Shallow Deformation Features of the Imperial and Michoacán Fault Systems From Subsurface Imaging
Session: Amphibious Seismic Studies of Plate Boundary Structure and Processes
Type: Oral
Date: 4/20/2021
Presentation Time: 10:45 AM Pacific
Description:
Accommodating 30 – 45 mm/yr of slip and hosting two >M6 earthquakes in the past century, the Imperial Fault (IF) is a large player in Southern California’s fault system. Despite its contribution to regional seismic hazard and Pacific/North American plate boundary motion, both the IF system and its interactions with other faults are not as well-understood as other regional faults. Seismicity studies identify event concentrations along linear structures west of the main trace of the IF, likely the El Centro-Weinert, Dixieland, and Michoacán faults. In addition, a geodetic investigation reveals deformation west of the main trace of the IF, best fit by a fault structure with a slip rate of ~15 mm/yr, aligning with the area near the Dixieland and Michoacán faults, and possibly accommodating a portion of the IF’s slip rate. It is difficult to obtain a full picture of this system and the interaction between structures, as we lack shallow subsurface geologic and imaging data.
To fill this gap, we collected high-resolution subsurface seismic data within the All American Canal in the Imperial Valley. These data focus on the mapped IF trace, and suggested westward fault traces by the US-Mexico border. With an acoustic compressed high intensity radar pulse (CHIRP) system, we imaged shallow deformation (~5-25m depth) on the mapped trace of the IF, as well as in the western regions proposed to accommodate slip. This deformation occurs as close as 10km west of the IF, and some of the most prominent shallow displacement occurs ~20km west of the IF. Here, we will show these findings, fault interpretations, and implications for tectonics in the region, as well as discuss possible corroborations between our data nearby cone penetration tests (CPT) and cores across the IF. These data may be useful to support or direct future paleoseismic and geophysical studies along this fault trace, and to understand better the interactions between the IF system and other fault systems in the region.
Presenting Author: Valerie Sahakian
Student Presenter: No
Authors
Valerie Sahakian Presenting Author Corresponding Author vjs@uoregon.edu University of Oregon |
Boe Derosier bderosie@ucsd.edu Scripps Institution of Oceanography, University of California, San Diego |
Thomas Rockwell trockwell@sdsu.edu San Diego State University |
Joann Stock jstock@gps.caltech.edu Caltech |
Neal Driscoll ndriscoll@ucsd.edu Scripps Institution of Oceanography, University of California, San Diego |
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Shallow Deformation Features of the Imperial and Michoacán Fault Systems From Subsurface Imaging
Category
Amphibious Seismic Studies of Plate Boundary Structure and Processes