boulders above, whereas it contains only sparse pebbles below (Figure 12). The change in grain size is coincident with the southward projection of the shallowest fault strand. Moreover, the base of Unit 3 appears to be displaced to the north beneath the fault by -40 cm. We interpret these observations that the base of Unit 3 has been faulted during the most recent surface rupture. The middle fault zone, which compresses several closely spaced, sub-parallel strands, truncates the top of the dark brown Unit 5 paleosol to the north of m5.5. The location and geometry of the fault-bounded pod of A horizon material exposed at the base of the north end of trench indicate that this material must have been displaced upward from an A horizon than is buried more deeply than Unit 5. Finally, on the east wall of the trench, the structurally lowest fault strand has displaced the top and base of Unit 5 -95 cm and >75 cm, respectively (Figure 11). This fault strand was not excavated on the west wall. In addition to this evidence for brittle faulting, the geometry of the Unit 3 colluvial gravel bed indicates that a significant portion of the reverse slip that reaches the surface at this site has been accommodated by folding. On the east wall, the gravel, although it 41 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. exhibits an overall concave-up profile consistent with our interpretation that it was deposited as a rockfall along a pre-existing slope, also exhibits two very moderately dipping to vertical sections whose cemeteries cannot be depositional (i. e., m4.0-m4.6 and m5.6-m6.5; Figure 11). Moreover, the uppermost and middle fault strands project upward to the inflection points at the bases of the vertical and moderately dipping sections on Unit 3. On the east wall, the geometry o f the deposit is somewhat different, but the unit does exhibit an anomalously steep dip between m3.1 and m4.9 (-45° overall, relative to the ground surface slop at 19°, with one section on the colluvial unit dipping beyond vertical at m3.9-m4.2). We interpret these steep dips as evidence that the colluvial bed was folded during the most recent surface rupture. This inference is supported by the fact that the long axes of all the clasts, which in the undeformed parts of the bed to the south o f m6.7 are oriented flat parallel to bedding, are oriented vertically in the vertical sections of the bed. We know the dips of all faults in the trench, so if we assume that Unit 3 had a relatively smoothly curving profile when it was deposited (an inference supported by the very gradual and smooth downslope change in thickness of the bed observed on both walls), then we can 'unfold' Unit 3 in order to estimate the amount of near-surface reverse displacement that has been consumed by folding. On the east wall, this reconstruction suggests that folding o f the vertical section of Unit 3 required -2 m of reverse slip. The concave-up section of the gravel bed between m4.6 and m5.5 required -1-2 m of slip, the large potential error limits caused by uncertainly about the exact fault dip. The structurally lowest strand does not appear to have accommodated significant folding. 42 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Adding the 3-4 m of reverse slip consumed by folding on the upper two strands to the "90 cm of reverse slip on the structurally lowest strand indicates that the fault zone exposed in the base of trench SD-2 has accommodated -4-5 m of total reverse slip. A similar reconstruction on the west wall suggests that total slip may be as little as ~3 m on the northern two strands, similar to the minimum estimate of slip on these two strands from the east wall. We cannot tell whether the slip occurred during more than one event, if all of the reverse slip did occur during one event, it would be consistent with a large earthquake (Mw 7, Wells and Coppersmith, 1994). Discussion The following discussion is based only on the results of the study at trench SD-1 due to the fact that no radiocarbon dates were returned from the AMS lab at the time of this thesis. Our paleoseismologic observations indicate that it has been at least 8,000 years since the most recent surface rupture on this strand of the Sierra Madre fault. Although several strands of the fault exist in the study area, the geomorphologic data indicate that the strand that we trenched is the only one with significant topographic expression, suggesting that it is the main, and probably the only, active strand at our trench site. This inference is supported by the large-diameter borehole data, which indicate that this strand accommodated at least 14 m of reverse slip between -24,000 and 8,000 years ago. This displacement is a minimum, because strata correlative with unit 7 in the footwall have been eroded off the hanging wall at the trench site. These relationships yield an average, minimum reverse slip rate for this strand of at least -0.6 mm/yr (measured over the 43 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. interval 24 ka-present) to -0.9 mm/yr (measured over the interval 24 ka to 8 ka only). We prefer the latter estimate because the absence of deformation in the unfaulted early- late Holocene strata exposed in the trench and boreholes suggests that the fault has been locked and storing elastic strain energy since at least 8 ka. The actual reverse slip rate could be somewhat faster if: (1) total slip has been much greater than the 14 m minimum; (2) the 14 m measured minimum slip occurred during a brief period between the maximum 24 ka and 8 ka limits provided by the trench and borehole observations; and (3) the single, -24 ka detrital charcoal sample recovered from borehole H-3 was reworked from an older deposit, and had a significant age when it was incorporated into unit 7. In this last case, unit 7 would be younger than the age of the charcoal sample, and the >14 m of reverse slip could have occurred during a much shorter period than 24-8 ka. Whatever the exact reverse-slip rate on the fault, the long elapsed time since the most recent event on the main active strand of the Sierra Madre fault suggests that at least the eastern part of the fault ruptures in infrequent, but therefore probably large, events. Any colluvial strata that may have been deposited during the most recent surface rupture at the trench site have been eroded, and we therefore cannot directly measure slip per event. Nevertheless, we can use the minimum reverse slip rate and the >8,000 year long interval since the most recent surface rupture to speculate about the magnitude of potential earthquakes on the eastern Sierra Madre fault. The minimum 0.6-0.9 mm/yr reverse slip rate implies that at least 4.6 to 7.0 m of elastic strain energy has been stored on the strand we trenched during the past -8,000 years. If we assume that all of this strain were to be accommodated during a single rupture, we can use regressions of average 44 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. and maximum slip against moment-magnitude to estimate the sizes of potential Sierra Madre fault events. If 4.6 m is the average slip across the rupture plane in a future event, this is equivalent to a Mw~7.5±0.2 earthquake; if 4.6 m is the maximum slip, this would be a M~7.2±0.15 event (Wells and Coppersmith, 1994). If 