Sensitivity of the Southern San Andreas Fault System to Tectonic Boundary Conditions and Fault Configurations

Herbert, Justin W.; Cooke, Michele L.

doi:10.1785/0120110316

Cited by 21 publications

(54 citation statements)

References 67 publications

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“…1) is a zone of active transpressional deformation, crustal thickening, and high topography (Matti et al, 1985(Matti et al, , 1992Harden and Matti, 1989;Spotila and Sieh, 2000;Yule and Sieh, 2003). The SAF zone on the north side of San Gorgonio Pass is a network of dextral-reverse faults with an overall north dip revealed by seismology (Yule and Sieh, 2003;Carena et al, 2004) and gravity and magnetic data (Langenheim et al, 2004(Langenheim et al, , 2005, a geometry consistent with the results of 3-D numerical modeling (Dair and Cooke, 2009;Cooke and Dair, 2011;Herbert and Cooke, 2012).…”

Section: Geologic and Tectonic Settingsupporting

confidence: 58%

“…Although the southern SAF in Coachella Valley is widely considered to be vertical (e.g., Meade and Hager, 2005;Loveless and Meade, 2011;Herbert and Cooke, 2012;Luo and Liu, 2012;Nicholson et al, 2013), recent seismic, geophysical, and modeling studies suggest that it dips steeply northeast (Lin et al, 2007;Fuis et al, 2012a;Lindsey and Fialko, 2013;Fattaruso et al, 2014). A small component of convergence across a northeast-dipping SAF can produce a vertical load that may drive northeast tilting of the Salton block (Fig.…”

Section: Controls On Crustal Tiltingmentioning

confidence: 99%

“…Historically, geophysical models have assumed a vertical dip on the fault (e.g., Meade and Hager, 2005;Smith-Konter and Sandwell, 2009;Loveless and Meade, 2011;Herbert and Cooke, 2012;Luo and Liu, 2012;Nicholson et al, 2013). Other studies suggest that the active Coachella segment of the SAF dips 60°-70° northeast based on seismicity patterns, aeromagnetic data, and modern strain documented with GPS and interferometric synthetic aperture radar (Lin et al, 2007;Fuis et al, 2012a;Lin, 2013;Lindsey and Fialko, 2013).…”

Section: Introductionmentioning

confidence: 99%

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Crustal-scale tilting of the central Salton block, southern California

Dorsey

Langenheim

2015

Geosphere

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The southern San Andreas fault system (California, USA) provides an excellent natural laboratory for studying the controls on vertical crustal motions related to strike-slip deformation. Here we present geologic, geomorphic, and gravity data that provide evidence for active northeastward tilting of the Santa Rosa Mountains and southern Coachella Valley about a horizontal axis oriented parallel to the San Jacinto and San Andreas faults. The Santa Rosa fault, a strand of the San Jacinto fault zone, is a large southwest-dipping normal fault on the west flank of the Santa Rosa Mountains that displays well-developed triangular facets, narrow footwall canyons, and steep hanging-wall alluvial fans. Geologic and geomorphic data reveal ongoing footwall uplift in the southern Santa Rosa Mountains, and gravity data suggest total vertical separation of ~5.0-6.5 km from the range crest to the base of the Clark Valley basin. The northeast side of the Santa Rosa Mountains has a gentler topographic gradient, large alluvial fans, no major active faults, and tilted inactive late Pleistocene fan surfaces that are deeply incised by modern upper fan channels. Sediments beneath the Coachella Valley thicken gradually northeast to a depth of ~4-5 km at an abrupt boundary at the San Andreas fault. These features all record crustal-scale tilting to the northeast that likely started when the San Jacinto fault zone initiated ca. 1.2 Ma. Tilting appears to be driven by oblique shortening and loading across a northeast-dipping southern San Andreas fault, consistent with the results of a recent boundary-element modeling study.

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Section: Geologic and Tectonic Settingsupporting

confidence: 58%

Section: Controls On Crustal Tiltingmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Crustal-scale tilting of the central Salton block, southern California

Dorsey

Langenheim

2015

Geosphere

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“…In southern California, plate interactions and fault structure are complex ( Fig. 1)-with a reduction of strike-slip rates along the San Andreas fault through the San Gorgonio Pass (Herbert and Cooke, 2012;McGill et al, 2012) and a transfer of deformation east of the San Andreas fault into the eastern California shear zone . Plate motion is also taken up on strikeslip faults subparallel to and west of the San Andreas fault, including the San Jacinto fault and Elsinore fault.…”

