Journal of Geophysical Research Earth Surface

Supporting Information forHigh-Resolution Mapping of Two Large-Scale Transpressional Fault Zones in theCalifornia Continental Borderland: Santa Cruz-Catalina Ridge and Ferrelo faults

Mark Legg1, Monica D. Kohler2, Natsumi Shintaku3, and Dayanthie Weeraratne 4

Mark Legg: Legg Geophysical, Huntington Beach, CA, USA

Monica D. Kohler: Department of Mechanical and Civil Engineering; California Institute of Technology, Pasadena, CA, USA

Natsumi Shintaku: Department of Geological Sciences, Brown University, Providence, RI, USA

Dayanthie Weeraratne: Department of Geological Sciences, California State University, Northridge, Northridge, CA, USA

Contents of this file

Text S1 Fault Triple Junctions Figures S1, S2, S4Tables S1 to S4.

Additional Supporting Information (Files uploaded separately)

Captions for Datasets Figure S3 Multichannel seismic reflection profiles across the northern Santa Cruz-Catalina Ridge (see Fig. 7 for profile locations).

Introduction This appendix of supplementary material consists of four figures, five tables, and a brief text that provide more detailed information relevant to the main paper. A list of references for the supplementary data is also included.

Figure S1 is a map of multichannel seismic reflection profiles in the northern California Continental Borderland available for the research project. The exploration industry and USGS data are available from the National Archive of Marine Seismic Surveys [NAMSS, 2006] and Infobank [2013].

Figure S2 shows seven stratigraphic columns for various locations in the California Continental Borderland that were published by scientists at the U.S. Geological Survey and California Geological Survey [Greene and Kennedy, 2007]. Updated stratigraphic data for some areas (Santa Monica Basin and

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San Pedro Basin) are being prepared by government and academic scientists as new data become available.

Figure S3 shows four multichannel seismic reflection profiles across the northern end of the Santa Cruz-Catalina Ridge. One (USGS-126E) is part of the USGS line 126 44-channel deep penetration data (2424 cu. in. tuned airgun source array); the other three are high-resolution, 24-channel, shallow penetration data (4-kjoule sparker source). All profiles are migrated sections. The USGS data were processed in Menlo Park and are available from NAMSS. The high-resolution lines were processed by Legg and are brute stacks using a constant velocity of 5000 ft/sec, and frequency-wave number migration at 4800 ft/sec. More thorough processing of these data is incomplete at present.

Figure S4 is a map showing the major faults interpreted for this study and used to estimate earthquake potential in the region.

Table S1 presents the map projection and geographic coordinates of the boundaries of raster multibeam bathymetry images used to interpret seafloor faulting for this study. These data can be used to georeference the images for use in a geographic information system (GIS).

Table S1B provides a list of the image file names for the multibeam bathymetry used in this study. These data are archived in the Southern California Earthquake Center Data Center.

Table S2 provides hypocentral location parameters for the earthquake focal mechanisms shown in this study. Location data are from the Southern California Seismic Network (SCSN) and include more accurate relocations when available from special studies.

Table S3 is a compilation of the major fault segments and sections mapped in this study used to estimate earthquake potential (maximum magnitude).

Table S4 is a compilation of large historic earthquakes in California, not on the San Andreas fault, used to provide examples of large complex earthquakes that may occur offshore southern California.

Text Section S1 Fault Triple Junctions provides more detailed discussion of fault triple junctions that were mapped in the Borderland and how these resemble major fault intersections mapped onshore in southern California. In addition, tectonic significance is discussed.

