Slip on faults in the Imperial Valley Triggered by the 4 April 2010 Mw 7.2 El Major earthquake as revealed by InSAR

Radar interferometry (InSAR) reveals surface slip on multiple faults in the Imperial Valley triggered by the 2010 Baja M7.2 earthquake. Co-seismic offsets occurred on the San Andreas, Superstition Hills, Imperial, Elmore Ranch, Wienert, Coyote Creek, Elsinore, Yuha Wells, and several minor faults near the town of Ocotillo at the northern end of the mainshock rupture. We documented right-lateral slip (< 40 mm) on northwest trending faults and left-lateral slip (< 40 mm) on southwest trending faults. Slip occurred on 15-km- and 20-km-long segments of the San Andreas Fault in the Mecca Hills (≤ 50 mm) and Durmid Hill (≤ 10 mm) respectively, and 23 km of the Superstition Hills Fault (≤ 37 mm). Field measurements of slip on the Superstition Hills Fault agree with InSAR and creepmeter measurements to within a few millimeters. Dislocation models of the InSAR data on the Superstition Hills Fault confirm that creep in this sequence, as in previous slip events, is confined to shallow depths (< 3 km). Map of Southern California and Northern Baja California. Black solid lines are major faults. Yellow solid lines are faults with observed offsets. Dashed black lines are National and State borders. White star is the epicenter of the 2010 April 4th El Major earthquake. Red dots are aftershocks within one month after the main rupture with magnitude greater than 5, blue 4-5, and green 3-4. Earthquake data are from the Southern California Earthquake Center. Fault names are abbreviated as follows: ERF, Elmore Ranch fault; SHF, Superstition Hills fault; SMF, Superstition Mountains fault; WF, Wienert fault; YWF, Yuha Wells Fault.