7.0 m is average slip in a future event, this would be a Mw -7.6±0.2 earthquake (Wells and Coppersmith, 1994), yielding a range of potential values of Mw -7.0 to 7.8. We re-emphasize, however, that the slip rate upon which these magnitude estimates are ultimately based is a minimum value, and that the higher end of this magnitude range is therefore probably more likely to be correct. The regressions of Dolan et al. (1995), specific to southern California earthquakes, yield a range of somewhat larger magnitudes from Mw 7.5-7.9 for average displacements of 4.6 and 7.0 m; Dolan et al. [1995] did not regress maximum slip against Mw. The long elapsed time interval since the most recent event on the eastern Sierra Madre fault is consistent with the apparent occurrence of only two events along the central reach of the fault since 15 ka in Altadena, 35 km to the west of San Dimas (Figure I) (Rubin et al.. 1998 ). Moreover, the minimum 4.6 to 7.0 m of stored slip on the eastern part o f the fault is consistent with the suggestion by Rubin et al. (1998) that the Sierra Madre fault produces an average of -5.5 m of reverse slip per event at that site. At both sites the fault has also experienced large surface displacements during latest Pleistocene-Holocene time; >14 m of reverse slip since -24 ka at San Dimas and -10.5 m o f reverse slip in Altadena during the past 15 ka (Rubin et al., 1998). 45 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. While these similarities may be merely coincidence, the large displacements suggested by the colluvial strata at the Altadena site and the long elapsed time since the most recent event at the San Dimas site argue that these are large events that rupture long stretches of the Sierra Madre fault. Such large displacements are typical of ruptures that involve large fault-plane areas (Wells and Coppersmith, 1994). Therefore, the most likely faulting scenario involves simultaneous rupture of large stretches of only the Sierra Madre fault. If this is the case, and if the long elapsed time since the most recent event on the eastern part of the fault is typical, then we speculate that the Altadena and San Dimas trench sites may record the same earthquakes. Alternatively, it is possible that the Sierra Madre fault sometimes ruptures together with contiguous faults, for example the Cucamonga or Raymond faults. Published paleoseismologic data, however, indicate that the Raymond fault has ruptured to the surface at least once, and possibly several times, since the most recent surface rupture on the eastern Sierra Madre fault (Figure 13) (Crook et al, 1987; Weaver and Dolan, in press). Bayarsayhan et al. (1996) have even suggested that the Sierra Madre fault could rupture together with the Mojave section of the San Andreas fault in southern California's "most devastating earthquake" scenario. Their suggestion is based on the geometric similarity between the Sierra Madre-San Andreas fault system and the faults that ruptured during the 1957 Mw -8 Gobi-Altay event in southern Mongolia. That event involved simultaneous rupture o f >300 km of the Bogd fault, a major left-lateral strike-slip fault similar to the San Andreas fault, and two long stretches of a north- dipping reverse fault system to the south that are similar to the Sierra Madre fault 46 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Raymond Fault |----- W eaver and Dolan, in p ress I 2-3 E vents i - 1 ?- ----------- pH 2-3 Events Crook et al., 1987 | Sierra Madre Fault Most R ecen t Event i This study ^ 1 ----------------------- 2 even ts, m ost recent <15ka 9 Rubin et al., 1998 ---------- 1 l I i i i i I 0 5 10 15 2 0 Age BP (ka) Figure 13. Comparison of rupture histories of the Sierra Madre fault with the Raymond fault. Note that there have probably been 2-3 surface rupturing events on the Raymond fault since the most recent surface rup turing event on the Sierra Madre fault. •t* -j (Florensov and Solonenko, 1963; Baljinnyam et al., 1993; Bayarsayhan et al., 1996). The >8,000-year-long current quiescent period on the eastern Sierra Madre fault, however, shows that the fault ruptures much less frequently than the San Andreas fault, which in this region exhibits a recurrence interval o f -100-130 years (Sieh, 1978; Sieh and Jahns. 1984; Fumal et al., 1993). Thus, something on the order of 60 to 80 San Andreas fault "Big Ones", that is Mw-7.5-8 earthquakes, have occurred since the most recent surface rupture on the eastern Sierra Madre fault. While these observations do not rule out the possibility that the Sierra Madre fault could rupture together with the San Andreas fault in a scenario similar to the 1957 Gobi-Altay earthquake, they indicate that such combined southern California events, if they ever occur, must be extremely rare. This is not to say that a major event involving rupture of a large section of the Sierra Madre fault by itself would not have serious repercussions for the Los Angeles metropolitan region. The largest events that have occurred on faults directly beneath the metropolitan region during the 150 to 200-year-long historic period are the 1971 Mw 6.7 San Fernando and 1994 Mw 6.7 Northridge events. The Mw >7 events suggested by the long elapsed time interval on the eastern Sierra Madre fault and the large slip per event measurements along the central part of the fault (Rubin et al., 1998) would be much larger than either the 1971 or 1994 events, and would differ from them in several important respects. Specifically, strong ground motions generated by a Mw >7 Sierra Madre fault event would be experienced over a much larger region, and the duration of these strong ground motions would be longer than for more moderate-sized events. 48 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Source directivity could also play a critical role in controlling damage patterns during a future Sierra Madre fault event. If a large earthquake were to nucleate near the base of the seismogenic zone, as occurred during the 1971 and 1994 events (Heaton, 1982; Scientists of the USGS and SCEC, 1994; Wald et al., 1995), updip directivity along the north-dipping Sierra Madre fault would focus energy southwards, directly towards the metropolitan region, including the Los Angeles Basin, the location of many older, multi story structures, as well as numerous high-rises. The stability of some of these high-rise structures during relatively close, large earthquakes has been the subject of intense scientific discussion (e. g.. Heaton and others, 1995). The >8.000 year-long elapsed period since the most recent surface rupture on the eastern Sierra Madre fault has important implications for seismic hazard calculations of the Los Angeles metropolitan region. The standard probabilistic seismic hazard assessment model for California (Petersen et al., 1996) assumes an average recurrence interval of 384 years for an assumed Mw 7.0 event size on the Sierra Madre fault. The slip rate on which this model is based, however, is 3±1 mm/yr (similar to the rate proposed for the Sierra Madre fault in WCGEP. 