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Isotropic source terms of San Jacinto fault zone earthquakes based on waveform inversions with a generalized CAP method

Ross, Z. E. and Ben-Zion, Y. and Zhu, L. (2015) Isotropic source terms of San Jacinto fault zone earthquakes based on waveform inversions with a generalized CAP method. Geophysical Journal International, 200 (2). pp. 1269-1280. ISSN 0956-540X. doi:10.1093/gji/ggu460.

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We analyse source tensor properties of seven M_w > 4.2 earthquakes in the complex trifurcation area of the San Jacinto Fault Zone, CA, with a focus on isotropic radiation that may be produced by rock damage in the source volumes. The earthquake mechanisms are derived with generalized ‘Cut and Paste’ (gCAP) inversions of three-component waveforms typically recorded by >70 stations at regional distances. The gCAP method includes parameters ζ and χ representing, respectively, the relative strength of the isotropic and CLVD source terms. The possible errors in the isotropic and CLVD components due to station variability is quantified with bootstrap resampling for each event. The results indicate statistically significant explosive isotropic components for at least six of the events, corresponding to ∼0.4–8 per cent of the total potency/moment of the sources. In contrast, the CLVD components for most events are not found to be statistically significant. Trade-off and correlation between the isotropic and CLVD components are studied using synthetic tests with realistic station configurations. The associated uncertainties are found to be generally smaller than the observed isotropic components. Two different tests with velocity model perturbation are conducted to quantify the uncertainty due to inaccuracies in the Green's functions. Applications of the Mann–Whitney U test indicate statistically significant explosive isotropic terms for most events consistent with brittle damage production at the source.

Item Type:Article
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URLURL TypeDescription
Ross, Z. E.0000-0002-6343-8400
Ben-Zion, Y.0000-0002-9602-2014
Additional Information:© The Authors 2015. Published by Oxford University Press on behalf of The Royal Astronomical Society. Accepted 2014 December 1. Received 2014 November 28; in original form 2014 April 10. The study was supported by the National Science Foundation (grants EAR-0838195 and EAR-1249701). The paper benefitted from useful comments of an anonymous referee and Editor Eiichi Fukuyama.
Group:Seismological Laboratory
Funding AgencyGrant Number
Subject Keywords:Fault zone rheology, Earthquake source observations, Seismic monitoring and test-ban treaty verification, Dynamics and mechanics of faulting
Issue or Number:2
Record Number:CaltechAUTHORS:20190423-155306997
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Official Citation:Z. E. Ross, Y. Ben-Zion, L. Zhu, Isotropic source terms of San Jacinto fault zone earthquakes based on waveform inversions with a generalized CAP method, Geophysical Journal International, Volume 200, Issue 2, February, 2015, Pages 1269–1280,
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:94903
Deposited By: George Porter
Deposited On:23 Apr 2019 23:00
Last Modified:16 Nov 2021 17:08

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