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Detailed 3D Fault Representations for the 2019 Ridgecrest, California, Earthquake Sequence

Plesch, Andreas and Shaw, John H. and Ross, Zachary E. and Hauksson, Egill (2020) Detailed 3D Fault Representations for the 2019 Ridgecrest, California, Earthquake Sequence. Bulletin of the Seismological Society of America, 110 (4). pp. 1818-1831. ISSN 0037-1106.

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We present new 3D source fault representations for the 2019 M 6.4 and M 7.1 Ridgecrest earthquake sequence. These representations are based on relocated hypocenter catalogs expanded by template matching and focal mechanisms for M 4 and larger events. Following the approach of Riesner et al. (2017), we generate reproducible 3D fault geometries by integrating hypocenter, nodal plane, and surface rupture trace constraints. We used the southwest–northeast‐striking nodal plane of the 4 July 2019 M 6.4 event to constrain the initial representation of the southern Little Lake fault (SLLF), both in terms of location and orientation. The eastern Little Lake fault (ELLF) was constrained by the 5 July 2019 M 7.1 hypocenter and nodal planes of M 4 and larger aftershocks aligned with the main trend of the fault. The approach follows a defined workflow that assigns weights to a variety of geometric constraints. These main constraints have a high weight relative to that of individual hypocenters, ensuring that small aftershocks are applied as weaker constraints. The resulting fault planes can be considered averages of the hypocentral locations respecting nodal plane orientations. For the final representation we added detailed, field‐mapped rupture traces as strong constraints. The resulting fault representations are generally smooth but nonplanar and dip steeply. The SLLF and ELLF intersect at nearly right angles and cross on another. The ELLF representation is truncated at the Airport Lake fault to the north and the Garlock fault to the south, consistent with the aftershock pattern. The terminations of the SLLF representation are controlled by aftershock distribution. These new 3D fault representations are available as triangulated surface representations, and are being added to a Community Fault Model (CFM; Plesch et al., 2007, 2019; Nicholson et al., 2019) for wider use and to derived products such as a CFM trace map and viewer (Su et al., 2019).

Item Type:Article
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URLURL TypeDescription
Plesch, Andreas0000-0002-3355-9199
Ross, Zachary E.0000-0002-6343-8400
Hauksson, Egill0000-0002-6834-5051
Additional Information:© 2020 Seismological Society of America. Manuscript received 31 January 2020; Published online 30 June 2020. This research was partially funded by the Southern California Earthquake Center (SCEC) under Award Number 19102 and is SCEC Publication Number 10096. The SCEC is funded by National Science Foundation (NSF) Cooperative Agreement EAR‐1600087 and the U.S. Geological Survey (USGS) Cooperative Agreement G17AC00047. The authors thank reviewers for their generous comments. Data and Resources: Detailed rupture trace data (Kendrick et al., 2019; K. Scharer, personal comm., 2019) was obtained from (last accessed September 2019). We have used hypocenters from the California Institute of Technology (Caltech)/U.S. Geological Survey (USGS) Southern California Seismic Network (SCSN); doi: 10.7914/SN/CI; stored at the Southern California Earthquake Data Center (doi: 10.7909/C3WD3xH1 and available at, last accessed September 2019). The hypocenters and magnitudes that are from the Caltech/USGS southern California earthquake catalog are described by Hutton et al. (2010). The most recent relocations of 2019 Ridgecrest seismicity and data availability are described in Hauksson et al. (2020). The quake template matching (QTM) catalog is available at (last accessed September 2019) and described in Ross, Trugman, et al. (2019). The digital fault representations prepared in this study are available in ASCII format in the supplemental material. They are provided in UTM zone 11 coordinates. In addition, these fault models will be incorporated in a subsequent release of the Southern California Earthquake Center (SCEC) Community Fault Model (CFM), available at (last accessed April 2020). Other utilized resources include the Quaternary fault and fold database for the United States by the USGS and California Geological Survey available at (last accessed September 2019) and the SCEC CFM Viewer available at (last accessed April 2020).
Group:Seismological Laboratory
Funding AgencyGrant Number
Southern California Earthquake Center (SCEC)19102
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Other Numbering System NameOther Numbering System ID
Southern California Earthquake Center10096
Issue or Number:4
Record Number:CaltechAUTHORS:20200828-144031127
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Official Citation:Andreas Plesch, John H. Shaw, Zachary E. Ross, Egill Hauksson; Detailed 3D Fault Representations for the 2019 Ridgecrest, California, Earthquake Sequence. Bulletin of the Seismological Society of America ; 110 (4): 1818–1831. doi:
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:105149
Deposited By: Tony Diaz
Deposited On:28 Aug 2020 22:06
Last Modified:28 Aug 2020 22:06

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