1995, and for the combined Sierra Madre-Verdugo fault system in Dolan et al., 1995 and ). This slip rate is much faster than the rate for the main, active strand of the eastern Sierra Madre fault that we document in this paper (0.6-0.9 mm/yr), and is also faster than the -1-2 mm/yr rates that have been documented on the central and western reaches o f the fault (Lindvall et al., 1995; Walls et al., 1998; in prep.). Moreover, our data and those of Rubin etal. (1998) suggest that the assumed Mw 7.0 size for hypothetical earthquakes used in the 49 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. probabilistic model may be smaller than at least some events that occur on the central and eastern parts o f the fault. These factors should be considered in any future probabilistic seismic hazard assessment models for southern California. The potential for large earthquakes (Mw >7) on the Sierra Madre fault should not come as a surprise. Numerous reverse fault systems elsewhere in the world that are similar to the Sierra Madre fault have generated large (Mw >7) earthquakes (e. g., 1964 Ms 7.5 Niigata, Japan [Kawasumi, 1973; Satake and Abe, 1983; Okamura etal., 1994]; 1978 Ms 7.4 Tabas-e-Golshan, Iran [Berberian, 1979; Hartzell and Mendoza, 1991; Berberian and Yeats, 1999]; 1980 Mw 7.3 El Asnam, Algeria [King and Vita-Finzi. 1981; Philip and Meghraoui, 1983; Swan. 1988]; 1992 Suusamyr, Kyrgyzstan [Mellors etal., 1997; Ghose et a l, 1997]; and 1999 Mw 7.6 Chi-Chi, Taiwan [Bilham and Yu, 2000; Shin et al., 2000]). In fact, several such large reverse fault earthquakes have already occurred in southern California during the historic period (e. g., December 21, 1812 western Transverse Ranges [Toppozada et al., 1981; Ellsworth, 1990]; 1927 Mw~7(?) Lompoc [Gawthorp, 1978; Savage and Prescott, 1978; Hanks, 1979; Helmberger et al., 1992; Satake and Somerville, 1992]; and 1952 Mw 7.3-7.5 Kem County [Hanks et al., 1975; Stein and Thatcher, 1981; Ellsworth, 1990]). Fortunately, the regions affected by strong ground motions during the previous large southern California events were sparsely populated when the earthquakes occurred, and damage and loss of life were minimal; this is certainly not the case for the densely populated areas that would be most directly affected by a large reverse-fault earthquake on the Sierra Madre fault. There is nothing "special" about the faults that have generated large reverse-fault events in southern 50 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. California and elsewhere around the world, and the evidence presented in this paper adds to a growing body of evidence that indicates that such large events could occur on reverse faults directly beneath or adjacent to the Los Angeles metropolitan region (e. g., Dolan et a l, 1995; Rubin et al., 1998; Shaw and Shearer, 1999). Future assessments of the seismic hazards facing the Los Angeles metropolitan region must therefore consider the possibility of very large ruptures along the Sierra Madre fault. Although such events may be less frequent and somewhat smaller than large-to-great earthquakes on the San Andreas fault, the proximity of large faults such as the Sierra Madre fault to the metropolitan region indicates that 'urban earthquakes' on these faults could cause at least as much, if not more, damage than a larger event on the more distant San Andreas fault. Conclusions Paleoseismologic data from the eastern Sierra Madre fault at San Dimas reveal a minimum reverse-siip rate of 0.6-0.9 mm/yr and an elapsed time interval since the most recent surface rupture on the main, active strand of the fault of >8,000 years. These observations suggest that the Sierra Madre fault ruptures in infrequent, but very large (Mw >7), earthquakes, much larger than any events that have occurred on any Los Angeles metropolitan Los Angeles faults during the 150- to 200-year-long historic period. Moreover, the long elapsed time interval since the most recent event on the eastern Sierra Madre fault implies that the fault in that region is in the late stages of a strain accumulation cycle. Large earthquakes on the Sierra Madre fault could conceivably involve simultaneous rupture of contiguous faults, such as the Cucamonga or Raymond faults. Published paleoseismologic data, however, indicate that the Raymond fault has 51 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. ruptured to the surface at least once, and possibly several times, since the most recent surface rupture on the eastern Sierra Madre fault. Previous authors have proposed that the Sierra Madre fault could sometimes rupture together with the San Andreas fault in southern California's "most devastating earthquake". The long elapsed time interval since the most recent eastern Sierra Madre fault event, however, shows that ~60 to 80 San Andreas fault "Big Ones" have occurred since the most recent surface rupture on the eastern Sierra Madre fault. Thus, if the Sierra Madre fault ever does rupture together with the San Andreas fault, then such events much be extremely rare. Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Bibliography Allen, C. R., Hanks, T. 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E.. 1978, Prehistoric large earthquakes produced by slip on the San Andreas Fault at Pallett Creek, California: Jour. Geophys. Res., v. 83, p. 3907-3939. Sieh, K. E., Jahns. R. H., 1984, Holocene activity of the San Andreas Fault at Wallace Creek. California: Geol. Soc. Amer. Bull., v. 95, p. 883-896. Stein, R. S., and Thatcher, W., 1981, Seismic and aseismic deformation asscociated with the 1952 Kern County, California, earthquake and relationship to the Quaternary history of the White Wolf fault: J. Geophys. Res. v. 86. p. 4913-4928. Stuiver, M. and P. Reimer, 1993, Radiocarbon Calibration Program Revision 4.1.2: Radiocarbon, v. 35, p. 215-230. Swan, F. H., 1988, Temporal clustering of paleoseismic events on the Oued Fodda fault, Algeria: Geology, v. 16, p. 1092-1095. Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Toppozada, T. R., Real., C. R., and Parke, D. L., 1981, Preparation o f isoseismal maps and summaries of reported effects from pre-1900 California earthquakes: Calif. Div. Mines Geol., Open-File Report 81-11, 182 pp. USGS Staff, 1975, Surface faulting: in The San Fernando, California, Earthquake of February 9, 1971, U. S. Geol. Surv. Prof. Paper 733, p. 55-76. Voelker, A. H. L., Samthein, M., Grootes, P. M., Erlenkeusser, H., Laj, C., Mazaud, A., Nadeau, M.-J., and Schleicher, M., 1998, Correlation of marine 14C ages from the Nordic seas with the GISP2 isotope record: Implications for 14C calibration beyond 25 ka BP: Radiocarbon, v. 40, p. 517-534. Walls, C„ Rockwell T., Mueller K., Bock, Y., Williams, S.. Pfanner, J., Dolan, J., and P. Fang, 1998, Escape tectonics in the Los Angeles metropolitan region and implications for seismic risk: Nature, v. 394, v. 356-360. Weaver, K. D., and Dolan, J. F., in press, Paleoseismology and seismic hazards of the Raymond fault, Los Angeles County, California: Bulletin of the Seismological Society of America. Wells, D., and Coppersmith, K ., 1995, New empirical relationships among magnitude, rupture length, rupture width, rupture area, and s urface displacement: Seismology Society of America Bulletin, v. 84. p. 974-1002. Wentworth, C. M., and Yerkes, R. F., 1971, Geologic setting and activity of faults in the San Fernando area: in The San Fernando, California, Earthquake of February 9, 1971, U. S. Geol. Surv. Prof. Paper 733, p. 6-16. Wesnousky, S., 1986, Earthquakes, Quaternary faults, and seismic hazard in California, Jour. Geophys. Res., 91, 12,587-12,631. WGCEP (Working Group on California Earthquake Probabilities), 1995, Seismic hazards in southern California: Probable earthquakes, 1994-2024: Bull. Seismological Soc. Amer., v. 85, p. 379-439. Wright, T. L., 1991, Structural geology and tectonic evolution of the Los Angeles Basin: in Biddle, K. T. (ed.), Active-Margin Basins, AAPG Memoir 52, p. 35-106. Yeats, R. S., 1981, Late Cenzoic structure of the Santa Susana fault zone: U.S. Geol. Surv. Prof. Paper 1339, p. 137-159. Ziony, J. I., and Jones, L. M., 1989, Map showing late Quaternary faults and 1978-84 seismicity of the Los Angeles region: U. S. Geol. Surv. Misc. Field Studies Map MF- 1964, 1:250,000. 