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Evidence for Latent Crustal Fluid Injection Transients in Southern California From Long-Duration Earthquake Swarms

Ross, Zachary E. and Cochran, Elizabeth S. (2021) Evidence for Latent Crustal Fluid Injection Transients in Southern California From Long-Duration Earthquake Swarms. Geophysical Research Letters, 48 (12). Art. No. e2021GL092465. ISSN 0094-8276. doi:10.1029/2021gl092465.

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Earthquake swarms are manifestations of aseismic driving processes deep in the crust. We examine the spatiotemporal distribution of aseismic processes in Southern California using a 12-years catalog of swarms derived with deep learning algorithms. In a core portion of the plate boundary region, which is not associated with elevated heat flow, we identify 92 long-duration swarms ranging from 6 months to 7 years that constitute 26.4% of the total seismicity. We find that 53% of the swarms exhibit ultra-slow diffusive patterns with propagating backfronts, consistent with expectations for natural fluid injection processes. The chronology of the swarms indicates that the aseismic driving processes were active at all times during 2008–2020. The observations challenge common views about the nature of swarms, which would characterize any one of these sequences as anomalous. The regional prevalence of these sequences suggests that transient fluid injection processes play a key role in crustal fluid transport.

Item Type:Article
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URLURL TypeDescription
Ross, Zachary E.0000-0002-6343-8400
Cochran, Elizabeth S.0000-0003-2485-4484
Additional Information:© 2021 American Geophysical Union. Issue Online: 15 June 2021; Version of Record online: 15 June 2021; Accepted manuscript online: 08 June 2021; Manuscript accepted: 26 May 2021; Manuscript revised: 03 May 2021; Manuscript received: 11 January 2021. The authors thank Andrea Llenos, Clara Yoon, Stephen Miller, and Pascal Bernard for reviewing the paper. The authors also thank Jonathan Smith for helpful comments on the initial manuscript. This study was supported by the National Science Foundation under award EAR-2034167. Data Availability Statement: All data used are publicly available from the Southern California Earthquake Data Center ( The developed catalog will also be publicly hosted at the SCEDC.
Group:Center for Geomechanics and Mitigation of Geohazards (GMG), Division of Geological and Planetary Sciences, Seismological Laboratory
Funding AgencyGrant Number
Subject Keywords:aseismic processes; deep learning; earthquake swarms; hydrogeology
Issue or Number:12
Record Number:CaltechAUTHORS:20210610-133645643
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Official Citation:Ross, Z. E., & Cochran, E. S. (2021). Evidence for latent crustal fluid injection transients in Southern California from long-duration earthquake swarms. Geophysical Research Letters, 48, e2021GL092465.
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:109470
Deposited By: Tony Diaz
Deposited On:10 Jun 2021 20:42
Last Modified:15 Nov 2022 19:09

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