Kinematics of Creep Events on the Imperial Fault

M. Morow Tan, Kathryn Materna, Roger Bilham, & Daniel B. Gittins

Submitted September 7, 2025, SCEC Contribution #14898, 2025 SCEC Annual Meeting Poster #TBD

The Imperial Fault (IF), located in Southern California’s Imperial Valley, is one of the fastest partially-creeping faults in California (Field et al., 2015). Deformation models suggest right-lateral slip rates of 20-35 mm/yr, showing the IF poses a significant source of hazard. Aseismic slip is a frequent mode of seismic moment release on the IF, and can be classified into four distinct creep modes: afterslip, triggered slip, spontaneous slip, and continuous creep. All four of these modes are present on the IF. Studies show centimeter-scale episodic creep events occur several times a decade (Donnellan et al., 2014; Materna et al., 2024), and the depth of creep is suggested to be about 3-4 km (Lindsey & Fialko, 2016).

To study the time-dependence and kinematics of aseismic slip on the Imperial Fault, we utilize ten years of Sentinel-1 InSAR data, combined with GNSS and creepmeters, to test kinematic models of creep events. We have identified 17 creep events on the IF and nearby Brawley Fault through InSAR that were previously unidentified by GNSS and creepmeters. Using deformation profiles of these creep events, we perform MCMC simulations of dislocation models to constrain depth of creep events and the slip of each dislocation. Preliminary results show that a graben structure near the northern terminus of the IF slips to depths of 2-3 km, while the IF has shallower slip to depths of ~1 km. The scaling between slip and depth can be used to constrain stress drop, and a prediction of recurrence time can be developed (Loveless & Meade, 2011). Understanding the kinematics and mechanics of creep events on the IF will help quantify the seismic hazard associated with one of California’s most active faults. Such findings have implications for stress transfer on faults in the area and a more unified understanding of the drivers of frictional slip in Southern California.

Citation
Tan, M., Materna, K., Bilham, R., & Gittins, D. B. (2025, 09). Kinematics of Creep Events on the Imperial Fault. Poster Presentation at 2025 SCEC Annual Meeting.

Related Projects & Working Groups
Tectonic Geodesy