S1 Fault Triple Junctions.Intersections between prominent faults within Borderland fault systems were

recognized by Crowell [1974] and described as convergent and divergent fault wedge tips. Based upon our detailed mapping of these intersections with the high-resolution bathymetry and seismic profiles, and the regional tectonic evolution, we prefer to describe these features as fault “triple junctions”. Legg et al. [2007] suggest that Borderland restraining bend triple junctions result from the bypass of Miocene transform faults with trends parallel to the Middle Miocene relative plate motion vector (~N55ºW) by younger right-slip faults that are more favorably oriented to the post-Miocene plate motion vector (~N40°W; Fig. 14). Triple junctions at opposite ends of the Santa Catalina Island block (Figs. 4, 6 and 8) resemble fault intersections along the San Bernardino Mountains segment of the San Andreas fault (Fig. 14; restraining bend northwest of Palm Springs, PS). The northern triple junction where the San Clemente fault merges with the Catalina Ridge fault (Fig. 6A) mirrors the intersection of the San Jacinto fault with the San Andreas fault at Cajon Pass. The San Clemente fault transfers significant right slip to the Santa Cruz-

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Catalina Ridge fault zone whereas the Catalina Ridge (and Catalina escarpment) fault appears to be cut-off and accommodates diminishing slip. A higher slip rate for the San Clemente fault is manifest in the abundant seismicity to the south and by sharply defined tectonic geomorphology along the San Clemente Island escarpment [Legg and Goldfinger, 2002].

The triple junction at the southern end of the Catalina Ridge (Fig. 8A) resembles the Banning Pass to Palm Springs section of the San Andreas fault system (Fig. 14). The San Pedro Basin fault bypasses the Catalina fault restraining bend by linking to the San Diego Trough fault; this is similar to how the Eastern California Shear Zone through the Mojave (Fig. 14) attempts to bypass the Big Bend of the San Andreas fault [Savage et al., 1990]. The process of fault bypass is more advanced in the Inner Borderland because it began during the middle to late Miocene epoch when the plate boundary deformation was focused offshore, before the opening of the Gulf of California and plate boundary jump to the southern San Andreas fault system. The Catalina fault may still be active, but at a reduced rate because Catalina Island uplift has ceased and is now subsiding [Castillo et al., 2012]. Northeast-facing (upslope direction) seafloor scarps along the base of Catalina Ridge Escarpment (Fig. 6A) may represent Holocene faulting. The scarp morphology may indicate subsidence or tilting of the island block down toward the northwest, but the character of faulting is undetermined at this time.

Major triple junctions along the Ferrelo fault zone recognized in this study include intersections with the transverse San Nicolas Island escarpment and with the southeast-trending faults along Tanner and Cortes Banks (Fig. 12). The San Nicolas Island fault resembles the transpeninsular Agua Blanca fault except that the former exhibits reverse slip on a moderately north-dipping fault and the latter exhibits right slip on a vertical fault. Both faults likely have a long history of complex deformation within the evolving transform plate boundary. The Outer Borderland crustal block rifted away from the northern Baja California continental margin [Howell and Vedder, 1981; Legg, 1991]. The branches from these triple junctions may provide important piercing points to define the initial breakaway geometry of the Outer Borderland block. Detailed investigation of the deformation in the sedimentary basins at these triple junctions could provide precise timing of important events during the evolution of the Pacific-North America transform plate boundary.

Relocation studies of two moderate Inner Borderland earthquakes with significant aftershock sequences provide evidence that multiple fault segments were involved in the rupture process (Figs. 6 and 8). Furthermore, these earthquake sequences were located at junctures between major faults (“triple junctions”) where some aftershock activity appears to occur on adjacent fault splays (Fig. 6A). Future large Borderland earthquakes are likely to involve complex ruptures with multiple fault segments active during rupture including branching to other major fault zones. For example, rupture on the San Clemente Island fault may propagate to the north and continue on the Santa Cruz-Catalina Ridge fault zone producing a major (M>7) earthquake (Table S3). Abundant youthful fault segments identified in the seafloor morphology and high-resolution seismic profiles provide numerous potential links for such long and complex earthquake rupture events (Figs. 6, 8, 10 and 11). The existence of major low-angle Miocene detachment faults throughout the region (Figs. 8 and 9) may provide additional subsurface (“blind faulting”) links to facilitate long and complex rupture events.

