ML110980790

Southern California Edison - Evaluation of California Energy Commission AB 1632 Report Recommendations, Appendix a, Cover Page Through Attachment A-2, Page A2-10

ML110980790
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Site:	San Onofre
Issue date:	12/31/2010
From:	GeoPentech, Southern California Edison Co
To:	Office of Nuclear Reactor Regulation
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APPENDIX A SEISMIC SOURCE CHARACTERIZATION

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SAN ONOFRE NUCLEAR GENERATING STATION SEISMIC HAZARD ASSESSMENT PROGRAM 2010 PROBABILISTIC SEISMIC HAZARD ANALYSIS REPORT APPENDIX A OUTLINE A

1.0 INTRODUCTION

A2.0 CHRONOLOGY OF PREVIOUS RELEVANT SEISMIC HAZARD ASSESSMENTS A3.0 TECTONIC AND GEOLOGIC SETTING A3.1 Physiographic Provinces in the Study Region A3.2 Tectonic History of the Inner Continental Borderland and Transverse Ranges A3.2.1 Phase 1 - Collision and Subduction A3.2.2 Phase 2 - Oblique Extension A3.2.3 Phase 3 - Transform Plate Boundary (Present)

A4.0 DATA AND OBSERVATIONS SUPPORTING THE NI/RC AS THE PRIMARY FAULT SOURCE A4.1 Geometry and Structural Analyses A4.2 Evidence for Activity A4.2.1 Paleoseismicity A4.2.2 Geomorphology A4.2.3 Seismology A4.2.4 GPS A5.0 DATA AND OBSERVATIONS SUPPORTING THE OBT AS THE PRIMARY FAULT SOURCE A5.1 Geometry and Structural Analysis A5.1.1 Geometry A5.1.2 Structural Analysis A5.2 Evidence for Activity A5.2.1 Paleoseismicity A5.2.2 Geomorphology A5.2.3 Seismology A5.2.4 GPS ATTACHMENT A ANNOTATED BIBLOGRAPHIES ATTACHMENT A SEISMIC SOURCE CHARACTERISTICS OF NI/RC FAULT SYSTEM ATTACHMENT A SEISMIC SOURCE CHARACTERISTICS OF OBT SYSTEM G.e o P.ent e c h December 2010 Page A-i

SAN ONOFRE NUCLEAR GENERATING STATION SEISMIC HAZARD ASSESSMENT PROGRAM 2010 PROBABILISTIC SEISMIC HAZARD ANALYSIS REPORT APPENDIX A SEISMIC SOURCE CHARACTERIZATION A

1.0 INTRODUCTION

This Appendix provides additional background information to support the judgments regarding the weights assigned to the alternative strike-slip and blind thrust end-member seismic source characterization models discussed in Section 2.0 of the main report. Brief summaries of key seismic hazard assessments that have been conducted specifically for the SONGS Units 2 and 3 and of the current community seismic source characterization model are given in Section A-2. Section A-3 outlines the,geologic and tectonic setting and history of the study region. Sections A-4 and A-5 provide additional discussion of the data and studies supporting the strike-slip fault source model (NI/RC as the primary fault source) and the blind thrust fault source model (OBT as the primary fault source), respectively. The following three Attachments are included in this Appendix and provide additional background information:

A-1 Annotated Bibliographies, which contain abstract summaries of selected references.

A-2 Seismic Source Characterization of Onshore RC Fault by Dr. Thomas Rockwell of San Diego State University.

A-3 Seismic Source Characteristics of Inner California Borderland's Blind Thrust Fault Systems by Dr. John Shaw and Dr. Andreas Plesch of Harvard University.

A2.0 CHRONOLOGY OF PREVIOUS RELEVANT SEISMIC HAZARD ASSESSMENTS During the 1970s and early 1980s, SCE, with the assistance of firms such as Dames & Moore, Fugro, Western Geophysical, Woodward-Clyde Consultants, and several independent consultants completed rigorous onshore and offshore investigations to identify and characterize nearby fault sources and to evaluate their impact on potential earthquake ground motion and tsunami hazards for licensing SONGS Units 2 and 3 (SCE, UFSAR). During these SCE licensing investigations, what was referred to then as the Offshore Zone of Deformation (OZD), was part of a system of faults that included the onshore NI to the north, the offshore South Coast Offshore Zone of Deformation (SCOZD) in the middle, and the RC Fault to the south as illustrated on Figure A-la. The SCOZD, the closest of these OZD source faults, islocated offshore about 8 km southwest of SONGS. This system of faults was identified as the controlling earthquake source in the deterministic assessment of earthquake ground motions completed at that time.

The Cristianitos Fault, which is the closest mapped fault (refer to Figures A-la, b, and c), is exposed in the sea cliff 915 m southeast of SONGS. Based on this exposure, the Cristianitos Fault was found by SCE (UFSAR) and Shlemon (1987) to have not displaced a 125 ka old marine terrace platform. Therefore, the Cristianitos Fault was not considered to be a fault source in the licensing earthquake ground motion assessment (SCE, UFSAR).

Other fault sources considered during the licensing of Units 1 and 2 to be capable of producing significant earthquake ground motions at SONGS. included the onshore San Andreas, San Jacinto, and G eoPen tech December 2010 Page A-1

SAN ONOFRE NUCLEAR GENERATING STATION SEISMIC HAZARD ASSESSMENT PROGRAM 2010 PROBABILISTIC SEISMIC HAZARD ANALYSIS REPORT the Elsinore fault zones, and the offshore Palos Verdes, Coronado Banks, Santa Catalina, San Diego Trough, and San Clement faults, as illustrated in Figures A-2a and b.

An updated seismic hazard assessment was conducted by SCE in 1995, with the assistance of Geomatrix Consultants, Risk Engineering, and Woodward-Clyde Consultants. During the 1995 PSHA (SCE, 1995),

offshore and onshore data relevant to the OZD, in particular the SCOZD, that had become available since the preparation of the SCE UFSAR, were evaluated. The results of a PSHA, which was completed in this study, also showed that the NI, the SCOZD, and the RC fault sources were the controlling sources for seismic hazard at SONGS.

In 2001, with the assistance of Fugro West, Geomatrix Consultants, and GeoPentech, SCE completed a re-assessment of the seismic source characteristics of the NI/SCOZD/RC and conducted a PSHA that specifically addressed the newly postulated blind fault sources in the vicinity of SONGS. Alternative source characterizations for this 2001 seismic hazard analysis were developed to capture the range of plausible fault geometries and interactions between postulated thrusts, including the OBT (Rivero et al.,

2000) and the San Joaquin Hills Blind Fault (SJBF) (Grant et al., 1999 and 2000), and strike-slip faults, including the NI/SCOZD/RC faults. Analysis of geodetic GPS data conducted as part of this assessment showed relative motion more consistent with north-northwest shear with little or no convergence across the ICB Province, or evidence of a regional "driving" force that would reactivate a large seismogenic thrust fault (SCE, 2001; Hanson et al., 2002; Moriwaki et al., 2002). Quaternary slip rates assigned to offshore blind thrust fault sources were modified from postulated higher long-term post-Pliocene slip rates (Rivero et al., 2000) to reflect constraints provided by the geodetic data and coastal marine terrace uplift rates.

UCERF 2, which was published by the 2007 WGCEP in 2008, represents the USGS current seismic source model for the southern California region. UCERF 2 primarily updated the state of knowledge on the southern California portion of the San Andreas Fault and the San Jacinto and Elsinore faults over what had previously been reported by a WGCEP in 1995. Postulated onshore blind thrust faults, such as the SJBF (Grant et al., 1999) were included in UCERF 2. However, postulated blind thrust faults in the ICB Province are not included in the source model used in UCERF 2, but were flagged by the authors of UCERF 2 as potential sources for future consideration.

There is ongoing debate within the technical community (e.g., Rivero and Shaw, 2001; Grant et al.,

2002; Grant and Rockwell, 2002; Rivero, 2004; Grant and Shearer., 2004; Rivero and Shaw, 2005; Ryan et al., 2009; Sorlien et al., 2009b; Rentz, 2010; Rivero and Shaw, 2010, in press; and many others) as to whether high-angle strike-slip faults or low angle reverse or thrust faults are the primary tectonic structures or faults accommodating the crustal motions in the vicinity of SONGS. The present study utilizes two end-member tectonic structural models (referred to as the strike-slip and blind thrust system models) to facilitate the characterization of the closest offshore faults that have been demonstrated to dominate the earthquake shaking hazard for SONGS. UCERF 2 was selected as the basis or reference for one end-member model because it represents the most recent technical community's consensus seismic source characterization model for California faults. In this strike-slip end-member model, the NI/RC Fault Zone is characterized as the closest, active, primary strike-slip fault to SONGS.

The source parameters from UCERF 2 used to characterize the NI/RC Fault Zone in the USGS (2008) and USGS (2009, PC) seismic hazard mapping studies are used in this study. For the blind thrust end-member model, the OBT is characterized as the primary contributing seismic source for SONGS. The OBT is SGeoPentech December 2010 Page A-2

SAN ONOFRE NUCLEAR GENERATING STATION SEISMIC HAZARD ASSESSMENT PROGRAM 2010 PROBABILISTIC SEISMIC HAZARD ANALYSIS REPORT included in the CFM (Plesch et al., 2007) and is identified in UCERF 2 as a potential fault source that should be given future consideration.

A3.0 TECTONIC AND GEOLOGIC SETTING Southern California is divided into several physiographic regions, or provinces based on the makeup of their geologic and tectonic characteristics. Refer to Figure 2-1 in the main portion of this report and Figures A-2a, b, c, and d for the' location of these provinces relative to SONGS and illustrations of their long and complex tectonic evolution. SONGS is located in the Peninsular Ranges Province, just east of its boundary with the ICB Province and to the south of the Transverse Ranges Province.

A summary of the geologic and tectonic characteristics of these physiographic provinces (Section A3.1) and a tectonic history that outlines the development of their key geologic and tectonic structures (Section A3.2 and Figures A-2a, b, c, and d) provide additional perspectives on the relationships between strike-slip and thrust faults in the region.

A3.1 Physiographic Provinces in the Study Region As seen on Figure A-2a, the Peninsular Ranges Province extends from Colorado Desert Province in Coachella/Imperial Valley on the east, well into Baja California on the south, and to the Transverse Ranges Province on the north. To the west, the ICB Province is almost entirely offshore, including Santa Catalina and San Clemente Islands. This province also includes the Palos Verdes Peninsula and the western portion of.the Los Angeles (LA) Basin. Similar to the Peninsular Ranges Province, the ICB Province is also bounded on the north by the Transverse Ranges Provinceand, also extends to the south offshore of Baja California. The Outer Continental Borderland Province (MMS, 2001 and Crouch and Suppe, 1993) bounds the ICB Province on the west.

The Peninsular Ranges and ICB provinces are dominated by northwest-southeast trending mountain ranges and intervening basins that extend from within Baja California to the southern border of the Transverse Ranges Province (CGS, 2002b). The Transverse Ranges province is dominated by east-west trending mountain ranges and intervening basins that extend from the Twenty-Nine Palms/Palm Springs area on the east to offshore of Point Conception and the Channel Islands on the west. The basins and ranges in the Peninsular Ranges, ICB, and Transverse Ranges Provinces are commonly separated by fault zones that trend parallel to the ranges and valleys. The LA Basin, located at the juncture of these three physiographic provinces, includes faults and folds with differing orientations resulting from the complex interaction between the northwest-trending Peninsular Ranges and ICB Provinces and the east-west-trending Transverse.Ranges Provinces.

As mentioned above, the physiography of both the ICB and the Peninsular Ranges provinces are composed of generally similar northwest-oriented faulted ridges and basins, with relatively steep slopes on the flanks of the uplifted ridges. However, there are distinct differences between the ICB and Peninsular Ranges provinces in their underlying basement rock composition and their structural relief their overlying sedimentary rocks, which suggest that it is appropriate to keep these two provinces separated. The ICB Province is underlain by the Catalina Schist basement rock complex and the Peninsular Ranges Province is underlain by a batholithic and older basement rock complex, as illustrated on Figures A-2c and A-2d&The ICB Province is bounded on the east by the NI/RC Fault Zone near the coast. The East Santa Cruz Basin Fault bounds the ICB Province on the west. The Peninsular Ranges afh G e o Pe n te ch December 2010 Page A-3

SAN ONOFRE NUCLEAR GENERATING STATION SEISMIC HAZARD ASSESSMENT PROGRAM 2010 PROBABILISTIC SEISMIC HAZARD ANALYSIS REPORT Province is bound on the west by the NI/RC Fault Zone and on the east by the Coachella and Imperial valleys with their San Andreas Fault System (refer to Figures A-2a and A-3).

A3.2 Tectonic History of the Inner Continental Borderland and Transverse Ranges Southern California's current complex tectonic and geologic setting resulted from a long and complicated history in crustal plate interaction that has culminated in today's San Andreas Fault being the dominate player in the predominate right-lateral strike-slip boundary between the Pacific and North American crustal plates (Figures A-2b and 2c) (Atwater, 1998; Nicholson et al., 1994; Bohannon and Geist, 1998; Fisher 2009; and Fisher et al., 2009a). This complex deformational history and resulting tectonic setting form the basis for interpreting the stratigraphy, faults and folds, and present seismotectonic setting of the Peninsular Ranges and ICB provinces in the area around SONGS.

Essentially, there have been three different phases of the crustal deformation, each with a-distinct style and pattern of deformation and resulting geology.

A3.2.1 Phase 1 - Collision and Subduction In the- Cretaceous and early Tertiary, the western side of the Continental Borderland was a convergent (subduction) plate boundary (Figure A-2b). During Cretaceous and Paleogene time (>24 Ma), the oceanic Farallon. plate was subducting beneath the continental crust of western North America, resulting in a continental margin arc-trench system. The subduction-related geology of California, when reconstructed, includes the Sierra Nevada granitic batholith that formed the roots of a magmatic arc, the metamorphic rocks along the arc front that form the foothills belt of the Sierra Nevada, the Great Valley Sequence of marine sedimentary rocks formed in the submarine fore-arc basin, the Coast Range ophiolite that was the oceanic floor of the fore-arc basin, and the Franciscan complex of accreted terrain metamorphic rocks formed in the accretionary wedge at the subduction front. These major geologic units are still recognizable in southern California, but, as illustrated on Figures A-2c and 2d, they have been broken up and re-organized by subsequent tectonic events (Atwater, 1998; Nicholson et al., 1994; Bohannon and Geist, 1998; Fischer, 2009; and Fisher et al., 2009a).

A3.2.2 Phase 2 - Oblique Extension Beginning in the late Oligocene and early Miocene (17 to 24 Ma), subduction gradually ceased along the western margin of North America when the East Pacific Rise (source of the Farallon and Pacific Plates) encountered the continental margin and, along with the Farallon Plate, was, in turn, subducted beneath North America (Figure A-.2b). A new plate boundary configuration resulted with the Pacific Plate in direct contact with the North American Plate along the strike-slip San Andreas Fault. The relative motion between the Pacific and North American Plates was no longer convergent, but rather largely right-lateral translational in nature.

During the Miocene (5 to 24 Ma), various crustal blocks along the North American margin' became attached to the northward-moving Pacific Plate (Atwater, 1998). This microplate capture led to extensional deformation of the upper plate of the subduction zone, rotation and translation of large crustal blocks, normal faulting, widespread Middle Miocene Volcanism, and a zone of oblique extension (transtension) in the Borderland (Kamerling and Luyendyk, 1979 and 1985; Wright, 1991; Nicholson et al., 1994; Fisher, 2009; and Fisher et al., 2009a). This oblique extension continued into the middle Pliocene (-4 Ma) and caused extensive ridge and basin (horst and graben) morphology (similar to block GeoP ent e c h December 2010 Page A-4

SAN ONOFRE NUCLEAR GENERATING STATION SEISMIC HAZARD ASSESSMENT PROGRAM 2010 PROBABILISTIC SEISMIC HAZARD ANALYSIS REPORT faulting in the Basin and Range Province) to occur in the ICB. This formed many of the generally northwest-trending basins and ridges of the ICB that are apparent today.

As schematically illustrated by Nicholson et al. (1994) in the sequence of maps shown on Figure A-2b, the western Transverse Ranges Province was one of these several captured rotating crustal blocks.

These blocks, while simultaneously being translated northward, were also rotated as much as 90 to 110 degrees in a clockwise direction (also refer to Figure A-2c) forming the east-west trending, western portion of the Transverse Ranges Province (Kamerling and Luyendyk, 1985; Crouch and Suppe 1993; and Bohannon and Geist, 1998). As the Transverse Ranges Province moved northward and rotated into its present position and the transform plate boundary continued to develop along the eastern edge of the rotating block, significant extension occurred in the Los Angeles Basin and ICB Province resulting in rapid basin subsidence and sedimentation accumulation during the Miocene and early Pliocene.

Approximately 4 to 5 Ma (during the early Pliocene), another reorientation of the plate boundary-in southern California and northern Mexico occurred. The plate boundary south of the Borderland and west of Baja California migrated eastward, splitting Baja California and coastal southern California off from the rest of North America, attaching these crustal blocks to the Pacific Plate (Figure A-2b). Since that time (about 5 Ma), the relative plate motion vector between the North American and Pacific Plates has been oriented approximately N37°W (Cande et al., 1995; Atwater and Stock, 1998). The southern San Andreas Fault was the manifestation of this new shift eastward of the plate boundary in southern California. The southern San Andreas and the northern San Andreas are now connected through the well-known, large left restraining bend in the fault trace, (now referred to as the Mojave segment) thereby producing convergence across a wide area of the southern California, expressed most proximately in the Transverse Ranges Province (Clark et al., 1991; Wright, 1991; Schneider et al., 1996; Sorlien et al., 1999; and Seeber and Sorlien, 2000).

Thus,. overall, the tectonic setting in this portion of southern California changed in the Pliocene.from predominately transtensional to predominately transpressional. The increased convergence commonly resulted in diversely-striking Miocene normal faults being reactivated as reverse faults, and inversion of half-graben basins into anticlines (Yeats, 1987; Clark et al., 1991; Seeber and Sorlien, 2000). Significant transpression occurred across the newly-developing Transverse Ranges and portions of the LA Basin on numerous oblique reverse and blind faults, many of which are inverted normal faults (Pasadenan orogeny). Large scale, rapid uplift of crustal blocks north of the LA Basin occurred concurrently with gradual Uplift of the Palos Verdes Peninsula and the San Joaquin Hills, and subsidence and rapid sedimentation in the LA Basin (Wright, 1991).

A3.2.3 Phase 3 - Transform Plate Boundary (Present)

The present-day Pacific-North American. Plate boundary south of the Transverse Ranges Province in southern California is dominated by a broad zone of distributed right-lateral strike-slip motion. This motion affects an area extending from the San Andreas Fault in the east to-the offshore San Clemente Fault in the west (Figure A-la).

Various studies have estimated that approximately 48 to 52 millimeters per year (mm/yr) of right-lateral shear occurs across southern California (Bennett et al., 1996; DeMets and Dixon, 1999). The San Andreas Fault and several other strike-slip fault zones accommodate, most of the slip across the plate boundary (Jennings, 1994; Petersen et al., 1996). The Eastern California Shear Zone (east of San Andreas Fault) is believed to accommodate about 10 mm/yr of right-lateral slip (Bennett et al., 1996). The slip

• , GeoPen t e h December 2010 Page A-5

SAN ONOFRE NUCLEAR GENERATING STATION SEISMIC HAZARD ASSESSMENT PROGRAM 2010 PROBABILISTIC SEISMIC HAZARD ANALYSIS REPORT rate on the San Andreas Fault is variable, but ranges from about 10 to 35 mm/yr in southern California.

The most recent information from paleoseismic studies suggests thatthe San Jacinto Fault has a slip rate of about 15 to 20 mm/yr (C. Kendrick, USGS, 2007, PC), which exceeds the 12 mm/yr reported by the CGS and the SCEC. Geologic data suggest that the Whittier-Elsinore, NI onshore, and Palos Verdes faults have slip rates of about 5, 1, and 3 mm/yr, respectively (Cao et al., 2003).

Quaternary to Holocene offsets on the major fault zones within the Continental Borderland are interpreted to be primarily right-lateral strike-slip faults with a lesser vertical slip component, commonly referred to as oblique-slip faults. The San Pedro Basin Fault and the San Clemente Fault are two of the most active faults in the Borderland, but their slip-rates are largely unknown. Based on regional slip budgets and offsets of Miocene volcanic rocks, estimates of the slip-rates of the key faults in the ICB are as follows: the San Pedro Basin Fault has a slip-rate of 1 to 2 mm/yr and individual splays of the San Clemente Fault Zone (including the Santa Cruz-Catalina Ridge and Pilgrim Banks-Santa Barbara Island faults) have slip-rates of 1 to 4 mm/yr. GPS observations between 1986 and 1995 indicate that the total relative slip between the North American and Pacific plates is 49 +/- 3mm/yr. The estimated total relative slip-rate between the North American and Pacific Plates is reported by DeMets and Dixon (1999) to be about 52 mm/yr. While there are no permanent GPS stations on the eastern edge of the Pacific Plate, stations on Santa Catalina, San Clemente and San Nicolas Islands have shown 45.5, 47.5 and 48.5 mm/yr of slip with respect to stable North America, respectively (SOPAC, 2010). As shown in Figure A-3, the station on San Clemente Island, scip, is moving at a rate of 6 mm/yr with an azimuth of 41 degrees west of north relative to station, scms, in San Clemente (11 miles northeast of SONGS). These GPS velocities would suggest that the upper limit of postulated slip-rates for the offshore right-lateral strike-slip faults is slightly overestimated.

Using this more regional perspective and stepping closer to the area surrounding SONGS, two end models were utilized to facilitate the characterization of the closest offshore faults that have been demonstrated to dominate the seismic shaking hazard for SONGS. In this regard, UCERF 2 was selected as the basis for reference because it represents the most recent regionally documented seismic source characterization for California faults. Therefore, for the first end-member model, the NI/RC Fault Zone was selected because it was the only UCERF 2 model utilized bythe USGS (2008) and USGS (2009, PC) in developing the seismic hazard maps for the building code that applies to the area near SONGS. Similarly, the other end-member model selected was the OBT because of its postulated ability to generate large magnitude earthquakes on a fault plane that was proposed to extend eastward, under the coastline and beneath SONGS.

A4.0 DATA AND OBSERVATIONS SUPPORTING THE NI/RCAS THE PRIMARY FAULT SOURCE!

This section provides more detailed discussion of the available and relevant structural, geomorphology, paleoseismicity, seismology and GPS information that have been used to identify and characterize the NI/RC Fault'Zone as a predominantly high-angle, right-lateral, strike-slip -fault. The NI/RC Fault Zone is the closest primary seismic source fault to SONGS in the strike-slip end-member seismic source model included in this 2010 PSHA. Attachment A-2 presents Dr. Tom Rockwell's summary of current information concerning the NI/RC Fault Zone.

