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The Effects of Fault Roughness on the Earthquake Nucleation Process

Tal, Yuval and Hager, Bradford H. and Ampuero, Jean Paul (2018) The Effects of Fault Roughness on the Earthquake Nucleation Process. Journal of Geophysical Research. Solid Earth, 123 (1). pp. 437-456. ISSN 2169-9313. doi:10.1002/2017JB014746.

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We study numerically the effects of fault roughness on the nucleation process during earthquake sequences. The faults are governed by a rate and state friction law. The roughness introduces local barriers that complicate the nucleation process and result in asymmetric expansion of the rupture, nonmonotonic increase in the slip rates on the fault, and the generation of multiple slip pulses. These complexities are reflected as irregular fluctuations in the moment rate. There is a large difference between first slip events in the sequences and later events. In the first events, for roughness amplitude b_r ≤ 0.002, there is a large increase in the nucleation length with increasing br. For larger values of b_r, slip is mostly aseismic. For the later events there is a trade-off between the effects of the finite fault length and the fault roughness. For b_r ≤ 0.002, the finite length is a more dominant factor and the nucleation length barely changes with br. For larger values of b_r, the roughness plays a larger role and the nucleation length increases significantly with b_r. Using an energy balance approach, where the roughness is accounted for in the fault stiffness, we derive an approximate solution for the nucleation length on rough faults. The solution agrees well with the main trends observed in the simulations for the later events and provides an estimate of the frictional and roughness properties under which faults experience a transition between seismic and aseismic slip.

Item Type:Article
Related URLs:
URLURL TypeDescription
Tal, Yuval0000-0001-7308-9294
Hager, Bradford H.0000-0002-5643-1374
Ampuero, Jean Paul0000-0002-4827-7987
Additional Information:© 2017 American Geophysical Union. Received 21 JUL 2017; Accepted 27 DEC 2017; Accepted article online 29 DEC 2017; Published online 15 JAN 2018. We thank Allan Rubin, Eric Dunham, and Yoshihiro Kaneko for their thorough reviews and constructive comments. This work was supported by Aramco grant 6500009957 and the Southern California Earthquake Center (SCEC) grant 16108. SCEC is funded by NSF Cooperative Agreement EAR-1033462 and USGS Cooperative Agreement G12 AC20038. Computer code used in this work has been cited in the references, and numerical data are available to anyone upon request.
Group:Seismological Laboratory
Funding AgencyGrant Number
Southern California Earthquake Center (SCEC)16108
USGSG12 AC20038
Subject Keywords:Dynamics and Mechanics of Faulting; Dynamics: Seismotectonics; Earthquake Dynamics; Earthquake Interaction, Forecasting, and Prediction; Seismicity and Tectonics
Issue or Number:1
Record Number:CaltechAUTHORS:20180314-111622058
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Official Citation:Tal, Y., Hager, B. H., & Ampuero, J. P. (2018). The effects of fault roughness on the earthquake nucleation process. Journal of Geophysical Research: Solid Earth, 123, 437–456.
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:85308
Deposited By: Tony Diaz
Deposited On:15 Mar 2018 03:35
Last Modified:15 Nov 2021 20:27

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