NASA - National Aeronautics and Space Administration

The 4 April 2010 M 7.2 El Mayor-Cucapah earthquake that occurred in Baja California, Mexico and terminated near the U.S. Mexican border caused slip on the Imperial, Superstition Hills, and East Elmore Ranch Faults. The pattern of slip was observed using radar interferometry from NASA’s Uninhabited Aerial Vehicle Synthetic Aperture Radar (UAVSAR) instrument collected on 20–21 October 2009 and 12–13 April 2010. Rightlateral slip of 36 6 9 and 14 6 2 mm occurred on the Imperial and Superstition Hills Faults, respectively. Leftlateral slip of 9 6 2 mm occurred on the East Elmore Ranch Fault. The widths of the zones of displacement increase northward suggesting successively more buried fault motion to the north. The observations show a decreasing pattern of slip northward on a series of faults in the Salton Trough stepping between the El MayorCucapah rupture and San Andreas Fault. Most of the motion occurred at the time of the M 7.2 earthquake and the UAVSAR observations are consistent with field, creepmeter, GPS, and Envisat observations. An additional 28 6 1 mm of slip at the southern end of the Imperial Fault over a <1 km wide zone was observed over a 1 day span a week after the earthquake suggesting that the fault continued to slip at depth following the mainshock. The total moment release on the three faults is 2.3 3 102321.2 3 1024 dyne cm equivalent to a moment magnitude release of 4.9–5.3, assuming shallow slip depths ranging from 1 to 5 km.