58 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Appendix 1: SD-1 Borehole Logs Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. SD-1 Borehole Abbreviations a/a as above ang angular bg beige bl blue brn brown ccl charcoal eg coarse grained cists clasts cly clay/clayey cobb cobb coh cohesive decomp decomposed dk dark FeO Iron Oxide fg fine grained glndra glendora grn green grn green gy grey Ig large loc locally Is limestone med medium mg medium grained mod moderately mtx matrix nod nodules or orange pebb pebble predom predominately purp purple qtzite quartzite slt/slty silt/silty sm small sm small ss sandstone subang subangular v very vole volcanic w / with wt white Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Depth meters feet Borehole Log SD-H1 SD-H1 at meter mark 26.7 in trench SD-1 10 11 12 13 14 15 16 17 20 F i r s t S a m p l e r e t r i e v e d a t 1 7* 8* 1 G Y R 6 / 8 r d - b m d y , s r r w n e d p u e n t e p e b b c t s t . m e d p e b b v o l e d s t 1 0 Y R 5 . S B b g s i t y d y . 1 0 * 3 0 % s m - m e d p u e n t e p e b b c i s t , c a r b v e m i n g 1 0 Y R 4 . 5 / 6 r d - b m s l t y d y . c o n , - 2 0 % s m p e b b c i s t s 25 30 35 40 45 50 T T — --- ' :' > . . -•V - N - l , - y * — \ 1 . V \ . . m ? : pT -cegs; ' ; ' X ,'A iV * '£> 55 I-'-v . , ' ' - i 1 • J w . I \ • S ? — * : • - T >x,^7U s i * .-.Ti - i ' - ■ ' '■ •T 3,4-C. r l7 ^ 1 - 1 0 Y R 6 . 5 / 8 b g s a n d y s l t y d y . 2 0 % s m - m e d p e b b p u e n t e c i s t s , n o c a r b . s i c o h 1 0 Y R 5 / 6 y e t - b g s l t y d y . n o c a r b . 1 5 % s m p u e n t e p e b b d s t s 1 0 Y R 5 / 8 b g s a n d y s l t y c l y . 3 0 % s m - m e d p e b b p u e n t e & v o l e c i s t s 1 0 Y R 5 / 8 r d - b m s l t y d y . m o i s t , v c o h . < 5 % m i x e d c i s t s , n o c a r b 9 Y R 5 . 5 / 8 p g s a n d y s i t . m o d c o h . m i x e d s m - t g p e b b c i s t s , m e d g l n d r a c o b b 1 0 Y R 4 / 3 v a r c o l o r ( p u r p . b g . w m . y e t ) b a n d e d s l t y d y . 1 0 % s m - l g p e b b m i x e d c i s t s , n o c a r b 1 0 Y R 5 / 8 d k b m s a n d y s i t . 1 5 % m i x e d d s t s . l o c a l c a r b v e m i n g o n s m - m e d p e b b d s t s 7 .5 Y R 3 / 3 p u r p - b m s l t y s a n d , m o d c o n . 1 0 % s m - m e d p e b b d s t s . c a r b 9 Y R 4 / 4 b m s a n d y s l t y c l y . 5 % s m p e b b m i x e d d s t s . l o c c a r b v e i n s 1 0 Y R 3 / 4 r d * b m s l t y d y . 1 0 % e g s a n d - i g p e b b c a r b c o a t e d m i x e d d s t s ( g l n d r a p r e d ) 7 .5 Y R 4 / 4 7 .5 Y R 4 / 4 1 • s 7 .5 Y R 3 . 5 / 2 - I V * \ t. 1 - ‘ o : 1 0 Y R 4 / 4 v . s. / L . \ • N • * . 1 0 Y R 5 . 5 / 6 • ' > * I * " 1 0 Y R 5 . 5 / 6 tt b m s a n d y s l t y d y m t x . 5 - 1 0 % s m - m e d p e b b s e s p e & p u e n t e c i s t s , m o d c o n . n o g l n d r a S Y R 2 . 5 2 d k b m s l t y d y . 5 - 1 0 % s m - m e d p e b b d s t s . c a r b c o a t i n g S v e i n m g 1 0 Y R 3 . 5 / 2 b g - b m s l t y c l y m t x . 2 0 % e g s a n d - i g p e b b p u e n t e a n d s e s p e c i s t s , c a r b c o a t e d , c o n 1 0 Y R 3 . 5 / 3 b g - m e d b m s a n d y s l t y d y m t x 1 0 % s m - m e d p u e n t e A s e s p e d s t s . c o l o r b a n d i n g , l ittle c a r b 1 0 Y R 4 / 6 m e d b g - b m s a n d y s l t y d y . s m p e b b - s m c o b b m i x e d c a r b c o a t e d d s t s 1 0 Y R 3 / 4 m e d b m d y s l t y s a n d m t x . 1 0 % s m - i g p e o b p u e n t e 8 s e s p e c i s t s , n o c a r b 1 0 Y R ^ 3 d k b m w / b g - b m s t r e a k s s l t y d y , m e d - c g s a n d . < 5 % s m d s t s . li t t l e c a r b Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Depth meters feet 17 18 19 60 Borehole Log SD-H1 (cont’ d) i y • ^ - V - ' • = \ '- ,0 ' :' O T V - r " * ., i _ *= N - i 1 0 Y R 3 . 5 / 4 d k b m c l y s i t m t x , 5 % e g s a n d - m e d p e b b m i x e d c i s t s , v c o n . o n e s m c o b b g l n d r a d s t 10 Y R 4 / 6 m e d b m d y s l t y s a n d m t x . 5 % e g s a n d - s m p e b b s e s p e S p u e n t e d s t s . v c o n 1 0 Y R 3 / 4 b g - b m t o m e d - b m d a y s i t m t x . 2 5 - 4 0 % e g s a n d - l g p e b b g l n d r a . s e s p e . p u e n t e . q t z i t e d s t s . m o d c o n t O Y R 4 / 4 m e d b m d y s a n d m t x . 3 0 % s m p e b b - s m c o b b m i x e d d s t s . Ig q u i t e c o b b p r e s e n t 1 0 Y R 4 / 4 m e d b m c l y s a n d m t x . 6 0 % s m p e b b - s m c o b b m i x e d c i s t s , w e a t h e r e d g r a n i t e c o b b & q t z i t e I g c o b b 20 65 T o t a l d e p t h - 6 4 '9 * / 1 9 7 m Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Depth meters feet Borehole Log SD-H2 SD-H2 at meter mark 32.3 in trench SD-1 10 11 First Sample retrieved at 17X J’ 20 25 30 35 . 1 0 Y R 5 / 6 1 — . 1 0 Y R 5 / 6 ^ r — 1 0 Y R 4 . 5 / 6 • * * — ■ ^ < ' - - N 1 0 Y R 5 / 6 1 — n v . v n . ' " r ~ 9 Y R 5 / 6 s . ^ / • ^ . 1 • X * \ . r ~ P f - 1 0 Y R 4 / 4 7 .5 Y R 4 / 4 1 • — *'■ ' ~ • | ' 7 5 Y R 4 / 3 1 0 Y R 4 . 5 / 4 1 0 Y R 4 / 3 — i - ". 1 0 Y R 3 / 2 i ' f ■ % 1 0 Y R 4 / 3 1 0 Y R 4 / 3 r d - b m s l t y c l y m t x , e g s a n d - s m c o b m i x e d c i s t s , c o h . c a r b c o a t i n g & v e i n s a/a b u t w / 1 5 % s m p e b b - m e d c o b b m i x e d c i s t s , c a r b r d - b m c l y s a n d , g l n d r a n c h . 3 0 % c g s a n d - m e d p e b b m i x e d c i s t s . 5 0 c m g l n d r a c o b b p r e s e n t it b m s l t y c l y s a n d . 4 0 % s m p e b b * m e d c o b b m i x e d c i s t s , p r e d g l n d r a c o b b . c a r b c o a t i n g m e d b m d y s a r d . 1 5 % s r r H g p e b b m i x e d d s t s . l i t t l e c a r b c o a t i n g o n c i s t s b m t o p u r p b a n d e d d y s a n d . < 5 % s m g l n d r a p e b b d s t s . n o c a r b it p u r p s i r / s a n d , v f n a b i e . 3 0 % m e d p e b b - m e d c o b b r o u n d e d g l n d r a d s t s it p u r p s l t y s a n d . < 5 % e g s a n d - m e d p e b b g l n d r a d s t s p u r p b e i g e s l t y f g - m g s a n d . 6 0 % s m - m e d p e b b g l n d r a d s t s . c a r b v e m i n g p u r p b g d y s l t y f g - c g s a n d . 2 0 % m e d - i g c o b b . c a r b c o a t i n g p u r p b g d y s l t y m g s a n d . 2 0 % m e d p e b b - m e d c o b b g l n d r a d s t s . c a r b c o a t i n g & v e i n s m e d b m d y s t t y f g - c g s a n d . 4 0 % s m - l g p e b b p u e n t e & g l n d r a d s t s . c a r b c o a t i n g m e d d k b m d y s l t y t g - m g m t x . 4 0 % e g s a n d - s m b o u l d e r p u e n t e & g l n d r a d s t s ( g l n d r a b o u l d e r ) , c a r b c o a t i n g & v e i n s T o t a l d e p t h • 3 5 ’4 " / 1 0 . 