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Published June 10, 2016 | Supplemental Material
Journal Article Open

Deeper penetration of large earthquakes on seismically quiescent faults

Abstract

Why many major strike-slip faults known to have had large earthquakes are silent in the interseismic period is a long-standing enigma. One would expect small earthquakes to occur at least at the bottom of the seismogenic zone, where deeper aseismic deformation concentrates loading. We suggest that the absence of such concentrated microseismicity indicates deep rupture past the seismogenic zone in previous large earthquakes. We support this conclusion with numerical simulations of fault behavior and observations of recent major events. Our modeling implies that the 1857 Fort Tejon earthquake on the San Andreas Fault in Southern California penetrated below the seismogenic zone by at least 3 to 5 kilometers. Our findings suggest that such deeper ruptures may occur on other major fault segments, potentially increasing the associated seismic hazard.

Additional Information

© 2016 American Association for the Advancement of Science. Received 27 December 2015; accepted 11 May 2016. This study was supported by the U.S. Geological Survey (USGS) (grant G14AP00033), the National Science Foundation (NSF) (grants EAR 1142183 and 1520907), and the Southern California Earthquake Center (SCEC, funded by NSF cooperative agreement EAR-0529922 and USGS Cooperative agreement 07HQAG0008). This is SCEC contribution no. 6139. Numerical simulations for this study were carried out on the CITerra Dell cluster at the Division of Geological and Planetary Sciences of the California Institute of Technology. We thank J.-P. Ampuero, J.-P. Avouac, E. Hauksson, and M. Simons for helpful discussions and comments on the manuscript. Earthquake catalogs and fault-slip models are compiled from published literature and publicly available sources. Numerical data are available from the authors upon request.

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October 9, 2023
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