Section: Introductionmentioning

confidence: 99%

“…To date, most models investigating deformation, stress, rupture, and ground shaking have assumed that the southern San Andreas fault is vertical (e.g., Carena et al, 2004;Becker et al, 2005;Meade and Hager, 2005;Smith-Konter and Sandwell, 2009;Spinler et al, 2010;Loveless and Meade, 2011;Herbert and Cooke, 2012;Luo and Liu, 2012). However, seismicity, seismic imaging, aeromagnetic data, and recent strain observations from global positioning system (GPS) and interferometric synthetic aperture radar (InSAR) suggest that the active Coachella segment of the San Andreas fault dips 60°-70° NE (Lin et al, 2007;Fuis et al, 2012;Bauer et al, 2013;Fuis et al, 2013;Lin, 2013;Lindsey and Fialko, 2013).…”

Section: Introductionmentioning

confidence: 99%

Sensitivity of uplift patterns to dip of the San Andreas fault in the Coachella Valley, California

2014

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Three-dimensional mechanical simulations of the San Andreas fault system within the Coachella Valley in southern California produce deformation that matches geologic observations and demonstrate the firstorder impact of fault geometry on uplift patterns. To date, most models that include the Coachella Valley segment of the San Andreas fault have assumed a vertical orientation for this fault, but recent studies of seismicity and geodetically observed strain suggest that this segment of the fault may dip 60°-70° to the northeast. We compare models with varied geometry along this segment of the fault and evaluate how well they reproduce observed uplift patterns in the Mecca Hills and Coachella Valley. Incorporating wellconstrained fault geometry in regional models will provide a more accurate understanding of active faulting in southern California, which is critical for rupture and hazard modeling that is used to identify regions most susceptible to earthquake damage.We have tested three boundary-element method models for the active geometry of the Coachella Valley segment of the San Andreas fault: one contains a vertical Coachella segment, the second contains a northeast ~65° dipping Coachella segment, and the fi nal alternative contains a vertical Coachella segment plus a subparallel northeast-dipping fault at depth. This fi nal model honors the geometric interpretation of seismicity from the Southern California Earthquake Center Community Fault Model version 4.0. The models containing vertical Coachella Valley segments both produce uplift between the San Andreas and San Jacinto faults that is more uniformly distributed than geologic observations suggest, and these models fail to produce uplift in the Mecca Hills. The dipping model produces tilting of the Coachella Valley consistent with geologic observations of tilting between the San Jacinto and San Andreas faults. The dipping model also produces relative subsidence southwest of the fault and localized uplift in the Mecca Hills that better match the geologic observations. These results suggest that the active Coachella Valley segment of the San Andreas fault dips 60°-70° to the northeast.

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Influence of fault connectivity on slip rates in southern California: Potential impact on discrepancies between geodetic derived and geologic slip rates

2014

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Along the San Bernardino strand of the San Andreas fault (SAF) and across the eastern California shear zone (ECSZ), geologic slip rates differ from those inverted from geodetic measurements, which may partly be due to inaccurate fault connectivity within geodetic models. We employ three-dimensional models that are mechanically compatible with long-term plate motion to simulate both fault slip rates and interseismic surface deformation. We compare results from fault networks that follow mapped geologic traces and resemble those used in block model inversions, which connect the San Jacinto fault to the SAF near Cajon Pass and connect distinct faults within the ECSZ. The connection of the SAF with the San Jacinto fault decreases strike-slip rates along the SAF by up to 10% and increases strike-slip rates along the San Jacinto fault by up to 16%; however, slip rate changes are still within the large geologic ranges along the SAF. The insensitivity of interseismic surface velocities near Cajon Pass to fault connection suggests that inverse models may utilize both an incorrect fault geometry and slip rate and still provide an excellent fit to interseismic geodetic data. Similarly, connection of faults within the ECSZ produces 36% greater cumulative strike-slip rates but less than 17% increase in interseismic velocity. When using overconnected models to invert GPS for slip rates, the reduced off-fault deformation within the models can lead to overprediction of slip rates. While the nature of fault intersections at depth remains enigmatic, fault geometries should be chosen with caution in crustal deformation models.

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Sensitivity of the Southern San Andreas Fault System to Tectonic Boundary Conditions and Fault Configurations

Cited by 21 publications

References 67 publications

Crustal-scale tilting of the central Salton block, southern California

Crustal-scale tilting of the central Salton block, southern California

Sensitivity of uplift patterns to dip of the San Andreas fault in the Coachella Valley, California

Influence of fault connectivity on slip rates in southern California: Potential impact on discrepancies between geodetic derived and geologic slip rates

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