A4.1 Geometry and Structural Analyses The geometry of a fault, as well as its flanking lithology, provide the geologic and tectonic structural information for estimating how that fault will rupture in the future; this information in turn is needed to

,.eo Pent e ,eh December 2010 Page A-6

SAN ONOFRE NUCLEAR GENERATING STATION SEISMIC HAZARD ASSESSMENT PROGRAM 2010 PROBABILISTIC SEISMIC HAZARD ANALYSIS REPORT model the resulting earthquake ground motions that will impact facilities, such as SONGS. In addition to geometry and structural geologic information about the San Andreas Fault and other active strike-slip faults in the world, subsurface data from the oil fields under the LA Basin along the onshore NI portion of the NI/RC Fault Zone lead to the development of the classic theory of wrench fault tectonics (Moody and Hill, 1956; Wilcox et al., 1973; Harding, 1973; Yeats, 1973; Barrows, 1974; Harding 1985). In simplistic terms, as illustrated on Figure A-4a, the primary principal behind wrench fault theory is that, as high-angle, crustal-through-going, strike-slip faults progressively propagate through overlying more recently deposited sediments, they initially form a broad, near-surface zone of subsidiary faults in a flower-like pattern (refer to Figure A-4b). The orientation of these subsidiary faults is at oblique angles to the primary strike-slip fault and the direction of crustal deformation. These conjugate subsidiary faults vary in theirgeometry and style of faulting (i.e., normal, reverse, thrust, strike-slip, or oblique-slip) depending on their orientations relative to the strike and dip of the primary strike-slip fault. As the displacement of these more recently deposited sediments increases, the broad, flower-like pattern progressively narrows into the primary trace of the fault. The subsidiary fault patterns are most prominent in en echelon step-overs or bends in the trace of the primary, high-angle, strike-slip fault. As illustrated on Figures A-4a and A-4b, for right-lateral strike-slip faults right step-overs produce localized zones of tension expressed in subsiding blocks bracketed by normal or transtensional oblique slip faults.

Examples of the en echelon right step-overs along the NI/RC Fault Zone are the subsiding San Diego Bay and Bolsa Chica and Anaheim Bay wetlands. Left step-overs produce localized.zones of compression expressed in rising blocks bracketed by thrust, reverse, or transpressional oblique slip faults. Examples of these left step-overs along the NI/RC Fault Zone are Mount Soledad, Signal Hill, Domingues Hills, and Baldwin Hills.

SCE (UFSAR), with the assistance of Woodward-Clyde Consultants (1980), completed a thorough re-analysis of the oil well records and available geologic data from the oil fields between Newport Beach and Westwood (an example is provided on Figure A-5). This independent assessment concluded that the oil field data supported the wrench fault model and that a high-angle, right-lateral strike-slip fault dominated by the NIlFault Zone, and estimated that the long term slip rate on the fault was about 0.5 mm/yr. More recent work in examining oil well and groundwater well data from western Los Angeles County by Dr. Dan Ponti of the USGS (2010, PC) further supports the dominance of the high-angle strike-slip fault in the NI Fault Zone as illustrated in Figure A-6.

Data supporting thi characteristics of the offshore part of the NI/RC Fault Zone are more limited. The continuity of the NI/RC Fault Zone, between its southern onshore trace near La Jolla and its onshore traces north of Newport Beach was first suggested by Moore (1972). SCE (UFSAR), through Western Geophysical Company, completed rigorous offshore marine seismic reflection surveys to assess potential faulting offshore of SONGS (Western Geophysical Company, 1972). Track lines of these surveys and their interpreted faults are shown on Figure A-7a. This offshore work supported the conclusion that the closest primary seismic source fault to SONGS is the offshore continuation of the high-angle, ýright-lateral, strike-slip NI/RC Fault Zone, whose characteristics are reflected in the wrench fault style of tectonics present in the northern and southern onshore portions of the fault zone.

Little has changed. in the geoscience community's overall assessment of the NI/RC Fault Zone characterization as a strike-slip fault zone since the SCE's original investigations were completed. Some refinements were made in the mapped offshore traces of the faults by Fischer and Mills (1991) (Figure A-7b); Ryan et al. (2009) (Figure A-7c); Sorlien et al. (2009b). (Figure A-7d); and Conrad et al. (2010)

(Figure A-7e). Figure A-7f illustrates a map containing the USGS (2009) Quaternary Fault and Fold o tech December 2010 Page A-7

SAN ONOFRE NUCLEAR GENERATING STATION SEISMIC HAZARD ASSESSMENT PROGRAM 2010 PROBABILISTIC SEISMIC HAZARD ANALYSIS REPORT Database in the ICB. The changes in the NI/RC Fault Zone's seismic characteristics by Fischer and Mills (1991) were incorporated in the source models used in SCE (1995 and 2001) and those by Ryan et al.

(2009), Sorlien et al. (2009b), and Conrad et al. (2010) were considered in this PSHA. Other research, including Grant and Shearer (2004), Fisher (2009), Fisher et al. (2009a), Fisher et al. (2009b), Lee et al.

(2009), Rockwell (2010a and 2010c), proprietary work completed by Fugro, Inc., and work currently underway by Dr. Dan Ponti of the USGS along the onshore NI Fault and its subsidiary traces north of Long Beach, further supports the weights assigned herein to a high-angle, strike-slip characterization of the NI/RC Fault Zone as the closest primary source fault to SONGS in the strike-slip end-member model incorporated into this PSHA.

Most notable of this more recent research is the work completed by Ryan et.al. (2009), which essentially is an independent assessment of the available data reviewed during SCE's earlier work (Western Geophysical Company, 1972) on the characteristics of the faults located offshore of SONGS. Some of the proprietary marine geophysical survey data recently obtained by the USGS from WesternGeco and used by Ryan et al. (2009) was purchased by SCE years ago. Ryan (2010, PC) indicated that the results of the USGS's independent assessment of the data are in general agreement with the results of SCE's previous investigations and analysis of the faulting off-shore of SONGS, as seen by comparing Figure A-7a and A-7c.

USGS (2009) considers the NI/RC Fault Zone to be a primary, high-angle, right-lateral, strike-slip seismic source fault, with relatively minor alternatives to its most northern on-shore geometry.

A4.2 Evidence for Activity A4.2.1 Paleoseismicity The results of the SCE (UFSAR) (Woodward-Clyde).analysis of the oil field data (see example on, Figure A-5 from Freeman et al., 1992) showed that, although the quality of the data varied between the different oil fields, the best fit of that data indicated about 0.5 mm/yr of strike-slip displacement across'the main trace of the NI Fault. Slip rate estimates for the northern on-shore part of the NI/RC Fault Zone have been made by Fischer and Mills (1991), Freeman et al. (1992), Law/Crandall, Inc. (1993), Shlemon et al.

(1995), Grant et al. (1997), and Franzen and Elliott (1998). In combination, these estimates suggest a wide range in slip-rate between 0.4 to 3.0 mm/yr for the onshore RC segment. More thorough and extensive paleoseismic investigations conducted by Lindvall and Rockwell (1995) and Rockwell (2010a and 2010c) support seismic source characteristics assigned to the southern onshore portion of the NI/RC Fault Zone in the San Diego area (summarized in Attachment A-2). Detailed 3D fault trenching in that work further supports the dominate high-angle, right-lateral, strike-slip style of faulting along the NI/RC Fault Zone with slip-rates estimated to be between 1.5 and 2.5 mm/yr. Offshore the paleoseismic data along the NI/RC Fault Zone has been more limited. Fischer and Mills (1991), based. on their re-assessment of seismic reflection data available at that time, estimated a slip-rate of about 0.8 mm/yr, but were careful to qualify their estimate based on the limitations of their available data. Recent, high resolution marine geophysical surveys, like the USGS (Conrad et al., 2010) survey over the San Diego Trough Fault and the Rentz (2010) survey off the coast over the inner shelf between Dana Point and Carlsbad (refer to Figure A-8a), are providing more useable data to assess the paleoseismic record beneath the ICB.

High-resolution seismic data on the inner shelf has been used to constrain the recency of displacement on the Cristianitos Fault. Using this data, which is illustrated on Figure 8b, Rentz (2010) notes that what G e o P e n t e ch December 2010 Page A-8

SAN ONOFRE NUCLEAR GENERATING STATION SEISMIC HAZARD ASSESSMENT PROGRAM 2010 PROBABILISTIC SEISMIC. HAZARD ANALYSIS REPORT subtle surface relief is observed locally on the inner shelf is of eroded, partially buried, bedrock remnants of "...adjacent geologic formations with different erosive properties." As Rentz (2010) suggests, "this differential erosion may be responsible for the trend of the San Mateo promontory, the highstand relief in the seismic profiles, and the -9.6 km wide shelf," off of the coast between Dana Point and Carlsbad. Further, they conclude that in the area of their survey, "There is no observed offset of the overlying Holocene sediment packages, which would be expected if deformation was ongoing"; further supporting the SCE (UFSAR) conclusion that the Cristianitos Fault is inactive.

A4.2.2 Geomorphology The geomorphology along the onshore parts of the NI/RC Fault Zone clearly supports the dominance of a high-angle strike-slip fault. As Dr. Rockwell presents in more detail in Attachment A-2, displaced stream channels in RC Fault are predominately offset right-laterally. Although the location and geomorphology defined by the NI/RC Fault Zone is less obvious in other parts of San Diego due to urban development, Dr. Rockwell presents in Attachment A-2, a late 19th century cartographer's sketch that shows a linear topographic lineament, which correlates with the present known location of the NI/RC Fault Zone. The pattern of this lineament across San Diego's hilly terrain supports the presence of an active near-vertical, right-lateral fault plane along this trace of the NI/RC Fault Zone.

The linear surface trace of the NI/RC Fault Zone through the western part of the LA Basin, particularly between Newport Beach and Long Beach, and the presence of localized uplifted hills and plateaus and intervening subsiding lowlands and wetlands is consistent with the presence of an underlying strike-slip dominated wrench fault system.

Between Newport Beach and La.Jolla, the onshore geomorphology is characterized by a flight of emergent marine terraces (Figure A-9). The relatively uniform altitude of these surfaces suggests uniform uplift that does not appear to be consistent with the varying dips and long-term rates of slip postulated for the OBT. The sequence of emergent marine terraces have been mapped and described by Shlemon (1978), Kern and Rockwell (1992), Lajoie et al. (1992), and Grant et al. (1999),(refer to Figure A-9). Dating of the emergent MIS 5e/5a marine terraces at 125/80 ka by these auithors,'suggests regionally uniform coast uplift at a rate of about 0.13 to 0;14 mm/yr. Along the coastal San Joaquin Hills, the uplift rate may be as high as 0.21 to 0.27 mm/yr (Grant et al., 1999).

The presence and regionally persistent elevations of these onshore marine terraces, which are subparallel with the trend of the NI/RC Fault Zone, are more in concert with a nearby strike-slip faulting rather than a regionally persistent underlying thrust fault with changing dip angles, as proposed by Rivero et al. (2000) and Rivero (2004). As suggested by Mueller et al. (2009), the uniform uplift of these late Pleistocene uplifted marine: terraces is more likely tied to regional tilting or "flexure of the crust driven largely by heating and thinning of the upper mantle beneath the Gulf of California and eastern Peninsular Ranges." Locally, this regional uplift is amplified by transpressional bends and en echelon step overs in the NI/RC Fault Zone leading to the higher uplift rates such as those tied of the San Joaquin Hills (Grant et al., 1999, 2000, and 2002) and Mount Soledad (Rockwell, 2010).

A relatively low-relief offshore continental shelf and the consistent 400-foot depth of its shelf break, is' evident in the bathymetry extending along the coast between Palos Verde Peninsula to the Mexican Border, as illustrated in Figure A-10. This geomorphology also is inconsistent with a regionally persistent underlying thrust fault with changing dip angles, as proposed by Rivero et al. (2000) and Rivero (2004).

G e o P en t e ch December 2010 Page A-9

SAN ONOFRE NUCLEAR GENERATING STATION SEISMIC HAZARD ASSESSMENT PROGRAM 2010 PROBABILISTIC SEISMIC HAZARD ANALYSIS IREPORT This uniform low-relief surface, which correlates to the last glacial maximum sea level low-stand at approximately 19 to 21 ka, is more consistent with a through-going strike-slip fault, such as the.NI/RC.

Recent marine geophysical surveys along this shelf by Rentz (2010) are consistent with this conclusion by associating the wider shelf offshore between Dana Point and Carlsbad Canyon, in contrast to the width of the rest of the self between Newport Beach and Dana Point and between Carlsbad Calnyon and La Jolla, to more erosion resistant bedrock formations. However, agreeing that the width of the shelf is at least in part is controlled by erosion patterns, based on new multibeam data acquired by the USGS in November 2010, Dr. Ryan (2010, PC) notes that there are major changes in erosion patterns across the San Mateo Point area and suggest that the San Mateo fold and thrust belt, located to the west of the NI/RC Fault Zone, does contributes to the shelf width. She also noted that the shelf morphology would be primarily controlled by sea level cycles, especially considering the low slip rate estimates for the offshore reverse and thrust faults.

A4.2.3 Seismology Seismology data from the ICB, as a tool to he!p resolve the location and geometry of faults in this province, has limitations due to the paucity of nearby stations, limited azimuthal coverage, and uncertainties in the underlying velocity structure. Recognizing these limitations, Astiz and Shearer (2000) used improved methods to refine the locations of earthquakes that occurred in the Borderland: between 1981 and 1997. Rivero et al. (2000) and Rivero (2004) utilized Astiz and Shearer (2000), in particular the 1986 ML 5.3 Oceanside Earthquake, to support the offshore thrust fault models as discussed below in Section A-5.

Grant and Shearer (2004) also re-analyzed the 1981 M <3.0 cluster of earthquakes located about 10 km northwest of Oceanside and a 2,000 cluster of seismic events offshore of Newport Beach (refer to Figure A-11). Their work, especially the analysis of earthquakes northwest of Oceanside, supports a high-angle fault plane at depths of 12.5 to 13 km, This orientation of hypocenters and the their depth suggest the presence of a deep-rooted, high-angle, strike-slip fault (i.e., the NI/RC Fault Zone), rather than a low-angle reverse or thrust fault (i.e., the OBT). This supports the high-angle, strike-slip, end-member model containing the NI/RC Fault Zone as the closest primary seismic source fault to SONGS.

The 2,000 cluster of earthquakes offshore of Newport Beach also indicate a high-angle fault, such as the NI/RC Fault Zone, but this cluster is located west of the surface trace of the NI/RC Fault Zone and occurs at a depth of 6.5 to 7 km. The shallow depth of these earthquakes, however, does not preclude the possible presence of a seismogenic thrust fault plane passing beneath the high-angle structure.

Marrying the epicenter data from the M 5.3, 1986 Oceanside Earthquake with the new trace of theSan Diego Trough Fault, recently re-located by new USGS offshore marine geophysical surveys (Conradet al.,

2010 and Ryan, 2010, PC) is in contrast with the thrust mechanism of that event being correlated with the Thirtymile Bank Blind Thrust (TMBT) as suggested by Rivero et al. (2000) and Rivero (2004). As seen on Figure A-12, the Oceanside event occurred near the San Diego Trough Fault at a left bend in that fault's trace. This relationship supports the occurrence of a thrust event within a high-angle, right-lateral, strike-slip fault system and not the occurrence of a thrust event on a regionally persistent underlying blind thrust fault.

Ge oP en tech G December 2010 "Paqe A-10 44W

SAN ONOFRE NUCLEAR GENERATING STATION SEISMIC HAZARD ASSESSMENT PROGRAM 2010 PROBABILISTIC SEISMIC HAZARD ANALYSIS REPORT A4.2.4 GPS Clockwise rotation of crustal blocks in the ICB Province, suggested in SCE (2001), has been emphasized by Ryan et al. (2009). The rotating block proposed by Ryan et al. (2009) has been plotted along with geodetic data on Figure A-13 to qualitatively analyze whether geodetic data collected in southern California supports possible block rotation. Figure A-13 shows the best estimate of long-term velocities for permanent continuous GPS stations with respect to station ID scms in San Clemente. As shown on Figure A-13, stations in the southern portion of the Peninsula Range crustal block (shown in purple) appear to show slight clockwise rotation about the scms reference station. It is noted that the velocity vectors are presented in an exaggerated scale (1 inch equals 15 mm/yr) for effect. The tension and compression caused by this block rotation would likely lead to the reactivation of some portions of the Oceanside detachment as thrust faults and some portions as normal faults. Some portions would likely remain inactive, making it kinematically incompatible with the postulated through-going, regional thrust model. Conversely, Late Quaternary inactivity of the OBT fault offshore of Carlsbad and La Jolla, as suggested by Sorlien et al. (2009b), is consistent with this block rotation model.

Similarly, a qualitative analysis of geodetic data was prepared with respect to San Clemente Island as previously shown in Figure A-3. The visual trend of the relative velocities presented on Figure A-3 is in strong agreement with the strike-slip end-member seismic source characterization model for the ICB Province. It is noted that the velocities are presented in a smaller scale than in the previous figure (1 inch equals 5 mm/yr), In a qualitative sense, no tension or compression is observed in the relative velocities between Santa Catalina or San Clemente Islands and the Peninsula Range as would be expected in the blind thrust end-member model. The geodetic data (velocities and uncertainties) presented on Figures A-3 and A-13 are based on the public archive preserved by the Scripps Orbit and Permanent Array Center (SOPAC) and includes all permanent continuous GPS stations installed in southern California between 1995 and 2008 with at least 1.5 years of data collected.

A5.0 DATA AND OBSERVATIONS SUPPORTING THE OBT AS THE PRIMARY FAULT SOURCE This section provides more detailed discussion of the available and relevant structural, geomorphology, paleoseismicity, seismology and GPS information that have been used to identify and characterize the OBT as the closest primary seismic source fault to SONGS. This summary is based primarily on Rivero (2004), Rivero and Shaw (2005), and Rivero and Shaw (2010, in press). Attachment A-3 presents Dr. John Shaw's and Dr. Andreas Plesch's assessment of the seismic source characteristics and current information concerning the OBT Fault based primarily on the work summarized in these publications.

Figures A-14 through A-27 present illustrations supporting the data and observations described in this section of Appendix A. This information forms the basis for the blind thrust seismic source characterization end-member model used in the 2010 PHSA.

The OBT model is based on recognition of an extensive offshore low-angle fault by previous workers (Fischer and Mills, 1991; Crouch and Suppe, 1993; Rivero et al., 2000; Rivero and Shaw, 2010, in press).

Rivero et al. (2000) first postulated that regional offshore thrust faults are primary, regional-scale active faults. These workers suggest that Mesozoic subduction zones (Phase 1) were reactivated as detachment surfaces during rotation of the Transverse Ranges in the Miocene (Phase 2), and that subsequent transpression in the Pliocene and Quaternary has resulted in structural inversion (Phase 3).

According to Rivero et al. (2000) the OBT forms a regionally continuous fault extending from Laguna Beach to at least the US-Mexican Border. Fault rupture scenarios by Rivero et al. (2000) suggest the G Pe. nt e c h December 2010 Page A-1I

SAN ONOFRE NUCLEAR GENERATING STATION SEISMIC HAZARD ASSESSMENT PROGRAM 2010 PROBABILISTIC SEISMIC HAZARD ANALYSIS REPORT potential to generate large (Mw 7.1-7.6) earthquakes that would control seismic hazards in the adjacent coastal area.

These regionally extensive blind thrusts are inferred to interact at depth coevally with displaced high angle, strike-slip or oblique-slip faults, such as the NI/RC Fault Zone and the other high-angle, strike-slip faults in the ICB, which are illustrated in Figure A-14. This blind thrust system model was further developed and described by Rivero (2004), Rivero and Shaw (2005), and Rivero and Shaw (2010, in press). Figure 2-2 in the main text provides a copy of the CFM developed by Plesch et al. (2007), which illustrates the OBT and TMBT fault sources included in this alternative seismic source model. These postulated blind thrust fault sources were addressed in UCERF 2 (WGCEP, 2008) as being considered for future deformation model development, but they are not in the current USGS source characterization model (USGS, 2009, PC).

Utilizing available seismic data Rivero and Shaw (2010, in press) and Shaw and Plesch (Attachment A-3) characterized the blind thrust fault sources (i.e., the OBT and TMBT) and associated hanging wall and footwall subsidiary faults. Possible structural scenarios that represent potential interactions between thesteeply-dipping strike-slip faults and the low-angle blind thrust fault sources are outlined'in Figure A3-2. Steeply-dipping, right-lateral strike-slip faults, such as the NI and RC, are incorporated into Rivero's (2004) blind thrust seismic source characterization model as highly segmented and offset faults under the argument that continuous, through-going, strike-slip faults, as primary fault sources are not kinematically compatible with the several km of shortening documented on the OBT Fault.

The key data and analyses that Rivero (2004), Rivero and Shaw (2005), and Rivero and Shaw (2010, in press) present in support of the OBT as a primary regional-scale active blind thrust are discussed in the following sections.

A5.1 Geometry and Structural Analysis A5.1.1 Geometry The geometry and style of faulting associated with the OBT are less well understood than for many other faults in southern California. Until recently, studies of blind faults and large oblique reverse faults in southern California focused primarily on the Transverse Ranges Province and the LA Basin where higher rates of contractional strain were expected. The work of Shaw and Suppe (1996) identified the Compton blind thrust as part of an active regional fault bend fold system in the western LA Basin. The OBT may be inferred to be an analog and possible extension of this system further to the southeast into the ICB Province. Although the offshore setting of the ICB Province poses challenges to the identification and characterization of blind thrust faults, the Oceanside detachment surface that is interpreted to be the OBT is clearly imaged in many offshore seismic reflection profiles.

The prominent reflector in the seismic data, now interpreted to be the OBT, originally was mapped by Western Geophysical Company (1972). Western Geophysical mapped a regional unconformity or disconformity at the top of acoustical basement, and mapped faults in 'cover sediments' offsetting upper Miocene strata above this surface (Figure A-7a). Subsequent studies described the. regional disconformity as an extensional breakaway detachment fault surface (Figure A-2a-d), and identified it throughout much of the ICB Province (e.g., Crouch and Suppe, 1993 and Bohannon and Geist, 1998). The exposed detachment surface became an erosional unconformity that was subsequently coyered by Miocene and younger sediments.

