UAVSAR observations of triggered slip on the Imperial, Superstition Hills, and East Elmore Ranch Faults associated with the 2010 M 7.2 El Mayor‐Cucapah earthquake

Abstract

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. Right‐lateral slip of 36 ± 9 and 14 ± 2 mm occurred on the Imperial and Superstition Hills Faults, respectively. Left‐lateral slip of 9 ± 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 Mayor‐Cucapah 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 ± 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 × 1023−1.2 × 1024 dyne cm equivalent to a moment magnitude release of 4.9–5.3, assuming shallow slip depths ranging from 1 to 5 km.

The 2012 Brawley swarm triggered by injection-induced aseismic slip

“…Aseismic slip might actually be a common result of fluid pressure increase as suggested from experimental fluid injection studies (Bourouis and Bernard, 2007;Cornet et al, 1997;Hamilton and Meehan, 1971;Scotti and Cornet, 1994) and observations of natural systems (Doubre and Peltzer, 2007). However, most often, aseismic slip might go unnoticed for lack of geodetic monitoring.…”

Spatio-Temporal Mapping of Plate Boundary Faults in California Using Geodetic Imaging

“…It has been deployed globally, but the main focus has been in California where it supports a number of investigations. UAVSAR has been used to image deformation after three earthquakes ranging in magnitude from 5.2 to 7.2 [38][39][40]. UAVSAR produces images with 1 m spatial resolution for phase change images and 7 m for images that have been unwrapped.…”

“…The 2010 M7.2 El Mayor-Cucapah earthquake triggered slip on numerous faults north and northeast of the rupture between the Mexican border and the SAF [38,111,112]. These networks of faults connect the El Mayor-Cucapah rupture with the Elsinore, San Jacinto, and SAF.…”

“…Additionally the Eureka Peak fault actively creeps following large earthquakes [7,120]. The San Jacinto fault shows no evidence of triggered slip or creep based on examination of seven years of UAVSAR observations implying that the fault is locked, stronger, and may produce larger earthquakes [1,38].…”

“…When combined with GPS measurements, a much better assessment can be made of how deeply shallow slip extends and the extent of off fault deformation. Though UAVSAR measurements are not as accurate as GPS they have proven useful for identifying localized slip across faults [38][39][40], including faults triggered by distant earthquakes [72,112]. In general, significant triggered slip is several cm, outside the error of the UAVSAR measurements.…”