8 m Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Depth meters feet 5 20 Borehole Log SD-H3 SD-H3 at meter mark 15 in trench SD-1 10 11 12 13 14 15 16 25 30 35 First Sample retrieved at I8a 0a . t ^ r ' ririr 40 45 50 sm ■ -r-r^r-r. ' -r.— '-rrf H S : •2 p & I t f S3 •^vT': •TTT*-r\ ■ T .— 1 — . vT-> 1 0 Y R 5 / 6 b g s l t y c l y f g s a n d . 1 0 * 1 5 % s m - m e d p e b b p u e n t c i s t s , n o c a r b 1 0 Y R 4 / 6 b g s t t y c l y I g - c g s a n d . 2 0 % s m - i g p u e n t e p e b b . o n e m e d g l n d r a c o b b . n o c a r b 1 0 Y R 5 / 6 b g s l t y c l y f g - c g s a n d . 3 0 % s m p e b b - m e d d c o b b p u e n t e d s t s . n o c a r b 1 0 Y R 5 / 6 b m - b g s l t y c l y f g - c g s a n d . 1 0 % s m - m e d m i x e d p e b b . n o c a r b 1 0 Y R 5 / 6 b g c l y s t t y f g - c g s a n d . 1 5 % s m - i g p e b b p u e n t e d s t s . c d 7 5 Y R 4 / 6 m e d b m - b g d y f g - c g s a n d . 1 5 - 2 0 % s m p e b b - m e d c o b b m i x e d d s t s 7 5 Y R 4 / 6 d k b g t o m e d b m s l t y d y f g - c g s a n d , d i s t i n c t c o l o r l a y e r s . 2 0 % s m p e b b - s m c o b b m i x e d d s t s . 1 0 Y R 4 / 6 c a r b p r e s e n t 1 0 Y R 5 / 6 b m - b g d y f Q - c g s a n d , m o d c o n . 3 0 % s m p e b b - m e d c o b b m i x e d d s t s 1 0 Y R 4 / 6 1 0 Y R 3 . 5 / 4 b m b g d y f g - c g s a n d . < 1 % m e d p e b b o f q t z - f e i d d s t . o l d A * H z ? 1 0 Y R 4 / 4 m e d b m t o m e d b r - b g d y s l t y f g - c g s a n d , m o t t l e d m c o l o r . 1 - 5 % s m - i g p e b b m i x e d d s t s 1 0 Y R 3 / 2 10 Y R 3 / 6 m e d b g - b m d y s t t y f g - m g s a n d . 1 - 5 % e g s a n d - m e d p e b b p u e n t e 6 p e g m a t i t e c i s t s 1 0 Y R 4 / 6 b g c l y s t t y f g - c g s a n d . 5 % m e d p e b b - m e d c o b b p u e n t e a g l n d r a d s t s ( p r e d o m g l n d r a ) 1 0 Y R 3 / 3 m e d b m d y s l t y f g - m g s a n d . 2 0 % e g s a n d - s m c o b b m i x e d d s t s 1 0 Y R 4 / 4 m e d b m s l t y f g - c g s a i d , 5 % s m - m e d p e b b g l n d r a & p u e n t e p e b b 1 0 Y R 4 / 6 b g - b m d y s l t y f g - c g s a n d . 1 - 5 % s m p u e n t e p e b b . s m g m d r a & g r a m w p e g m a t i t e c o b b 1 0 Y R 4 / 4 b g - b m s i l t y f g - c g s a n d , m o d c o n . o r n o n - c o b s a n d d s t s . s m - i g p u e n t e d s t s . Ig p e b b - s m c o b b o r s a n d . 5 % d s t s 17 55 T o l a l d e p t h • 5 X 1 r / 1 6 . 4 m 64 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Depth meters feet 0 0 10 11 12 13 Borehole Log SD-H4 SD-H4 is 8 meters N12W of north end of trench SD-1 Color Description F i r s t S a m p l e r e t r i e v e d a t 2 7 * 10 15 20 25 30 40 I * ''* - lL-nT ' - ' • o * > T " v v \ . 7' !,->?£ '-X -- i h •=N'ir. 7' r ..x .• ** - * - - I*-'-.- '- > ; o \ - l r rSr <.x.- s*U ';^ > P • ' • A > • N " . \ . ■ i N • • ■\ - i-cis- T * — • r r - r ' . 1 0 Y R 3 / 2 d k b m d y s i t . 1 0 % s m p e b b p u e n t e d s t s . n o c a r d . A - H z . c o h 1 0 Y R 3 / 2 1 0 Y R 5 / 6 m e d b m t o b g s l t y c l y s a n d . 5 % s m p e b b d s t s . c o h . A - H z m e d b m t o b g b a n d e d s l t y d y s a n d . 1 5 % s m - m e d p e b b p u e n t e d s t s . c o h . c a r b v e i n s 1 0 Y R 5 . 5 / 6 b g s t t y d y s a n d . 5 % s m p e b b p u e n t e & v o l e d s t s . c o h . c a r b n o d 1 0 Y R 5 / 6 b g s t t y s a n d . 2 0 % s m p e b b - s m c o b b p u e n t e 4 w t d y d s t s . m o d c o h 1 0 Y R 5 / 6 b g s t t y d y s a n d . 2 5 % s m - m e d p u e n t e p e b b . m e d g r a n i t e a n d o r s s p e b b . m o d c o h 1 0 Y R 4 / 6 r d - b m s t t y s a n d , d e c o m p g r a n i t e c i s t . 3 0 % s m p e b b - s m c o b b p u e n t e d s t s . v t r i a b l e 7 5 Y R 3 / 4 r d - b m s l t y f g - c g s a n d , d e c o m p v o l e d s t . 1 0 % s m - m e d p u e n t e p e b b . f n a b l e 7 .5 Y R 3 / 4 r d - b m f g - c g s a n d , d e c o m p p e g m a t i t i c g r a n i t e . 1 5 % s m - m e d p e b b g r a n i t e , t ittle p u e n t e p r e s e n t , n o c o h e s i o n 7 S Y R 4 / 6 r d - b m s t t y f g - c g s a n d . 3 0 % s m p e b b - s m c o o b g r a n i t e a n g d s t s . n o c o h e s i o n 7 .5 Y R 4 / 6 r d - b m f g - c g s a n d . 5 % s m - t g a n g g r a n i t e d s t s . y t- w t d y s t t y f g s a n d m t x . 2 0 % s m - m e d a n g g r a n i t e 4 p u e n t e p e b b 1 0 Y R 5 / 6 y e l w t b a n d e d m t x . w t d y f g - c g s a n d m t x . y e l f g s a n d m t x . 3 0 % s m - t g g r a n i t e p e o b . l i t t l e c o n 7S5 Y F M / 6 r t - b g s l t y f g - c g s a n d m t x , 3 0 % s m - m e d g a n i t e p e b b c i s t s , l ittle c o h 7 5 Y R 4 / 6 o r - b g d y s t t y f g - c g s a n d m t x . 4 0 % s m - m e d g r a n i t e 4 c l y n o d p e b b . a n g g r a n i t e d s t s 1 0 Y R 5 / 6 w t t o it b g b a n d e d s l t y f g s a n d m t x . 6 0 % e g s a n d - s m p e b b g r a n i t e d s t s . m o d c o h 1 0 Y R 7 / 8 1 0 Y R S / 8 1 0 Y R 4 / 6 1 0 Y R 7 / 8 7 .5 Y R 5 / 8 7 .5 Y R 4 / 6 7 5 Y R 5 / 8 S Y R 5 / 8 1 0 Y R 7 / 8 1 0 Y R 5 / 6 G l e y 2 4 / 5 P B G l e y 2 4 / 1 0 B G l e y 2 4 / 5 P B G l e y 2 4 / 1 0 B 7 . 5 Y R 5 / 8 7 . 5 Y R 5 / 8 1 0 Y R 3 / 2 G l e y 2 6 / 5 8 G l e y 2 4 / 1 0 B G l e y 2 5 / 5 P B G l e y 2 4 / 5 P B b g t o v it b g s l t y f g s a n d m t x . 4 0 % e g s a n d - s m p e b b w t d s t s ( d e c o m p g r a n i t e ? ) , w t t o b g D a n c i n g b g t o w t s l t y d y f g s a n d m t x . 5 0 % e g s a n d - i g p e b b a n g d s t s . a p p a r e n t d e c o m p g r a n i t e , m o d c o n r d - b m s t t y c l y m t x . 4 0 % m g s a n d - s m p e b b s u b r o u n d e d d s t s , c o h . g r a n i t e c i s t s p r e s e n t r d - b g s l t y f g s a n d m t x . 4 0 % e g s a n d - m e d p e b b s u b a n g v o t e d s t s . l i t t l e c o h r d - b g c l y s l t y f g - m g s a n d m t x . 3 0 % d s t s . e g s a n d - s m p e b b s u b r o u n d e d v o l e d s t s . b f - g y f g - c g s a n d u n i t a p p e a r s a s c h a n n e l s w a t e r s e e p a g e a p p a r e n t b l - g y s l t y f g s a n d m t x . s m p e b b d s t s ( 5 % ) . s m c o b b o f f e l d s p a r - n c h d s t s ( 1 0 % ) b l - g y s t t y d y m t x . c o m p i g g l n d r a p e b b & s m - i g g l n d r a d s t s . F e O c o a t i n g p r e s e n t o n s o m e d s t s b l - g y t o g m - g y s l t y f g s a n d m t x . s m - i g s u b r o u n d e d p e b b . F e O o n 2 5 % o f d s t s . f n a b l e , v w e t in a u g e r v w e t b l - g y s t t y f g s a n d . 4 0 % s m p e b b - i g c o b b s u b r o u n d e d g l n d r a d s t s 65 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Depth meters feet 13 45 14 15 16 17 18 19 20 21 22 50 55 60 65 70 Borehole Log SD-H4 (cont'd) , T . C ^ V , s p arer r . T . ^ i y t IS S ± . x -= - r^X ; \ v * N .• 'Tl 'L -X i£V>: •x'£r 1—' \. • \ - f r^TTv 1 I-' \ . • T n .- . / »_ \ . ■ \ - r i • N \ . ,;?T. 1 — n \ . • \ - r s . / • Color Description G ! e y 2 4 / 5 P B 1 0 Y R 3 / 2 1 0 Y R 3 / 2 G l e y 2 4 / 1 0 6 G i e y 2 4 / 5 P B G l e y 2 5 / 5 P B 1 0 Y R 3 / 2 G l e y 2 7 .S / 5 P B g o 75 d o T o t a l d e p t h • 7 5 5 * / 2 2 . 