Ge o Pý.ent ech G December 2010 ,Page A-12

SAN ONOFRE NUCLEAR GENERATING STATION SEISMIC HAZARD ASSESSMENT PROGRAM 2010 PROBABILISTIC SEISMIC HAZARD ANALYSIS REPORT Rivero (2004) presents a detailed map (Figure 2-6) showing the locations of seismic profile data used to constrain the location and geometry of the OBT as developed by Rivero et al. (2000) and described by Rivero and Shaw (2005), and Rivero and Shaw (2010, in press). More than 10,000 km of industry seismic reflection profiles, well data, seismicity, and seafloor geologic maps were analyzed. The structural analysis employed kinematic and forward modeling techniques based on quantitative structural relationships between fold shape and fault geometry (Suppe, 1983; Suppe and Medwedeff, 1990; Mount et al., 1990; Erslev, 1991; and Almendinger, 1998). Advanced three-dimensional modeling techniques were used to generate full representations of fault surfaces and key stratigraphic markers.

The lateral extent and geometric segmentation of the active blind-thrust ramps were determined by mapping of direct fault plane reflections and associated fold trends throughout the basin areas covered by the seismic grid. The three-dimensional modeling also was used to quantify the distribution of dip slip on the active fault system, and to further constrain the geometrical analysis (Rivero, 2004).

The geometry of the two segments of the OBT as represented in the CFM (Plesch et al., 2007), which is used to characterize the OBT for this study, therefore, is based on a systematic and comprehensive analysis of offshore deep seismic reflection data.

The geometry of the OBT as mapped by Rivero and Shaw consists of two segments of differing sizes and dips. The OBT has been mapped over an area of more than 1800 km 2, and extends to the south beyond the mapped limits of the fault at the US-Mexican Border. The northern segment averages 14 degree dip, and the southern segment averages 25 degree dip (Rivero et al., 2000). The geometry Of the OBT is described in greater detail in Attachment A-3 and Rivero (2004).

A5.1.2 Structural Analysis Rivero (2004) presents a comprehensive structural analysis of faults in the ICB, focusing on the tectonic reactivation of the Oceanside and Thirtymile detachments as blind-thrust faults. As an outgrowth of the studies presented in Rivero et al. (2000), this analysis generated more precise three-dimensional representations of the faults and estimates of long-term slip rates. More advanced three-dimensional modeling techniques and fault-related fold theories were employed to identify and to describe active blind-thrust faulting and folding induced by thereactivation of the OBT and the TMBT in the Dana Point, Carlsbad and TMBT regions. Over 10,000 km of industry seismic reflection profiles, well data, seismicity, and geologic maps were used. Rivero (2004) performed kinematic and forward modeling structural analysis techniques based on quantitative structural relationships between fold shape and fault geometry. He also used advanced 3D modeling techniques to generate full representations of fault surfaces and key stratigraphic horizons, and provided evidence for present day strain partitioning produced by the interaction of the low-angle thrusts and vertical strike-slip faults (Figures A-16, A-18 through A-20, A-22, and A-26).

The structural analysis led Rivero and Shaw to postulate Pliocene and Quaternary oblique compression.

and structural reactivation processes as the originating mechanism of the regional blind-thrust fault system (Rivero and Shaw, 2010, in press). This reactivation generated regional structural wedges cored by faulted basement blocks that inverted sedimentary basins (Figures A-15 and A-16) in the hanging wall of the Miocene detachments (Rivero, 2004). The Miocene detachment break-away zone and Pliocene through Quaternary reactivated blind thrust, as well as emergent thrust faults such as the San Onofre Thrust, located in the hanging wall of the OBT, were mapped (Figures A-17 through A-20). From these results, earthquake scenarios based on the structural interaction of active blind-thrust faults and major S Geo Pentech December 2010 Page A-13I

SAN ONOFRE NUCLEAR GENERATING STATION SEISMIC HAZARD ASSESSMENT PROGRAM 2010 PROBABILISTIC SEISMIC HAZARD ANALYSIS! REPORT strike-slip faults were developed for the ICB Province (see discussion in Attachment A-3). By defining new long-term slip rates, Rivero (2004) concluded that simple and complex earthquake sources could produce large earthquakes (M 7.0 to M 7.6) with recurrence intervals from 970 to 1,810 years (Attachment A-3).

Rivero (2004) notes that it is not possible to directly measure the long-term amount of contractional slip on the OBT because it is generally blind. However, since the location of the OBT is constrained in the region, he used area balancing methods to constrain fault slip. He also evaluated alternative slip values derived from balanced structural interpretations located across several of the major contractional trends observed in the study area as an additional constraint. Excess-area balancing methods were modified.and used to invert for the amount of contractional slip consumed by the OBT (Figures'A-24 and A-25), since the spatial location and geometry (dip value) of this fault were assumed by Rivero 2004 to be well-known in the study region.

Balanced and restored cross sections based on available seismic data and well data suggest approximately 2.2 to 2.7 km of shortening across the OBT during the last 1.8 to 2.4 Ma (Rivero and Shaw, 2010, in press; Attachment A-3). This suggests an average slip rate of about 1 mm/yr oný the OBT, although shortening rate estimates vary significantly along strike (Figures A-24 and A-25).

A5.2 Evidence for Activity Blind thrusts by definition do not extend to the surface and thus cannot be observed directly. Secondary deformation related to folding and faulting in the hanging wall of the blind thrust is used to identify and characterize recent movement on such fault sources. The following two subsection's (4.2.1 Paleoseismicity and 4.2.2 Geomorphology) describe evidence and methods used to evaluate evidence for activity and provide constraints slip rates for the OBT and related structures.

A5.2.1 Paleoseismicity Fault trenching or other paleoseismic data are not available for the OBT. The offshore location of the near-surface projected traces of the main thrust and back thrusts mapped by Rivero (2004) precludes direct observation of the surface deformation that may be associated with these tectonic structures.

The Compton blind thrust, which is postulated to be an onshore equivalent of the OBT, may provide an analog to the OBT.

Leon et al. (2008) employed a multidisciplinary methodology that uses a combination of high-resolution seismic reflection profiles and borehole excavations to suggest a link between blind faulting on the Compton thrust at seismogenic depths directly to near-surface folding. They concluded from these studies that the Compton blind thrust fault is active and has generated at least six large-m'agnitude earthquakes (Mw 7.0 to 7.4) during the past 14,000 years that deformed the Holocene strata record.

Growth strata (discrete sequences that thicken sequentially across a series of buried fold scarps) are interpreted to be associated with uplift events on the underlying Compton thrust ramp.

Rivero et al. (2000) interpret the San Joaquin Hills Blind Thrust (SJHBT) as a backthrust to the OBT.

Rivero (2004) estimates that M 7.1 and M 7.3 events would occur on average every 1,070 to 1,430 and 1,480 to 1,960 years, respectively, on the OBT where the SJHBT is linked with the OBT. Grant et al.

(1999) also suggest that a backthrust that soles into the OBT is a viable structural model, although less preferred than one in which movement of the SJHB is the product of partitioned strike-slip and G.e o Pe,.n t eech December 2010 iPage A-14

SAN ONOFRE NUCLEAR GENERATING STATION SEISMIC HAZARD ASSESSMENT PROGRAM 2010 PROBABILISTIC SEISMIC HAZARD ANALYSIS REPORT compressive shortening across the NI/RC Fault Zone. They calculated average recurrence times of 1,650 to 3,100 years for moderate-magnitude earthquakes (based on an average uplift event of 1.3 m; Grant et al., 2002).

A5.2.2 Geomorphology Rivero et al. (2000) provides a viable structural model that explains the localized uplift of the San Joaquin Hills as a backthrust in the hanging wall of the OBT (Figure A-21). They interpret an offshore extension of this structure that is imaged in seismic data as forming above a shallow blind thrust ("Shelf Monocline Trend" on Figure A-21) with an average southwest dip value of 23 degrees. This shallow fault is restricted to the hanging wall of the OBT at depth, and they interpret that this shallow fault soles into the OBT forming a structuralwedge (Medwedeff, 1992; Mueller et al., 1998 and Rivero, 2004) (Figure A-21 and A-26). Quaternary uplift of the San Joaquin Hills as manifested by emergent marine terraces, therefore, is interpreted as evidence of Quaternary reactivation of the OBT (Figure A-23).

On a more regional scale, Rivero and Shaw suggest that emergent marine terraces along the entire coast between southern Orange County and northern Baja California show evidence for regional uplift of approximately 0.13 to 0.14 mm/yr (Kern and Rockwell, 1992), and may be the surface manifestation of Quaternary uplift in the hanging wall to the OBT (Rivero et al., 2000 and Rivero, 2004; Attachment A-3).

Seafloor fold and fault scarps associated with the OBT (Figures A-4b, A-16, A-18, A-19, and A-20) also suggest .recent contractional activity (Rivero et al., 2000 and Rivero, 2004). Structural inversion and associated reactivation of normal faults commonly produce broad regions of positive structural relief characterized by the development of broad anticlines located directly on top of extensional rollovers and syn-extensional stratigraphic wedges (Figure A-15). Rivero (2004) concludes that thrust motion on the OBT generated four prominent contractional fold trends. Three of these trends are foreland-directed structures, namely the San Mateo; the San Onofre and the Carlsbad trends (Figures A-17 through A-20). These active structures are characterized by thrust sheets that extend laterally for 10 to 20 km, and produce prominent fold and fault scarps on the sea floor. The fourth trend is characterized by hinterland thrusting, which is manifested in a laterally continuous monocline that controls the relief and bathymetric expression of the continental shelf. This monocline is interpreted to result from the interaction between a shallow west-dipping back thrust system and the deep-seated, east-dipping OBT.

Geomorphically, youthful seafloor scarps and folds above fault tiplines have been documented on multibeam bathymetry data and seismic reflection data. Growth folding and offset of Late Quaternary strata are locally apparent on the seismic records, documenting active seafloor uplift on the continental slope in the vicinity of the San Mateo, San Onofre, and Carlsbad faults (Sorlien et al., 2009b; Ryan et al.,

2009 and Rivero and Shaw, 2010, in press).

A5.2.3 Seismology Seismicity in the offshore region is generally diffuse and scattered as compared to more spatially correlated patterns associated with many strike-slip active faults in the Peninsular Ranges on the mainland (Astiz and Shearer, 2000). The focal mechanism of the 1986 ML 5.6 Oceanside event suggests that the main shock during that event had reverse motion (Hauksson and Jones, 1988). Most importantly, Astiz and Shearer (2000) document a shallow, east-dipping plane of seismicity at a depth of between 10 and 15 km beneath the continental slope and shelf west of San Diego based on relocation of G eP t e c h December 2010 PageA-15

SAN ONOFRE NUCLEAR GENERATING STATION SEISMIC HAZARD ASSESSMENT PROGRAM 2010 PROBABILISTIC SEISMIC HAZARD ANALYSIS REPORT 1981-1997 earthquakes (Figure A-27). The standard errors associated with these earthquake locations are less than 1.5 kni. Astiz and Shearer (2000) suggest that these focal mechanisms document the existence of an active, low-angle east-dipping fault in the Coronado Banks Region that may be part of a larger system of offshore thrust faults like the OBT. Rivero (2004) cites this low angle plane of seismicity as evidence for contractional activity on the OBT.

A5.2.4 GPS As previously noted, the geodetic data (velocities and uncertainties) presented on Figures A-3 and A-13 are based onthe public archive preserved by the Scripps Orbit and Permanent Array Center (SOPAC) and includes all permanent continuous GPS stations installed in southern California between 1995 and 2008 with at least 1.5 years of data collected. The GPS data collected to date generally does not support regional compression or extension normal to the postulated OBT. However, it is noted that the current status of geodetic data can be considered inconclusive due to the following:

• Data reduction has quantitative limitations due to the uncertainty caused by locking effects that are dependent upon the characterization of major strike-slip faults in the Continental Borderlands.

• Currently, GPS stations in the vicinity of SONGS are either located on what would be the locked part of the OBT where resolution of low postulated slip rates are within the uncertainty of the GPS measurements or they are located too close to the Elsinore Fault to show any gradient of shortening across the area in question.

" There are very few GPS stations in the vicinity of SONGS and even fewer in the offshore region of the Continental Borderlands; one continuous station exists on San Clemente Island and two on Catalina Island.

0 There are many sources with unknown slip-rates in the ICB Province making it difficult to resolve the low magnitude of slip postulated on either the OBT or the NI/RC Fault Zone system.

• ,G.eoP. en t ,h December 2010 !Page A-16

I

,4 ' '\Ii 0 20OMiles K Scale Approximate FAULT RECENCY CLASSIFICATION

-Faults that displace Holocene (- 10 ka) or latest Pleistocene (- 20 ka) deposits or geomorphic surfaces

- Faults that displace late Quaternary (- 780 ka) deposits or geomorphic surfaces

- Quaternary faults (1.8 Ma)

- Faults that displace pre-Qualemary deposits. Receny of last displacement for offshore faults generally not known.

Orly selected faults from Jennings (1992) are shown.

SCE (2001) QUATERNARY FAULT MAP FGR GeoPentech SAN ONOFRE NUCLEAR GENERATING STATION SEISMIC HAZARD ASSESSMENT PROGRAM

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G e o Pe n te c h SAN ONOFRE NUCLEAR GENERATING STATION I SEISMIC HAZARD ASSESSMENT PROGRAM

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derland, respectively; T-AF-Tosco-Arbreojos fault; MP-Magdelena plate; red areas-regions /

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CENOZOIC EVOLUTION OF THE lFIGURE

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lip ii'.

lip lip 114.lip T-PArote PLATIR k PAOCIC PLA75 76 Si-C 3V*

PACIC PAOM PLAYI PLAT.

200I I Usm A B 117. lip lip lie" C D Palinspastic maps of Cairia continental borderland and adjacent regions for past 20 m.y. Light gray areas are accretionary rocks of Franciscan Complex or belts that are litbologically similar to that complex. Medium gray areas we underlain by foreare strata. Dark gray areas are known outcrops of foreart strata. Area in wavy lined pattern is Catalina Schist belt White areas are floored by batholithlc basement rocks. Fine line is modem shordine and island configuration, shown deformed and displaced for reference in earlier models. Heavy ims are major faults that arethought to be active during time represented. Dashed doubleline is fanlt-bounded margin ofCatalina Schist belt. Dashed boxed line is active mar-gin of extending region within Catalina Schist belt Arrows show approximate trajectories of areas with respect to North Ameelca. (A) 20 Ma, time period prior to mest of the deformation. (B) 15 Ma; time period in migrating-hinge phase ofextension. (C) 5 Ma; time period in dispersed right-nor-mal-slip phase of extension. (D) Preset-day configuration.

Source: Bohannon and Geist (1 998)

LATE CENOZIC PALINSIPASTIC RECONSTRUCTION FIGURE MAPS OF THE CONTINENTAL BORDERLAND A-2c 0 GeoPentech

...... .... - SAN ONOFRE NUCLEAR GENERATING STATION SEISMIC HAZARD ASSESSMENT PROGRAM

Toc

\'\~SaI1 N 0

oJ.

'p p

itr SAN ONOFRE NUCLEAR GENERATING STATION SIMPLIFIED MAP OF CALIFORNIA o

1 G- e-1..... . .. . BORDERLAND PROVINCES WITH SEISMIC HAZARD ASSESSMENT PROGRAM ONSHORE AND OFFSHORE FAULT TRACES

4 p '19 P452 hs 4.

Legend SONGS Facility Location Fixed GPSStation

• Relative GPS Stations Relative Velocity Vector (Scale I* - 15 mm/yr)

"-* 95% Confidence Band NOTES:

1) c~mw Deb Rekd )SVApM0"edWW P.mA N A20 V*0 {SOPAC.2010) 20kp 40kr 6Gkrn 8Ok

,.,G eo P e-nt echK. SAN ONOFRE NUCLEAR GENERATING STATION GEODETIC DATA FIGURE SEISMIC HAZARD ASSESSMENT PROGRAM VELO CITY RELATIVE TO SCIP A-3

Releasing Bend/Step Over Primary High-Angle Pull-Apart Basin Right-Lateral Subsidiary Down-Dip Normal Faults & Synclines Strike Slip Fault I Primary High-Angle Right-Lateral Strike Slip Fault Restraining Bend/Step Over l Subsidiary Reverse Thrust Faults &Anticlines Clockwise Rotation of Block Results in Compression & Tension Modified from Moody and Hill (1956), Wilcox et al. (1973), and Harding (1973)

G Pe n t e c h SAN ONOFRE NUCLEAR GENERATING STATION FIGURE SEISMIC HAZARD ASSESSMENT PROGRAM I A-4a

POSITIVE SAN MATEO ANTICLINE / FLOWER OUTER THRUST-FOLD COMPLEX FOLD COMPLEX STRUCTURE A 'I 1L I I u5 t NI/RC FAULT ZONE NOTES. (1) Modified from Fischer and Mills (1991)

(2) Presented in SCE (2001)

Geo Pe n te c h G SAN ONOFRE NUCLEAR GENERATING STATION EXAMPLE OF A POSITIVE FIGURE a SEISMIC HAZARD ASSESSMENT PROGRAM FLOWER STRUCTURE A-4b

A7' 0

oamoI 3.

4)?

,- \ 0 nom

• - Dmwhiad *MdAuW (FAULT?RANE09MMnONTOPOF TOTA LPOW~S' I CR ZOKOMI EAK MO In-wI - raUawmA01U*uM A X ROANEWEL I No uA of Otmr fl HE ak CODREATA1N WELLS -

EXPLANA11OI Soutsai of ChwN HiDFault E.LOG

%-fntsma mdsdvlty LOwE WIVbRZWOI PIU tUppv fhpeu Fm.)

Source: Freeman et al. (1 992)

LONG BEACH OIL FIELD WELL MAPS AND LOGS FIGURE GeoPentech SAN ONOFRE NUCLEAR GENERATING STATION SEISMIC HAZARD ASSESSMENT PROGRAM

Modified from Pond (2010) eI3SAN GcoPct ONOFRE NUCLEAR GENERATING STATION I TUTUA OE WSESMIC HAZARDASSESSMENT PROGRAM OE OFTE N AL5NFCR ABAI AMAD3-TUTU KR A-6

L a.

FAULTING AND FOLDING OF COVER SEDIMENTS (OFFSHORE REGION)

(Western Geophysical, 1972) lit Faults offsetting Horizon B (Upper Miocene) from Western Geophysical (1972)

• Extensional Breakeway" from Rivero & Shaw (2001)

C3 Region ofactivefolding from Rlvero & Shoaw(2001)

-6 Ion NOTES: (1) Modified from Western Geophysical (1972) and Rivero and Shaw (2001)

(2) Presented in SCE (2001)

OFFSHORE FAULT AND FOLD MAP FIGURE BY WESTERN GEOPHYSICAL (1972) A-7a G~eoPentech SAN ONOFRE NUCLEAR GENERATING STATION SEISMIC HAZARD ASSESSMENT PROGRAM

i.-33 2i"'A IN 33 25V IOrsofze 33r I' o10 20 Kl~omgterv 0 5 10 mlbes JOULA NOTES: (1) Modified from Fischer and Mills (1991)

(2) Presented in SCE (2001)

FAULT AND FOLD MAP OF THE INNER CONINENTAL FIGURE Ge~nehBORDERLAND AND COASTAL REGION IA-7b GeoPentech

. . .SAN ONOFRE NUCLEAR GENERATING STATION SEISMIC HAZARD ASSESSMENT PROGRAM

0 11 7.33 W 0W 11 7.67 0 W 118.00 11 8.00°W 11 7.67°W 117.33°W 33.67°N 33.33ON 33.00 0 N 32.670 N OFFSHORE FAULT MAP BY RYAN ET AL. (2009) FIGURE IA7 GeoPentech

........... SAN ONOFRE NUCLEAR GENERATING STATION SEISMIC HAZARD ASSESSMENT PROGRAM

%gfll wells/cores

\ right-lateral fault S(oblique) thrust

.... *. Pre-Quaternary Quaternary parts

+ Oceanside thrust Newport Beach

. San Clemente SONGS 11 .. i I Ný4isuen Catalina Island Knoll Oceanside-,

not mapped \

not mapped l+ not mapped 1--

10 km OFFSHORE FAULT MAP BY SORLIEN ET AL (2009b) FIGURE IA7 GeoPentech

.. ....... SAN ONOFRE NUCLEAR GENERATING STATION SEISMIC HAZARD ASSESSMENT PROGRAM

OFFSHORE FAULT MAP BY CONRAD ET AL. (2010) FIGURE 0 GeoPentech I A-Te

.......... .SAN ONOFRE NUCLEAR GENERATING STATION SEISMIC HAZARD ASSESSMENT PROGRAM

-1 I

A SAN ONOFRE NUCLEAR GENERATING STATION QUATERNARY FAULT AND FOLD DATABASE SEISMIC HAZARD ASSESSMENT PROGRAM OFFSHORE FAULT MAP FROM USGS (2009)

'N

'N 33N W4 NOTE: Based on Rentz (2010)

SEISMIC LINE INTERPRETATIONS FIGURE IA8 GeoPentech

........... SAN ONOFRE NUCLEAR GENERATING STATION SEISMIC HAZARD ASSESSMENT PROGRAM

LINE DL10 0 15.

30.

Dep~th IN 45-60.

7S.

0 . 1. .-

SW If-is.

30, Depthm)45.

75 51 I~l LINE DL06 a SIN 15 30 Depth

" 45 do 75 Rm Sof 0 A NE!

7 75 is idKm .

LINE SC18 0 NW 006 OL9 at to Rml ou DO DO SE 15 30

-I'M ~ - I 75 NOW NOTES. (1) Based on Rentz (201 0)

(2) Locations of seismic lines shown In Figure 8a FIGURE SEISMIC LINE INTERPRETATIONS AIUb GeoPentechA-8b SAN ONOFRE NUCLEAR GENERATING STATION SEISMIC HAZARD ASSESSMENT PROGRAM

ibLiUk

-M' R1 Awof"AI tW um~i~

,uciwk£jl1aaS .1

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g. RatIO Sak.AI MY N1VO - wIaeno IRa fwoMO snUm MESA ~ ~ iw -_

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.... I ...

-~

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11%wllo.4R -IEAEe."C.WWWF4.110 r o q"A 1 Mp 01 . 0 a90" 1C w a 1$10w y k " o " &*t OFewd Osawe.Say9 mayow, M19 O~ o.

to¶

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A

..- RELICT BEACH RI)GE RELCT SEA CLFF FAULT 0

LOMA 13! NESTOR (118 LI)

14. BIRO ROCK (81 ka) 13 13 SOI.EDAO MOLCJYAN plýý14 14 c G  % '4%r l

, r SANIONOFRC S3UFf 13 NOTES: (1) Top is from Kern & Rockwell (1992); Bottom is from Lajoie et al. (1 992)

(2) Bottom Dresented in SCE (2001)

MAP OF MARINE TERRACES FIGURE SGeoPentechIA-SAN ONOFRE NUCLEAR GENERATING STATION SEISMIC HAZARD ASSESSMENT PROGRAM

Shelf Break

• eCorrelates to last glacial I1 maximum sea level low stand (-21-19 ka)

• Maintains uniform depth Modified from NOAA (2001, 2008), CSUMB (2010), and CaSIL (2006)

O P.e.n.ht,ech. I SAN ONOFRE NUCLEAR SEISMIC HAZARD GENERATING ASSESSMENT STATION PROGRAM MAP OF SHELF BREAK FIGURE A-10

33.8 ,,

33.6

-N W qb.

