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Seismotectonics and Fault Geometries of the 2019 Ridgecrest Sequence: Insight From Aftershock Moment Tensor Catalog Using 3-D Green's Functions

Wang, Xin and Zhan, Zhongwen (2020) Seismotectonics and Fault Geometries of the 2019 Ridgecrest Sequence: Insight From Aftershock Moment Tensor Catalog Using 3-D Green's Functions. Journal of Geophysical Research. Solid Earth, 125 (5). Art. No. e2020JB019577. ISSN 2169-9313. https://resolver.caltech.edu/CaltechAUTHORS:20200420-135541379

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Abstract

The 2019 M_w 7.1 Ridgecrest earthquake occurred on 6 July, preceded by the M_w 6.4 foreshock on 4 July 2019. These two earthquakes occurred close in space and time with partially overlapping surface ruptures and aftershock patterns, raising the question of the relationship between the two events. Geological surveys and satellite observations provide important constraints on the surface traces of faulting. However, the subsurface fault geometries, which are important for understanding the regional stress field, earthquake initiation, propagation, and termination, are not well resolved. In this study, moment tensor solutions for 256 earthquakes in the 2019 Ridgecrest sequence were determined by waveform inversion using 3‐D velocity model. The obtained moment tensor solutions show rotations of the stresses after mainshock, indicating the ratio of mainshock stress drop to the background stress to be 0.5–0.9. The obtained moment tensor catalog also facilitates a better understanding of the subsurface fault geometries, including (1) splay faults and antithetic faults in the northwest aftershock zone; (2) shallow flower structures near the M_w 7.1 epicenter; and (3) subparallel faults in the southeast aftershock zone. The aftershocks' studies suggest the very complex surface ruptures near the 2019 Ridgecrest M_w 7.1 epicenter are near‐surface features that linked to a simple large throughgoing fault at >5 km depth. We also found that the southeastern‐most aftershocks, which are located less than a kilometer from the Garlock fault trace, have significant different strike directions from that of the Garlock fault, indicating the central Garlock fault remains seismically quiet.


Item Type:Article
Related URLs:
URLURL TypeDescription
https://doi.org/10.1029/2020jb019577DOIArticle
ORCID:
AuthorORCID
Wang, Xin0000-0002-6180-0058
Zhan, Zhongwen0000-0002-5586-2607
Additional Information:© 2020 American Geophysical Union. Issue Online: 19 May 2020; Version of Record online: 19 May 2020; Accepted manuscript online: 20 April 2020; Manuscript accepted: 13 April 2020; Manuscript revised: 03 April 2020; Manuscript received: 07 February 2020. We thank the Southern California Earthquake Center (SCEC) and the Southern California Earthquake Data Center (SCEDC, doi:10.7909/C3WD3xH1) for providing public access to the SCEC Unified Community Velocity Model (https://www.scec.org/research/ucvm), Community Stress Model (https://www.scec.org/research/csm), and the seismic waveform data (https://scedc.caltech.edu). This work is supported by USGS/NEHRP Grant G19AP00030, SCEC 2019 Award 19011, and Air Force Research Grant 18C0058. We thank for Zachary Ross for providing the earthquake seismicity catalog. We thank Egill Hauksson, Liqing Jiao, Yu Wang, Jean‐Philippe Avouac, and Joann Stock for useful discussions. We are also grateful to editor Rachel Abercrombie and two anonymous reviewers for their constructive comments, which help improve the quality of this paper. The earthquake moment tensor catalog obtained in this study can be found in the supporting information.
Group:Seismological Laboratory
Funders:
Funding AgencyGrant Number
USGSG19AP00030
Southern California Earthquake Center (SCEC)19011
Air Force Office of Scientific Research (AFOSR)18C0058
Subject Keywords:Moment tensor inversion; 3D velocity model; Stress rotation; Dynamic overshoot; Fault geometries; Ridgecrest
Issue or Number:5
Record Number:CaltechAUTHORS:20200420-135541379
Persistent URL:https://resolver.caltech.edu/CaltechAUTHORS:20200420-135541379
Official Citation:Wang, X., & Zhan, Z. (2020). Seismotectonics and fault geometries of the 2019 Ridgecrest sequence: Insight from aftershock moment tensor catalog using 3‐D Green's functions. Journal of Geophysical Research: Solid Earth, 124, e2020JB019577. https://doi.org/10.1029/2020JB019577
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:102665
Collection:CaltechAUTHORS
Deposited By: Tony Diaz
Deposited On:20 Apr 2020 21:08
Last Modified:27 May 2020 22:43

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