9 m b l - g y s l t y f g - m g s a n d . 2 0 % e g s a n d - m e d p e b b a n g ( e l d s p a r - n c h d s t s . m e d b m s l t y f g s a n d i n t e r s p e r s e d ( > 5 % o f t h e s a m p l e ) b l - g y s l t y f g s a n d . 2 0 % e g s a n d - m e d p e b b a n g f e l d s p a r - r i c h d s t s . w t & it g y d y n o d u l e s , f n a b l e m t x . o n e u n i d e n t i f i a b l e t y p e I g c o b b b l - g y t o l t - g y b a n d e d d y s l t y f g s a n d m t x . 2 5 % e g s a n d - l g p e b b f e l d s p a r d s t s . m e d b m s l t y s o i l ? i n t e r s p e r s e d it g y s t t y f g s a n d . 5 % r o u n d e d e g s a n d f e l d s p a r c i s t s G l e y 2 7 / 1 0 B v it g y d e c o m p g r a n i t e ? , s l t y f g s a n d c o m p , m e d g y - t t g y b a n d , m o d c o h 1 0 Y R 3 / 2 G l e y 2 7 /1 O B it t o m e d g y u n i t s , it g y i s d e c o m p g r a n i t e , m e d g y i s d y s i t m t x w / s m r o u n d e d p e b b - 1 0 % . t a i r l y c o h G i e y 2 S 'l O B m e d g y s t t y f g s a n d . 3 0 % m e d p e b b - i g c o b b a n g t o r o u n d e d d s t s . n o c o h e s i o n G i e y 2 4 / 5 P B b l - g y s l t y f g - m g s a n d m t x . 3 0 % e g s a n d - s m b o u l d e r s u b r o u n d e d t o r o u n d e d f e i d s p a r - n c n d s t s . G l e y 2 7 / 5 P B f a i r l y c o n 1 0 Y R 2 . 7 / 2 d k g y - o m c l y s l t y f g s a n d m t x . 1 5 % e g s a n d - m e d r o u n d e d f l a t m u d s t o n e p e b b m f l u x o f w a t e r i n c r e a s e d , p r o o p e r c h e d w a t e r t a b l e a b o v e d a y 1 0 Y R 2 . 7 / 2 d k g y b m s l t y d y f g s a n d m t x . 3 0 % s m p e b b - i g c o b b i s d s t s 1 0 Y R 3 /1 v d k b m p l a s t i c d y w / p i n k g r a n i t e & m e d b m d y i n t e r s p e r s e d , v c o h 1 0 Y R 3 / 3 m e d b m s l t y d y . 5 % e g s a n d - m e d p e b b d s t s . v p l a s t i c d y 1 0 Y R 4 / 3 m e d b m s l t y d y . < 1 % m e d s a n d - s m p e b b r o u n d e d c i s t s , o n e Ig a n g a n o r t h o s i t e c o b b . v c o h 1 0 Y R 3 / 3 m e d b m s l t y c l y . 5 % m e d s a n d - s m p e b b s u o a n g - s u b r o u n d e d p u e n t e & v o l e d s t s . v c o n 1 0 Y R 3 / 4 i t - m e d b m s a n d y s l t y d y . s m - i g p u e n t e & v o ic c i s t s , s m s u b r o u n d e d a n o r t h o s i t e b o u i d e d . h i g h f y c o h 1 0 Y R 3 / 2 d k b m s l t y s a n d d y m t x . e g s a n d - l g p u e n t e p e b b . s m - m e d r o u n d e d g l n d r a c o b b . 5 - 1 0 % c i s t s , h i g h l y c o h 1 0 Y R 4 / 3 m e d b m s l t y c l y f g - c g s a n d m t x . 2 0 % r o u n d e d v o i c & g l n o r a m e d p e b b - m e d c o b b . c o h 1 0 Y R 3 . S 3 d k b m d y s l t y f g - c g s a n d . 1 0 % s m - m e d p u e n t e p e b b . s m - i g g l n d r a c o b b . m o d c o h 1O Y R 5 4 m e d b m f g - m g s a n d d y . 5 % e g s a n d - m e d p e b b p u e n t e A g l n d r a p e b b . h i g h l y c o h 1 0 Y R 3 / 4 d k b m s l t y d y . < 1 % e g d s t s . v c o h . b g s l t y s a n d . 3 5 % s m p e b b - i g p e b b g l n d r a A p u e n t e d s t s . 10 Y R 5 / 6 m o d c o h 7 S Y R 4 / 4 r d - b m s t t y d y . 1 % e g s a n d - m e d p e b b p u e n t e d s t s . h i g h l y c o h 7 .5 Y R 4 / 6 o r - o m s t t y d y s a n d , 1 % e g s a n d - s m p e b b p u e n t e & d e c o m p g r a n i t e d s t s . h i g h l y c o h 7 . 5 Y R 5 / 8 o r * d m d y s f t y s a n d . < 1 % e g s a n d d s t s . w t d y n o d u l e s t h r o u g h o u t , c o h 66 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Depth meters feet 4 15 10 11 12 Borehole Log SD-H5 SD-H5 at meter 57 of trench SD-1 Description 20 25 15 16 17 30 35 40 13 - 14 45 50 55 Color F i r s t S a m p l e r e t r i e v e d a t 1 5 ’11* 1 0 Y R 5 / 6 o r - b g d y s i t y s a n d . < 5 % s m - m e d v o l e & p u e n t e c t s t s . f n a t X e 1 0 Y R 5 / 8 o r - b g d y s t t y f g - m g s a n d . 2 0 % e g s a n d - s m p e b b p u e n t e & v o l e d s t s . t g p u e n t e s s c o n g l o m e r a t i c i g c o b b 5 Y 6 / 4 7 5 Y R 5 / 8 o r * t)0 c l y s t t y s a n d m t x w / p i s t a c h i o g m d y s i t ( Q o u g e ? ) . 3 0 % s m - i g p e b b p u e n t e & v o l e c i s t s 5 Y 6 / 4 p i s t a c h i o g m d y s t t y s a n d , o r - b g s i t y s a n d m o t t l e d . 1 0 % e g s a n d - s m p e b b p u e n t e & v o t e c i s t s , c o h 7 . 5 Y R 4 / 6 3 Y 6 / 5 7 5 Y R 5 / 8 Q r n * b g s t t y d y s a n d . 2 0 % e g s a n d - s m p e b b p u e n t e & m i x e d d s t s . c o h 5 Y 6 / 4 6 Y R 5 / 8 o r * fcQ , 0 0 m m o t t l e d c l y s t t y f g - m g s a n d , l a y e r o t c l s t - n c h e g s a n d . 2 5 % c t s t s . v o l e & p u e n t e d s t s . 5 Y 6 / 4 0 10 (3 c o f t 7 5 Y R 4 / 6 2 . 5 Y 6 / 6 o r .t> g t o r d - b m t o p i s t a c h i o g m b a n d e d s t t y s a n d y m t x . < 5 % e g s a n d - s m p e b b d s t s . f n a b i e 7 . S Y R 5 / 6 o r - b g s t t y d y s a n d m t x . 1 5 % s m - i g p e b b p u e n t e & v o l e d s t s . s m w t g o u g e b a n d s , c o n 1 0 Y R 5 / 6 2 .5 Y 6 / 6 3 Y 6 / 4 p r e d o m b g s t t y c l y s a n d w / w t t o r e d t o o r b a n d s . < 5 % e g s a n d - s m p e b b d t s . c o h 7 5 Y R 4 / 5 1 0 Y R 5 . S / 6 b g s t t y d y s a n d w / r d t o g y - w t g o u g e . < 5 % e g s a n d d s t s . c o h 1 0 Y R 6 / 8 2 .5 Y 6 / 4 7 .5 Y 5 / 8 1 0 Y R 5 / 6 7 . 5 Y R 5 / 8 7 S Y R 5 / 8 7 . S Y R 5 / 8 G l e y 2 4 / 1 0 6 G l e y 2 S S P B G l e y 2 3 / 5 P B 7 S Y R 5 / 8 o r - b g s t t y d y s a n d m t x . g m t o r e d t o w t b a n d i n g , e g s a n d - s m p e b b d s t s . c o h o r t o g m t o r d g o u g e ( s t t y d y ) . 1 % s m p e b b c i s t s , c o h o r - b g s t t y d y s a n d w / r d t o w t t o g m b a n d s , m o i s t m e d b m s t t y s a n d d y m t x 1 5 % s m o il s h a l e p e b b d s t s o r - b g t o m e d b m s t t y c t y s a n d , n o d s t s . c o h . b f - g y s t t y f g s a n d m t x < 5 % s m p e b b c t s t s o f s a m e c o m p , f n a b i e w a t e r m s a m p l e s b t - g y c l y s t t y f g s a n d m t x s m - m e d p e b b d s t s . c o h . m e d b m s t t y d y s a n d . 2 0 % s m - i g p e b b o il s h a l e & s i l i c e o u s s h a l e d s t s . c o h 1 0 Y R 3 / 3 . 5 m o i s t m e d b m s t t y d y s a n d . 4 0 % s m - i g o il s h a J e p e b b d s t s 1 0 Y R 3 / 6 m o i s t d k b m s i t y d y s a n d . 4 0 % s m - i g p e b b o il s h a l e d s t s . m o d c o h 1 0 Y R 3 / 6 d k g y - b m d y s i t m t x 6 0 % s m - m e d p e b b o il s h a l e d s t s 1 0 Y R 2 / 2 7 S Y R 5 / 8 1 0 Y R 3 / 6 1 0 Y R 2 / 2 d k b m d y s t t m t x s m - m e d o il s h a l e p e b b . s m p e b b - s m c o b b s i l i c e o u s s h a l e d s t s d k g y - b m d y s t t y m t x 6 0 % s m - m e d o il s h a l e p e b b . v w e t 2 . 5 Y 3 /1 d k g y d y s t t m t x 3 0 % e g s a n d - m e d p e b b o il s h a l e d s t s . v w e t . c o n 1 0 Y R 3 / 6 1 0 Y R 3 / 2 G l e y 2 4 / 5 P B d k g y d y s t t m t x 4 0 % s m - i g p e b b p e b b o il s h a l e d s t s . v w e t 2 . 5 Y 3 / 2 2 .5 Y 3 / 2 d k g y d y s t t . 5 0 % s m - m e d o il s h a l e d s t s . s u b a n g - s u b r o u n d e d c i s t s , w e t G l e y 2 4 / 1 O B 1 0 Y R 5 / 4 p u r p d y s t t y s a n d m t x 5 0 % s m p e b b - m e d c o b b s u b r o u n d e d - r o u n d e d g t n d r a d s t s . v w e t 2 . 