33.4 -C 33.2 _-.

0 10 km

-117.5 Source: Grant and Shearer (2004)

RELOCATED EPICENTERS FROM THE 1981 OCEANSIDE IFIGURE AND 2000 NEWPORT BEACH EARTHQUAKE CLUSTERSI A-1 Ia GeoPentech

... SAN ONOFRE NUCLEAR GENERATING STATION SEISMIC HAZARD ASSESSMENT PROGRAM

LOCATION A A A, 12.Or

-12.5 33.27 - E (D 1-

.4 a, A a.

4-j 13.0 33.26 - 0 0.5km I I I I I I 13.& * * *

• I 0.4 0.8

-117.52 -117.51 Distance (kin)

Longitude PLAN VIEW PROFILE VIEW LOCATION B B, 33.555 -

"(D a, B' 9' 0

33.550 9

_J 0 7[

33.545 0 0.5 km iiiiliiiil 11111 0.0 0.5 1.0 1.5

-117.870 -117.860 Distance (kin)

Longitude PLAN VIEW PROFILE VIEW NOTES: (1) Modified from Grant and Shearer (2004)

(2) Locations of "A" and "B"shown in Figure A-i1 a RELOCATED EPICENTERS FROM THE 1981 OCEANSIDE FIGURE AND 2000 NEWPORT BEACH EARTHQUAKE CLUSTERS IA-11 b Geoentch

..... tech.. SAN ONOFRE NUCLEAR GENERATING STATION SEISMIC HAZARD ASSESSMENT PROGRAM

NOTE: Based on Ryan (2010, personal communication)

RELOCATED EPICENTERS FROM THE FIGURE

~GeoPent_ eeh 1986 OCEANSIDE EARTHQUAKE SEQUENCE IA-1_2 SAN ONOFRE NUCLEAR GENERATING STATION SEISMIC HAZARD ASSESSMENT PROGRAM

IL

\

/ ',,~

.=\

478S Leigend Rotating

'*' SONGS Facility Location (From Ryan et al.,

'Ar Fixed GPS Statien

• Relative GPS Stations pow ..J.-

NOTES:

Relative Velocity Vector (Scale 1 - 5 mm/yr) 95% Confidence Band N

1) D.* I SVrivOrbh J PA S-e t Amr0 Cortte R*IWn Ve~ofiel (SOPAC.2010)

I 40km 60km 8k

__G e o P en t e c h SAN ONOFRE NUCLEAR GENERATING STATION GEODETIC DATA FIGURE

- e SEISMIC HAZARD ASSESSMENT PROGRAM VELOCITY RELATIVE TO SCMS A-13

33.00 N 32.5 0N 32.00 N 31.5 0 N SIMPLIFIED FAULT MAP FOR BAJA CALIFORNIA, FIGURE

__GeoPentech G PhMEXICO REGION BY RYAN ET AL. (2009) A-1 4

...... SAN ONOFRE NUCLEAR GENERATING STATION SEISMIC HAZARD ASSESSMENT PROGRAM

Post-riftSequence Syn-rift Sequence CrystallineBasement Conceptual model of basin inversion of a half-graben structure due to transpressional tectonics and wedging [modified after Bally, 1984]. (A) Development of the half-graben and associated roll-over structure by normal slip on an extensional detachment (B) Basin inversion phase characterized by development of a hanging-wall wedge and asymmetrical contractional folds due to the reactivation of the ex-tensional detachment.

Source: Rivero (2004)

SCHEMATIC DIAGRAM OF BASIN INVERSION FIGURE PROCESS AND EVOLUTION A-1 5

............ SAN ONOFRE NUCLEAR GENERATING STATION SEISMIC HAZARD ASSESSMENT PROGRAM

r-Zoe of Brod Codedroinel Fokikfg _S A

E

.2 NE Trend 0

B

_ -2"2

-Basament 1 km R

- -- 4 rollover panel E Top oPco Fm. ] Pliocene a) g syn-nft sequence 11I 1 Top Rperyto MNTop Fm.Fm I.j Minocene Monterrey .on 7 Ig* Top CatalinaSchist ] Mesozoic b) ]post-rift sequence i Seismic examples of basin inver-e son structures associated with activity of the Oceanside Thrust. (A) Half-graben reactiva-tion along a lateral ramp of the Oceanside Thrust. (B) Tip-fold structure developed by syn-contractional contractional reactivation of the Carlsbad fault, c) sequence which is located within the hanging wall block of the Oceanside Thrust. In both cases divergent termination of the seismic reflections within the Monterrey Fm. define the stratigraphic ex-Tpansion of the syn-rift sequence. Similarly, the inversion structure phase of basin inversion is well recorded by the contractional geometry, internal onlap term ina-tions, and general thinning of the syn-contractional Pico Fin. on the crest of the anticlines. Inset: Con-ceptual model of basin inversion after Bally [1984] and Letouzey [1990]. (a) Development of the exten-sional half-graben and associated rollover structure, (b) Period of quiescence and sedimentation of the post-rift sediments, (c) Reactivation of the normal fault with development of asymmetrical contractional fold. The model highlights the stratigraphic relationships between the three main tectonosequences char-acteristics of basin inversion. Location of the seismic lines is shown in Figure 3.5.

SEISMIC REFLECTION PROFILE INTERPRETATIONS OF FIGURE BASIN INVERSION STRUCTURES FROM RIVERO (2004) A-1 6

__ GeoPen~t~ech I SAN ONOFRE NUCLEAR GENERATING STATION SEISMIC HAZARD ASSESSMENT PROGRAM

118.00BW 117.75'W G eo Pen t e c h SAN ONOFRE NUCLEAR GENERATING STATION I SEISMIC HAZARD ASSESSMENT PROGRAM

- 0flIkW)

-1 I-

-2 I

P*~/.N Z.- o A-s. Tho.

- 0 f- h,-I

--k No-fw, k,~I~oo~o~~oI

• q~In.N-fo, m#o 5k.,

1-21 oo--

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ActIo SUbmadie FoklýTbnWSOl I-

-- 4 s.c*n .7 Pi7 Un*

If A L,.4.A..,.i 9;~ ____NB

.2 SAN ONOFRE NUCLEAR GENERATING STATION SEISMIC REFLECTION PROFILE AND INTERPRETATION a Gso !!A T jrch, OF THE SAN MATEO TREND FROM RIVERO (2004)

FIGURE SEISMIC HAZARD ASSESSMENT PROGRAM A-19

no T ~

F~d.TNE~ _ME

-1 X-. 0-r V-4 14"h- X-

- krmnd.l .iU -2 G c o P e ii t ec b SAN ONOFRE NUCLEAR GENERATING STATION SEISMICREFLECTION PROFILE ANDINTERPRETATION FIGURE

. .SEISMIC HAZARD ASSESSMENT PROGRAM OF THE CARLSBAD TRENDFROMRIVERO(2004) A-20

Diatrimarnic representatton of the main stcmrual elemem and trends observed alongtransecn X-X', Y-Y', and Z-Z. The rapresntation illustrate; the lateralcontlimdty of the offshore-dippieg mornocine. ad the role of the Oceanside thru as a regitonalbanaldetachment level. Theý diagram alsohighlights thecomplex arrangemnts of themodern contractional trends withint the activesubmarine fold-thrust belt. and thdecontrd induced by theMfiotne normal fault sysrenandthe propagptini stuctural wedge in their location. A common pitfall in smtrturalinterpretation Is also evident, the most important fold sttuessre in a profile do nor necessaily correlat acrossthe trends(Le:obseoned the transicion of the San Mateo andSanOnofre antdcines betweenproiles 2 and 3). Seve4r basement riderslocatedon top of the Oceanside thrust have been indetsli*d based on local saisoricexpresslen. Some geometries have been simplified for clarity. The presenc* of the Newport-lIglewoodstrike-slip fault is inferred as restricted to themonoceeinlocation on Plate 3. Some modem amounts of dexradmovenmet in the contractional trendsis compatible with the interpretation and cannot be completely ruled out.

Modified from Rivero(2004)

SGe aP e ntech SAN ONOFRE NUCLEAR GENERATING STATION 3D STRUCTURAL MAPOF FOLDINGANDTHRUSTING FIGURE

.. . k. SEISMIC HAZARD ASSESSMENT PROGRAM OFFSHORE SANONOFRE A-21

San Onofre Trend A - 0 (sea level)

-1

"-I 2

.___*NE B 0 (sea level) 2

- si--- i-,! ---

T)' -!

3 hi In 4

4 ERETop Repetto Fm.

MICE Top CapistranoFm MOM Top MonterreyFm lmm Top San Onofre Breccia SEISMIC REFLECTION PROFILE AND INTERPRETATION OF FIGURE SAN ONOFRE TREND FROM RIVERO (2004) 1A-22 Ge~nehTHE

• G ...... ech SAN ONOFRE NUCLEAR GENERATING STATION SEISMIC HAZARD ASSESSMENT PROGRAM

SantaAna River Fr San Joaquin Hills Blind-Thrust 6

El I',

Depth (km)

-2 -4 -6 Inner California Blind-Thrust System Source: Rivero (2004)

SCHEMATIC DIAGRAM RELATING THE INNER CALIFORNIA FIGURE 0 eoeteh BLIND THRUST SYSTEM To THE SAN JOAQUIN HILLS IA-2 3 SAN ONOFRE NUCLEAR GENERATING STATION SEISMIC HAZARD ASSESSMENT PROGRAM

Computed contractional slip on the Oceanside Thrust derived using the excess-area method discussed in Appendix B.

Dashed lines represent maximum and minimum values yielded by the method, when accounting for uncertainties on the geometrry of the Oceanside Thrust, and on the depth-conversion process. Fault slip measurements derived from balanced structural interpretations (Plates to 3, and Figure 3.1l), and slip estimates derived from GPS analysis [Kier and Mueller. 1999] are also shown.

CONTRACTIONAL FAULT Sup [imn] -vS- HomzorTAL DISTANCE [Kim]

ors NoJATaxvRNo Ts NORTHERN SOUTfWN 33.5e 30'-

20 .-

1.0-1.5 Figure II T -"

• Slip estimated from balanced crooss sections 05, + Slip estimated from GPS analysis 33.o" e[afr Kier and Muller, 1999 10 20 30 40 50 60 70 89 90 100 Horizontal Distance [Ian]

SEISMOGENIC AREAs Segment I: 1,242.0 cm2 Segment II: 1,921.3 Io2 Total Area (Segment I + II): 3,163.5 kni VARIABILITY OF CONTRACTIONAL SLIP G e o P e n t echh SAN ONOFRE NUCLEAR GENERATING STATION ALONG THE OBT FAULT LENGTH SEISMIC HAZARD ASSESSMENT PROGRAM FROM RIVERO (2004)

1.2

- -. since Venturian times (ca. 1.8 My) 1.1 -

- since Repettian times (ca. 2.4 My) 1.0-I 0.8-0.7- a 0.6 4.... -

0.5 'I 10 20 30 40 50 60 70 80 90 100 Horizontal Distance [kin]

G e oP e n t e c h SAN ONOFRE NUCLEAR GENERATING STATION PLOT OF MAXIMUM SUP RATES FIGURE 0-........--....-.............. SEISMIC HAZARD ASSESSMENT PROGRAM FOR THE OBT FROM RIVERO (2004) A-25

NE Monocline Trend Newport-Inglewood Fault (?)

Back-Thrust (multi-ramp geometry)

Ncrmal Newpcet-Ingmood Fault (7)

--- ] Late Miocene to Present

- Middle Miocene and older

=Mesozoic (Catalina Schist)

Source: Rivero (2004)

G e o P e n t e ch SAN ONOFRE NUCLEAR GENERATING STATION SCHEMATIC DIAGRAM SHOWING FIGURE SEISMIC HAZARD ASSESSMENT PROGRAM POSSIBLE OF ACTIVE STRUCTURAL CONFIGURATION OBT AND ACTIVE NI/RC FAULTS FIUR A-26

20

-20 0 20 E offset (kn")

4 A A, 0

0 0

0 0 0

• • 0*0'~1* i: *.

Dv.",.,

6.*

-to 0 10 SW- NEpro/le (kin)

Source: Astiz and Shearer (2000)

RELOCATED CORONADO BANK EPICENTERS FGR GeoPentec~hIA-7

...... en . SAN ONOFRE NUCLEAR GENERATING STATION SEISMIC HAZARD ASSESSMENT PROGRAM

SAN ONOFRE NUCLEAR GENERATING STATION SEISMIC HAZARD ASSESSMENT PROGRAM 2010 PROBABILISTIC SEISMIC HAZARD ANALYSIS REPORT APPENDIX A - ATTACHMENT A-1 ANNOTATED BIBLIOGRAPHIES INTRODUCTION The following references were considered in determining the weights for the end-member models discussed in Section 2.4. These references, in whole or in part, address the seismotectonic setting of southern California and the Continental Borderlands. Specifically, these authors offer information bearing on the structural, seismologic, paleoseismic, geomorphic, and/or geodetic character of the region. For convenience, the annotated bibliographies are subdivided into these same character categories.

ANNOTATED BIBLOGRAPHIES Moore, G.W., 1972, Offshore extension of the Rose Canyon fault, San Diego, California: US Geological Survey Professional Paper 800-C, C113-C116.

STRUCTURAL

" First suggested possible offshore extension of Holocene active traces of the Rose Canyon Fault Zone based on "a net of subbottom acoustic profiles spaced about 5 km apart." The survey completed by the USGS and Scripps Institution extending from La Jolla into Camp Pendleton (up to latitude 330 20').

" Pointed out that straight sections are relatively narrow (0.5 km wide) with wider reaches "as much as 2 km wide at curves."

" Indicated that "...Cretaceous and Tertiary sedimentary rocks that are generally nearly flat lyingbut dip moderately to steeply within and near the fault zone..."

" "The greatest local uplift lies adjacent to an S-shaped bend in the Rose Canyon fault..."

" "This uplift is believed to have resulted from compression there as a consequence of right-lateral strike-slip movement along the fault."

" Further stated that "Corey (1954) and the other previously cited investigations that extrapolated the Rose Canyon fault to the northwest connected it with the Newport-Inglewood fault zone, near which the 1933 Long Beach earthquake of magnitude 6.3 occurred. The offshore evidence of the present study agrees with such a projection, at least as far north as Camp Pendleton."

Ehlig, P.L., 1977, Geologic report on the area adjacent to the San Onofre Nuclear Generating Station northwestern San Diego County, CA, for Southern California Edison Company, 31 September 1977, 32 PP.

STRUCTURAL

• Marine terraces near SONGS "do not appear to be deformed or tilted."

GeoPentech December 2010 Page"A1-1

SAN ONOFRE NUCLEAR GENERATING STATION SEISMIC HAZARD ASSESSMENT PROGRAM 2010 PROBABILISTIC SEISMIC HAZARD ANALYSIS REPORT Hauksson, E., 1987, Seismotectonics of the Newport-lnglewood fault zone in the Los Angeles basin, southern California: Bulletin of the Seismological Society of America, v. 77, no. 2, p. 539-561.

SEISMOLOGY

• Shows focal mechanism solutions for 37 earthquakes along and near the onshore portion of the NI in Los Angeles and Orange Counties. Seventy-eight percent (78%) of these solutions are predominately strike-slip events; most of these are located along the main trace of the fault. The reverse or thrust events are mostly situated northeast or southwest of the main trace, most pronounced being along the Compton-Los Alamitos Fault to the northeast, but parallel to the trend of the of the NI.

Fischer, P.J. and Mills, G.I., 1991, The offshore Newport-lnglewood - Rose Canyon fault zone, California:

structure, segmentation and tectonics in Abbott, P.L., and Elliott, W.J., eds., Environmental Perils San Diego Region: San Diego, San Diego Association of Geologists, p. 17-36.

STRUCTURAL

" "We used new (1989) digitally processed seismic reflection data with an average spacing of 1.5 km, in conjunction with older digital data and a grid of closely spaced, high resolution analog profiles, to map the geology of the inner margin." Three major fault segments of the offshore NI/RC zone between Newport Beach and La Jolla and their geology are described

" Dana Point segment between Newport Beach and Las Pulgas Canyon is 43 km long, Oceanside segment between Las Pulgas Canyon and Encinitas is 32 km long, and Del Mar segment from Carlsbad to La Jolla is 34 km long.

" "Piercing points between Newport Beach and the correlative Cristianitos-San Onofre-Oceanside faults indicate that an average of 7 km of right-lateral displacement has occurred along the NIZ since early Pliocene time."

" "Between San Mateo Point and Oceanside, multiple thrust faults and thrust generated folds or fault-propagation folds were mapped along the slope of the inner margin, west of the NI-RC fault zone...They may be separated into an inner thrust fault-fold complex that is probably a part of the flower structure of the NIFZ, and an -outer thrust-fold complex. The inner thrust fault complex is located near mid-slope, about at the 500 m isobath while the outer thrust complex follows the base of the slope near the 700 m isobath."

" The main thrust fault of the inner thrust-fold complex is between 3 and 4 km beyond the she*,-bre~k and dips 20-30degrees east.

• "The main thrust of the outer thrust-fold complex trends southeast along the base of the slope of the inner margin. It is southwest-vergent and dips about 9 degrees east shoreward of the thrust ramp."

• "At this time, a most probable slip rate of 1 mm/yr for the NI-RC zone is suggested."

• "At this time, it appears that the most probable horizontal slip rate for the NI-RC zone is between 1.3 mm/yr and 2.1 mm/yr. If the Quaternary slip rates are emphasized the most probable modern (?) slip rate is between 0.8 and 1.3 mm/yr, or about 1 mm/yr."

• "The thrust faults along the inner margin are active, as is evidenced by their surficial topographic expression and the displacement of Quaternary reflectors."

G eo P e n t e eh December 2010 Page Al-2

SAN ONOFRE NUCLEAR GENERATING STATION SEISMIC HAZARD ASSESSMENT PROGRAM 2010 PROBABILISTIC SEISMIC HAZARD ANALYSIS REPORT

• "A potential seismic hazard,- that has not been considered along the inner margin south of Dana Point, is posed by the thrust faults mapped off San Mateo Point-San Onofre to Oceanside and possible south to Encinitas."

SEISMOLOGY

• "The focal mechanisms are in general agreement with right-lateral, strike-slip faulting along the northwest trending NI-RC zone."

Hauksson, E., and Gross, S., 1991, Source parameters of the 1933 Long Beach earthquake: Bulletin of the Seismological Society of America, v. 81, no. 1, p. 81-98.

STRUCTU RAL

" "The existence of a small normal component in the mechanism and in the geological cross sections suggests that the southwestern block of the Los Angeles basin is still subsiding."

" Recent data suggests that "most geological structures adjacent to the NIF are not secondary features resulting from wrench faulting (Wright,. 1990 [sic]) but are rather primary structures resulting from north-south compression of the basin (Hauksson, 1990)."

" "[A]bsence of a thrust component is consistent with the slip partitioning model of the seismotectonics of the Los Angeles basin by Hauksson (1990)."

" In the slip partitioning model by Hauksson (1990), "strike-slip faulting on vertical faults and thrust faults on gently dipping faults replace a system of oblique faulting...[t]he almost pure strike-slip mechanism of the 1933 earthquake and the pure thrust mechanism for the 1987 (ML=5. 9 ) Whittier Narrows earthquake are consistent with this slip partitioning model."

SEISMOLOGY

" Relocated 1933 (Mw 6.4) mainshock "showed right-lateral motion along the NIF [Newport-Inglewood Fault] with a small normal component."

" The "centroidal depth [of the mainshock] was 10+/-2 km."

" The "best fitting focal mechanism shows right-lateral strike-slip motion with a minor normal component."

" "Both the focal mechanism of the 1933 main shock and the spatial distribution of aftershocks indicate that the earthquake occurred on the NIF."

" Woodward-Clyde (1979) determined a different focal mechanism for the main shock based on first motion polarities and suggested the earthquake was not on the Newport-lnglewood Fault; this study by Hauksson is more accurate because it is based on fitting the whole teleseismic waveforms.

• The "rupture initiated near the Huntington Beach-Newport Beach City boundary and extended unilaterally to the northwest to a distance of 13 to 16 km."

• "[N]o reliable surface rupture was reported."

• "The main shock caused 85-120 cm of slip at depth."

GEOPMORPHOLOGY

• "[P]rominent surface expression [of the Newport-lnglewood Fault] may be a manifestation of the basement boundary rather than being primarily caused by the right-lateral offset,"

.G e o Fe nJ e c h December 2010 Page Al1-3

SAN ONOFRE NUCLEAR GENERATING STATION SEISMIC HAZARD ASSESSMENT PROGRAM 2010 PROBABILISTIC SEISMIC HAZARD ANALYSIS REPORT (i.e., metamorphic basement on the west juxtaposed against metaseds and volcanic on the east).

Legg, M.R., 1991, Developments in understanding the tectonic evolution of the California Continental Borderland: Special Publication no. 46, Society for Sedimentary Geology, p. 291-312.

STRUCTURAL

" "[T]ranspressional structure along the offshore NI fault zone and prominent northwest-trending thrust faults at the base of the continental slope west of Newport and San Juan Capistrano suggest northeast-southwest convergence in this area."

" Post-Miocene north-south/northeast-southwest shortening in northern Borderland, extension or transtension on inner Borderland faults from latitude of San Diego southward.

" Palos Verdes Hills Fault is "recognized to have significant thrust or oblique-dextral reverse slip components."

SEISMOLOGY

" "[S]hortening in northeastern Borderland is manifested by the numerous earthquakes with reverse-faulting mechanisms."

" "[T]hrust-fault earthquake mechanisms have been observed as far south as the northern

• end of the San Diego trough."

Wright, T.L., 1991, Structural geology and tectonic evolution of the Los Angeles basin, California in Biddle, K.T., ed., Active margin basins: American Association of Petroleum Geologists Memoir 52, p.35-134.

STRUCTURAL

" "The Newport-Inglewood fault zone (NIFZ) is the best known structural feature of the Los Angeles basin (Figure 7)."

" "The zone has long been considered a classical example of the development of en echelon folds and faults along a deep-seated-strike-slip fault...."

" Numerous examples are provided of the dominance of Pliocene and later strike slip displacements and the significant variations in their corresponding vertical displacements.