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Large earthquakes (M>7) typically involve long and complex rupture patterns that may involve multiple faults (Table S4). The 1992 Landers, the 1872 Owens Valley, and the 2010 El Major-Cucapah, and the 1999 Hector Mine earthquakes were large strike-slip events with complex rupture patterns through extended continental crust. The 1952 Kern County earthquake involved reverse slip with a component of left-lateral strike slip. The complexity of faulting mapped along the major Borderland fault zones is similar and equally likely to sustain future large earthquake ruptures.

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Figure S1. Map showing tracklines of digital multichannel seismic reflection surveys (MCS) available in the study area. Data include exploration industry lines available from the NAMSS (black), USGS high-resolution profiles (green), and various university high-resolution profiles (magenta). Red lines are faults mapped in this study. Not all of the data shown were used in this study, although published geologic maps and cross-sections based on special studies of various survey data were used to prepare the fault maps and interpretations presented here. CAT = Santa Catalina Island, SCZ = Santa Cruz Island, SMB = Santa Monica Basin; SPB = San Pedro Basin; SRCR = Santa Rosa-Cortes Ridge; SRI = Santa Rosa Island, SCL = San Clemente Island, SBI = Santa Barbara Island, LA = Los Angeles. EK = Emery Knoll, EK rim = offset rim of Emery Knoll crater [Legg et al., 2004].

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Figure S2. Stratigraphy of the northern California Continental Borderland around the Ferrelo and Santa Cruz-Catalina Ridge fault zones based on seafloor samples (dart cores and dredge) and high-resolution seismic reflection profiles. Location of stratigraphic columns shown in Figure S1. [Modified from Greene and Kennedy, 1987]

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Figure S4. Map showing major late Quaternary faults mapped for this study. San Clemente fault zone mapping based on Legg and Goldfinger [2002]. Fault parameters for earthquake potential are listed in Table S3.

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Table S1A. Geographic location of multibeam bathymetry map images.

Reference X (pixels) Y (pixels) Longitude Latitude

North Borderland (1200 dpi)[Legg1_100m_315_grad.tif]*

NW Corner 523 96 -121° 00.0’ 34° 30.0’SE Corner 8459 7165 -117° 00.0’ 31°30.0’

North Borderland (800 dpi)[Legg1_100m_090_grad.tif – 5044x5252]*

NW Corner 1 1 -121° 00.0’ 35° 00.0’SE Corner 5044 5252 -117° 00.0’ 31°30.0’

[Legg1_100m_180_grad.tif – 5124x4561]*

NW Corner 0 0 -121° 00.0’ 34° 30.0’SE Corner 5124 4561 -117° 00.0’ 31°30.0’

Catalina (800 dpi)[Legg2_100m_90.tif – 5297x4259]*

NW Corner 2 3 -119° 36.0’ 34° 05.0’SE Corner 5294 4257 -117° 30.0’ 32° 40.0’

[Legg2_100m_180.tif – 5046x4059]*

NW Corner 2 3 -119° 36.0’ 34° 05.0’SE Corner 5042 4056 -117° 30.0’ 32° 40.0’

North Ferrelo (800 dpi)[Legg3_100m_90.tif – 5048x3273]*

NW Corner 2 7 -120° 40.0’ 34° 05.0’SE Corner 5044 3267 -118° 40.0’ 33° 00.0’

[Legg3_100m_180.tif – 4809x3118]*

NW Corner 3 7 -120° 40.0’ 34° 05.0’SE Corner 4802 3113 -118° 40.0’ 33° 00.0’

South Ferrelo (800 dpi)[Legg4_100m_90.tif – 5150x4347]*

NW Corner 2 5 -120° 00.0’ 33° 20.0’SE Corner 5146 4342 -118° 00.0’ 31° 40.0’

[Legg3_100m_270.tif – 5606x4734]*

NW Corner 0 9 -120° 00.0’ 33° 20.0’SE Corner 5601 4731 -118° 00.0’ 31° 40.0’

*Raster image file name includes region (Legg1), grid size (100m), sun angle (045), and gradient color scheme (grad) where appropriate. Parameters in table above were used to georeference the map in a Geographic Information System and include the map corner locations in XY (pixels) and geographic coordinate systems. Map Projection is World Mercator, NAD83. The raster image files are available through the Southern California Earthquake Data Center (www.scecde.org).

