Source analysis using regional empirical Green's functions: The 2008 Wells, Nevada, earthquake

Abstract

We invert three‐component, regional broadband waveforms recorded for the 21 February 2008 Wells, Nevada, earthquake using a finite‐fault methodology that prescribes subfault responses using eight MW∼4 aftershocks as empirical Green's functions (EGFs) distributed within a 20‐km by 21.6‐km fault area. The inversion identifies a seismic moment of 6.2 x 1024 dyne‐cm (5.8 MW) with slip concentrated in a compact 6.5‐km by 4‐km region updip from the hypocenter. The peak slip within this localized area is 88 cm and the stress drop is 72 bars, which is higher than expected for Basin and Range normal faults in the western United States. The EGF approach yields excellent fits to the complex regional waveforms, accounting for strong variations in wave propagation and site effects. This suggests that the procedure is useful for studying moderate‐size earthquakes with limited teleseismic or strong‐motion data and for examining uncertainties in slip models obtained using theoretical Green's functions.