" "Harding concluded that the structures within the zone "may be taken as a unit and related dynamically to one type of deformation -wrenching."

" "There are dissenting views to this interpretation. Yeats (1973) found it satisfactory for the late Pliocene and Quaternary history of the Newport-lnglewood zone, but too simple for the late Miocene and early.Pliocene. It does not account for the fact that most of the more diversely oriented normal and reverse faults (except for Inglewood oil field) became inactive during the Pliocene whereas the en echelon right-lateral slip faults of the Newport-Inglewood zone continued to be active through the Pleistocene."

• "Each of the Neogene episodes has probably involved regional right-lateral simple shear, but along the NIFZ itself, total right-lateral slip since the middle Miocene has not exceeded 3km (Yeats, 1973) or about 1-2 mi. Evidence of this from the subsurface is compatible with the GeonPent eh December 2010 Page Al-4

SAN ONOFRE NUCLEAR GENERATING STATION SEISMIC HAZARD ASSESSMENT PROGRAM etmtof2010 PROBABILISTIC SEISMIC HAZARD ANALYSIS REPORT estimate of 0.5 mm/year during the past 5 m.y. (Guptill and Heath, 1981) and 0.4-0.8 mm/year (Bird and Rosenstock, 1984)."

• "Classic wrench-fault deformation, however, is not the primary cause of most of the anticlinal features along the NIFZ. In the preceding discussion we have seen that many of these structures do not conform to a pattern of en echelon folding, but are related to local basement geometry and perhaps to a wide zone of pervasive shear within the basement.

Along the southern NIFZ, the Long Beach, Seal Beach, and Huntington Beach (onshore) structures are block-edged force folds (Harding and Tuminas, 1988) forced along the middle to late Miocene block boundary. Offshore Huntington Beach has been constricted against the Offshore Newport ridge. Dominguez is a part of the El Segundo-Lawndale-Alondra fold trend, complicated by offset on the NIFZ. Inglewood (and perhaps Potero) formed in concert with uplift of the Las Cienegas block that buckled the sedimentary wedge against shallow basement of the western shelf (Wright, 1987d)."

" Although Hazenbush and Allen 1958 implied a 0.5mm/yr to 1.0mm/yr slip rate since mid-Miocene on the NIFZ in Huntington Beach, "detailed subsurface mapping of oil fields along the NIFZ has revealed a variety of structural patterns and histories, and many of these cannot easily be reconciled with a pure strike-slip origin."

" "Faults within the San Andreas transform system may utilize relict zones of crustal weakness formed during earlier terrane accretion."

" "In analyzing Pasadenan deformation, the flake-tectonics model is more appropriate than the fold-and-thrust-belt model, although both models incorporate aseismic detachment at midcrustal depths. The flake-tectonics model is valid for all phases of Neogene deformation, both transtensional and transpressive, in the Los Angeles region."

" "The transition between the strong compressive shortening of the Transverse Ranges and the moderate right slip of the Peninsular Ranges blocks occurs systematically across the Los Angeles basin. Those relationships... show contrasting structural styles on the two sides of the basin. The northeast flank is dominated by blind thrusts of the Transverse Ranges system that flatten with depth. The southwest flank features right-oblique faults of the Peninsular Ranges system that steepen into near-vertical zones of active seismicity.";

"Viewed south to north (GG' to AA'), these cross sections confirm the gradual change from extension at the southern end of the basin to compressive shortening at the northern end...."

" "Relative motion between crustal flakes may involve rifting and separation, transform movement, or collision and shortening, combinations of these, and superposition of several modes over time. Local structures are shaped not by regional stress fields embracing areas hundreds of miles across but by the interaction of adjacent tectonic flakes, creating basement blocks and sedimentary wedges that may differ significantly in their densities, ductilities, and thermal characteristics."; "In shaping local structure, the influence of these internal features of the shallow crust may be as important as the orientation of the stresses being applied."

" "In forming a structure, the shape of the mold counts for as much as how the hammer is swu ng."

" "All of those structures developed within a wide region of pervasive right slip associated with the evolving San Andreas transform zone. Nevertheless, strike-slip folding caused by displacement along an individual fault is not a dominant factor in the genesis of structures in the Los Angeles basin, though it may well have contributed to deformation along the Ge(onPent*eh December 2010 Page Al-5

SAN ONOFRE NUCLEAR GENERATING STATION SEISMIC HAZARD ASSESSMENT PROGRAM 2010 PROBABILISTIC SEISMIC HAZARD ANALYSIS REPORT northern NIFZ (Figure 9) and perhaps the deformation along the Santa Monica fault (by left slip). That mechanism and other classic patterns of fold and fault development have been nullified by the effects of preexisting basement blocks and sedimentary wedges."

Kern, J.P., and Rockwell, T.K., 1992, Chronology and deformation of Quaternary marine shorelines, San Diego County, California in Kern, J.P., and Rockwell, T.K., eds., Quaternary Coasts of the United States:

Marine and Lacustrine Systems, Special Publication no. 48, Society for Sedimentary Geology, 377-382.

STRUCTURAL

" Mapping of shorelines provides evidence for uniform uplift of the entire coastal zone in San Diego County (downtown San Diego to Oceanside) at a rate of 0.13 to 0.14 m/kyr during the Quaternary with exception of areas deformed locally by the Rose Canyon Fault Zone.

" Both higher and lower uplift rates are observed along the Rose Canyon Fault Zone, which is shown by its effects on shoreline configurations to have been active for at least the past million years.

" The average long-term uplift rate for the San Diego region is similar to those for other areas of coastal California that are dominated by strike-slip tectonics.

GEOPMORPHOLOGY

" Shoreline angle elevations are estimated for 16 shorelines estimated to range in age from 80 ka to perhaps as old as 1.29 Ma.

• Shoreline geometry is modified both by regional uplift and by extensive faulting in the right-slip wrench system of the Rose Canyon Fault Zone.

Rockwell, T.K., Lindvall, S.C., Haraden, C.C., Hirabayashi, C.K., and Baker, E., 1992, Minimum Holocene slip rate for the Rose Canyon fault in San Diego, California, in Heath, E.G., and Lewis, W.L., eds., The Regressive Pleistocene Shoreline Coastal Southern California: South Coast Geological Society, Inc., 1992 Annual field Trip Guide Book No. 20, p. 55-64.

STRUCTURAL

• "Rose Canyon fault appears to feed directly into the Newport-lnglewood fault zone to the northwest. Although the Coronado Bank fault may also feed slip into the Newport-Inglewood fault zone, the rate determined for the Rose Canyon fault in this study also provides a minimum slip rate for [the offshore NI/RC]."

PALEOSEISMOLOGY

" Rose Canyon Fault is Holocene active based on radiocarbon dates obtained from charcoal deposited stratigraphically below a tectonically offset channel.

" Authors demonstrate offset of channel is likely all or mostly tectonic with no or very minimal deflection.

• Minimum slip rate of the Rose Canyon Fault of -1 mm/yr is afforded from the trenching, presuming 8.7 m of brittle slip in ~8150 years.

SGeoPentech December 2010 Page Al -6

SAN ONOFRE NUCLEAR GENERATING STATION SEISMIC HAZARD ASSESSMENT PROGRAM 2010 PROBABILISTIC SEISMIC HAZARD ANALYSIS REPORT

• The "actual rate could be substantially higher if the age of the [tectonically offset] channel is as much as 1000 years younger than the age of [the radiocarbon date obtained from the charcoal]."

GEOPMORPHOLOGY

" Rose Canyon Fault is late Pleistocene active based on a 17-28 ka terrace riser offset 33-35 m.

" Maximum slip rate of the Rose Canyon Fault of -2 mm/yr is based on the maximum offset of the terrace riser (35 m) in the minimum amount of time (17 ka).

Crouch, J.K., and Suppe, J., 1993, Late Cenozoic tectonic evolution of the Los Angeles basin and Inner California Borderland: A model for core complex-like crustal extension: Geological Society of America Bulletin, v. 105, p. 1415-1434.

STRUCTURAL

" Propose large magnitude (>200 km) crustal extension formed LA Basin, Inner California Borderlands, and Southern California Borderlands in major late Cenozoic rifting.

" Several current right lateral strike slip structures originated as high-angle normal faults prior to Pliocene.

" "Faults such as the Newport-lnglewood and Whittier-Elsinore originated as high-angle, hanging-wall normal faults above detachments and hence, modern strike slip along these faults may end downward against the detachments."

" Image detachment fault over regional extent, from -San Clemente to Oceanside.

" From San Clement to Oceanside, "30-km-long fold and thrust belt underlies the continental slope seaward of the Newport-lnglewood fault zone."

" "[The] detachment fault has become reactivated in places and now accommodates northeast-southwest-directed contraction that has formed the overlying fold and thrust belt."

" "Crustal shortening, which began in Pliocene time, appears to still be active."

" "Thrust faults within this belt appear to be rooted into the former detachment, and crustal shortening has structurally inverted (uplifted and folded) a former sediment-filled trough situated along the Newport-Inglewood fault zone."

Bohannon, R.G., and Geist, E., 1998, Upper crustal structure and Neogene tectonic development of the California Continental Borderland: Geological Society of America Bulletin, v..110, n. 6, p. 779-800.

STRUCTURAL

" "The California continental borderland structural province offshore of the southwestern United States and northwestern Mexico is nearly as wide as the Basin and Range province, but it is less well known...."

" "[P]late interactions are generally thought to have caused the borderland deformation, but the specific history and style of tectonism has been debated."

" "Luyendyk et al. (1980) used paleomagnetic evidence to argue that the western Transverse Ranges had undergone 90*-105* of clockwise rotations, about vertical axes, mostly during middle to late Miocene time. Numerous way have been proposed to explain the clockwise GeoPentech December 2010 Page Al-7

SAN ONOFRE NUCLEAR GENERATING STATION SEISMIC HAZARD ASSESSMENT PROGRAM 2010 PROBABILISTIC SEISMIC HAZARD ANALYSIS REPORT rotation and most of these link the rotation with large amounts of strike slip in the adjacent nonrotated regions to the north and south."

" "The linked rotation-strike-slip models do not explain the most pronounced lithotectonic abnormality-the regional occurrence of the Catalina Schist that forms the basement of the inner continental borderland and the western part of the Los Angeles basin."

" Other authors have suggested "that the Catalina Schist was exposed, from an undetermined depth, through a process of tectonic unroofing in a large inner continental borderland rift that developed behind the clockwise-rotating beam of the western Transverse Ranges."

" "The Peninsular Ranges and Catalina Schist boundary has commonly been drawn at the near-vertical Newport-Inglewood and Rose Canyon fault system (e.g., Vedder, 1987).

However, Crouch and Suppe (1993) described the boundary as a detachment- fault surface that dips gently to the east in the subsurface north of Oceanside. They used industry seismic-reflection data to support their view. Our data corroborate the findings of Crouch and Suppe (1993) in that the Newport-lnglewood and Rose Canyon fault system is entirely within sedimentary rocks of the Peninsular Ranges belt on line 120 (Fig. 6), and we imaged a similar deeply buried, low-angle fault having an east dip at about the same depth and position as Crouch and Suppe's (1993) detachment fault. We think that the entire Peninsular Ranges-Catalina Schist boundary is along a low-angle detachment fault, which we call the Oceanside detachment fault."

" "The Oceanside detachment fault is defined in the seismic data by several aligned, high-amplitude reflections with gentle apparent east.... These project eastward to an indistinct east-dipping reflection beneath the shelf...and they project westward and upward, through a zone of discontinuous, short reflections, to a series of east-dipping reflections...beneath the western part of the gulf.... We locate the breakaway zone of the detachment fault at the inclined reflections beneath the western part of the gulf."

" "Numerous fault zones interrupt the coherency of the reflections that makes up the upper plate of the Oceanside detachment fault and some of these appear to disturb the sea floor."

" "The Newport-lnglewood zone is inclined steeply east and it penetrates the entire reflective sequence, including the sea floor. The fault may have a strong normal component of offset.

Most of the lesser steep faults appear either to merge downward with the detachment or they truncate at it. This could also be true of the Newport-Inglewood fault zone, although clear documentation is lacking in our data."

" "Between the Gulf of Santa Catalina and the San Clemente Island region, there are several small fault-bounded and internally faulted basins....Much of the fill is probably syntectonic....It is not possible to determine the age of the basin fill."

" "The San Clemente Island-Cortes Bank region is within the Nicolas forearc belt....Overall deformation within the Nicolas forearc belt is slight and most of the belt remains intact.

There are numerous small structural basins, filled with middle Miocene and younger strata, that are bounded by young faults with pronounced normal separations, and these indicate that the belt was deformed by an episode of extensional and possibly strike-slip tectonism."

" "The boundary between the Nicolas forearc and Catalina Schist belts is a prominent west-dipping fault...that has been called the East Santa Cruz basin fault."

"It is not possible to determine the magnitude and sense of slip from the seismic data, but the East Santa Cruz basin fault is assumed to have a large amount of right slip.... It probably also has incurred a large, but unknown, amount of normal displacement....The fault appears to break through to the surface...."

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SAN ONOFRE NUCLEAR GENERATING STATION SEISMIC HAZARD ASSESSMENT PROGRAM 2010 PROBABILISTIC SEISMIC HAZARD ANALYSIS REPORT

" "The East Santa Cruz basin fault may splay into a group of west-dipping faults on north and west flanks of Sixtymile Bank...and between the East Cortes basin and the Blake Knolls."

" "The boundary between the Nicolas forearc and western Transverse Ranges belts is just south of the northern Channel Islands....[C]ontinuous reflectors...end abruptly at a steep fault that penetrates the seismic section to all depths. We call this the Channel Island fault zone."

" "The extensional basins, which serve to define the borderland structural province, formed during Miocene to Pliocene time."

" "Many of the largest basin-bounding faults...might still be active."

" "Most of the large northwest-oriented, basin-bounding faults exhibit characteristics that are consistent with a strong strike-slip component in addition to the large vertical separations that can be documented....They have long and straight fault traces and commonly have opposing down-thrown sides along the same fault trace.....

" "We think that the Oceanside detachment fault...is the primary structure upon which the schist basement was uplifted relative to the Peninsular Ranges batholithic basement along the east side of the Catalina Schist belt."

• "We propose a two-stage model of upper crustal extension. The inner borderland rift formed during the early stage, beginning in early Miocene time when the western Transverse Range belt was oriented more or less north-south. The Catalina Schist was uplifted from middle crustal levels and exposed in the rift as the western Transverse Ranges began to rotate and the Nicolas forearc belt began to be displaced to the west. Most of the modern borderland physiography formed in the later stage, which began at the end of middle Miocene time. The later stage occurred in conjunction with the bulk of the rotation of the western Transverse Ranges. The later stage is primarily one of right-normal faulting in the borderland. Some parts of the borderland may still be in a right-normal slip regime."

• "[T]here has been approximately 100 km of extension across the part of the borderland...About 60 km of that extension took place during the early stage as the result of a migrating hinge of localized uplift and extension. About 40 km of extension occurred during the later stage as the result of distributed faulting on right-normal faults having northwest orientations."

• "We speculate that, after 15 Ma, the pattern of borderland deformation changed from localized extension (migrating hinge-flexural uplift model) to more distributed shear on rightOnormal slip on faults with north-northwest trends."

- "The Channel Island fault zone and the Santa Cruz Island and related faults, which also probably have curved traces...are viewed as left-slip zones that compensate for differences between the southwest end of the rotating western Transverse Ranges...."

SEISMOLOGY

• "Patterns of seismicity (Legg, 1985) suggest that...the San Clemente, Coronado Bank, San Diego Trough, and Palos Verdes Hills faults, may be active."

SGe o Pentech December 2010 Page Al-9

SAN ONOFRE NUCLEAR GENERATING STATION SEISMIC HAZARD ASSESSMENT PROGRAM 2010 PROBABILISTIC SEISMIC HAZARD ANALYSIS REPORT Kier, G., and Mueller, K., 1999, Flexural modeling of the northern Gulf of California Rift: relating marine terrace uplift to the forebulge on a subsiding plate: Southern California Earthquake Center 1999 internship final report, 11 pp., [1].

STRUCTU RAL

" "Therefore, shortening must occur between 0.89 and 2.39 m/ka to achieve between 14+/-0.03 and 0.25+/-0.03 m/ka vertical uplift on a fault dipping 6-9 degrees. Using standard vector analysis we rotated the coordinate axes of the regional velocity field to calculate the component normal to the strike of the Oceanside fault as shown in figure 1 (SCEC Data Center, 1999). We then compare the regional surface velocity normal to the fault to the velocity required for current terrace uplift rates. This shows that the current surface shortening is within the range that would generate current uplift patterns but relies on the assumption that velocities at depth are consistent with surface velocities. The northern and southern terminations of the Oceanside fault are at approximately the San Joaquin Hills and the U.S. Mexican border respectively (John Shaw, work in progress)."

" "Of the three models tested in this project, uplift due to forebulging on a subsiding plate provides the best fit model for the observed uplift of marine terraces."

Grant, L.B., Mueller, K.J., Gath, E.M., Cheng, H., Edwards, R.L., Munro, R., and Kennedy, G., 1999, Late Quaternary uplift and earthquake potential of the San Joaquin Hills, southern Los Angeles basin, California: Geology, v. 27, p. 1031-1034.

STRUCTURAL

" "Indications of late Quaternary folding are present in the San Joaquin Hills at the southern margin of the Los Angeles basin."

" "The San Joaquin Hills are the topographic expression of a northwest-trending anticlines between San Juan Capistrano and Huntington Mesa."

• "Uplift of the San Joaquin Hills began in the early Pleistocene."

• "Analysis of emergent marine terraces in the San Joaquin Hills...and 230Th dating of solitary corals from the lowest terraces reveal that the San Joaquin Hills have risen at a rate of 0.21-0.27 m/k.y. during the past 122 k.y."

• "The location and thickness of Holocene sediments in the San Joaquin Hills suggest that tectonic uplift continued during the middle to late Holocene."

• "[W]e do not have direct evidence for Holocene activity of the San Joaquin Hills thrust."

• "A fault-bend fold model with movement on a northwest-vergent thrust fault best explains the elevations of marine terraces....'

" "In [one] interpretation the San Joaquin Hills thrust is a backthrust that soles into the Oceanside detachment (Bohannon and Geist, 1998) as part of a wedge-thrust structure."

" "We prefer to interpret movement of the San Joaquin Hills blind thrust to be the product of partitioned strike slip and compressive shortening across the Newport-lnglewood fault zone."

G e o entech December 2010 Page Al-10

SAN ONOFRE NUCLEAR GENERATING STATION SEISMIC HAZARD ASSESSMENT PROGRAM 2010 PROBABILISTIC SEISMIC HAZARD ANALYSIS REPORT Bender, E.E., 2000, Late Quaternary uplift and earthquake potential of the San Joaquin Hills, southern Los Angeles basin, California - COMMENT: Geology, v. 28, no. 4, p. 383.

STRUCTURAL

" "Grant and et al. (1999) [sic] rather unequivocally demonstrated that the San Joaquin Hills...have risen at a rate of 0.021-0.027 mm/yr over the past 122 k.y. Based largely on geomorphic evidence, they attribute this uplift as a fault-bend fold above a southwest-dipping blind thrust fault."

" Flower structures "have been shown to exist along the Newport-lnglewood fault zone (Harding, 1979; Wright, 1991), and the extensive, nearly vertical faulting observed in the San Joaquin Hills is suggestive of such a structure extending off of the fault zone."

" "It appears more likely, on geologic grounds, to suggest that the uplift within the San Joaquin Hills is generated by squeezing upward along the Newport-lnglewood fault zone in shortening deformation accompanying northwest-southeast horizontal shear or transpression."

Grant, L.B., Mueller, KJ., Gath, E.M., and Munro, R., 2000, Late Quaternary uplift and earthquake potential of the San Joaquin Hills, southern Los Angeles basin, California - REPLY: Geology, v. 28, no. 4,

p. 384.

STRUCTURAL

" "Bender's conclusion that uplift within the San Joaquin Hills is generated by squeezing upward along the Newport-lnglewood fault zone by shortening that accompanies northwest-southeast horizontal shear (i.e., transpression) agrees with our statement that,

'We prefer to interpret movement of the San Joaquin Hills blind thrust to be the product of partitioned strike-slip and compressive shortening across the southern Newport-lnglewood fault zone,' (p. 1034, Grant et al., 1999)."

" "However, we disagree with Bender's assertion that the structure of the San Joaquin Hills and proximity to the Newport-lnglewood fault make a blind thrust model unattractive."

" The "San Andreas fault in central California [is described by Wilcox et al. (1973)] as an example of a wrench fault with a series of en echelon folds on the eastern side of the fault.

These folds (anticlines) are now known to be underlain by seismogenic blind thrust faults (Stein and Yeats, 1989; Stein and Ekstrom, 1992) created by transpressive strain partitioned across western California (Lettis and Hanson, 1991). A similar structural relationship probably exists between the Newport-lnglewood fault zone and the San Joaquin Hills."

" "Our data do provide strong evidence that the San Joaquin Hills are rising in response to a potentially seismogenic, underlying blind fault, and we suggest that this potential earthquake source should be included in regional seismic hazard models."

G eoPentech December 2010 Page Al-11

SAN ONOFRE NUCLEAR GENERATING STATION SEISMIC HAZARD ASSESSMENT PROGRAM 2010 PROBABILISTIC SEISMIC HAZARD ANALYSIS REPORT Astiz, L., and Shearer, P.M., 2000, Earthquake locations in the Inner Continental Borderland, offshore Southern California: Bulletin of the Seismological Society of America, v. 90, no. 2, p. 425-449.

STRUCTURAL

• Evidence in article forms the basis of several arguments regarding the location, geometry, and style of faulting in the offshore structural models.

SEISMOLOGY 0 "[F]ault geometries in this complex region [referring to offshore southern California] are often poorly constrained due to lack of surface observations and uncertainties in earthquake locations and focal mechanisms. To improve the accuracy of event locations in this area, we apply new location methods to 4312 offshore seismic events that occurred between 1981 and 1997 in seven different regions within the Borderland."

0 "Obtaining accurate locations for these events is difficult, due to the lack of nearby stations, the limited azimuthal coverage, and uncertainties in the velocity structure for this area."

0 "in general, our relocated events have small estimated relative location errors and the events are more clustered than the SCSN catalog locations"; "...under ideal conditions offshore events can be located to within I to 2 km of their true locations."

M "Our final locations for most clusters are well correlated with known local tectonic features."

2 "We can relate the 1981 Santa Barbara Island (ML =5.3) earthquake with the Santa Cruz fault, the 13 July 1986 Oceanside (ML = 5.3) sequence with the San Diego Trough fault zone, and events near San Clemente Island with known trace of the San Clemente fault zone."