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Table S1B. List of image files of multibeam bathymetry used for this study.ALBACORE - Multibeam Bathymetry Raster Image Files Legg1_100m_180.epsiLegg1_100m_225.epsiLegg1_100m_270.epsiLegg1_nborderland_100m.epsiLegg2_100m_180.epsiLegg2_100m_225.epsiLegg2_100m_270.epsiLegg2_catalina_50m.epsiLegg2_catalina_100m.epsiLegg3_100m_180.epsiLegg3_100m_225.epsiLegg3_100m_270.epsiLegg3_nferrelo_100m.epsiLegg4_100m_180.epsiLegg4_100m_225.epsiLegg4_100m_270.epsiLegg4_sferrelo_100m.epsi\GradColor\Legg1_100m_045.epsiLegg1_100m_090.epsiLegg1_100m_135_grad.epsiLegg1_100m_180_grad.epsiLegg1_100m_225_grad.epsiLegg1_100m_270_grad.epsiLegg1_100m_315_grad.epsiLegg1_100m_360.epsiLegg1_200m_135_grad.epsiLegg1_200m_180_grad.epsiLegg1_200m_225_grad.epsiLegg1_200m_270_grad.epsiLegg1_200m_315_grad.epsi

Gradient color scheme raster images with all eight (8) sun angles were prepared only for the larger area (North Borderland – Legg_100m) maps. Raster images (tiff) were produced at 1200 dpi pixel resolution for gradient version of North Borderland, 800 dpi for other regions. Original images created at CSU Northridge were in epsi format.

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Table S2. Earthquakes in the California Continental Borderland with focal mechanisms.

# F Year Mo Day Time Long(deg)

Latitude(deg)

D (km)

Mw/ML Location

37 t 2015 02 09 01:45:03 -115.665 31.526 1.9 4.9 SE San Miguel Flt, N Baja36 Io 2014 11 10 08:42:42 -118.653 32.867 5.4 4.1 W of San Clemente Island35 t 2014 03 05 02:24:23 -119.355 31.383 2.1 5.0 W of Patton Escarpment34 l 2013 05 31 13:24:52 -119.1305 33.6863 10.71 3.09 Santa Cruz-Catalina Ridge33 t 2012 12 14 10:36:02 -119.582 31.1643 17 6.3/ W of Patton Escarpment32 i 2012 05 30 05:14:01 -119.058 33.6918 16.42 3.67/3.98 Santa Cruz-Catalina Ridge31 iot 2012 01 03 14:18:56 -119.4492 33.1947 18.37 3.72/4.14 San Nicolas Island30 2011 11 29 06:56:09 -119.0510 33.6063 16.0 3.3 Santa Cruz-Catalina Ridge29 2011 06 11 08:17:48 -119.0433 33.623 8 3.61/3.53 Santa Cruz-Catalina Ridge28 iot 2010 08 24 05:42:17 -119.0330 33.5152 16.9 3.9/3.97 Santa Barbara Island27 iot 2009 11 15 22:45:27 -119.3018 33.1655 6 4.21/4.35 San Nicolas Island26 2009 10 08 03:31:18 -118.2507 33.1655 3.73 4.16/3.73 San Clemente Canyon25 2009 6 20 01:00:31 -119.0067 32.8997 14.21 3.82/4.11 Catalina Crater24 i 2008 12 31 11:05:05 -118.80 33.95 3.0 5.04/3.17 Point Dume23 i 2008 12 07 15:39:02 -119.3237 33.8673 11.54 3.53/3.47 Santa Cruz-Catalina Ridge22 i 2007 09 09 13:11:49 -117.3381 32.7820 5.74 4.0 Crespi Knoll21 2005 10 19 08:51:26 -118.145 32.4967 10 4.09/4.26 North San Clemente Basin20 2005 10 18 00:29:15 -118.1472 32.4343 10 3.71/3.64 North San Clemente Basin19 2005 10 16 21:11:35 -118.1633 32.4545 10 4.9/4.99 North San Clemente Basin18 2005 10 04 06:18:07 -118.0975 32.6207 6 3.15/3.34 North San Clemente Basin17 2005 08 12 06:35:55 -118.1105 32.5882 10 3.43/3.58 Fortymile Bank16 o 2005 07 24 12:59:43 -119.761 33.674 6 4.01/4.11 West Santa Cruz Basin15 o 2005 04 21 13:26:37 -120.0265 33.6597 6 3.88/3.8 Santa Rosa-Cortes Ridge14 o 2005 04 21 06:36:19 -120.0333 33.657 6 3.89/3.95 Santa Rosa-Cortes Ridge13 i 2001 08 16 22:06:29 -118.2757 32.8055 12.9 4.2 North San Clemente Basin12 i 2001 08 16 18:04 -118.3030 32.7667 9.87 4.4 San Clemente Canyon11 it 1988 11 20 05:39:28.

