Interferometric synthetic aperture radar observations of the 1994 Double Spring Flat, Nevada, earthquake (M5.9): Main shock accompanied by triggered slip on a conjugate fault

[1] The 1994 Double Spring Flat (DSF) earthquake (M5.9) was the largest earthquake to strike Nevada in more than 30 years. It occurred in the Sierra Nevada-Basin and Range Transition Zone within a step-over region between two major normal faults. Descending and ascending ERS interferograms show a maximum range change of 8.5 cm which is the coseismic ground displacement associated with this normal, oblique-slip, moderatesized earthquake. Elastic inverse modeling and surface displacements across coseismic ground cracks suggest that two different event sources could account for the observed deformation. The first source was the main shock with right-oblique slip on the northnorthwest striking DSF fault. The second source was normal faulting on a shallow, northnortheast striking, elongated plane (conjugate to the DSF fault). These two sources are consistent with the pattern of postevent seismicity, and we suggest that the second source represents seismic and aseismic slip triggered by the main shock. Calculations of changes in Coulomb failure stress show that the main shock encouraged normal slip on this plane.