0 "Our locations define a northeast-dipping fault plane for the Oceanside sequence, but in cross-section the events are scattered over a broad zone (about 4 km thick)....This could either be an expression of fault complexity or location errors due to unaccounted for variations in the velocity structure."

0 "104 Events recorded between 1981 and 1997 that occur near Coronado Bank in the SCSN catalog, are relocated closer to the San Diego coast and suggest a shallow-angle, northeast-dipping fault plane at 10 to 15 km depth."

• "We plot 65 events, those with standard errors less than 1.5 km.... Locations for events near the Coronado Bank region...occur at 10 to 15 km depth along an apparent northeast dipping fault close to the San Diego Coast."

E "It is possible that these faults are shallow-angle thrust or detachment faults seen in seismic reflection data...to mark the boundary between the Peninsular Ranges to the east and the Catalina Schist best to the west" 0 "If the Oceanside and/or Coronado events indeed occur on portions of a much larger system of offshore thrust faults, this would have important implications because it would establish that these faults are seismically active and a potential source of large future offshore events."

• GeoPe ntech December 2010 Page Al-12

SAN ONOFRE NUCLEAR GENERATING STATION SEISMIC HAZARD ASSESSMENT PROGRAM 2010 PROBABILISTIC SEISMIC HAZARD ANALYSIS REPORT Rivero, C., Shaw, J.H., and Mueller, K., 2000, Oceanside and Thirtymile Bank blind thrusts: implications for earthquake hazards in coastal southern California: Geology, v. 28, no. 10, p. 891-894.

STRUCTURAL

" Oblique convergent slip at depth may be partitioned separately onto NI/RC and OBT (model

" "San Joaquin Hills are formed by northeast-vergent anticline that uplifts and defines marine terraces... [offshore imaging confirms] it formed above a shallow blind thrust [dipping -23° southwest that is] restricted to the hangingwall of the [OBT]; at depth, we interpret that this shallow fault soles into the [OBT]."

SEISMOLOGY

• From seismology (i.e. 1986 Oceanside earthquakes), interpretation suggests Thirtymile Bank Thrust is through-going and not cut by San Diego Trough; if logic is extrapolated to OBT, then OBT is through-going and not cut by NI/RC Fault.

• "[R]elocated mainshock and aftershocks of [1986] Oceanside earthquake [are] clustered at

-8 km depth and [define] a 25-30° east-dipping surface" consistent with slip on Thirtymile Bank Thrust fault plane and an epicenter ~14-17 km east of San Diego Trough Fault.

GEOPMORPHOLOGY

• Imaged thrusts are "commonly associated with pronounced seafloor fold scarps."

GEODETIC

• Geodetic observations from Kier & Mueller (1999) indicate "as much as 2 mm/yr of NE-SW convergence between Catalina Island and the coast."

Ponti, D.J., 2001, Changing deformation rates through time: insights from new Quaternary stratigraphic studies in the Los Angeles basin, California [abstract]: American Geophysical Union 2001 Fall Meeting, 10-14 December 2001, abstract #S12E-11.

STRUCTURAL

" Geologically-derived fault slip and fold deformation rates may only be applicable when rate of deformation is constant over time.

" "[S]tratigraphic analysis of Quaternary deposits in [the LA Basin] show [the rate of] fold growth has not been constant during the last -1 Ma."

" "[C]onstant deformation should not be broadly presumed without specific supporting evidence."

December 2010 Page A1-13

• GeoPep~tec.~

GeoPentech December 2010 Page Al1-1 3

SAN ONOFRE NUCLEAR GENERATING STATION SEISMIC HAZARD ASSESSMENT PROGRAM 2010 PROBABILISTIC SEISMIC HAZARD ANALYSIS REPORT Rivero, C., and Shaw, J.H., 2001, 3D geometry and seismogenic potential of the Inner California Borderland blind thrusts system [abstract]: Southern California Earthquake Center Proceedings and Abstracts, 23-26 September 2001, p. 105-106.

STRUCTURAL

" "Inner Continental Borderland blind-thrust system includes a pair of inverted Miocene extensional detachments...reactivated as low-angle thrust faults during the Pliocene."

" "Thrust motions on these detachments produced several trends of contractional fault-related folds (e.g., San Mateo and Carlsbad structures) that partition oblique convergence with regional strike-slip systems."

SEISMOLOGY

• "Earthquake hypocenters...suggest that the Inner California blind thrust system is active and seismogenic."

Sliter, R.W., Ryan, H.F., and Normark, W.R., 2001, Does recent deformation at the base of slope provide evidence of a connection between the Newport-lnglewood and the Rose Canyon fault zones offshore southern California? [abstract], American Geophysical Union 2001 Fall Meeting, 10-14 December 2001, abstract #S11A-0531.

STRUCTU RAL

" Previous work by others suggests NIFZ and RCFZ connect along the continental shelf "with the main deformation occurring near the shelf edge."

" "[O]bserve sediments at the seafloor deformed near the base of the slope at water depths of about 700 m on [multichannel seismic reflection] data between Dana Point and Oceanside."

" Observe folding of seafloor between Oceanside and Carlsbad at 300 m depth.

" "[D]ata show recent faulting on the shelf (< 100 m water depth) associated with the Rose Canyon fault from Carlsbad to La Jolla."

" "[I]nterpret the base of the slope faulting to be related to a strand of the NIFZ...that may connect with the RCFZ by a left step near Carlsbad, as evidenced by recent folding of the seafloor."

Grant, L.B., and Rockwell, T.K., 2002, A northward propagating earthquake sequence in coastal southern California?: Seismological Research Letters, v. 73, no. 4, p. 461-469.

STRUCTURAL

" Faults within the Coastal Fault Zone (>300 km in length) "appear to be kinematical linked."

" "At a minimum, the Coastal Fault Zone extends from Beverly Hills, California (USA) southeast to the Punta Banda peninsula in Baja California (Mexico) and includes both [the] onshore and offshore...NIFZ (northern and southern segments), the offshore NIFZ, the Rose Canyon Fault, the Descanso strand of the offshore Coronado Bank Fault, and the Agua Blanca Fault."

" "The offshore NIFZ is a structurally complex zone of folds and faults."

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SAN ONOFRE NUCLEAR GENERATING STATION SEISMIC HAZARD ASSESSMENT PROGRAM 2010 PROBABILISTIC SEISMIC HAZARD ANALYSIS REPORT

" "Continuity of the offshore and southern NIFZ was debated. Several studies (e.g., Barrows, 1974; Fischer and Mills, 1991) have concluded that they are continuous or kinematically linked, and therefore the offshore NIFZ is assumed to be seismogenic."

" "An upper bound slip rate of 3.5 m/yr has been estimated (Fischer, 1992) based on total offset with an estimated age of2 Ma (Crouch and Bachman, 1989), but the Holocene slip rate is probably lower."

" "Fischer and Mills (1991) report a seismically active positive flower structure and thrust complex approximately 240 km long."

" "Several highOangle faults in the [San Joaquin Hills (SJH)] may be strands of the ancestral NIFZ (Bender, 2000) and show evidence of Quaternary surface rupture (Grant et al., 2000).

Based on measurements of late Quaternary and Holocene uplift, the SJH have been interpreted to be underlain by an active blind thrust fault (Grant et al., 1999, 2000, 2002).

Movement of the SJH blind fault may be kinematically linked to the NIFZ (Grant et al., 1999, 2000), the offshore Oceanside Fault (Rivero et al., 2000), or both."

SEISMOLOGY

" "Scattered seismicity occurs along the [NIFZ], although events are difficult to locate accurately due to poor station coverage."

" "The date of most recent rupture of the offshore NIFZ is not known [sic], although seismic-reflection observations and microseismicty indicate that it was during the Holocene."

" "Toppozada et al. (1981) estimated a M>6.5 [earthquake] and proposed a coastal or offshore location for the 1800 earthquake. If this interpretation is correct, the earthquake could have occurred on the offshore NIFZ."

" The onshore NIFZ northern and southern segments "have been seismically active during the historic period."

" "Despite relatively high historic levels of microseismicty, the northern NIFZ may be a seismic gap."

" "The recent seismicity suggest that the northern NIFZ might be in the latter stages of its seismic cycle."

PALEOSEISMOLOGY

" "[R]ecently published fault investigations in the northern Baja California peninsula (Mexico) and coastal southern California (USA) reveal evidence for geologically contemporaneous or sequential earthquakes along a >300-km-length, predominantly strike-slip seismic zone

[which] includes structures previously mapped as the Agua Blanca, Rose Canyon, San Joaquin Hills, and southern Newport-lnglewood Fault zones."

" "The historic and paleoseismic records indicate that the Coastal Fault Zone has ruptures from the Agua Blanca to the southern NIFZ within the last few centuries, with the possible exception of the northern NIFZ and portions of the offshore NIFZ."

" "Thedate of the last surface rupture of the northern NIFZ is not known."

" "[T]he paleoseismic data and historic observations suggest that the northern NIFZ has not ruptured as recently as other sections of the Coastal FaultZone."

GEODETIC

• "GPS measurements indicate that approximately 14% of the total Pacific-North America Plate motion occurs west of the Elsinore Fault, most likely distributed across the San GeoPentech .December 2010 Page Al1-15

SAN ONOFRE NUCLEAR GENERATING STATION SEISMIC HAZARD ASSESSMENT PROGRAM 2010 PROBABILISTIC SEISMIC HAZARD ANALYSIS REPORT Clemente, Newport-lnglewood, Rose Canyon, and other coastal or offshore faults (Bennett et al., 1996)."

OTHER

" "Seismic hazard associated with [the Coastal Fault Zone] has been recognized for decades...but is still poorly quantified...due, in part, to the difficulty of integrating observations onshore and offshore."

" "[T]he coastal faults have lower slip rates and longer recurrence intervals than many onshore faults and therefore are calculated to represent relatively low hazard... [h]owever, if we examine the entire zone, we find that it ruptured most recently in a temporal cluster or propagating sequence of large earthquakes. Therefore the hazard may be high if the sequence or cluster is still in progress."

• "The southern California coastal fault zone [sic] might be in the later stages of [a]

multicentury failure sequence."

Grant, L.B., Ballenger, L.J., and Runnerstrom, E.E., 2002, Coastal uplift of the San Joaquin Hills, southern Los Angeles basin, California, by a large earthquake since A.D. 1635: Bulletin of the Seismological Society of America, v. 92, no. 2, p. 590-599.

STRUCTURAL

• "The San Joaquin Hills...are the surficial expression of a faulted anticline parallel to the active Newport-lnglewood fault zone...."

• "Grant et al. (1999, 2000) proposed that uplift was generated by movement on an underlying blind thrust fault due to partitioned strike-slip and compressive shortening across the southern Newport-lnglewood fault zone."

" Study of marsh deposits in Newport Bay, "a late Pleistocene erosional gap between the northern San Joaquin Hills and Newport Mesa."

" Prior work by Stevenson (1954) suggested "the marsh bench was created by emergence of late Holocene marshland and subsequent death of the elevated marsh community.

Stevenson (1954) hypothesized that 'the greater height of the 'marsh bench' in the central area is probably the result of movement during Recent time of a major anticline and fault system which cut through the Bay in a NW-SE direction."'

" "The pattern of uplift reported by Stevenson (1954) is consistent with both the geomorphic expression of the San Joaquin Hills and the expected vertical displacement field that would be generated by coseismic growth of the San Joaquin Hills."

" "Our data agree with Stevenson's (1954) hypothesis that the marsh bench emerged due to tectonic uplift of the San Joaquin Hills."

" "The spatial pattern of emergent -shorelines and marsh deposits roughly mimics the topographic expression of the San Joaquin Hills and is consistent with a tectonic origin."

" "The marsh bench and coastal benches could not have formed solely by erosion or deposition due to a sea level highstand because the elevations are different at different locations and the average elevations are different on each side of Newport Bay and along the open coast. Therefore, the most plausible mechanism for creating both the marsh bench and coastal platforms is emergence by tectonic uplift."

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SAN ONOFRE NUCLEAR GENERATING STATION SEISMIC HAZARD ASSESSMENT PROGRAM 2010 PROBABILISTIC SEISMIC HAZARD ANALYSIS REPORT

" "The age of the marsh bench is constrained by radiocarbon dating.... Active marsh deposition and growth must have ceased on the marsh bench sometime after our samples were deposited."

" "Uplift of the San Joaquin Hills must have occurred after A.D. 1635, the earliest plausible age of the marsh bench."

" "Several fault models have been proposed to explain uplift and folding of the San Joaquin Hills. Grant et al. (1999) developed a model of a blind thrust fault dipping 30* to the southwest. Bender (2000) proposed that uplift is occurring in response to movement of the steeply dipping, strike-slip Newport-lnglewood fault system. Both types of faults may have contributed to uplift during the late Quaternary (Grant et al., 2000). A third model proposed by Rivero et al. (2000) attributes uplift to movement of a large regional thrust, the northeast-dipping Oceanside fault extending offshore of the San Joaquin Hills south to Oceanside and San Diego."

" "Several observations suggest that the San Joaquin Hills are underlain by a fault that is distinct from the NIFZ, although they may be linked kinematically."

• "Other topographically prominent anticlines, such as Signal Hill, are located within the structurally complex NIFZ and are associated with step-overs (Barrows, 1974). In contrast, the San Joaquin Hills anticline is east of the main NIFZ, and there is a releasing bend at the mouth of the Santa Ana River where the fault goes offshore (Morton and Miller, 1981) near the northern San Joaquin Hills."

SEISMOLOGY

" The 28 July 1769 historic earthquake is "a good candidate for the most recent earthquake that raised the San Joaquin Hills coastline."

" "Other candidates for the San Joaquin Hills earthquake occurred on 22 November 1800 and 10 July 1855."

" "There are no other documented earthquakes that could have generated more than 1 -m uplift of the San Joaquin Hills after 1855, so we conclude that uplift and the causative earthquake occurred between A.D. 1635 and 1855."

" "Based on out interpretations of the data, this region was more seismically active in the preinstrumental period."

GEOMORPHOLOGY

• "In the San Joaquin Hills, wave erosion and coastal processes have formed a suite of shore platforms extending from the modern shoreline up to an elevation of greater than 300 m above sea level, indicating late Quaternary tectonic uplift."

" "[T]here is common agreement that modern and ancient shorelines are geomorphic indicators of sea level relative to land."

" "Along the open coast of the San Joaquin Hills, the lower emergent platform and shoreline are a few meters above the lowest (modern) wave-cut platform and several meters below any previously mapped or dated shoreline.... Based on position between the modern shoreline and dated shorelines at higher elevation, the lower emergent shoreline should be younger than 83 ka (stage Sa sea level highstand).... Therefore, the lowest emergent platform and shoreline...are most likely Holocene age (stage 1 sea level highstand)."

" "Most emergent Holocene shorelines in tectonically active areas are less than 6000 yr old and reflect coseismic uplift rather than sea level fluctuation or large storms."

GeoPentech December 2010 Page A1-17

SAN ONOFRE NUCLEAR GENERATING STATION SEISMIC HAZARD ASSESSMENT PROGRAM 2010 PROBABILISTIC SEISMIC HAZARD ANALYSIS REPORT

" "Changes in pollen types, as well as sedimentation, reported from a core of San Joaquin Marsh (Davis, 1992) are consistent with an interpretation of latest Holocene tectonic uplift of the San Joaquin Hills. San Joaquin Marsh is currently a freshwater marsh located between the city of Irvine and upper Newport Bay.... Radiocarbon dates and analysis of pollen from core sediments show that San Joaquin marsh responded to changes in relative sea level during the Holocene (Davis, 1992). After approximately 4500 yr B.P., freshwater pollen types were replaced with salt marsh types as marsh flora responded to the Holocene sea level highstand (Davis, 1992). Freshwater conditions returned briefly circa 3800, 2800, 2300, and after 560 yr. B.P."

" A "possible explanation is that tectonic uplift of the San Joaquin Hills elevated San Joaquin Marsh above sea level, causing a return to freshwater conditions."

Grant, L.B., and Shearer, P.M., 2004, Activity of the offshore Newport-Inglewood Rose Canyon Fault Zone, coastal southern California, from relocated microseismicity: Bulletin of the Seismological Society of America, v. 94, no. 2, p. 747-752.

STRUCTURAL

• Structure of offshore NI/RC may be like onshore Newport-Inglewood Fault, with multiple strike-slip strands.

SEISMOLOGY

• Relocated two microearthquake clusters associated with offshore NI/RC: 1981 Oceanside cluster (19 events) and 2000 Newport Beach cluster (7 events).

• 1981 Oceanside cluster not associated with 1986 Oceanside earthquake sequence.

• The "events [in the 1981 Oceanside cluster] align along a north-northwest trend about 0.5 km long...[and] define a nearly vertical plane between 12.5 and 13.0 km depth" and are

'approximately parallel to the fault zone."

" The "strike, dip, and location of a plane fit by these events are consistent with active strike-slip faulting" on the offshore NI/RC Fault Zone.

• Composite waveform polarities "are consistent with a right-lateral strike-slip focal mechanism," but "cannot eliminate other possible focal mechanisms."

" "[F]ive of seven events [in the 2000 Newport Beach cluster] are aligned in a pattern consistent with a shallow (7 kin) north-northwest-striking, vertical or steeply dipping active fault," but polarities are too small for focal mechanism solutions.

" Overall, dataset too sparse to determine if there is (or is not) a through-going strike-slip fault zone.

" The "location and ~13 km depth of the Oceanside cluster suggests that the [OBT] is terminated by active strike-slip faults."

Geo Peo n tech December 2010 Page Al -18

SAN ONOFRE NUCLEAR GENERATING STATION SEISMIC HAZARD ASSESSMENT PROGRAM 2010 PROBABILISTIC SEISMIC HAZARD ANALYSIS REPORT Rivero, C.A., 2004, Origin of active blind-thrust faults in the southern Inner California Borderlands, unpublished Ph.D. Dissertation: Harvard University, 146 pp.

STRUCTURAL

• "Several of [the] contractional and extensional structures [offshore Dana Point] were previously interpreted as wrench-related thrusts and folds, and as 'flower structures' produced by active offshore segments of the Newport-Inglewood."

• "[I]nterpret most of the contractional trends sole into, and do not cross, the [OBT]."

• Complex faulting in basin inversions may be "prone to be confused with flower structure."

• "Shallow slip partitioning is the most likely description of the structural relationship between the Thirtymile Bank and San Diego Trough faults."

• "In many cases, seismic reflection data indicate previously interpreted strike-slip fault splays correspond with active hinges of contractional anticlines produced by...motion on a deep structural wedge."

• OBT Segment I (Dana Point to south of Carlsbad) slip rate 0.88-1.17 mm/yr; M 7.1 -4 return interval (RI) = 1070-1430 yrs; M 7.3 -4 RI = 1480-1960 yrs.

• OBT Segme~nt II (south of Carlsbad to south of San Diego) slip rate 0.70-0.94 mm/yf; M 7.3

-- RI = 1840-2470 yrs.

• OBT full length, M 7.5 -Rl-=2030-3390 yrs.

GEOPMORPHOLOGY

• "[L]ocal asymmetric anticlines with bathymetric expression, sitting on top of regional rollovers" are associated with mapped structures (proposed thrust systems).

" "Structural wedge system above the [OBT] shows a spatial correlation with the occurrence of Quaternary uplift in adjacent coastal areas," e.g. San Joaquin Hills, and marine terraces and strand lines along coastal Orange and San Diego Counties.

Rivero, C., and Shaw, J.H., 2005, Fault-related folding in reactivated offshore basins, California in Interpretations of Contractual Fault-Related Folds, An American Association of Petroleum Geologists Seismic Atlas, Studies in Geology, No. 53, Department of Earth and Planetary Sciences: Harvard University, Cambridge, MA, 3 pp.

STRUCTURAL

" "The San Mateo anticline developed by the upward propagation of reverse slip during the inversion of Miocene half-grabens."

• Oceanside detachment "is not folded by the contractional structures; thus we interpret that the San Mateo Anticline is formed by thrusting ramping up from this detachment surface."

" San Mateo ramp is also folded by a younger, deeper thrust.

" San Mateo thrust and underlying thrust "terminate in structural wedges...that propagate slip back to the hinterland...as no foreland structures that could account for the transfer of slip exist beyond the San Mateo anticline."

" "[I]nterpret the San Mateo Anticline as an imbricated fault-bend fold produced by the upward propagation of contractional slip from an inverted normal fault into multiple detachment levels."

GeoPentech December 2010 Page A1-19

SAN ONOFRE NUCLEAR GENERATING STATION SEISMIC HAZARD ASSESSMENT PROGRAM 2010 PROBABILISTIC SEISMIC HAZARD ANALYSIS REPORT

• "The back-limb geometry...indicates the presence of a deeper structure [that] refolds the shallow thrust sheet of the San Mateo Anticline in a way consistent with a break-forward system."

• Estimated total shortening offshore the San Clemente region is 2.5 km.

• "The San Mateo anticline is an imbricated fault-bend fold originated by basin inversion processes" along a thrust that "reactivated a segment of a northeast-dipping Miocene normal fault."

• "The phase of basin inversion also reactivated a Miocene low-angle detachment as the

[OBT]" and the OBT "transferred contractional slip to associated synthetic and antithetic normal structures, inverting a major graben-boundary fault, and generating a regional structural wedge [that] controls the location of a prominent monocline with bathymetric expression."

Legg, M.R., Goldfinger, C., Kamerling, M.J., Chaytor, J.D., and Einstein, D.E., 2007, Morphology, structure and evolution of California Continental Borderland restraining bends in Cunningham, W.D., and Mann, P., eds., Tectonics of Strike-Slip Restraining and Releasing Bends: Geological Society, London, Special Publications, 290, p. 143-168, doi: 10.1144/SP290.3.

STRUCTU RAL

" A "restraining bend exists where the fault curves or steps to the left when following the fault trace. Crowding of crustal material by lateral movement into the fault bend produces uplift and crustal thickening...."

" "Right-slip on irregular fault traces in the California Continental Borderland "has produced numerous restraining bend pop-ups that exhibit distinctive seafloor morphology."

" "The submarine basins of the Borderland range in depth from a few hundred metres to more than 2000 m...erosion is greatly diminished in these deep basins compared with subaerial regions, so that pop-up morphology is well preserved on the seafloor."

" "The San Clemente fault zone includes a 60-km-long restraining bend that exhibits prominent seafloor uplift in the 1300-m deep Descanso Plain offshore of northwest Baja California...."

• San Clemente Fault bed region minimum uplift rate is 0.47 to 0.70 m/ka.

• "The Catalina Fault forms an 80-km-long restraining double bend (cf. Crowell 1974) between the Santa Cruz-Catalina Ridge and San Diego Trough fault zones. Uplift due to oblique convergence along this transpressional fault has produced Santa Catalina Island and the wide submerged shelf and slope surrounding the island."