5 Y 3 / 2 1 0 Y R 5 / 4 p u r p d y s t t y I g - c g s a n d m t x 4 0 % s u b r o u n d e d t o r o u n d e d s m p e b b - s m c o b b g t n d r a & p u e n t e d s t s 1 0 Y R 4 / 3 p u r p d y s t t y l g - c g s a n d . 3 0 % s u b r o u n d e d - r o u n d e d s m p e b b - m e d c o b b g i n d r a & p u e n t e d s t s T o t a l d e p t h - 5 5 ’0 * / 1 6 . 8 m 67 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Depth meters feet 15 First Sample retrieved at ISO* Borehole Log SD-H6 SD-H6 at meter 42 of trench SD-1 Color Description 20 25 30 10 11 12 13 14 15 16 17 35 40 45 50 55 1 0 Y R 5 / 4 1 0 Y R 4 . 5 / 3 5 1 0 Y R 5 .5 / 4 1 0 Y R 5 . 5 / 4 1 0 Y R 5 / 3 t O Y R 5 / 3 . 5 ^ 1 0 Y R 4 / 3 1 0 Y R 4 / 4 1 0 Y R 4 / 4 1 0 Y R 5 / 6 ~ r .— . — . . t O Y R 5 . 5 / 6 ■ ~ r~ . -jr. s s i 1 0 Y R 5 / 4 1 0 Y R 4 / 3 r l > 4 F r 7 . . v . 4 T - 7 * \ t O Y R 4 . 5 / 3 7 .5 Y R 5 / 6 1 0 Y R 5 / 3 1 0 Y R 5 / 3 5 m e d b m s t t y s a n d m t x . 5 0 % s m p e b b - i g c o b b r o u n d e d g l n d r a c i s t s , n o c o h 1 0 Y R 3 . 5 / 3 m e d b m s i t y s a n d m t x . 6 0 % s m p e d b * s m c o b b g l n d r a c t s t s . l i t t l e c o h w a t e r in b o r e h o l e t O Y R 5 . 5 / 6 p u r p - G m s a n d s t t y . 1 % s m g l n d r a p e b b . m o d c o h p i s t a c h i o g m c t y n n d o n g l n d r a d s t s T o t a l d e p t h • 5 7 * 6 * / 1 7 . 5 m t O Y R 5 / 3 m e d b m d y s t t y s a n d . 3 0 % s m - i g s u b a n g - s u b r o u n d e d g l n d r a p e b b . c o h 1 0 Y R 5 / 4 m e d b m d y s i t y s a n d . 6 0 % s m p e o b - i g c o b b r o u n d e d g l n d r a d s t s . m o d c o h 1 0 Y R 4 . 5 / 4 m e d b m s i t y c l y s a n d . 3 0 % s m p e b b - s m c o b b g i e n d r a d s t s . c o h 1 0 Y R 5 / 4 m e d b m s t t y d y s a n d , s m p e b b - m e d c o b b g l n d r a d s t s . c o h . d k b m s a n d s i t y d y . < 5 % e g s a n d - s m p e b b g l n d r a d s t s . w t d y ( g o u g e ? ) p r e s e n t , v c o h 2 . 5 Y 6 / 6 y i* b g s t t y d y s a n d , p r e d o m s m - m e d p u e n t e p e b b . s m - m e d g l n d r a d s t s p r e s e n t . 3 5 % d s t s . v c o h 1 0 Y R 5 / 6 t O Y R 4 / 4 i t b m d y s t t y s a n d . 2 0 % s m - i g p u e n t e & g l n d r a p e b b . c o h 1 0 Y R 4 / 3 . 5 m e d b m s t t y c t y s a n d . 2 0 % s m - l g g l n d r a & p u e n t e p e b b d s t s . c o h 1 0 Y R 3 / 2 1 0 Y R 5 / 6 m e d b m s t t y d y s a n d . 1 5 % s n v i g g l n d r a & p u e n t e p e b b . c o h . t O Y R 4 / a d k b m & it b g b a n d e d d y s t t y s a n d , b g i s p r e d o m s m p u e n t e p e b b . d k b m p r e d o m e g g l n d r a & p u e n t e s a n d , b o t h c o h 1 0 Y R 3 / 2 d k b m s i t y s a n d . 1 0 % s m - l g p u e n t e & g l n d r a p a b b . m o d c o h g g Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Depth meters feet 15 20 25 30 10 11 12 13 14 15 16 17 35 40 45 50 55 . . - H -■■r-.— r-. —r-V .% .^ 3 Borehole Log SD-H7 SD-H7 at meter 36.5 of trench SD-1 Color Description e v e d a t 16'6* 1 0 Y R S * 6 it b g d y s i t y s a n d . 2 0 % s m p e b b - s m c o b b p u e n t e & g l n d r a d s t s . c o h . c a r t v e i n s 1 0 Y R 5 / 6 m e d b g d y s i t y s a n d . 2 0 % s n v f g p u e r * e & g l n d r a p e b b . c o h . c a r b v e i n s 9 Y R 5 / 8 m e d b m d y s t t y s a n d . 1 5 % s m - l g p u e n t e . g l n d r a . & g r a n i t e , p e b b . m o d c o h 1 0 Y R 5 / 6 1 0 Y R S / 3 . 5 p u r p - b m d y s t t y s a n d . 3 0 % s m p e b b - s m c o b b g l n d r a d s t s . c o h 1 0 Y R 3 / 4 p u r p - b m s t t y s a n d . 5 % s m - m e d g l n d r a p e b b . l ittle c o n . c o n t a i n s p u e n t e s a n d 1 0 Y R 3 5 / 3 p u r p - b m s t t y s a n d . 1 % s r r v l g g t n d r a p e b b . m o d c o h . c o n t a i n s p u e n t e s a n d * . i \ - r ‘ '•Si'Ls tv-j v 1 - . s ' i ' • •_ > ' - 7 1 L & i''- t O Y R 5 / 4 9 Y R 5 / 4 1 0 Y R 4 / 4 t O Y R 3 / 2 2 .5 Y 5 / 4 I O Y R 4 / 4 - t- r r 2.5YR 5/4 r . ~r. — r . - ; r . _ 10YR3/3 10YR 5/6 10YR3/2 '— r :* -f -. •T — .-r-.-r.—. -r-r-r'-r*. 10YR6/6 10YR 3 / 3 1 1 0 Y R 4.5/4 10YR 4/6 • * V \ . it p u r p - b m s t t y s a n d . 1 0 % s r r H g g t n d r a p e b b . li t t l e c a r b v e m m g . li t t l e c o n p u r p - o m d y s t t y s a n d . 2 0 % s m p e b b - s m c o b b g l n d r a d s t s . m o d c o h . c a r b c o a t i n g o n s o m e d s t s m e d - t t b m d y s i t y s a n d , c a r o v e m m g , 5 % s m - i g g l n d r a p u e n t e . q t z p e b b . c o h p u r p - b m d y s t t . 8 0 % s m p e b b - f g c o b b g l n d r a d s t s . c o n 1 0 Y R 4 / 3 m e d b m d y s t t . 2 0 % s m - i g g t n d r a p e b b . c o h 1 0 Y R 4 / 3 1 0 Y R 4 / 3 p u r p b m d y s t t . 4 0 % s m p e b b - s m b o u l d e r g l n d r a d s t s . m o d c o h y i - b g d y s i t . p u e n t e e g s a n d , w t c a r b g o u g e - 5 - 7 c m t h i c k , c o h y t - b g d y s t t y s a n d , e g s a n d - s m p e b b p u e n t e d s t s . c o h . d k b m s t t y d y s a n a s m - i g g l n d r a p e o b . c o h d k b m s t t y d y . 1 5 % e g s a n d - m e d p e b b g l n d r a c t s t s . h i g h l y c o h d k b m s t t y c l y s a n d . 1 0 % s m - m e d p e b b g l n d r a d s t s . c o h it b m s t t y s a n d y d y . s m - m e d p u e n t e p e b b . s m p e b b - s m c o b b g l n d r a d s t s . 1 5 % d s t s . c o h m e d b m s t t y s a n d y d y . s m - t g p u e n t e & g l n d r a d s t s . m a n y f r a c t u r e d g r a n i t e p e g m a t i t e c o b b . h i g h l y c o h . 5 0 % d s t s 7 .5 Y R 3 / 4 m e d - d k b m s t t y d y . 4 0 % s m p e b b - m e d c o b b g l n d r a & p u e n t e d s t s . n i g h t y c o n 7 .5 Y R 3 / 2 d k b m s t t y s a n d y d y . 2 0 % e g s a n d - m e d b e b b p u e n t e . g t n d r a . & q t z i t e d s t s . v c o h 7 S Y R 3 / 2 d k b m s a n d y d y . 1 5 % e g s a n d - s m p e b b p u e n t e & g t n d r a d s t s . v c o h 1 0 Y R 5 . 5 / 8 y t - b g s t t y c l y s a n d . 2 0 % s m - m e d p u e n t e & g l n d r a p e b b . m o d c o h . c a r b v e m m g 7 . 5 Y 4 / 4 7 . S Y R 5 / 8 1 0 Y R S / 6 1 0 Y R 3 / 2 T o t a l d e p t h - S S U " 1 1 7 . 3 m 'O Y R 3 1 3 o r - b g s t t y d y s a n a 1 5 % s m - m e d p u e n t e 4 g l n d r a p e b b . v c o h . m e d b m s t t y d y s a n a 1 0 % s m - m e d p u e n t e & g t n d r a d s t s . v c o h v d k b m d y s t t y s a n a 1 5 % e g s a n d - s m p e b b g l n d r a . g r a n i t e . & p u e n t e d s t s . m o d c o h . d k b m d y s t t y s a n d . 1 0 % e g s a n d - f g p e b b p u e n t e 3 g l n d r a d s t s . m o d c o h 69 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Appendix 2: Field logs, SD-1 Trench (photocopies) Oversized Illustrations Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 3 p* W T I « ? (*• * * *-r* 3 " " * • ------- ■v W > l r « ' ‘ Mv;“iu«ni( ^ 'rr~ • - V*--* 5 v**<AJi • i . m S " a - f c ^ ' V b*< Reproduced with permission of the copyright owner. 