4-118.0822 33.5068 11.70 4.83 San Gabriel Canyon

10 it 1986 07 13 13:47:08 -117.8583 32.9783 8.8 5.8Ms/5.3

Crespi Knoll

9 it 1981 09 04 15:50:50 -119.060 33.682 11.48 6.0/5.3 Santa Cruz-Catalina Ridge8 i 1975 01 12 21:22:14.

8-117.988 32.758 15.3 4.8 Fortymile Bank

7 t 1973 02 21 14:45 -119.04 34.07 5.3/5.9 Point Mugu6 it 1973 08 06 23:29:17 -119.475 33.987 16.0 5.0 Anacapa Island5 it 1969 10 24 08:29:12 -119.193 33.291 10.0 5.1 NW San Clemente Ridge4 t 1964 12 22 20:54:33.

2-117.117 31.811 2.3 6.2Ms/

5.4Offshore Ensenada

3 i 1951 12 26 00:46:54.0

-118.350 32.817 0 5.9Ms San Clemente Island

2 t 1933 03 11 01:54 -117.972 33.659 13 6.3 Long Beach1 t 1927 11 04 05:51 -120.9 34.35 10 7.0 Offshore Point Arguello

F – Figure (map) i = Inner Borderland (Fig. 4); o = Outer Borderland (Fig. 10); t = Tectonic (Fig. 13); Time – Origin Time (UTC); D = Depth Magnitude – Mw = Moment Magnitude, ML = Local Magnitude, Ms = Surface Wave MagnitudeWhite Rows – Moment Tensor, High Variance Reduction (A-quality solutions); Light Gray – Low Variance Reduction (<40% B-quality solutions); Dark Gray – First-Motion SolutionsData from SCSN Moment Tensor Database www.data.scec.org/mtarchive/; USGS pasadena.wr.usgs.gov/recenteqs/; Legg [1980]; Corbett [1984]; Hauksson and Jones [1988]; Hauksson and Gross [1991]; Helmberger et al [1992]; Cruces and Rebollar [1992]; Yang et al. [2012]

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Table S3. Major fault sections and segments – Borderland transpresional fault system.

[Fault sections in italics; ID corresponds to Fig. S4]

ID Fault Name Length (km) Width (km) Mmax*

I San Clemente Fault System >600 15 8.25IA Santa Cruz – Catalina Ridge 170 15 7.61

North End 19 15 6.43IA1 Pilgrim Banks – N&S 66 15 7.13IA2 Pilgrim Banks North 30 15 6.74IA3 Pilgrim Banks South 36 15 6.83IIB Santa Catalina Island 160 15 7.49IIB2 Catalina Ridge 63 15 7.11IIB3 Catalina Escarpment 87 15 7.27IIC Gulf of Santa Catalina – North San Diego Trough 90 15 7.29IIC2 Crespi Knoll 30 17 6.80

