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Searching for Transient Slow Slips Along the San Andreas Fault Near Parkfield Using Independent Component Analysis

Michel, Sylvain and Jolivet, Romain and Lengliné, Olivier and Gualandi, Adriano and Larochelle, Stacy and Gardonio, Blandine (2022) Searching for Transient Slow Slips Along the San Andreas Fault Near Parkfield Using Independent Component Analysis. Journal of Geophysical Research. Solid Earth, 127 (6). Art. No. e2021JB023201. ISSN 2169-9313. doi:10.1029/2021jb023201.

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The Parkfield segment of the San Andreas Fault (SAF) sits at the transition between the locked Cholame segment to the South and the SAF creeping segment to the North. The Parkfield segment hosts regular ~M_W 6 earthquakes followed by postseismic deformation. Recent studies based on geodetic data have highlighted spatial and temporal variations of aseismic slip rate in addition to postseismic slip along this section of the fault. We combine Global Navigation Satellite Systems (GNSS) and seismicity data over the 2006–2018 period to detail a comprehensive picture of transient slip events. We produce a catalog of relocated seismicity and repeating earthquakes. We use a variational Bayesian independent component analysis decomposition on GNSS data to separate geodetic deformation due to non-tectonic sources from signals of potential tectonic origin. We then reconstruct the temporal evolution of fault slip and detect potential slip transients. Those events, determined as mostly aseismic with the exception of one related to a M_W 4.8 earthquake, occur more frequently during the 2004 M_W 6 post-seismic period than during the subsequent inter-seismic phase. Our study illustrates the rich dynamics of seismic and aseismic slip during both post- and inter-seismic periods along active faults.

Item Type:Article
Related URLs:
URLURL TypeDescription ItemANSS Comprehensive Earthquake Catalog waveforms from the network BK waveforms from the network BP waveforms from the network NC ItemIRIS ItemUNAVCO
Michel, Sylvain0000-0001-7878-6603
Jolivet, Romain0000-0002-9896-3651
Gualandi, Adriano0000-0002-3100-8932
Larochelle, Stacy0000-0001-6161-5605
Gardonio, Blandine0000-0002-5305-5350
Additional Information:© 2022. American Geophysical Union. Issue Online: 20 June 2022. Version of Record online: 20 June 2022. Accepted manuscript online: 10 June 2022. Manuscript accepted: 16 May 2022. Manuscript revised: 10 May 2022. Manuscript received: 07 September 2021. This study has been funded by the Centre National d’Etudes Spatiales (CNES) postdoctoral fellowship. This project has received funding from the European Research Council (ERC) under the European Union's Horizon 2020 research and innovation program (project Geo-4D, Grant Agreement 758210). RJ acknowledges funding from the Institut Universitaire de France. SM, BG, and RJ acknowledge funding from the Laboratoire de Recherche Commun Yves Rocard (ENS/CEA). AG acknowledges funding from the European Research Council Advanced Grant 835012 (TECTONIC). The calculations were performed using MATLAB. The study complies with FAIR Data standards. We thank Jean-Philippe Avouac for his comments on an early version of the manuscript. We thank the anonymous reviewers and the Associate Editor for insightful comments which helped improve the study substantially. Data Availability Statement. We use the instrumental seismicity catalogue from the ANSS Comprehensive Earthquake Catalog (ComCat) ( The seismic waveforms from the network BK (, BP ( and NC (, were downloaded through IRIS ( The Low Frequency Earthquake catalog is taken directly from Shelly, 2017. The GNSS data were acquired by UNAVCO (Network of Americas project) and processed by the Jet Propulsion Laboratory (; MEaSUREs program).
Group:Seismological Laboratory
Funding AgencyGrant Number
Centre National d’Études Spatiales (CNES)UNSPECIFIED
European Research Council (ERC)758210
Institut Universitaire de France (IUF)UNSPECIFIED
European Research Council (ERC)835012
Subject Keywords:Parkfield; post-seismic deformation; slow slip events; variational Bayesian independent component analysis; repeating earthquakes
Issue or Number:6
Record Number:CaltechAUTHORS:20220715-744511000
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Official Citation:Michel, S., Jolivet, R., Lengliné, O., Gualandi, A., Larochelle, S., & Gardonio, B. (2022). Searching for transient slow slips along the San Andreas Fault near Parkfield using independent component analysis. Journal of Geophysical Research: Solid Earth, 127, e2021JB023201.
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:115659
Deposited By: George Porter
Deposited On:18 Jul 2022 16:37
Last Modified:18 Jul 2022 16:37

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