SOURCE PARAMETERS OF THE JUNE 29, 1992 LITTLE SKULL MOUNTAIN EARTHQUAKE FROM COMPLETE REGIONAL WAVE-FORMS AT A SINGLE STATION

The June 29, 1992, m(b)=5.5, Little Skull Mountain earthquake occurred 20 km southeast of Yucca Mountain within the boundaries of the Nevada Test Site. This event was recorded at a very broadband station located about 310 km to the east at Kanab, Utah. Both body and surface waves from this single station were used in a grid search technique for the best fitting double couple moment tensor. The technique minimizes the misfit between reflectivity generated complete synthetic seismograms and the three-component displacement dam via a search over the strike, dip and rake of the source. In the passband of 50-15 s period, the grid search results in a well defined, nearly pure normal mechanism with a strike of 35-degrees, a dip of 54-degrees, a rake of -87-degrees, and a seismic moment of 4.1 x 10(17) N-m. Applying the same technique to the large aftershock on July 5, 1992 we obtain a somewhat less well defined minimum with a strike of 358-degrees, a dip of 36-degrees, a rake of -177-degrees, and a moment of 4.3 x 10(15) N-m. The minimum-compression axes of these mechanisms are consistent with northwest-southeast extension in the Basin and Range.