• Model for restraining bend evolution:

o "First, the strike of the principal displacement zone (PDZ) in the major restraining bends is parallel to the Miocene Pacific-North America (PAC-NOAM) relative motion vector(s)."

o "Second, the major faults within the restraining bend pop-up have very steep to vertical dips."

o "Third, the pop-up structures for the major restraining bends have structurally inverted Miocene basins."

o "Fourth, there is an overall right-stepping en echelon character to the major right-slip fault pattern of the Borderland."

G eoPent eh December 2010 Page Al-20 W ---,-`-.--, --- ,"I'll,

SAN ONOFRE NUCLEAR GENERATING STATION SEISMIC HAZARD ASSESSMENT PROGRAM 2010 PROBABILISTIC SEISMIC HAZARD ANALYSIS REPORT Campbell, B.A., Sorlien, C.C., Cormier, M., and Alward, W.S., 2009, Quaternary deformation related to 3D geometry of the Carlsbad fault, offshore San Clemente to San Diego [abstract], Southern California Earthquake Center Proceedings and Abstracts, 12-16 September 2009, v. 19, p. 263.

STRUCTURAL 0 Parts of Carlsbad-Coronado fault system coincide with the SCEC CFM OBT.

Mueller, K., Kier, G., Rockwell, T., and Jones, C.H., 2009, Quaternary rift flank uplift of the Peninsular Ranges in Baja and southern California by removal of mantle lithosphere: Tectonics, v. 28, TC5003, doi:10.1029/2007TC002227.

STRUCTURAL

" Presents argument for the model that the elevated terraces along the Pacific coast of northern Baja California and southern California are the result of the distal effect of "flexture of the elastic lithosphere driven largely by heating and thinning of the upper mantle beneath the Gulf of California (and the Salton Trough) and eastern Peninsular Ranges."

" "Pliocene strata deposited at sea level along the Pacific coastline in southern California have not been uplifted significantly above Quaternary marine terrace deposits."

Ponti, D.J., and Ehman, K.D., 2009, A 3-D sequence-based structural model for the Quaternary Los Angeles basin, California [abstract]: Southern California Earthquake Center Proceedings and Abstracts, 12-16 September 2009, vol. 19, p. 262-263.

STRUCTURAL

" "A 3-D sequence-based structural/stratigraphic model for the Los Angeles Basin is being developed by the USGS for use in earthquake hazards and groundwater resources research."

" "The Quaternary section reaches a maximum thickness of more than 1280 m in the Lynwood area east of the Newport-Inglewood (N-I) fault zone. In the west basin, the Quaternary section reaches its greatest thickness (>410 m) in San Pedro Bay just east of the Palos Verdes fault. Of the inter-basin structures that impact the Quaternary section, the Compton-Alamitos fault (Wright, 1991) is the most prominent. Discreet faulting of mid-late Pleistocene deposits and structural relief of up to 300 m is suggested by the seismic data and by anomalous water levels near Los Alamitos. West of the N-I fault, two W-NW-trending inter-basin faults offset mid-late Pleistocene sediments and may serve to consume slip from the N-I. The M4.7 Hawthorne earthquake of May 18, 2009 was located near the northernmost of these structures and has a fault-plane solution consistent with the geometry and kinematics of this fault as evidenced in the geology."

GeoPentech December 2010 Page AI-21

SAN ONOFRE NUCLEAR GENERATING STATION SEISMIC HAZARD ASSESSMENT PROGRAM 2010 PROBABILISTIC SEISMIC HAZARD ANALYSIS REPORT Ryan, H.F., Legg, M.R., Conrad, J.E., and Sliter, R.W., 2009, Recent faulting in the Gulf of Santa Catalina:

San Diego to Dana Point in Lee, H.J., and Normark, W.R., eds., Earth and Science in the Urban Ocean: The Southern California Continental Borderland: Geological Society of America Special Paper 454, p. 291-315, doi: 10.1130/2009.2454(4.5).

STRUCTURAL

" Where the Rose Canyon FZ "is imaged on industry MCS records, [it] forms a complex flower structure near the shelf break" (offshore Encinitas).

" "[M]ain strand of [offshore] Newport-lnglewood FZ forms a prominent positive flower structure" (offshore San Onofre).

" NI/RC bend/connection "is accommodated by reverse faulting...faulting dies off rapidly

[away from bend/connection], however folding continues [from] Carlsbad Canyon [to] near the left step [in] Newport-lnglewood FZ."

" "[I]ndustry seismic reflection profiles suggest the [OBT] might not be continuous," and it is "uncertain [whether OBT] offsets San Onofre FZ south of San Mateo Point."

" "[lack sufficient data] to determine whether or not [OBT] intersects and offsets Newport-Inglewood FZ."

• "[S]outh of La Jolla Fan Valley...little evidence for shortening associated with [OBT]."

• Of the main, through-going offshore faults, the "more northerly...tend to be transtensional and the more westerly [tend to be] transpressional."

• Key issue of San Mateo FZ and Carlsbad FZ: are these reverse faults "indicative of broad scale contraction...related to the reactivation of the Oceanside detachment as a blind thrust...or related to more localized complexities associated with slip partitioning along Newport-lnglewood FZ."

• "[U]plift of marine terraces along much of the coastline between Newport Beach and La Jolla provides possible evidence for the large-scale reactivation of the entire Oceanside detachment surface as a blind thrust"..."however, uplift of terraces could also be explained by transpression along Newport-lnglewood FZ."

"'[A]lthough a low-angle detachment surface is imaged...throughout much of the offshore Gulf of Santa Catalina, there is not unequivocal evidence that it has been reactivated as an uninterrupted active thrust fault."

Sorlien, C.C., Campbell, B.A., Alward, W.S., Seeber, L., Legg, M.R., and Cormier, M., 2009a, Transpression along strike-slip restraining segments vs. regional thrusting in the Inner California Continental Borderland [abstract]: Southern California Earthquake Center Proceedings and Abstracts, 12-16 September 2009, v. 19, p. 264.

STRUCTURAL

" The OBT "has little effect on the -2.5 Ma horizon above [it], and a regional anticline

• expected due to deeper blind thrust slip beneath the Gulf of Santa Catalina is lacking."

" "Significant Plio-Quaternary folding is only present where the [OBT] bends to merge with the Carlsbad fault."

" Carlsbad Fault is oblique-right reverse, "SW-verging thrust slip [on it] contributes to uplifting continental shelf...and San Joaquin Hills."

. Ge oPen tech December 2010 Page A1-22

SAN ONOFRE NUCLEAR GENERATING STATION SEISMIC HAZARD ASSESSMENT PROGRAM 2010 PROBABILISTIC SEISMIC HAZARD ANALYSIS REPORT Sorlien, C.C., Campbell, B.A., and Seeber, L., 2009b, Geometry, kinematics, and activity of a young mainland-dipping fold and thrust belt: Newport Beach to San Clemente, California, USDI/USGS Award No. 08HQGRO103 Final Technical Report, 25 pp.

STRUCTURAL

" "[R]ight lateral NI fault [is] part of a larger 3D system of oblique-right reverse faults."

" The central OBT does not deform early Quaternary seds and has "normal separation near

[the] base of [the] Pliocene horizon."

" Northwest OBT coincides with San Mateo/Carlsbad Fault; progressive tilting in hangingwall forelimb indicates subsidence; Newport Beach/Oceanside slope and shelf and San Joaquin Hills being uplifted on San Mateo/Carlsbad Fault.

" Southeast OBT coincides with Coronado Bank Fault, locally pure right lateral.

Conrad, J.E., Ryan, H.F., and Sliter, R.W., 2010, Tracing active faulting in the Inner Continental Borderland, Southern California, using new high-resolution seismic reflection and bathymetric data

[abstract]: Seismological Society of America 2010 Annual Meeting, Seismological Research Letters, v.81, no. 2, p. 347.

STRUCTURAL

" Based on recent high resolution. seismic and bathymetric surveys, the mapped traces of the Palos Verde, Coronado Bank, San Diego Trough, and San Pedro Faults have been significantly altered.

• Indicate that the-Avalon Knoll Fault also-shows evidence of recent offsets and "these faults are thought to accommodate about 5-8 mm/yr of slip .... but it is not clear how slip on these faults is distributed...."

Re-defined the Catalina Fault as inactive and report the Catalina Island is subsiding rather than rising.

• Presented the USGS's latest map of the NI/RC fault system, but do not discuss itspecifically.

• The key value is the more accurate map of the San Diego Trough Fault and correlating this more location and mapped configuration with its associated step-overs and the 1986 Oceanside earthquake (See Ryan, 2010, personal communication).

Ponti, D., 2010, personal communication.

STRUCTURAL

• Amplifying on Ponti, D.J. and Ehman, K.D. (2009), "At present, faults are highly simplified in the model; we have not accounted for every known structure in the basin, but instead have focused on modeling faults that have an apparent impact on groundwater flow... Vertical terminations of the faults have also not yet been tightly constrained."

SEISMOLOGY

• "The Charnock fault, originally proposed by Poland and others (1959) to explain groundwater anomalies within Pleistocene sediment, may in fact correspond with a more (G e o P.e n t e c h December 2010 Page A1-23

SAN ONOFRE NUCLEAR GENERATING STATION SEISMIC HAZARD ASSESSMENT PROGRAM 2010 PROBABILISTIC SEISMIC HAZARD ANALYSIS REPORT NW-trending structure identified by Wright (1991) that appears associated with a trend of seismicity evident in recent relocations. The M4.7 Inglewood earthquake of May.18, 2009 was located near the southern end of this seismicity tren(d) and has a fault-plane solution consistent with the geometry and kinematics of this fault as evident in the geology."

Rivero, C., and Shaw, J.H., 2010, in press, Active folding and blind-thrust faulting induced by basin inversion processes, Inner California Borderlands: Tectonics, submitted for consideration of publication 2010, 45 pp.

STRUCTURAL

" "We evaluate several different styles. of geometric and kinematic interactions between high-angle strike-slip faults and the low-angle detachments, and favor interpretations where deep oblique slip is partitioned at shallow crustal levels into thrusting and right-lateral strike-slip faulting. "

" "Restored and Balanced cross-sections provide a minimum SW-directed slip of 2.2-2.7 km on the Oceanside Thrust, and illustrate the role of this detachment in controlling the process of basin inversion and the development of the overlying fold-and-thrust belt."

• "Interpret observations to reflect a complex mixture of strike-slip and blind-thrust faulting in the Inner Borderlands that is similar to the style of deformation in the onshore LA basin."

• "Miocene low-angle normal (detachment) faults... that were reactivated by basin inversion processes initiated in the Late Pliocene, during the onset of the modern transpressional regime."

" "[N]ew geometric representations of the offshore Newport-Inglewood, Rose Canyon, and San Diego Trough fault zones...consistent with basin inversion processes and the presence of both active blind-thrust and strike-slip faults in the southern Inner California Borderlands."

" "[P]rovide insight into the subsurface geometries of complex zones where coeval active strike-slip and thrust faults interact. Both types of fault systems are deemed likely to be active, and should be considered in the context of regional earthquakei hazards assessment."

• "[M]otion on the Oceanside Thrust generated four prominent contractional fold trends.

Three of these are foreland-directed structures (San Mateo, San Onofre, andclCarlsbad Trends) that produce prominent fold scarps at the seafloor...suggesting Quaternary activity.

The fourth is a backthrust (hinterland-directed) system...manifested in a laterally continuous monocline that controls the relief and bathymetric expression of the shelf."

" "[C]ontractional and extensional structures represent local restraining and releasing bends along the offshore extension of the Rose Canyon strike-slip fault. At depth, the NI and RC strike-slip fault zones intersect with the Oceanside Thrust...at relatively shallow levels of-4km in the north and deeper -10 km in the south. Data are insufficient to uniquely define the manner in which these two fault systems interact. Scenarios where the two fault systems interact at depth in a manner consistent with their coeval activity are favored."

SEISMOLOGY

• "The Inner Borderlands do not display the apparent spatial correlation between EQ activity and regional strike-slip fault zones that is observed around the onshore region of the Peninsular Ranges...Seismicity in this area is diffuse and scattered."

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SAN ONOFRE NUCLEAR GENERATING STATION SEISMIC HAZARD ASSESSMENT PROGRAM 2010 PROBABILISTIC SEISMIC HAZARD ANALYSIS REPORT Rockwell, T., 2010, personal communication.

GEOPMORPHOLOGY

" 3-D trenching and "Paleoseismic work along the onshore Rose Canyon fault zone in the City of San Diego clearly demonstrates that the fault has sustained recurrent Holocene activity

" "Considering that the surface soil represents a long period of stability, it is not possible to simply space the timing of all six events equally for the past 9.3 ka. In fact, if the interpretation is correct that the surface soils represent at least 5 ka of development, then five of these events occurred as a cluster in the period between about 9.3 and 5 ka, with an average interval of recurrence of less than 1 ka."

" "If the fault principally behaves in a clustered seismicity mode, and if the five early Holocene events represent such a cluster, then one must consider the possibility that the recent earthquake of ca. AD 1650 represents a return to activity and is possibly the first in the next cluster of large earthquakes."

Rockwell, T.K., 2010, Appendix A, Attachment A-2, Seismic source characteristics of onshore Rose Canyon fault, for GeoPentech, Inc., 14 pp.

STRUCTURAL

" "Marine terraces on the southwest flank of the uplift (Kern, 1977; Kern and Rockwell, 1992),

along with the presence of the Linda Vista Formation marine terrace alluvium capping Mount Soledad, attest to the higher rate of uplift of the restraining bend area (0.25 mm/yr) relative to the surrounding coastal plain (0.13 mm/yr) (Kern and Rockwell, 1992), with the background regional uplift attributed to rift-flank uplift from extension in the Gulf (Mueller et.al., 2009)."

" The combination of the releasing step plus a change in fault strike make the Oceanside step a likely (northern) termination zone for ruptures, although a through-going rupture cannot be precluded."

" "However, the San Joaquin Hills may represent uplift associated with a step from the northern termination of the Rose Canyon to the Newport-lnglewood fault zone."

"If the Oceanside step-over is a barrier to rupture propagation, it would divide the Rose Canyon fault into two roughly similar-length sections: a 65 km segment from San Diego Bay to Oceanside, and a 55 km segment from Oceanside to the San Joaquin Hills...one cannot preclude rupture of the entire Rose Canyon fault for a distance of more than 100 km.

However, I consider this model a lower likelihood than rupture of individual segments and weight it a 25%, versus 75%f for the more segmented rupture behavior."

PALEOSEISMOLOGY The "most recent earthquake occurred sometime between AD 1523 and 1769. These 3-D trenching data further suggest that about 3 m of right lateral, strike-slip displacement occurred during this event, with a 1:10 ratio of vertical to horizontal displacement."

GeoPentech December 2010 Page Al-25

SAN ONOFRE NUCLEAR GENERATING STATION SEISMIC HAZARD ASSESSMENT PROGRAM 2010 PROBABILISTIC SEISMIC HAZARD ANALYSIS REPORT

" "In particular, the onshore data supports the argument that the high-angle, right-lateral, strike-slip as NI/RC Fault System is a primary seismic source fault whereas the nearby, shallow-dipping normal, oblique, and reverse faults are subsidiary."

" Paleoseismic data further suggest a termination zone near the San Joaquin Hills and "that the San Joaquin uplift is structurally tied to the coastal system of strike-slip faults."

GEOPMORPHOLOGY

" "The level of activity is indicated by both the relatively large lateral deflections of stream channels that are incised into low marine terraces (Figure A-4-4), and by the results of the three-dimensional trenching. These observations suggest a lateral ilip rate of about 2 mm/yr during the late Quaternary (Rockwell, 2010a)."

" "For the southern termination, the right-step between the Rose Canyon and Descanso faults forms the depression occupied by San Diego Bay (Figure A-4-1, and is likely large enough (>5 km) to arrest dynamic slip."

OTHER

• "... I suggest using the maximum slip rate range of 1.1 to 2.5 mm/yr, with the best:iestimate of 1.5-2.5 mm/yr, with the following weights: 0.5 (0% weight), 1.0 (10% weight), '1.5 (30%

weight), 2.0 (40% weight), 2.5 (20% weight), and 3.0 (0% weight)." In order to accommodate the possibility of clustering "I would suggest using the long-term rate (the above) with an 80% weight, and consider using an alternate weighting scheme for slip rate (in mm/yr) with a 20% overall weight as follows: 0.5 (0% weight), 1.0 (10% weight), 1.5 (30% weight), 2.0 (30% weight), 2.5 (20% weight), and 3.0 (10% weight)."

Ryan, H., 2010, personal communication.

STRUCTURAL

" Does not see OBT as single large structure, but rather small segments reactivated, possibly by block rotation and localized transpression in the San Diego Trough/Gulf of Santa Catalina region.

" San Diego Trough Fault connects in north with San Pedro Basin Fault, rather than Catalina Ridge.

" At the behest of the California Geological Survey, the extent of the OBT was mapped using industry MCS data available at the.USGS NAMSS web site. The.main OBT reflector is quite strong and well imaged off of San Mateo point (e.g., Crouch and Suppe, 1993). Following this prominent reflector on strike lines that extend along most of the Gulf of Catalina, it was not possible to tie the reflector to the OBT mapped south of the area around San Mateo Point. Hence, it is difficult to justify a pervasive areal extent of the OBT.

" High-resolution reflection profiles imaging folds within the hanging wall of the OBT show reflectors with increasing tilt with depth behind one of the prominent folds. Although this may indicate active folding/uplift, it is not possible to preclude the possibility!ithat the progressively tilted beds are from sediment waves, which are pervasive in the area, owing to the close proximity.of the San Mateo channel and fan system.

" Notes no evidence for Holocene connection between Coronado Banks Fault and Palos Verdes Fault, contrary to what is depicted in UCERF 2 and the CFM.

G oe P e n t e c-h December 2010 Page Al-26 lid

SAN ONOFRE NUCLEAR GENERATING STATION SEISMIC HAZARD ASSESSMENT PROGRAM 2010 PROBABILISTIC SEISMIC HAZARD ANALYSIS REPORT New USGS surveys planned for spring and summer of 2010.

SEISMOLOGY

• Comparison of the newly acquired map trace of the San Diego Trough Fault (as was currently being refined by Conrad, J.E.) with the Astiz and Shearer (2000) relocated epicenters of the 1986 Oceanside events indicates the earthquakes very clearly match a right step in the San Diego Trough Fault, which clearly explains the oblique thrust focal mechanisms in this earthquake sequence rather than the model presented in Rivero et al.

(2000) and Rivero (2004).

Shaw, J.H., and Plesch, A., 2010, Appendix A, Attachment A-3, Seismic source characteristics of Inner California Borderland's blind thrust fault systems, for GeoPentech, Inc., 15 pp.

STRUCTURAL

• 1986 Oceanside thrust earthquake and "extensive research of hundreds of proprietary oil industry marine geophysical seismic reflection survey lines, lead us to infer the presence of two distinct, active thrust fault systems located offshore of southern Orange County and San Diego County."

• The "OBT extends at least from Laguna Beach to the Mexican border and may dip under the shoreline."

• "The slip rate was estimated for the OBT based on measures of fault offsets and uplift using the marine geophysical seismic reflection survey data and estimates of the ages of the deformed geologic formations."

• "We recognize that others believe that right-lateral strike slip faults (model 1) dominate the tectonics off-shore of Orange and San Diego Counties. However, based on the currently available data, we would assign a weight of '0' to rupture model 1 [as it] is not kinematically compatible with the large amount of displacement we document on the OBT."

E "[I]t is unclear whether the shallow dipping thrust faults (such as the OBT) are primary seismic source faults, with the steeply dipping, right-lateral, strike-slip faults, such as the NI or RC faults, being subsidiary, or whether the steep, strike-slip faults are the primary seismic sources, and the thrust faults are subsidiary."

• "Association of the OBT and the San Joaquin Hills thrust, combined with the patterns of uplifted coastal marine terraces, further support fault activity."

Z "At the depths and locations where data is necessary to resolve the uncertainty...regarding the intersection between the NI/RC and the OBT, the faults are within the basement rocks and the velocity contrast/acoustic impedance of the basement rocks either side of where these faults are inferred to be interacting is not likely to be significant enough to produce adequate reflectors in the marine geophysical seismic reflection surveys."

a "[I]t is doubted whether high energy, deep penetrating 2-D or 3-D seismic surveys can retrieve the necessary data to be able to unequivocally resolve this particularly important uncertainty."

SEISMOLOGY G e. P e n t e ch December 2010 Page Al1-27

SAN ONOFRE NUCLEAR GENERATING STATION SEISMIC HAZARD ASSESSMENT PROGRAM 2010 PROBABILISTIC SEISMIC HAZARD ANALYSIS REPORT

"[R]everse/thrust focal mechanism solution tied to the offshore 1986 Oceanside (ML 5.3)

Earthquake demonstrated that active blind thrust faults also exist in Southern California's inner Continental Borderland."

GEODETIC

• Research and analysis considered "GPS data from the SCEC Crustal motion Map that Kier and Mueller (1999) used...our sense is that these geodetic data are poorly constrained....Thus, there is a large uncertainty with this rate deformation, but at present we simply lack another means to estimate this rate."

Wetmore, P.H., Malservisi, R., Fletcher, J., Alsleben, H., Callihan, S., Springer, A., and Gonz~lez-Yajimovich, 0., 2010, in review, Transtension within a restraining bend domain of a transform plate boundary: the role of block rotations and the reactivation of preexisting crustal structures: Geological Society of America Lithosphere, submitted for consideration of publication 2010, 17 pp.

STRUCTURAL

" "Given its structural context the ABF should be characterized by a significant component of contractional dip-slip motion. However, the ABF is uniquely characterized by nearly pure strike-slip displacements along the east-west trending eastern portion and an increasing normal component of dip-slip motion along western segments where its trend becomes more northwesterly."

" "The net effect is to connect regions of high extension in the Gulf of California with those in the northern Continental Borderlands."

" "However, the kinematics and distribution of faults that accommodate the plate motion exhibit profound along-strike variations and the margin can be separated into three distinct tectonic domains."

• "The Gulf of California forms the southern segment of the plate margin where a system of en echelon transform and spreading centers accommodate integrated transtensional shearing across a relatively narrow deformation belt along the axis of the gulf."

• "In the northern plate-boundary segment, most of the shearing is accommodated by the San Andreas Fault system. Dextral strike-slip faults in this domain are kinematically coordinated with folds and thrust faults to produce strongly transpressional shearing."

