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Nucleation and early seismic propagation of small and large events in a crustal earthquake model

Lapusta, Nadia and Rice, James R. (2003) Nucleation and early seismic propagation of small and large events in a crustal earthquake model. Journal of Geophysical Research B, 108 (B4). Art. No. 2205. ISSN 0148-0227. doi:10.1029/2001JB000793.

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Earthquake nucleation and early seismic propagation are studied in a two-dimensional strike-slip fault model with depth-variable properties. The fault is governed by the Dieterich-Ruina rate and state friction law. We use an efficient and rigorous numerical procedure for elastodynamic analysis of earthquake sequences on slowly loaded faults developed by Lapusta et al. [2000]. We find that for decreasing values of the characteristic slip distance of the friction law, small events appear at the transition from the locked to creeping behavior toward the bottom of the seismogenic zone. Small and large events have very similar nucleation phases in our simulations. Here, by “nucleation phase” we mean gradually accelerating aseismic slip in a small slowly expanding zone before the breakout of the dynamic, seismically detectable event. Moment acceleration (to which velocity seismograms are proportional) in early stages of seismic propagation exhibits irregular fluctuations, in the form of speedups and slowdowns in the moment release rate, consistently with observations as reported by Ellsworth and Beroza [1995]. Our simulations show that such irregular moment acceleration can, at least in part, be due to the heterogeneous stress distribution imprinted on the fault by the arrest of previous small events and by stress concentrations at the borders of creeping regions and to partial arrest of the rupture in velocity-strengthening fault regions which inhibit seismic slip.

Item Type:Article
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URLURL TypeDescription
Lapusta, Nadia0000-0001-6558-0323
Additional Information:© 2003 by the American Geophysical Union. Received 10 July 2001; revised 11 July 2002; accepted 6 January 2003; published 18 April 2003. These studies were supported by the Southern California Earthquake Center (SCEC) and by USGS grant 99-HQ-GR-0025 to Harvard University. SCEC is supported by NSF Cooperative Agreement EAR-8920136 and USGS Cooperative Agreements 14-08-0001-A0899 and 1434-HQ-97AG01718. This is SCEC contribution 609. We are grateful to Bill Ellsworth, Rachel Abercrombie, Paul Segall, and Greg Beroza for insightful suggestions and discussions as well as to Mitsuhiro Matsu’ura and an anonymous reviewer for helpful comments. We also thank Bill Ellsworth, Greg Beroza, and David Schaff for giving the permission to use their figures and for providing digital copies of them.
Funding AgencyGrant Number
Southern California Earthquake Center (SCEC)UNSPECIFIED
Subject Keywords:earthquake nucleation phase; event clustering; irregular moment release; stress concentrations; rate and state friction; earthquake sequences
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Other Numbering System NameOther Numbering System ID
Southern California Earthquake Center (SCEC)609
Issue or Number:B4
Record Number:CaltechAUTHORS:20130308-133521256
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Official Citation:Lapusta, N., and J. R. Rice, Nucleation and early seismic propagation of small and large events in a crustal earthquake model, J. Geophys. Res., 108(B4), 2205, doi:10.1029/2001JB000793, 2003
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:37419
Deposited By: Tony Diaz
Deposited On:15 Apr 2013 19:48
Last Modified:09 Nov 2021 23:28

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