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Title: Stress-Drop and Source Scaling of the 2019 Ridgecrest, California, Earthquake Sequence

Abstract

Stress drop, while difficult to measure reliably and at scale, is a key source parameter for understanding the earthquake rupture process and its relationship to strong ground motion. Here, we use a P-wave spectral decomposition approach, designed for large and densely sampled datasets, to measure earthquake stress drop in the region surrounding the 2019 Ridgecrest, California, earthquake sequence. With more than 11,000 measurements of earthquake stress drop in the 20-yr time period from 2000 through 2019, this dataset provides an opportunity to understand how coseismic stress changes and how other geophysical factors relate to the distribution of stress drop and its evolution in space and time. We observe a mild but persistent deviation from self-similar scaling, with larger events having systematically higher stress drops, though this trend depends on the assumption of an omega-square source spectral model. Earthquake stress drop increases with hypocentral depth in this study region, and the Ridgecrest aftershocks tend to have higher stress drops than the pre-event seismicity. This is in part due to their deeper hypocenters. Coherent spatial patterns of stress drop in the aftershock sequence correlate with the slip distribution of the M 7.1 mainshock, whose northwest rupture tip terminated in a long-lived zone ofmore » enervated stress drop. Although physical interpretation of these results is complicated by the trade-offs between the timing, depth, and location of these earthquakes, the observations provide new insight into the physics of the earthquake source in an area of renewed seismic activity in southern California.« less

Authors:
ORCiD logo [1]
  1. Univ. of Texas, Austin, TX (United States); Los Alamos National Lab. (LANL), Los Alamos, NM (United States)
Publication Date:
Research Org.:
Los Alamos National Lab. (LANL), Los Alamos, NM (United States)
Sponsoring Org.:
USDOE National Nuclear Security Administration (NNSA); USDOE Laboratory Directed Research and Development (LDRD) Program
OSTI Identifier:
1739942
Report Number(s):
LA-UR-20-20288
Journal ID: ISSN 0037-1106
Grant/Contract Number:  
89233218CNA000001; 20180700PRD1
Resource Type:
Journal Article: Accepted Manuscript
Journal Name:
Bulletin of the Seismological Society of America
Additional Journal Information:
Journal Volume: 110; Journal Issue: 4; Journal ID: ISSN 0037-1106
Publisher:
Seismological Society of America
Country of Publication:
United States
Language:
English
Subject:
58 GEOSCIENCES; Aftershocks; body waves; California; coseismic processes; earthquakes; elastic waves; geologic hazards; natural hazards; P-waves; seismic waves; Southern California; stress drops; United States; waveforms; Ridgecrest earthquake 2019

Citation Formats

Trugman, Daniel T. Stress-Drop and Source Scaling of the 2019 Ridgecrest, California, Earthquake Sequence. United States: N. p., 2020. Web. doi:10.1785/0120200009.
Trugman, Daniel T. Stress-Drop and Source Scaling of the 2019 Ridgecrest, California, Earthquake Sequence. United States. https://doi.org/10.1785/0120200009
Trugman, Daniel T. 2020. "Stress-Drop and Source Scaling of the 2019 Ridgecrest, California, Earthquake Sequence". United States. https://doi.org/10.1785/0120200009. https://www.osti.gov/servlets/purl/1739942.
@article{osti_1739942,
title = {Stress-Drop and Source Scaling of the 2019 Ridgecrest, California, Earthquake Sequence},
author = {Trugman, Daniel T.},
abstractNote = {Stress drop, while difficult to measure reliably and at scale, is a key source parameter for understanding the earthquake rupture process and its relationship to strong ground motion. Here, we use a P-wave spectral decomposition approach, designed for large and densely sampled datasets, to measure earthquake stress drop in the region surrounding the 2019 Ridgecrest, California, earthquake sequence. With more than 11,000 measurements of earthquake stress drop in the 20-yr time period from 2000 through 2019, this dataset provides an opportunity to understand how coseismic stress changes and how other geophysical factors relate to the distribution of stress drop and its evolution in space and time. We observe a mild but persistent deviation from self-similar scaling, with larger events having systematically higher stress drops, though this trend depends on the assumption of an omega-square source spectral model. Earthquake stress drop increases with hypocentral depth in this study region, and the Ridgecrest aftershocks tend to have higher stress drops than the pre-event seismicity. This is in part due to their deeper hypocenters. Coherent spatial patterns of stress drop in the aftershock sequence correlate with the slip distribution of the M 7.1 mainshock, whose northwest rupture tip terminated in a long-lived zone of enervated stress drop. Although physical interpretation of these results is complicated by the trade-offs between the timing, depth, and location of these earthquakes, the observations provide new insight into the physics of the earthquake source in an area of renewed seismic activity in southern California.},
doi = {10.1785/0120200009},
url = {https://www.osti.gov/biblio/1739942}, journal = {Bulletin of the Seismological Society of America},
issn = {0037-1106},
number = 4,
volume = 110,
place = {United States},
year = {2020},
month = {5}
}