The 2008 Wells, Nevada, Earthquake Sequence: Source Constraints Using Calibrated Multiple-Event Relocation and InSAR

The 2008 Wells, Nevada, earthquake represents the largest domestic event in the contiguous United States outside of California since the October 1983 Borah Peak earthquake in southern Idaho. We present an improved catalog, magnitude complete to 1.6, of the foreshock-aftershock sequence, supplementing the current U.S. Geological Survey Preliminary Determination of Epicenters catalog with 1928 well-located events. To create this catalog, both subspace and kurtosis detectors are used to obtain an initial set of earthquakes and associated locations. The latter are then calibrated through the implementation of the hypocentroidal decomposition method and relocated using the Bayesloc relocation technique. We additionally perform a finite-fault slip analysis of the mainshock using Interferometric Synthetic Aperture Radar (InSAR) observations. By combining the relocated sequence with the finite-fault analysis, we show that the aftershocks occur primarily up-dip and along the southwestern edge of the zone of maximum slip. The aftershock locations illuminate areas of postmainshock strain increase; aftershock depths, ranging from 5 to 16 km, are consistent with InSAR imaging, which shows that the Wells earthquake was a buried source with no observable near-surface offset.