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Further reproduction prohibited without permission. < > (« , 1 * 1 r < l 3 v tv iMuU s F j * W ‘ 1 .. • im tt » U »*4 ■ tw o. iB-Xl ■ 3 3 « c 4 » c v * pete ^ / 4 w ^ 1% ( f» c«u, • « t (p r * Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. R eproduced with permission of the copyright owner. Further reproduction prohibited without permission. R eproduced with perm ission of the copyright owner. Further reproduction prohibited without permission. R eproduced with permission of the copyright owner. Further reproduction prohibited without permission. R eproduced with permission of the copyright owner. Further reproduction prohibited without permission. R eproduced with permission of the copyright owner. Further reproduction prohibited without permission. C lto j UMtt iw *4j m t i-W m v i U Vo w ft^wV V** irctlir V «sv^e fcfdd«l a^V'Wt. H , * v i * « - f i l l y (v i* m« . k V » X | « A i cU<V ictesilun . v 0*'Vf ivixV mI *•» cl*th t *'b»4<le ~ Zo> l " i h»'* » !♦ > hs*'t «ft. )}:f-«U lr||«l g jv K . y t I . «iy< oa> ) c V k>^ c«n>f) k .tW , f . \ > W i V . f r J ' (»iV »r»V | t . (A k v \> , A m K.s*V“ l' L 7 V ( i M h W ) Ibmlmi I Itftl '% * M t .* c»4.^W j t 'V i * f*i*i * * V j Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. R eproduced with permission of the copyright owner. Further reproduction prohibited without permission. j rtjlAij t\\t, «#«*« « * * ! S V r 2 f tU c h J CD-.lS" O* * 4 < & A V l f ^ I c V ^ I - J * « « - ‘ v ' ^ D lC . jr^-Wn, A 4»mC| cmixWl i - cl»i+r h* r« to t j I - j - I5 » * 3 » * • < * * * f* ’ i.f 4 # > H e r • « h4 lrt\i * * V * C > tc ^ * - P * * « U V. i f f . taw t-M . b««t * T £ r ‘ lUt'tn A ^ 3 * ~ . Tlii+tm: t f - ' f > 7 C l* i U • \ 8 %Mrw* (» < iV 4 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. R eproduced with permission of the copyright owner. Further reproduction prohibited without permission. Wt»» 4 » > v o l. tiV t- ftiwt ^(«(<«V i [ \ t k c h J Z f l - k r 0* . rtfs* J V \ovl £ | A :L i nJ »Jf iul * A » » v t f . . ; i ^ R ••••if/ i K H .I f* (to < y | _ r T _ , - r — — 1 < U * l,s * tff% 6lr<ta f«t axirS Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. R eproduced with permission of the copyright owner. Further reproduction prohibited without permission. / V ° f H M l X W w **> • < . ifc y »v£«k {213s* ■ * JV,*.f j«yy* < U v > « l 4 -< i* k • * ll* w ^' » •» < . < 4 > » - l e « H l | | '■ > .* ♦ * i*» fciv fc* ( " « \ ( t a f t V * * ? > r % , » v 1 y4 S P eV f « K .W i« •#< )H«yi. » • Sit « r » r * V « » n 4»m < n»A,. V . H W ^»"W* kfvi i v ^ > i l» 3 r * i Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 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Further reproduction prohibited without permission. S t, I- rl Hi * R eproduced w ith perm ission of the copyright owner. Further reproduction prohibited w ithout perm ission. R eproduced with permission of the copyright owner. Further reproduction prohibited without permission. Appendix 3: Field logs, SD-2 Trench (photocopies) Oversized Illustrations Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. I < \ g r * % k W*ll M 4/ j V . X i i . w t 5 ? i f - - * : . > ^ i l t ^ 1 .1 * v . i , l ' ' ' * • - - -■ 'fc. ' J l»lh ' < J T U O ^ i . ; 2 0 « * » , ovtXx* V > j ■ ' - 7 1 ’ V.OU* t t * • ® % 'a * » M V « 4 H \ 5 *X*v''K > ^iJ, I \>t L 5 i .L l i r i M i a j t r..*.«» '^ID i o V V o r n d u > jf t. 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S \ > k V M ) 1 (j+yS ■ 4 y T i. e iy c l n I ; 2 0 - 5 S f t » ( * t '.I V *4 ik \ s 1 1 > 1 V f •' ~T r* » r c V . 1-1-1-00 50k- v T f * = * # . iY**^ orM Kfc^ m i £ '** V ^ ^ U t u r u j y ^ p6«\«bW T .0 * ;• tn ,1' t"l M. rl I . r^uj'V C t * i ui i « = „ . & , s ‘ “~ - ^*V4»tK V n«*> V v — W -i + > ••'* < « + \ + « - ! \ V « . - 1 « U < 1 '^il P < i ' s w « t . ' < _ ; a '4 * H - * - |f ~«*0*-'kt.. * '* i y * . v \ L s t • fc»!3Ss^e » • » i i . U K Ck < I . J - I S i * n * / * < . , ^ * < g r . j ; * v i ^ & $ & > . \ v - * > . - m ^ w ^ ^ w " i V i - g i 2™ ^ M I * h y M '* * -* * -^ P , \ * k ; I. LI- A I * * * 4S A , ' 4 k .V < r* v « * ^ — - x - .- s a a a f e iE + v * ' ^ * - t - »»-* ^ £ . i . , / + » m i» « K ‘S v . o . c * ^ .tfW u W v.«. k**! ^<* •* 5 * ' ' | ^ pk ^ t‘» ft > !•» '* * X-ft ► T *V'«w» i% <w 3 |l. « , / {.,? 81 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 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Further reproduction prohibited without permission. l r i 0 B * 1 0 i ii u s t> z e.sV "• l + + i3 ♦ +• 14 15 Ifc 1 • ' / iM «,.( . . . ( 1 4 + I * 3r^,sL U slVv^ckj '**f o A . »W W oJ A t-. <«44><V. -4- 5 * W . 914 '■ > ■ • t3 , iovO /i »nt». • ■r" ■ • » - - vjj'wUH (m W»-V M k { \T tq (»oU 4/4) » » * 1 _ /o — & •* « . S « W y^ * p V *o* t«» > l 4 ^ t U - W < 4 I k M U !» • il>U ]| "5------- l*i > i t . U ig iv V * * » V£k fcW ” V \ ***4 * . » r ~ » • - * " 7 + # iv , ^ + + ■ + « / 3 ^ c t n - -• ^ . c f , v ; . * r — “ | >>n V \ ^ ~ ^ 't-r-i#-T-f— r^ i— j ._ .,_ I jj-» g .ik.U ,^ 4 MMU -N » . 7 l"T 1 •' 1 ' f c ,+ ’^**r t i 4 lo + II + 11 f 12 4 - •4 1 - •S > 4 I G + - n 82 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. R eproduced with permission of the copyright owner. Further reproduction prohibited without permission. S \ > 2 ^ • { H v- ' V 0 ^ ln» t\* ( k V - .o < > > # » ' y l • . *•■ r -r— . w lO '1 f' w .lu n * 1 /0 fclt, ^T 1 — i r~i— r— r- t> W ft tv s 6^ ft PonXfl'*1 , c l« n ^ > * 4 *j/ <*lt s r * 1 5*1, y n t +■ ? • + < \ c j \ * - O . o m A S > * + +- <6 +* i t r~ i Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. R eproduced with permission of the copyright owner. Further reproduction prohibited without permission. I *•1 •/S 26 SX>2 • { H i > C V < ‘ X ’ ‘ c ' ° ^ v - > ' 1,0*^ fir. T -i/- y I r + t - t— ? — r t ' * ' f « * ~ «\\t. ^ ,1 '® ^ 1 |i) ^ * IV | •U’ Y > ■ * > tu *'tCS^ ; niiilW \#f, SI* M r r - r r - . , I ' \‘*\ — i — i— i— r - t X M B n* U B lk>c\lr*{ * ^ 5 J -+. ■ ■ - - . t + i* . ^ r- if*** S *l»yn o I Z '•%=>« ^ - ^ 4 2 r ' -r 21 83 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. R eproduced with permission of the copyright owner. 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Asset Metadata

Creator Tucker, Allan Zachary (author)

Core Title Paleoseismology and geomorphology of the eastern Sierra Madre fault: Evidence for a >8ka age of the most recent event

Contributor Digitized by ProQuest (provenance)

Degree Master of Science

Degree Program Geology

Publisher University of Southern California (original), University of Southern California. Libraries (digital)

Tag Geology,Geophysics,OAI-PMH Harvest

Language English

Permanent Link (DOI) https://doi.org/10.25549/usctheses-c16-36414

Unique identifier UC11337514

Identifier 1405255.pdf (filename),usctheses-c16-36414 (legacy record id)

Legacy Identifier 1405255.pdf

Dmrecord 36414

Document Type Thesis

Rights Tucker, Allan Zachary

Type texts

Source University of Southern California (contributing entity), University of Southern California Dissertations and Theses (collection)

Access Conditions The author retains rights to his/her dissertation, thesis or other graduate work according to U.S. copyright law. Electronic access is being provided by the USC Libraries in agreement with the au...

Repository Name University of Southern California Digital Library

Repository Location USC Digital Library, University of Southern California, University Park Campus, Los Angeles, California 90089, USA

Linked assets

University of Southern California Dissertations and Theses