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Depth Determination of the 2010 El Mayor‐Cucapah Earthquake Sequence (M≥4.0)

Yu, Chunquan and Hauksson, Egill and Zhan, Zhongwen and Cochran, Elizabeth S. and Helmberger, Donald V. (2019) Depth Determination of the 2010 El Mayor‐Cucapah Earthquake Sequence (M≥4.0). Journal of Geophysical Research. Solid Earth, 124 (7). pp. 6801-6814. ISSN 2169-9313. https://resolver.caltech.edu/CaltechAUTHORS:20190702-074604162

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Abstract

The 2010 M_W 7.2 El Mayor‐Cucapah earthquake ruptured a zone of ~120 km in length in northern Baja California. The geographic distribution of this earthquake sequence was well constrained by waveform relocation. The depth distribution, however, was poorly determined as it is near the edge of, or outside, the Southern California Seismic Network. Here we use two complementary methods to constrain the focal depths of moderate‐sized events (M ≥ 4.0) in this sequence. We first determine the absolute earthquake depth by modeling the regional depth phases at high frequencies (~1 Hz). We mainly focus on Pn and its depth phases pPn and sPn, which arrive early at regional distance and are less contaminated by crustal multiples. To facilitate depth phase identification and to improve signal‐to‐noise ratio, we take advantage of the dense Southern California Seismic Network and use array analysis to align and stack Pn waveforms. For events without clear depth phases, we further determine their relative depths with respect to those with known depths using differential travel times of the Pn, direct P, and direct S phases recorded for event pairs. Focal depths of 93 out of 122 M ≥ 4.0 events are tightly constrained with absolute uncertainty of about 1 km. Aftershocks are clustered in the depth range of 3–10 km, suggesting a relatively shallow seismogenic zone, consistent with high surface heat flow in this region. Most aftershocks are located outside or near the lower terminus of coseismic high‐slip patches of the main shock, which may be governed by residual strains, local stress concentration, or postseismic slip.


Item Type:Article
Related URLs:
URLURL TypeDescription
https://doi.org/10.1029/2018jb016982DOIArticle
ORCID:
AuthorORCID
Yu, Chunquan0000-0001-8681-8572
Hauksson, Egill0000-0002-6834-5051
Zhan, Zhongwen0000-0002-5586-2607
Cochran, Elizabeth S.0000-0003-2485-4484
Alternate Title:Depth Determination of the 2010 El Mayor‐Cucapah Earthquake Sequence (M greater than or equal to 4.0)
Additional Information:© 2019 American Geophysical Union. Received 3 NOV 2018; Accepted 22 JUN 2019; Accepted article online 2 JUL 2019; Published online 12 JUL 2019. Data and Resources: Event catalogs investigated in this study were obtained from the Southern California Earthquake Data Center (SCEDC) at Caltech (http://scedc.caltech.edu/eq‐catalogs, last accessed Oct, 2018). Broadband waveforms were retrieved from SCEDC and the Incorporated Research Institutions for Seismology (IRIS) Data Management Center (https://ds.iris.edu/ds/nodes/dmc/, last accessed October 2018). We appreciate the constructive review by S. Ni and an anonymous reviewer. Comments from Rob Graves and Sarah Minson helped improve the quality of this manuscript. We thank Shengji Wei for the coseismic rupture model of 2010 El Mayor‐Cucapah earthquake. This research was supported by USGS/NEHRP grants G16AP00147 and G18AP00028 and by the Southern California Earthquake Center (SCEC) (award 17044), which is funded by NSF Cooperative Agreement EAR‐1033462 and USGS Cooperative Agreement G12AC20038. C. Y and Z. Z are partially supported by National Science Foundation NSF grants 1722879 and 1829496. We used GMT from Wessel et al. (2013) to make Figure 1. We used waveforms and parametric data from the Caltech/USGS Southern California Seismic Network (SCSN), doi:10.7914/SN/CI, stored at the Southern California Earthquake Data Center, doi:10.7909/C3WD3xH1.
Group:Seismological Laboratory
Funders:
Funding AgencyGrant Number
USGSG16AP00147
USGSG18AP00028
Southern California Earthquake Center (SCEC)17044
NSFEAR-1033462
USGSG12AC20038
NSFEAR-1722879
NSFEAR-1829496
Subject Keywords:Regional depth phases; Waveform modeling; Absolute and relative depth; 2010 El Mayor‐Cucapah Earthquake sequence
Issue or Number:7
Record Number:CaltechAUTHORS:20190702-074604162
Persistent URL:https://resolver.caltech.edu/CaltechAUTHORS:20190702-074604162
Official Citation:Yu, C., Hauksson, E., Zhan, Z., Cochran, E. S., & Helmberger, D. V. (2019). Depth determination of the 2010 El Mayor‐Cucapah earthquake sequence (M ≥ 4.0). Journal of Geophysical Research: Solid Earth, 124, 6801–6814. https://doi.org/10.1029/2018JB016982
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:96872
Collection:CaltechAUTHORS
Deposited By: Tony Diaz
Deposited On:02 Jul 2019 19:12
Last Modified:09 Jan 2020 00:16

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