Location and mechanism of the Little Skull Mountain earthquake as constrained by satellite radar interferometry and seismic waveform modeling

Abstract

We use interferometric synthetic aperture radar (InSAR) and broadband seismic waveform data to estimate source parameters of the 29 June 1992, M_s 5.4 Little Skull Mountain (LSM) earthquake. This event occurred within a geodetic network designed to measure the strain rate across the region around Yucca Mountain. The LSM earthquake complicates interpretation of the existing GPS and trilateration data, as the earthquake magnitude is sufficiently small that seismic data do not tightly constrain the epicenter but large enough to potentially affect the geodetic observations. We model the InSAR data using a finite dislocation in a layered elastic space. We also invert regional seismic waveforms both alone and jointly with the InSAR data. Because of limitations in the existing data set, InSAR data alone cannot determine the area of the fault plane independent of magnitude of slip nor the location of the fault plane independent of the earthquake mechanism. Our seismic waveform data tightly constrain the mechanism of the earthquake but not the location. Together, the two complementary data types can be used to determine the mechanism and location but cannot distinguish between the two potential conjugate fault planes. Our preferred model has a moment of ∼3.2 × 10^(17) N m (M_w 5.6) and predicts a line length change between the Wahomie and Mile geodetic benchmarks of ∼5 mm.

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