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Published October 2017 | Published + Supplemental Material
Journal Article Open

Delayed Seismicity Rate Changes Controlled by Static Stress Transfer

Abstract

On 15 June 2010, a M_w5.7 earthquake occurred near Ocotillo, California, in the Yuha Desert. This event was the largest aftershock of the 4 April 2010 M_w7.2 El Mayor-Cucapah (EMC) earthquake in this region. The EMC mainshock and subsequent Ocotillo aftershock provide an opportunity to test the Coulomb failure hypothesis (CFS). We explore the spatiotemporal correlation between seismicity rate changes and regions of positive and negative CFS change imparted by the Ocotillo event. Based on simple CFS calculations we divide the Yuha Desert into three subregions, one triggering zone and two stress shadow zones. We find the nominal triggering zone displays immediate triggering, one stress shadowed region experiences immediate quiescence, and the other nominal stress shadow undergoes an immediate rate increase followed by a delayed shutdown. We quantitatively model the spatiotemporal variation of earthquake rates by combining calculations of CFS change with the rate-state earthquake rate formulation of Dieterich (1994), assuming that each subregion contains a mixture of nucleation sources that experienced a CFS change of differing signs. Our modeling reproduces the observations, including the observed delay in the stress shadow effect in the third region following the Ocotillo aftershock. The delayed shadow effect occurs because of intrinsic differences in the amplitude of the rate response to positive and negative stress changes and the time constants for return to background rates for the two populations. We find that rate-state models of time-dependent earthquake rates are in good agreement with the observed rates and thus explain the complex spatiotemporal patterns of seismicity.

Additional Information

© 2017 American Geophysical Union. Received 22 MAR 2017; Accepted 29 AUG 2017; Accepted article online 30 AUG 2017; Published online 14 OCT 2017. The authors would like to thank Ross Stein and Volkan Sevilgen for the initial interest in this work. K. Kroll thanks R. Stein and V. Sevilgen for their instruction on the Coulomb v3.3 modeling software. We would also like to thank R. Stein and Tom Parsons for providing internal USGS reviews and three anonymous journal reviewers for their constructive feedback on the manuscript. Figures in this manuscript were generating using R (R Development Core Team, 2008) and GMT (Wessel et al., 2013). The HYS and YHS earthquake and focal mechanism catalogs can be downloaded from the following Southern California Earthquake Data Center websites: http://scedc.caltech.edu/research-tools/alt-2011-dd-hauksson-yang-shearer.html and http://scedc.caltech.edu/research-tools/alt-2011-yang-hauksson-shearer.html, respectively. This work was supported by This work was supported by NSF | GEO | Division of Earth Sciences (EAR) [10.13039/100000160] (EAR-1135455). Additional support for the first author came from Lawrence Livermore National Laboratory through institutional postdoctoral support. Lawrence Livermore National Laboratory is operated by Lawrence Livermore National Security, LLC, for the U.S. Department of Energy, National Nuclear Security Administration under Contract DE-AC52-07NA27344.

Attached Files

Published - Kroll_et_al-2017-Journal_of_Geophysical_Research__Solid_Earth.pdf

Supplemental Material - jgrb52305-sup-0001-suplementary.pdf

Supplemental Material - jgrb52305-sup-0002-suplementary.pdf

Supplemental Material - jgrb52305-sup-0003-suplementary.pdf

Supplemental Material - jgrb52305-sup-0004-suplementary.pdf

Supplemental Material - jgrb52305-sup-0005-suplementary.pdf

Supplemental Material - jgrb52305-sup-0006-suplementary.pdf

Supplemental Material - jgrb52305-sup-0007-suplementary.pdf

Supplemental Material - jgrb52305-sup-0008-suplementary.pdf

Supplemental Material - jgrb52305-sup-0009-suplementary.pdf

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Created:
August 21, 2023
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