Structure and Earthquake Offsets on the San Andreas Fault at the Wrightwood, California, Paleoseismic Site

Weldon, Ray J.; Fumal, Thomas E.; Powers, T.J.; Pezzopane, Silvio K.; Scharer, Katherine M.; Hamilton, J. C.

doi:10.1785/0120000612

Cited by 58 publications

(61 citation statements)

References 20 publications

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“…Previous studies suggest that complex surface faulting may become simpler at depth as faults coalesce onto prominent structures, so-called flower structures [Weldon II et al, 2002;Bozkurt and Koçyiôit, 1996;Wei et al, 2011]. Active flower structures have been observed along major well-developed strike-slip fault systems such as the southern San Andreas fault [Weldon II et al, 2002], along other major strike-slip fault systems in Southern California [Harding, 1985[Harding, , 1988Dooley and McClay, 1996], and along the North Anatolian fault [Bozkurt and Koçyiôit, 1996]. Conversely, it has also been shown that highly active, immature strike-slip fault systems may consist of parallel throughgoing fault strands, with secondary splays at varying orientations [Rybicki, 1973;Segall and Pollard, 1980;Reasenberg and Ellsworth, 1982].…”

Section: Introductionmentioning

confidence: 99%

Aftershocks of the 2010 M_w 7.2 El Mayor‐Cucapah earthquake reveal complex faulting in the Yuha Desert, California

et al. 2013

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[1] We detect and precisely locate over 9500 aftershocks that occurred in the Yuha Desert region during a 2 month period following the 4 April 2010 M w 7.2 El Mayor-Cucapah (EMC) earthquake. Events are relocated using a series of absolute and relative relocation procedures that include Hypoinverse, Velest, and hypoDD. Location errors are reduced to 40 m horizontally and 120 m vertically. Aftershock locations reveal a complex pattern of faulting with en echelon fault segments trending toward the northwest, approximately parallel to the North American-Pacific plate boundary and en echelon, conjugate features trending to the northeast. The relocated seismicity is highly correlated with published surface mapping of faults that experienced triggered surface slip in response to the EMC main shock. Aftershocks occurred between 2 km and 11 km depths, consistent with previous studies of seismogenic thickness in the region. Three-dimensional analysis reveals individual and intersecting fault planes that are limited in their along-strike length. These fault planes remain distinct structures at depth, indicative of conjugate faulting, and do not appear to coalesce onto a throughgoing fault segment. We observe a complex spatiotemporal migration of aftershocks, with seismicity that jumps between individual fault segments that are active for only a few days to weeks. Aftershock rates are roughly consistent with the expected earthquake production rates of Dieterich (1994). The conjugate pattern of faulting and nonuniform aftershock migration patterns suggest that strain in the Yuha Desert is being accommodated in a complex manner.

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Section: Introductionmentioning

confidence: 99%

Aftershocks of the 2010 M_w 7.2 El Mayor‐Cucapah earthquake reveal complex faulting in the Yuha Desert, California

et al. 2013

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“…1). Here, fortuitous depositional circumstances have preserved a ∼25 m section of alternating clastic sediments and peats that are disturbed by ground rupture (Fumal et al, 1993;Fumal, Weldon, et al, 2002;Weldon, et al, 2002). These sediments apparently were deposited on a gently inclined alluvial fan surface that forms as a side tributary (Government Canyon tributary) debouched into the axial drainage (Swarthout Creek).…”

Section: Application Of Bayesian Mcmc Sampling Methodsmentioning

confidence: 99%

“…This site contains the most complete and well-documented record of ancient earthquakes along the SAF (Fumal et al, 1993;Biasi and Weldon, 1994;Biasi, et al, 2002;Fumal, Weldon, et al, 2002;Weldon, et al, 2002;Weldon et al, 2004), and the Bayesian ID methodology has been used to estimate the marginal PDFs for layer ages, earthquakes, and recurrence intervals at the site (Biasi and Weldon, 1994;Biasi et al, 2002). Thus, the site provides an excellent test case for comparing the impact of different approximations of Bayes's rule on the joint posterior probability density.…”

Section: Application Of Bayesian Mcmc Sampling Methodsmentioning

confidence: 99%

“…These sediments apparently were deposited on a gently inclined alluvial fan surface that forms as a side tributary (Government Canyon tributary) debouched into the axial drainage (Swarthout Creek). Only the uppermost ∼12 m of the disturbed section have been documented in detail (Fumal et al, 1993;Fumal, Weldon, et al, 2002;Weldon et al, 2002), and it is this section on which we concentrated our analysis. Cross-cutting relationships between sediments and groundrupturing structures that were documented in a total of 38 excavations and natural exposures provide evidence for 14 events since A.D. 500 .…”

Section: Application Of Bayesian Mcmc Sampling Methodsmentioning

confidence: 99%

“…These questions are a central theme in paleoseismology (e.g., Sieh, 1978a,b;Sieh and Jahns, 1984;Grant and Sieh, 1994;McCalpin, 1996), and their answers serve as important inputs to seismic hazard evaluations (e.g., Working Group on California Earthquake Probabilities (WGCEP), 1988; WGCEP, 1995;WGCEP, 2003) and provide essential information about long-term rupture segmentation of faults (e.g., Schwartz and Coppersmith, 1984;Sieh, 1996). Along the central and southern San Andreas fault (SAF), a number of paleoseismic studies reveal the timing and recurrence of up to 14 ancient earthquakes at the Wrightwood site (e.g., Fumal, et al, 1993;Fumal, Weldon, et al, 2002;Weldon, et al, 2002). Because these paleoseismic sites span a substantial length of the central and southern SAF (Fig.…”

