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Diverse volumetric faulting patterns in the San Jacinto fault zone

Cheng, Yifang and Ross, Zachary E. and Ben-Zion, Yehuda (2018) Diverse volumetric faulting patterns in the San Jacinto fault zone. Journal of Geophysical Research. Solid Earth, 123 (6). pp. 5068-5081. ISSN 2169-9313. doi:10.1029/2017JB015408.

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We examine locations, magnitudes, and faulting types of post‐2000 earthquakes in the trifurcation area of San Jacinto fault zone to clarify basic aspects of failure processes in the area. Most M ≥ 3.5 events have strike‐slip mechanisms, occur within 1 km of the main faults (Clark, Buck Ridge, and Coyote Creek), and have hypocenter depths of 10–13 km. In contrast, many smaller events have normal source mechanisms and hypocenters in intrafault areas deeper than 13 km. Additional small events with hypocenter depth <13 km occur in off‐fault regions and have complex geometries including lineations normal to the main faults. Five moderate earthquakes with M 4.7–5.4 have high aftershock rates (~150 M ≥ 1.5 events within 1 day from the mainshock). To obtain more details on aftershock sequences of these earthquakes, we detect and locate additional events with the matched filter method. There are almost no aftershocks within 1 km from the mainshocks, consistent with large mainshock stress drops and low residual stress. The five aftershock sequences have almost no spatial overlap. While the mainshocks are on the main faults, most aftershocks are located in intrafault and off‐fault regions. Their locations and spatial distribution reflect the mainshock rupture directions, and many also follow structures normal to the main faults. The significant diversity of observed features highlights the essential volumetric character of failure patterns in the area. The increasing rate of moderate events, productive aftershock sequences, and large inferred stress drops may reflect processes near the end of a large earthquake cycle.

Item Type:Article
Related URLs:
URLURL TypeDescription
Cheng, Yifang0000-0002-6507-5607
Ross, Zachary E.0000-0002-6343-8400
Ben-Zion, Yehuda0000-0002-9602-2014
Additional Information:© 2018 American Geophysical Union. Received 26 DEC 2017; Accepted 21 MAY 2018; Accepted article online 27 MAY 2018; Published online 16 JUN 2018. The study was supported by the National Science Foundation (grants EAR‐1551411 and EAR‐1722561). The paper benefitted from comments by Shimon Wdowinski, an anonymous referee, and the Associate Editor. The waveform data and initial seismicity catalogs used are publicly available via the Southern California Earthquake Data Center (2013) ( The seismicity catalogs produced in this study are available in the supporting information, with the exception of the 2016 sequence which is available in the open‐access supporting information of Ross, Hauksson, and Ben‐Zion (2017).
Group:Seismological Laboratory
Funding AgencyGrant Number
Issue or Number:6
Record Number:CaltechAUTHORS:20180529-081945138
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Official Citation:Cheng, Y., Ross, Z. E., & Ben‐Zion, Y. (2018). Diverse volumetric faulting patterns in the San Jacinto fault zone. Journal of Geophysical Research: Solid Earth, 123, 5068–5081.
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:86646
Deposited By: Tony Diaz
Deposited On:29 May 2018 16:13
Last Modified:15 Nov 2021 20:40

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