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Connecting depth limits of interseismic locking, microseismicity, and large earthquakes in models of long-term fault slip

Jiang, Junle and Lapusta, Nadia (2017) Connecting depth limits of interseismic locking, microseismicity, and large earthquakes in models of long-term fault slip. Journal of Geophysical Research. Solid Earth, 122 (8). pp. 6491-6523. ISSN 2169-9313. doi:10.1002/2017JB014030.

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Thickness of the seismogenic zone is commonly determined based on the depth of microseismicity or the fault locking depth inferred from geodetic observations. The relation between the two estimates and their connection to the depth limit of large earthquakes remain elusive. Here we explore the seismic and geodetic observables in models of faults governed by laboratory-based friction laws that combine quasi-static rate-and-state friction and enhanced dynamic weakening. Our models suggest that the transition between the locked and fully creeping regions can occur over a broad depth range. The effective locking depth, D_(elock), associated with concentrated loading and promoting microseismicity, is located at the top of this transition zone; the geodetic locking depth, D_(glock), inverted from surface geodetic observations, corresponds to the depth of fault creeping with approximately half of the long-term rate. Following large earthquakes, D_(elock) either stays unchanged or becomes shallower due to creep penetrating into the shallower locked areas, whereas D_(glock) deepens as the slip deficit region expands, compensating for the afterslip. As the result, the two locking depths diverge in the late interseismic period, consistent with available seismic and geodetic observations from several major fault segments in Southern California. We find that D_(glock) provides a bound on the depth limit of large earthquakes in our models. However, the assumed layered distribution of fault friction and simple depth estimates are insufficient to characterize more heterogeneous faults, e.g., ones with significant along-strike variations. Improved observations and models are needed to illuminate physical properties and seismic potential of fault zones.

Item Type:Article
Related URLs:
URLURL TypeDescription
Jiang, Junle0000-0002-8796-5846
Lapusta, Nadia0000-0001-6558-0323
Additional Information:© 2017 American Geophysical Union. Received 25 JAN 2017; Accepted 14 JUL 2017; Accepted article online 20 JUL 2017; Published online 15 AUG 2017. This study was supported by the United States Geological Survey (grants G14AP00033 and G16AP00117), National Science Foundation (grants EAR 1142183 and 1520907), and the Southern California Earthquake Center (SCEC, funded by NSF Cooperative Agreement EAR-1033462 and USGS Cooperative Agreement G12AC20038). This is SCEC contribution 7171. J.J. was also supported by a Green Foundation Postdoctoral Fellowship in the Institute of Geophysics and Planetary Physics, Scripps Institution of Oceanography, University of California, San Diego. We thank Pablo Ampuero, Jean-Philippe Avouac, Tom Heaton, and Mark Simons for helpful discussions and comments on an earlier draft of the manuscript. We thank Yuri Fialko and David Sandwell for discussions on the topic. Numerical data are available upon request to the authors.
Group:Seismological Laboratory
Funding AgencyGrant Number
Southern California Earthquake Center (SCEC)UNSPECIFIED
University of California, San DiegoUNSPECIFIED
Subject Keywords:fault mechanics; rate-and-state friction; dynamic weakening; microseismicity; geodetic locking; large earthquakes
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Other Numbering System NameOther Numbering System ID
Southern California Earthquake Center7171
Issue or Number:8
Record Number:CaltechAUTHORS:20171005-104503035
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Official Citation:Jiang, J., and N. Lapusta (2017), Connecting depth limits of interseismic locking, microseismicity, and large earthquakes in models of long-term fault slip, J. Geophys. Res. Solid Earth, 122, 6491–6523, doi:10.1002/2017JB014030
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:82115
Deposited By: Tony Diaz
Deposited On:05 Oct 2017 21:51
Last Modified:15 Nov 2021 19:48

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