Section: Introductionmentioning

confidence: 99%

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Deducing Paleoearthquake Timing and Recurrence from Paleoseismic Data, Part II: Analysis of Paleoseismic Excavation Data and Earthquake Behavior along the Central and Southern San Andreas Fault

Hilley¹,

Young²

2008

Bulletin of the Seismological Society of America

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Determining the timing of paleoearthquakes is a central goal of paleoseismology and serves as an important input to seismic hazard evaluations. Herein, we develop a Bayesian statistical method for refining the ages of strata and earthquakes and calculating the recurrence of earthquakes based on data from paleoseismic excavations. Our work extends previous paleoseismic Bayesian modeling by simultaneously calculating the joint posterior probability density of recurrence intervals, earthquake ages, and layer ages. To estimate this joint posterior density, we employed the Metropolis-Hastings Markov-Chain Monte Carlo (MCMC) sampling method. We used the Wrightwood paleoseismic excavation site as a test bed for our method by comparing the results derived from our simulation to those of previous studies. We found that for stratigraphic order constraints, our results agreed well with previously used methods; however, when peat growth was used to constrain the minimum time that separates layers from one another, a systematic aging of strata in the lower portion of the stratigraphic column resulted. Inspection of our results indicated that, rather than representing a minimum time that separates layers, peat growth instead determined the strata's ages exactly when a constant peat-growth rate was prescribed. Using this information, we developed a new method of improving layer age, earthquake age, and recurrence interval estimates at sites where peat-bearing layers are present. This method generally produces layer-age estimates with less variance than previous methods and requires that both proximal stratigraphic constraints and trenchwide constraints be obeyed. The benchmarking of the MCMC simulation results shows that simulation provides an effective and efficient way of improving estimates of layer ages, earthquake ages, and recurrence intervals.

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Recovery of secular deformation field of Mojave Shear Zone in Southern California from historical terrestrial and GPS measurements

2015

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The 1992 Mw 7.3 Landers and 1999 Mw 7.1 Hector Mine earthquakes struck the Eastern California Shear Zone (ECSZ) in the Mojave Desert, Southern California. Coseismic and postseismic deformation from these events affect efforts to use Global Positioning System (GPS) observations collected since these events to establish a secular surface velocity field, especially in the near field of the coseismic ruptures. We devise block motion models constrained by both historical pre‐Landers triangulation and trilateration observations and post‐Landers GPS measurements to recover the secular deformation field and differentiate the postseismic transients in the Mojave region. Postseismic transients are found to remain in the Southern California Earthquake Center Crustal Motion Map Version 4, Plate Boundary Observatory, and Scripps Orbit and Permanent Array Center GPS velocity solutions in the form of 2–3 mm/yr excess right‐lateral shear across the Landers and Hector Mine coseismic ruptures. The cumulative deformation rate across the Mojave ECSZ is 13.2–14.4 mm/yr, at least twice the geologic rate since the late Pleistocene (≤6.2 ± 1.9 mm/yr). Postseismic GPS time series based on our secular velocity field reveal enduring late‐stage transient motions in the near field of the coseismic ruptures that provide new constraints on the rheological structure of the lower crust and upper mantle.

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Structure and Earthquake Offsets on the San Andreas Fault at the Wrightwood, California, Paleoseismic Site

Cited by 58 publications

References 20 publications

Aftershocks of the 2010 M_w 7.2 El Mayor‐Cucapah earthquake reveal complex faulting in the Yuha Desert, California

Aftershocks of the 2010 M_w 7.2 El Mayor‐Cucapah earthquake reveal complex faulting in the Yuha Desert, California

Deducing Paleoearthquake Timing and Recurrence from Paleoseismic Data, Part II: Analysis of Paleoseismic Excavation Data and Earthquake Behavior along the Central and Southern San Andreas Fault

Recovery of secular deformation field of Mojave Shear Zone in Southern California from historical terrestrial and GPS measurements

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Structure and Earthquake Offsets on the San Andreas Fault at the Wrightwood, California, Paleoseismic Site

Cited by 58 publications

References 20 publications

Aftershocks of the 2010 Mw 7.2 El Mayor‐Cucapah earthquake reveal complex faulting in the Yuha Desert, California

Aftershocks of the 2010 Mw 7.2 El Mayor‐Cucapah earthquake reveal complex faulting in the Yuha Desert, California

Deducing Paleoearthquake Timing and Recurrence from Paleoseismic Data, Part II: Analysis of Paleoseismic Excavation Data and Earthquake Behavior along the Central and Southern San Andreas Fault

Recovery of secular deformation field of Mojave Shear Zone in Southern California from historical terrestrial and GPS measurements

Contact Info

Product

Resources

About

Aftershocks of the 2010 M_w 7.2 El Mayor‐Cucapah earthquake reveal complex faulting in the Yuha Desert, California

Aftershocks of the 2010 M_w 7.2 El Mayor‐Cucapah earthquake reveal complex faulting in the Yuha Desert, California