" In the central domain of the plate margin, shearing is marked by the"Big Bend" of the San Andreas Fault, which "[I]inks plate-margin shearing along coastal California with that in the Gulf of California. In many ways the central domain is a transitional region between the two radically different domains to the north and south. However is also has unique pattern of faulting that is distinct from the other two domains. Although thrust faults and folds are present throughout the northern half of the central domain (Zoback and Zoback, 1980; Bartley et al., 1993) horizontal contraction is largely accommodated by conjugate strike-slip faults."

" Major late Miocene normal faults form an important kinematic component of deformation in the southern half of the central domain, but extreme crustal thinning is partially compensated by north-south shortening associated with detachment folds and conjugate strike-slip faults.

G e oP en te c h December 2010 Page A1-28 W -1111111ý11- `--"-',----

SAN ONOFRE NUCLEAR GENERATING STATION SEISMIC HAZARD ASSESSMENT PROGRAM 2010 PROBABILISTIC SEISMIC HAZARD ANALYSIS REPORT APPENDIX A - ATTACHMENT A-2 SEISMIC SOURCE CHARACTERISTICS OF ONSHORE ROSE CANYON FAULT By Dr. Thomas Rockwell San Diego State University INTRODUCTION The following document has been prepared at the request of Southern California Edison (SCE) in consultation with technical members of their Seismic Hazard Assessment Program (SHAP).

The onshore traces of the Rose Canyon (RC) Fault Zone, as currently mapped through San Diego, are shown on Figure A2-1 (Rockwell, 2010a). The onshore evidence for the presence and recent activity of the Rose Canyon Fault Zone is abundant, with tectonic geomorphic expression of the active traces clearly evident in early aerial photography (Treiman, 1993; Lindvall and Rockwell, 1995, Rockwell, 2010a). As presented in Ro'ckwell (2010a), 3-D trench data suggest that the most recent earthquake on the fault that resulted in surface rupture occurred sometime between AD 1523 and 1769. These 3- D trenching data further suggest thatabout 3 m of right-lateral, strike-slip surface displacement occurred during this event, with a 1:10 ratio of vertical to horizontal displacement.

Although the evidence for onshore rupture of the RC fault is not specific to the fault traces offshore of SONGS, these onshore data are some of the only available to address the size and frequency of earthquakes that may be expected from the Newport-lnglewood-Rose Canyon (NI/RC) Fault System, and therefore supports its seismic source characteristics. In particular, the onshore data supports the argument that the high-angle, right-lateral, strike-slip N!/RC Fault System is a primaryseismic source fault whereas the nearby, shallow- dipping normal, oblique, and reverse faults are subsidiary.

The following sections of this appendix provide more information regarding:

1. How the onshore RC data supports the conclusion that the high-angle, right- lateral, strike-slip NI/RC Fault System is the primary seismic source fault, as Was concluded during the 1980s licensing of the plant, and as was recently incorporated into the preparation of the current version of the National Seismic Hazard Map (USGS, 2009);

2. Why these data are appropriate to use to define the current model of the NI/RC Fault System for incorporation into the update of the plant's Probabilistic Seismic Hazard Assessment, and the update of its deterministic tsunami assessment with a Probabilistic Tsunami Hazard Assessment; and

3. The identification of recommended future research that will further strengthen our understanding of the potential hazards associated with the NI/RC Fault System.

PRESENCE AND LEVEL OF ACTIVITY The active surface trace of the RC fault can clearly be mapped southward from the La Jolla coastline, up over Mount Soledad, down through Rose Canyon, across the San Diego River Valley, through Old Town San Diego and downtown San Diego, and across Coronado Island based on analysis of early aerial Ge o P e nt e c h G December 2010 Page A2-1 1W " ý11111`1`1-1`1- "11,1111-1

SAN ONOFRE NUCLEAR GENERATING STATION SEISMIC HAZARD ASSESSMENT PROGRAM 2010 PROBABILISTIC SEISMIC HAZARD ANALYSIS REPORT photography (Treiman, 1993, Lindvall and Rockwell, 1995, Rockwell, 2010a). The location of the fault is marked by the presence of scarps, deflected drainages, a sag and several pressure ridges, all of which attest to its recent activity (Figure A2-2). Most of these features also demonstrate that the faultbhas been repeatedly active throughout the late Quaternary with essentially the same kinematic motion. The traces beneath San Diego Bay have been imaged by shallow seismic techniques, where several strands of the fault clearly cut Holocene marine sediments (Kennedy and Clarke, 1996), also indicating that the Rose Canyon fault is young and active. Surprisingly, an early (Glover, 1876) artists rendition of Newtown (present day downtown San Diego) shows the trace of the fault as a scarp and several deflected drainages precisely where recent trenching has determined to be the main traces of the fault (see Figure A2-3), and supports the recency of displacement that has been demonstrated in the trenching studies (Lindvall and Rockwell, 1995; Rockwell, 2010a).

The linearity of the fault trace across hilly topography argues that the fault maintains a steep dip through much of San Diego, except in the Mount Soledad area, where the fault appears to dip to the southwest beneath the uplift. The fault strike in this area is also more westerly, consistent with a restraining bend geometry that has resulted in the uplift of the mount. Marine terraces on the, southwest flank of the uplift (Kern, 1977; Kern and Rockwell, 1992), along with the presence of the Linda Vista Formation marine terrace alluvium capping Mount Soledad, attest to the higher rate of uplift of the restraining bend area (0.25 mm/yr) relative to the surrounding coastal plain (0.13 mm/yr) (Kern and Rockwell, 1992), with the background regional uplift attributed to rift-flank uplift from extension in the Gulf (Mueller et al., 2009).

The level of late Quaternary fault activity is indicated by both the relatively large lateral deflections of stream channels that are incised into low marine terraces (Figure A2-4), and by the results of the three-dimensional trenching. These observations suggest a lateral slip rate of about 2 mm/yr during the late Quaternary (Rockwell, 2010a).

SEISMIC CHARACTERISTICS The expected length of a future rupture on the Rose Canyon fault may be limited by structural controls, such as steps, bends, and changes in strike that may be large enough to terminate dynamic rupture. For the southern termination, the right-step between the Rose Canyon and Descanso faults forms the depression occupied by San Diego Bay (Figure A2-1), and is likely large enough to arrest dynamic slip.

This step exceeds 5 km in step-over width (Figure A2-5), which is more than the largest releasing"step that has been ruptured through in historical, well-documented strike-slip earthquakes (Wesnousky, 2008). Based on this, the southern termination of future large earthquakes on the Rose Canyon fault is expected to be in San Diego Bay.

For the northern termination, there are several structural features that may play a role,.but none are as large as the step across San Diego Bay. The left bend in the Rose Canyon fault that facilitated the uplift of Mt. Soledad is only on the order of a couple kilometers in cross-fault dimension (Figure A2-5)' and many historical earthquakes have ruptured through bends and steps of such dimensions (Wesnousky, 2008) (cf. the 1968 Mw6.4 Borrego Mountain earthquake ruptured across the 1.5-2 km wide Ocotillo Badlands with less than a half meter of displacement, Clark, 1972). Thus, the Mt. Soledad bend and uplift is not likely to be large enough to define a rupture segment boundary, especially if the Rose Canyon fault has 3 m of displacement in Rose Creek. Furthermore, it is a continuous surface fault G e oP.e nPt~e c h December 2010 0Page A2-2

.5

SAN ONOFRE NUCLEAR GENERATING STATION SEISMIC HAZARD ASSESSMENT PROGRAM 2010 PROBABILISTIC SEISMIC HAZARD ANALYSIS REPORT through the region of this bend based on the geomorphology and extensive local trenching (Lindvall and Rockwell, 1995; Rockwell and Murbach, 1999).

Farther north, the Rose Canyon fault steps to the right (releasing step) near Oceanside, but the dimensions of the step are only on the order of 2-3 km or so (Figure A2-5). This can be a significant barrier to rupture in moderate earthquakes, but is less likely to stop a large dynamic displacement.

More significantly, however, the Rose Canyon fault has a more westerly strike to the northwest of this step, and the change in azimuth is on the order of 15 degrees from the average strike of the fault between Oceanside and San Diego Bay. The combination of the releasing step plus a change in fault strike make the Oceanside step a likely termination zone for ruptures, although a through-going rupture cannot be precluded.

The SONGS sits along the coast between Oceanside and the San Joaquin Hills uplift, and there are no major, obvious structural complexities that can be used to segment the Rose Canyon fault along this stretch. However, the San Joaquin Hills may represent uplift associated with a step from the northern termination of the Rose Canyon to the Newport- Inglewood fault zone. Grant et al. (2002) consider the uplift as the consequence of slip on a blind thrust, but likely structurally linked to the Newport-Inglewood fault zone (Grant et al., 1999, 2000). A closely related model is that the Rose Canyon fault bends northward and steps left across the hills to the Newport Inglewood fault, producing uplift by slip on the low-angle accommodation fault. An alternative model is that the San Joaquin uplift is related to a blind thrust system, the Oceanside thrust, that accommodates shortening in the Borderland (Rivero et al., 2000). In any case, the San Joaquin uplift is astructural complexity and may serve to segment the offshore zone of faulting.

An approach to shedding light on this problem, and to better constrain the likely sizes and termination zones for future earthquakes associated with the Rose Canyon and Newport-lnglewood faults, is to assess the current paleoseismic data in terms of whether they support co-seismic rupture of these faults together in the past. Grant and Rockwell (2002) documented the occurrence of a sequence of large earthquakes that ruptured the coastal zone of faults in the past few hundred years, but was pre-historical in age. This sequence involved the onshore Agua Blanca fault in northern Baja California, as well as the onshore Rose Canyon fault in San Diego and the San Joaquin Hills fault beneath Newport Bay, and was succeeded by the 1933 rupture of the Newport- Inglewood fault in Los Angeles Basin (Figure A2-6). Based on radiocarbon dating of the most recent earthquakes on these three faults, this sequence appears to have propagated northward, because rupture of the Agua Blanca fault is apparently the oldest of the events. In actuality, the dates of these three events all overlap to some degree, but there is the appearance that events to the north are younger than those to the south. Furthermore, it is unlikely that an earthquake ruptured both the Agua Blanca- Descanso and Rose Canyon faults simultaneously because of the large step-over at San Diego Bay. Combined with the occurrence of the 1933 event, which is clearly the youngest, the interpretation presented by Grant and Rockwell (2002) seems reasonable. Alternatively, as the most recent event on the Rose Canyon fault overlaps with the interpreted uplift of Newport Bay, it is possible that the entire Rose Canyon fault ruptured in a large earthquake just prior to the Mission period, and that the Newport Bay uplift is a consequence of this event. Because of the inherent problems in precise radiocarbon dating in this time period, this question may be difficult to resolve. Nevertheless, the occurrence of the sequence (or single event) supports the idea that the San Joaquin uplift is structurally tied to the co'astal system of strike-slip faults.

Ge o P e n t e c h December 2010 Page A2-3

SAN ONOFRE NUCLEAR GENERATING STATION SEISMIC HAZARD ASSESSMENT PROGRAM 2010 PROBABILISTIC SEISMIC HAZARD ANALYSIS REPORT There is a clearer difference in timing between Rose Canyon and onshore Newport- Inglewood fault ruptures (Figure A2-6; compiled from Grant et al., 1997; Grant and Rockwell, 2002; Leon, et al., 2009),

which argues against the likelihood of a very long rupture. Although the timing is similar, Grant and Rockwell argue that the pre-Mission sequence of ruptures represent multiple events, and likely propagated northward, culminating in the relative small M6.4 1933 Long Beach earthquake. It is noteworthy that the 1933 earthquake is not known to have ruptured the surface, and there were plenty of people around who should have noticed a significant rupture. Grant et al. (1997) use this observation to argue that the Holocene events identified for the Newport-lnglewood fault at Bolsa Chica likely represent larger earthquakes than that which occurred in 1933.

The pre-historic Newport-lnglewood and Compton-Los Alamitos events are nearly indistinguishable in timing (Figure A2-6), considering their large uncertainties. Nevertheless, they both have a similar return period for large earthquakes - those that can be identified by CPT and core correlation techniques, which implies that theyare larger than 1933. One could argue that the Compton Los Alamitos ahnd Newport- Inglewood faults ruptured together in the largest earthquakes, suggesting that they are kinematically linked. This may supportWright's (1991) interpretation of the Compton fault as a high angle oblique splay of the Newport-lnglewood fault. In any case, it is clear that the 1933 earthquake is smaller, and it was not associated with a large event on the Compton structure. Barrows (1974)1does, however, document that the area between the Los Alamitos and Newport-lnglewood faults was uplifted in the 1933 earthquake (Figure A2-7), again indicating a structural tie between these structures.i Rose Canyon fault has a very different paleoseismic record of past earthquakes than those faults to the north. The Rose Canyonfault experienced a cluster of events in the early Holocene, followed by a hiatus of several thousand years (Figures A2-6)(Rockwell, 2010a). Although one could argue that the mid-Holocene event documented at Bolsa Chica on the Newport-lnglewood.fault could correlate to one of the mid-Holocene Rose Canyon events, it is clear that the others do not, as there are no other recognized events during this cluster at Bolsa Chica. Unfortunately, the San Joaquin Hills record is too short (one event) to assess whether there is a correlation between Rose Canyon events and uplift at Newport Bay. Nevertheless, it appears that the Rose Canyon earthquake history is generally dissimilar to that of the Newport-Inglewood fault, which likely means that these faults do not typically rupture together.

In summary, the Rose Canyon fault is interpreted as a distinct seismic source that does not likely rupture with the Newport-lnglewood fault to the north, nor.the Agua Blanca-Descanso fault to the south. If the Oceanside step-over is a barrier to rupture propagation, it would divide the Rose Canyon fault into two roughly similar-length sections: a 65 km segment .from San Diego Bay to Oceanside, and a 55 km segment from Oceanside to the San Joaquin Hills. From the short paleoseismic record at Newport Bay, it is not possible to test long-term patterns of recurrence between these two segments. Further, due to the overlap in ages between the most recent ruptures inferred for these two segments (assuming the Newport Bay uplift is associated with a northern Rose Canyon rupture that involved the SanJoaquin Hills), one cannot preclude rupture of the entire Rose Canyon fault for a distance of more than 100 km.

However, I consider this model a lower likelihood than rupture of individual segments and weight it at 25%, versus 75% for the more segmented rupturebehavior.

For PSHA and PTHA seismic source characterization model, I suggest using the maximum slip rate range of 1.1 to 2.5 mm/yr, with the best estimate of 1.5-2.5 mm/yr, with the following weights:

0.5 (0% weight)

G e o Pe n tech December 2010 ýPage A2-4

SAN ONOFRE NUCLEAR GENERATING STATION SEISMIC HAZARD ASSESSMENT PROGRAM 2010 PROBABILISTIC SEISMIC HAZARD ANALYSIS REPORT 1.0 (10% weight) 1.5 (30% weight) 2.0 (40% weight) 2.5 (20% weight) 3.0 (0% weight)

For calculations that involve lapse time sincethe most recent event (time-based probabilities), you may want to consider that the Rose Canyon fault apparently behaves in a clustered mode, where the time between events within a cluster is shorter than the average long-term recurrence interval. This can be viewed, in effect, as variations in short term slip rate, with the period between about 10-5 ka having a higher rate than the long term average (Figure A2-8), the rate from 5-0.5 ka being essentially zero, and the current rate somewhat uncertain. Considering that the fault experienced a recent large earthquake after several thousand years of quiecence, and if it is reasonable to assume that we have entered another cluster which reflects a short-term increase in slip rate, then it follows that the time to the next event will be shorter than that inferred from the long-term average. Rockwell (2010a) inferred the intra-cluster recurrence interval to be less than 1 ka, with five events between 9.3 and 5 ka. This yields a recurrence interval of about 900 years within that cluster. If each event was'as large as the most recent event, about 3 m, this would suggest a slip rate of more than 3 mm/yr for this interval. Considering that short and long-term fault behavior of faults is somewhat enigmatic and a current topic of debate within the scientific community (see Rockwell, 2010b), I would suggest using the long-term rate with an 80%

weight, and consider using an alternative weighting scheme for slip rate (in mm/yr) with a 20% overall weight as follows:

0.5 (0% weight) 1.0 (10% weight) 1.5 (30% weight) 2.0 (30% weight) 2.5 (20% weight) 3.0 (10% weight)

KEY REMAINING UNCERTAINTIES There are two key uncertainties that need to be resolved. For understanding the short and long-term pattern of earthquakes on the Rose Canyon fault, and their implications for future activity, it is critical to test the cluster model of Rockwell (2010a) by resolving whether there were any surface ruptures between about 5 and 0.5 ka. There was no deposition at the Rose Creek site during this period, and the inference of no ruptures is based on the strength of a soil that is developed across the earlier Holocene fault strands (Rockwell, 2010a), so it is possible that an event was missed or not well-recorded.

Paleoseismic investigations in mid-late Holocene sediments across the Rose Canyon fault could resolve G eeoPentech December 2010 Page A2-5

SAN ONOFRE NUCLEAR GENERATING STATION SEISMIC HAZARD ASSESSMENT PROGRAM 2010 PROBABILISTIC SEISMIC HAZARD ANALYSIS REPORT whether other events may have occurred, as well as potentially determine their amount of displacement. This may affect our perception of recurrence and earthquake magnitude along the Rose Canyon Fault.

The other remaining major question relates to the nature of the inferred shortening deformation suggested by Rivero et al. (2000) in the offshore region, and its relationship to the Rose Canyon fault.

Geodetic observations clearly see significant right-lateral shear between San Clemente Island and Monument Peak, but there is no observable shortening or extension (figure A2-9). In fact, the right-lateral nature of theAgua Blanca fault in Baja California, along with its westerly strike, could be interpreted that there should be a small amount of continuing extension in the Borderland region (Wetmore et al., 2010 in review). Therefore, the cause of the apparent folding in the offshore Inner Borderland Region (Rivero et al., 2000) remains open to interpretation.

There are other areas where similar patterns of deformation have been observed, and it may prove valuable to assess these areas in terms of their overall structural style and seismic potential. One area that appears to have slip partitioned between strike-slip and convergence is in central California. In this area, the San Andreas fault (at 35 mm/yr) is the undisputed dominant seismic source, both in terms of magnitude and frequency. Nevertheless, a small component of shortening, estimated at no more than 3 mm/yr from geodetic data, is partly expressed as a series of folds and blind thrust faults to the east of the San Andreas fault (Coalinga anticline, Kettleman Hills, etc.: Yerkes, 1990, Wentworth, 1990)i In this case, these secondary seismic sources are clearly seismically active, having produced several earthquakes in the M5.5- M6.5 range during the instrumental period, but~are subordinate to the San Andreas fault. However, in comparison to the Inner Borderland, the central California example is clearly different because 1) there are clearly-defined folds that overlieblind thrusts; 2) these folds have significant structural relief and fold Holocene terraces; 3) there is a clear geodetic signal to the shortening; 4) there are earthquakes with thrust mechanisms clearly associated with these structures.

In the Inner Borderland Region, the association is not nearly as clear. There is a Miocene detachment surface, above which there has apparently been some folding (Rivero et al., 2000). However, there is no recognizable geodetic signal of shortening, nor is the seismicity clearly associated with this inferred detachment surface. An analogous situation is present in the western Salton Trough along the southern San Jacinto fault zone.

The West Salton Detachment-SanJacinto Example: The West Salton Detachment underlies much of the western Salton Trough east of the Peninsular Ranges from Borrego Valley and to the South to the Mexican Border (Axen and Fletcher, 1998). In this area, the high-angle, right-lateral San Jacinto fault cuts and offsets the West Salton Detachment and is clearly the dominant structure. Of note is the ubiquitous presence of extensive folding in the Borrego Badlands, San Filipe Hills, and Fish Creek Badlands, .all of it post-detachment in age and all of it related to the continuing development of the southern San!iJacinto fault zone (Dorsey and Janecke, 2002; Lutz et al., 2006).

There are many similarities between the western Salton Trough and the Inner Borderland Region. First, there is young folding above the Miocene-Pliocene detachment system, with the folding in the western Salton Trough being of substantially greater magnitude and significance than the folding in the offshore region. Furthermore,the folding is not only associated with bends in the strike-slip faults, but rather, appears to be more regionally scaledand related to secondary space accommodation above the detachment surface driven by the dominant strike-slip faulting. Second, neither region shows a geodetic signal of convergence, but rather, GPS and InSAR show virtually pure strike slip at the regional scale for

• Ge oPe n t e ch December 2010 Page A2-6

SAN ONOFRE NUCLEAR GENERATING STATION SEISMIC HAZARD ASSESSMENT PROGRAM 2010 PROBABILISTIC SEISMIC HAZARD ANALYSIS REPORT the southern San Jacinto fault zone (see Fialko, 2006). Third, at least one fold grew during the 1987 Superstition Hills earthquake sequence in the western Salton Trough (Klinger and Rockwell, 1989), so there is a demonstrable association between strike-slip faulting and fold growth in this area. These and other similarities warrant a thorough examination and comparison between these two structural domains, in part because the western Salton Trough is well-studied and easily accessible.

RECOMMENDATIONS TOWARD RESOLVING REMAINING UNCERTAINTIES For the Rose Canyon Fault itself, there are potential paleoseismic study sites to resolve whether the fault sustained displacement between about 5 and 0.5 ka. The sediments within and adjacent to the San Diego River are of the appropriate age, as river aggradation probably ceased about the time sea level rose to its present level at about 5-6 ka, and after that, sedimentation on the flood plain has locally preserved alluvium of various ages in the 0.5 to 5 ka timeframe. One area that maypreserve such a record is in Old Town, where the landscape is only minimally altered. One potential site is in a golf course that essentially preserved the original topography; the fault is still expressed as a linear depression. The golf course property is owned by the City of San Diego, although it is currently under lease. Another potential site is close to the Lindvall and Rockwell (1995) trench site where a closed.

depression (sag) is observed in the 1928 and 1941 aerial photography. This is on private land, so access will likely be an issue. A third general site is in the flood plain of the San Diego River in Mission Valley.

The fault is expressed in the 1928 aerial photographs, so the fault location can be determined with some work. The fault location may be better determined with CPT or geophysical means, once it is approximately located by interpretation of the old aerial photography. It may be possible to trench along a street, once the fault is well located.

To assess and understand the significance of the folding above the detachment surface in the offshore region, I also recommend that we thoroughly document the structural styles, rates of folding and faulting, etc. for the analogous Western Salton Trough and compare to that of those observed for the Inner Borderland Region. We need to better understand the relationship between the strike-slip faulting and the folding in the Borderland, and the western Salton Trough is far more open to study and analysis because it is sub-aerial and easily accessible. In the southern San Jacinto fault zone, we can better understand how, and when, the folding occurred, and how it relates to the dominant strike-slip faulting, perhaps even to individual events. We should also reanalyze the geodetic signals of these two areas for a component of convergence and test whether a small shortening component can be precluded or accepted.

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