Shallow Surface Deformation on the Southern Imperial Fault System from Marine Subsurface Imaging Data

Valerie J. Sahakian, Neal W. Driscoll, Boe Derosier, Brian Oller, Alexis R. Klimasewski, & Joann M. Stock

Published August 15, 2019, SCEC Contribution #9825, 2019 SCEC Annual Meeting Poster #106

Hosting two >M6 earthquakes in the past century and estimated to accommodate 30 – 45 mm/yr of slip, the Imperial Fault (IF) system is a large component of Southern California tectonics. Despite its contribution to regional seismic hazard and Pacific/North American plate boundary motion, there are only 5 existing paleoseismic sites on the IF. None of these sites yield a direct strike-slip rate due to the absence of observable piercing points along the fault. Recent geodetic observations have identified a possible fault approximately 10 – 15km west of the existing IF fault trace, which may accommodate some of the slip that has been previously prescribed to the IF. Anthropogenic activity in this region obscures geomorphic evidence of faulting on both the IF and proposed westward fault, making this system a challenging target for identifying possible trenching sites.

In March 2019, we collected high-resolution subsurface imaging data within the All American Canal in the Imperial Valley, across the IF and suggested westward fault trace by the US-Mexico border. With an acoustic compressed high intensity radar pulse (CHIRP) system, we imaged shallow deformation in the region proposed to accommodate slip west of the IF. Here, we will show these data, as well as preliminary faulting interpretations and implications for tectonics in the region. 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 San Jacinto fault system in the region.

Key Words
Imperial Fault, Chirp, Imperial Valley, All American Canal

Citation
Sahakian, V. J., Driscoll, N. W., Derosier, B., Oller, B., Klimasewski, A. R., & Stock, J. M. (2019, 08). Shallow Surface Deformation on the Southern Imperial Fault System from Marine Subsurface Imaging Data. Poster Presentation at 2019 SCEC Annual Meeting.

Related Projects & Working Groups
Earthquake Geology