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Microseismicity on Patches of Higher Compression During Larger-Scale Earthquake Nucleation in a Rate-and-State Fault Model

Schaal, Natalie and Lapusta, Nadia (2019) Microseismicity on Patches of Higher Compression During Larger-Scale Earthquake Nucleation in a Rate-and-State Fault Model. Journal of Geophysical Research. Solid Earth, 124 (2). pp. 1962-1990. ISSN 2169-9313. doi:10.1029/2018jb016395.

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While many large earthquakes are preceded by observable foreshocks, the mechanism responsible for the occurrence of these smaller‐scale seismic events remains uncertain. One physical explanation of foreshocks with growing support is that they are produced by the interaction of slow slip with fault heterogeneity. Inspired by the suggestion from laboratory experiments that foreshocks occur on fault asperities (bumps), we explore rate‐and‐state fault models with patches of higher normal stress embedded in a larger seismogenic region by conducting 3‐D numerical simulations of their behavior over long‐term sequences of aseismic and seismic slips. The models do produce smaller‐scale seismicity during the aseismic nucleation of larger‐scale seismic events. These smaller‐scale events have reasonable stress drops, despite the highly elevated compression assigned to the source patches. We find that the two main factors contributing to the reasonable stress drops are the significant extent of the rupture into the region surrounding the patches and the aseismic stress release just prior to the seismic events. The smaller‐scale seismicity can only occur if a sufficient separation in nucleation scales between the foreshock‐like events and mainshocks is achieved. Our modeling provides insight into the conditions conducive for generating foreshocks on both natural and laboratory faults.

Item Type:Article
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URLURL TypeDescription
Schaal, Natalie0000-0003-4825-4344
Lapusta, Nadia0000-0001-6558-0323
Additional Information:© 2019. American Geophysical Union. Received 14 JUL 2018. Accepted 21 JAN 2019. Accepted article online 28 JAN 2019. Published online 18 FEB 2019. This study was supported by the National Science Foundation (grants EAR 1520907 and 1724686) and the Southern California Earthquake Center (SCEC), contribution 8972. SCEC is funded by NSF Cooperative Agreement EAR‐1600087 and USGS Cooperative Agreement G17AC00047. The numerical simulations for this work were run on the supercomputing cluster in the Caltech Division for Geology and Planetary Science. The data supporting the analysis and conclusions are given in figures and tables. We thank Greg McLaskey for insightful discussions about the laboratory experiments, Jean‐Philippe Avouac and Tom Heaton for helpful comments to the manuscript, and Junle Jiang for help with the simulation code.
Group:Center for Geomechanics and Mitigation of Geohazards (GMG), Division of Geological and Planetary Sciences, Seismological Laboratory
Funding AgencyGrant Number
Southern California Earthquake Center (SCEC)UNSPECIFIED
Subject Keywords:earthquake nucleation; foreshocks; microseismicity; rate‐and‐state friction; stress drops; earthquake triggering
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Other Numbering System NameOther Numbering System ID
Southern California Earthquake Center8972
Issue or Number:2
Record Number:CaltechAUTHORS:20190328-180954384
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Official Citation: Schaal, N., & Lapusta, N. ( 2019). Microseismicity on patches of higher compression during larger‐scale earthquake nucleation in a rate‐and‐state fault model. Journal of Geophysical Research: Solid Earth, 124, 1962– 1990.
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:94273
Deposited By: George Porter
Deposited On:29 Mar 2019 17:19
Last Modified:15 Nov 2022 21:41

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