Catalina Basin 138 15 7.45East San Clemente 32 15 6.77

III Ferrelo Fault System >380 10 7.56IIIA North Ferrelo 150 10 7.16

North Ferrelo NE 30-35 10 6.52North Ferrelo – 6 segments 10-22 ea 10 6.32Nidever Bank E 42 10 6.60

IIIB Mid Ferrelo 170 10 7.21Nidever Bank W 75-85 10 6.91Mid Ferrelo – 2 segments 18, 43 10 6.61South Ferrelo N 25-30 10 6.46

IIIC South Ferrelo >63 10 6.78South Ferrelo N 15-20 10 6.28South Ferrelo – 3 segments 6-22 ea 10 6.32

Velero BasinIIID Mapping Incomplete

*Maximum magnitudes were derived using methods and magnitude-area relationships as described by Stein [2007]. Empirical data for the magnitude-area curves are from large continental strike-slip earthquakes. Reverse or thrust earthquakes may have somewhat larger magnitudes for a given fault area. However, for the 1989 Loma Prieta earthquake (Mw=6.9) which had an estimated fault area of 640 km2 and oblique-reverse focal mechanism, the estimated maximum magnitude by the method used in the table above is 6.91 – virtually identical to the moment magnitude computed from the seismological data. Uncertainties in fault parameters, length and down-dip width exceed the uncertainty in maximum magnitude estimated from the empirical equations.

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Table S4. Large historic non-San Andreas California earthquakes with surface rupture

Year DateMonth Day Location M* Length

(km) Reference

1872 March 26 Owens Valley 7.8-7.9 >90 to 140

Beanland and Clark [1994]Hough and Hutton [2008]

1892 February 23 Laguna SaladaN. Baja California 7.2 >22 Mueller and Rockwell [1995]

Hough and Elliot, [2004]

1952 July 21 Kern County 7.7(MS) >34 Richter [1958]

1992 June 28 Landers - Mojave 7.3 80-85 Sieh et al. [1993]

1999 October 16 Hector Mine - Mojave 7.1 48 Treiman et al. [2002]

2010 April 4 El Major – CucapahN. Baja California 7.2 ~120 Hauksson et al. [2011]

*Moment magnitude; MS = surface wave magnitude

References.Beanland, S., and M. Clark (1994), The Owens Valley fault zone, eastern California, and surface faulting

associated with the 1872 earthquake, in U.S. Geol. Survey Bull. 1982, U.S. Government Printing Office, Washington, D.C.

Castillo, C. M., R. D. Francis, and M. R. Legg (2012), Constraints on late Quaternary subsidence of Santa Catalina Island from submerged paleoshorelines, American Geophysical Union, Annual Meeting, San Francisco.

Corbett, E. J. (1984), Seismicity and crustal structure studies of southern California: Tectonic implications from improved earthquake locations, PhD Thesis, Pasadena, California Institute of Technology, 231 p.

Crowell, J. C. (1974), Origin of late Cenozoic basins in southern California, in: Tectonics and Sedimentation, Special Publications – Society of Economic Paleontologists and Mineralogists (Society for Sedimentary Geology), Tulsa, OK, 22, 190-204.

Cruces, F. J., and C. J. Rebollar (1992), Source parameters of the 22 December 1964 (mb =5.4, MS = 6.2_offshore Ensenada earthquake, Physics of the Earth and Planetary Interiors. 66, 253-258.

Greene, H.G., and M.P. Kennedy (1987), Geology of the California continental margin: Explanation of the California continental margin geologic map series: California Division of Mines and Geology, Sacramento, Bulletin 207, 110 p.

Hauksson, E., and L. Jones (1988), The July 1986 Oceanside (ML=5.3) earthquake sequence in the Continental Borderland, southern California: Bull. Seis. Soc. Am., 78, 1885-1906.

Hauksson, E,, and S. Gross (1991), Source parameters of the 1933 Long Beach earthquake: Bull. Seis. Soc. Am., 81, 81-98.

