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Scales of Stress Heterogeneity Near Active Faults in the Santa Barbara Channel, Southern California

Persaud, Patricia and Pritchard, Edward H. and Stock, Joann M. (2020) Scales of Stress Heterogeneity Near Active Faults in the Santa Barbara Channel, Southern California. Geochemistry, Geophysics, Geosystems, 21 (1). Art. No. e2019GC008744. ISSN 1525-2027. https://resolver.caltech.edu/CaltechAUTHORS:20200210-081539156

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Abstract

The Santa Barbara Channel represents the offshore portion of the Ventura Basin in Southern California. Ongoing transpression related to a regional left step in the San Andreas Fault has led to the formation of E‐W trending en‐echelon fault systems that accommodate localized shortening across the basin. Recent studies have suggested that faults within the channel could be capable of a multisegment rupture and producing a M_w 7.7–8.1 tsunamigenic earthquake. However, dynamic rupture models producing these results do not account for stress heterogeneity. With only sparse information available on the stress field in this region, further borehole‐derived stress constraints are essential for obtaining a more comprehensive understanding of the hazards related to the complex fault systems. We used caliper logs from 19 wells obtained from industry to identify stress‐induced borehole breakouts beneath the Holly and Gail oil platforms in the channel. Our newly developed forward modeling technique provides constraints on the orientations and relative magnitudes of the three principal stresses. At Gail, we determine a reverse faulting stress regime (S_(Hmax) = 1.7; S_(hmin) = 1.6; SV = 1.0) and an S_(Hmax) azimuth of N45°E. Our results are consistent with local structures, which reflect deeper regional scale trends, and with similar studies onshore nearby. At Holly, an S_(Hmax) rotation from ~N36°W to ~N57°E occurs across ~100 m depth in a single well and differs from nearby results, indicating that short‐length scale (<10 km laterally and <1 km in depth) stress heterogeneity is associated with complex changes in fault geometry.


Item Type:Article
Related URLs:
URLURL TypeDescription
https://doi.org/10.1029/2019gc008744DOIArticle
ORCID:
AuthorORCID
Persaud, Patricia0000-0003-3462-7023
Stock, Joann M.0000-0003-4816-7865
Additional Information:© 2020 American Geophysical Union. Received 30 SEP 2019; Accepted 30 DEC 2019; Accepted article online 3 JAN 2020. We thank three anonymous reviewers, the Editor, Thorsten Becker, and the Editor in Chief, Claudio Faccenna, for their insightful comments and suggestions, which significantly improved this manuscript. The raw dataset of digital well curves used in this study was provided by oil companies in the Southern California area and is proprietary and subject to confidentiality agreements. The well names are anonymized. The well locations, well paths and depths, and all other information derived during the processing are presented in the paper. Figures were prepared with the Generic Mapping Tool (GMT) software (Wessel et al., 2013) and Petrel. We thank C. Sorlien, M. Kamerling, C. Nicholson, and R. Behl for sharing their work and Sorlien for compiling the seismic profiles shown in Figures 2c and 3c. We thank the Geology and Geophysics Department at Louisiana State University for supporting this project. Portions of this research were conducted with high performance computing resources provided by Louisiana State University (http://www.hpc.lsu.edu). This research was partly supported by the Southern California Earthquake Center (Contribution No. 8267). SCEC is funded by NSF Cooperative Agreement EAR‐1033462 & USGS Cooperative Agreement G12 AC20038.
Group:Seismological Laboratory
Funders:
Funding AgencyGrant Number
Southern California Earthquake Center (SCEC)UNSPECIFIED
NSFEAR-1033462
USGSG12 AC20038
Subject Keywords:Santa Barbara Channel; borehole breakouts; stress heterogeneity; Transverse Ranges; Southern California stress
Other Numbering System:
Other Numbering System NameOther Numbering System ID
Southern California Earthquake Center8267
Issue or Number:1
Record Number:CaltechAUTHORS:20200210-081539156
Persistent URL:https://resolver.caltech.edu/CaltechAUTHORS:20200210-081539156
Official Citation:Persaud, P., Pritchard, E. H., & Stock, J. M. (2020). Scales of stress heterogeneity near active faults in the Santa Barbara Channel, Southern California. Geochemistry, Geophysics, Geosystems, 21, e2019GC008744. https://doi.org/10.1029/2019GC008744
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:101186
Collection:CaltechAUTHORS
Deposited By: Tony Diaz
Deposited On:10 Feb 2020 18:00
Last Modified:03 Aug 2020 19:01

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