Steep-Dip Seismic Imaging of the Shallow San Andreas Fault Near Parkfield

Hole, J. A.; Catchings, R. D.; Clair, K. C. St.; Rymer, M. J.; Okaya, D. A.; Carney, B. J.

doi:10.1126/science.1065100

Cited by 56 publications

(57 citation statements)

References 17 publications

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“…Direct reflection imaging of steep faults is rare, with only a few examples in California (e.g., Shaw and Shearer, 1999;Hole et al, 2001;Bleibinhaus et al, 2007). The imaging method of Bauer et al (2013) represents a promising tool that can be applied to steep faults worldwide.…”

Section: Discussionmentioning

confidence: 99%

Subsurface Geometry of the San Andreas Fault in Southern California: Results from the Salton Seismic Imaging Project (SSIP) and Strong Ground Motion Expectations

Fuis¹,

Bauer²,

Goldman³

et al. 2017

Bulletin of the Seismological Society of America

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The San Andreas fault (SAF) is one of the most studied strike-slip faults in the world; yet its subsurface geometry is still uncertain in most locations. The Salton Seismic Imaging Project (SSIP) was undertaken to image the structure surrounding the SAF and also its subsurface geometry. We present SSIP studies at two locations in the Coachella Valley of the northern Salton trough. On our line 4, a fault-crossing profile just north of the Salton Sea, sedimentary basin depth reaches 4 km southwest of the SAF. On our line 6, a fault-crossing profile at the north end of the Coachella Valley, sedimentary basin depth is ∼2-3 km and centered on the central, most active trace of the SAF. Subsurface geometry of the SAF and nearby faults along these two lines is determined using a new method of seismic-reflection imaging, combined with potential-field studies and earthquakes. Below a 6-9 km depth range, the SAF dips ∼50°-60°NE, and above this depth range it dips more steeply. Nearby faults are also imaged in the upper 10 km, many of which dip steeply and project to mapped surface fault traces. These secondary faults may join the SAF at depths below about 10 km to form a flower-like structure. In Appendix D, we show that rupture on a northeast-dipping SAF, using a single plane that approximates the two dips seen in our study, produces shaking that differs from shaking calculated for the Great California ShakeOut, for which the southern SAF was modeled as vertical in most places: shorter-period (T < 1 s) shaking is increased locally by up to a factor of 2 on the hanging wall and is decreased locally by up to a factor of 2 on the footwall, compared to shaking calculated for a vertical fault.

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Section: Discussionmentioning

confidence: 99%

Subsurface Geometry of the San Andreas Fault in Southern California: Results from the Salton Seismic Imaging Project (SSIP) and Strong Ground Motion Expectations

Fuis¹,

Bauer²,

Goldman³

et al. 2017

Bulletin of the Seismological Society of America

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“…1 A schematic plot of a typical fault zone, after Chester and Logan (1986) Pinto Mountain faults, Southern California (Fialko et al 2002). In addition, many geophysical methods have been applied in deriving FZ properties such as gravity and electromagnetic surveys, seismic reflection and refraction, travel-time tomography, earthquake location, waveform modeling of FZ-reflected body waves, FZ head waves, and FZ trapped waves (e.g., Mooney and Ginzburg 1986;BenZion and Malin 1991;Ben-Zion et al 1992;Hole et al 2001;Prejean et al 2002;Waldhauser and Ellsworth 2002;Li et al 2002;McGuire and Ben-Zion 2005;Bleibinhaus et al 2007;Li et al 2007;Yang et al 2009;Roland et al 2012). In the following, I briefly review a few seismological and geodetic methods that have been used to derive FZ structure.…”

Section: Fz Properties and Their Effectsmentioning

confidence: 99%

Recent advances in imaging crustal fault zones: a review

Yang

2015

Earthq Sci

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Crustal faults usually have a fault core and surrounding regions of brittle damage, forming a low-velocity zone (LVZ) in the immediate vicinity of the main slip interface. The LVZ may amplify ground motion, influence rupture propagation, and hold important information of earthquake physics. A number of geophysical and geodetic methods have been developed to derive high-resolution structure of the LVZ. Here, I review a few recent approaches, including ambient noise cross-correlation on dense across-fault arrays and GPS recordings of fault-zone trapped waves. Despite the past efforts, many questions concerning the LVZ structure remain unclear, such as the depth extent of the LVZ. High-quality data from larger and denser arrays and new seismic imaging technique using larger portion of recorded waveforms, which are currently under active development, may be able to better resolve the LVZ structure. In addition, effects of the alongstrike segmentation and gradational velocity changes across the boundaries between the LVZ and the host rock on rupture propagation should be investigated by conducting comprehensive numerical experiments. Furthermore, high-quality active sources such as recently developed large-volume airgun arrays provide a powerful tool to continuously monitor temporal changes of fault-zone properties, and thus can advance our understanding of fault zone evolution.

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“…They most likely represent reflections at steeply dipping or near vertical structures in the center of the profiles (i.e. the main fault) and/or parts of diffraction hyperbolas related to strong point scatterers directly at the fault (see for example Hole et al, 2001). In the migration process ( Figure 8) these reflective events collapse into subvertical structures or single points.…”

Section: A C C E P T E Dmentioning

confidence: 99%

Shallow architecture of the Wadi Araba fault (Dead Sea Transform) from high-resolution seismic investigations

et al. 2007

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In a high-resolution small scale seismic experiment we investigated the shallow structure of the Wadi Araba Fault (WAF), the principal fault strand of the Dead Sea Transform System between the Gulf of Aqaba/Eilat and the Dead Sea. The experiment consisted of 8 sub-parallel 1 km long seismic lines crossing the WAF. The recording station spacing was 5 meters and the source point distance was 20 m.The first break tomography yields insight into the fault structure down to a depth Often the superficial sedimentary layers are bent upward close to the WAF. Our results indicate that this section of the fault (at shallow depths) is characterized by a transpressional regime. We detected a 100 to 300 m wide heterogeneous zone of deformed and displaced material which, however, is not characterized by low seismic velocities at a larger scale. At greater depth the geophysical images indicate a blocked cross-fault structure. The structure revealed, fault cores not wider than 10 m, are consistent with scaling from wear mechanics and with the low loading to healing ratio anticipated for the fault.

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Steep-Dip Seismic Imaging of the Shallow San Andreas Fault Near Parkfield

Cited by 56 publications

References 17 publications

Subsurface Geometry of the San Andreas Fault in Southern California: Results from the Salton Seismic Imaging Project (SSIP) and Strong Ground Motion Expectations

Subsurface Geometry of the San Andreas Fault in Southern California: Results from the Salton Seismic Imaging Project (SSIP) and Strong Ground Motion Expectations

Recent advances in imaging crustal fault zones: a review

Shallow architecture of the Wadi Araba fault (Dead Sea Transform) from high-resolution seismic investigations

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