Preliminary Finite - Source Study of the February 21 , 2008 Wells , Nevada Earthquake

Seismic moment tensor and finite-source analyses are performed for the 21 February 2008 Wells, Nevada earthquake. Using complete, intermediate period (10-50s), regional waveforms, and assuming the U. S. Geological Survey (USGS)-reported hypocenter, the best-fit moment tensor solution is a normal mechanism that strikes approximately northeast-southwest, consistent with the trend of Basin and Range faulting in the area. A moment magnitude (MW) of 5.9 was obtained. Using threecomponent displacement waveforms (period < 50s) from nearby EarthScope Transportable Array (TA) stations and the source parameters from the moment tensor analysis, a finite-source solution is calculated. The best-fit rupture plane dips southeast and the rupture velocity is 2.8 km/s (0.78β), though the rupture velocity is not well constrained. The preferred solution allowing for variable rake and rise-time results in a compact slip distribution where the maximum slip is 1-3 km deeper than the hypocenter and is skewed to the southeast, yielding a seismic moment of 1.25e25 dyne cm (MW 6.0). Finally, a finite-source inversion using interferometric synthetic aperture radar (InSAR) line-of-sight displacements results in a similar slip pattern, though the depth is decreased by about 5 km, and yields a scalar seismic moment of 1.68e25 dyne cm (MW 6.1).