Hauksson, E., J. Stock, K. Hutton, W. Yant, J. Antonio Vidal-Villegas, and H. Kanamori (2011), The 2010 MW 7.2 El Mayor-Cucapah earthquake sequence, Baja California, Mexico and southern California, USA: Active seismotectonics along the Mexican Pacific margin, Pure Appl. Geophys. 168, 1255-1277.

Helmberger, D. V., P. G. Sommerville and E. Garnero (1992) The location and source parameters of the Lompoc, California earthquake of 4 November 1927. Bull. Seis. Soc. Am., 82, 1678-1709.

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Hough, S. E., and A. Elliot (2004), Revisiting the 23 February 1892 Laguna Salada earthquake, Bull. Seis. Soc. Am., 94, 1571-1578.

Hough, S. E., and K. Hutton (2008), Revisiting the 1872 Owens Valley, California, earthquake, Bull. Seis. Soc. Am., 98, 931-949.

Howell, D. G., and J. G. Vedder (1981), Structural implications of stratigraphic discontinuities across the southern California borderland; in Ernst, W.G., ed., The Geotectonic Development of California, Rubey Volume 1: Prentice-Hall, Inc. Englewood Cliffs, New Jersey, 535-558.

Legg, M. R. (1980), Seismicity and tectonics of the inner continental borderland of southern California and northern Baja California, Mexico, MS thesis, University of California, Santa Diego, San Diego, California, 60 p.

Legg, M. R. (1991), Developments in understanding the tectonic evolution of the California Continental Borderland: in Osborne, R. H. ed. From Shoreline to Abyss, SEPM Shepard Commemorative Volume, 46, 291-312.

Legg, M. R., and C. Goldfinger (2002), Earthquake potential of major faults offshore southern California: Collaborative research with Oregon State University and Legg Geophysical: U.S. Geological Survey Final Technical Report, Grant No. 01HQGR0017, 24 pp.

Legg, M. R., C. Nicholson, C. Goldfinger, R. Milstein, and M. Kamerling (2004), Large enigmatic crater structures offshore southern California: Geophys. J. Int., 158, 803-815.

Legg, M. R., C. Goldfinger, M. J. Kamerling, J. D. Chaytor, and D. E. Einstein (2007), Morphology, structure and evolution of California Continental Borderland restraining bends: in Cunningham, W. D. & Mann, P. (eds), Tectonics of strike-slip restraining & releasing bends in continental and oceanic settings, Geological Society of London Special Publications, 290, 143-168.

Mueller, K. J., and T. K. Rockwell (1995), Late Quaternary activity of the Laguna Salada fault in northern Baja California, Mexico, Geol. Soc. Am., 107, 8-18.

National Archive of Marine Seismic Surveys (NAMSS) (2006), http://walrus.wr.usgs.gov/NAMSS/.Richter, C. F. (1958), Elementary Seismology, W. H. Freeman and Co., San Francisco, CA, 519-531.Savage, J. C., M. Lisowski, and W. H. Prescott (1990), An apparent shear zone trending north-

northwest across the Mojave Desert into Owens Valley, eastern California: Geophys. Res. Letters, 17, 2113-2116.

Sieh, K. L., L. Jones, E. Hauksson, K. Hudnut, and 16 others (1993), Near-field investigations of the Landers earthquake sequence, Science, 260, 171-176.

Stein, R. S., (2007), Earthquake Rate Model 2.2 of the 2007 Working Group for California Earthquake Probabilities, Appendix D: Magnitude-Area Relationships: U.S. Geological Survey Open-File Report 2007-1162, 10 pp.

Treiman, J. A., K. J. Kendrick, W. A. Bryant, T. K. Rockwell, and S. F. McGill (2002), Primary surface rupture associated with the MW 7.1 16 October 1999 Hector Mine earthquake, San Bernardino County, California, Bull. Seis. Soc. Am., 92, 1171-1191.

Yang, W., E. Hauksson, and P. M. Shearer (2012), Computing a large refined catalog of focal mechanisms for southern California (1981-2010): Temporal stability of the style of faulting, Seis. Soc. Am. Bull, 102, 1179-1194.

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