SURFACE-WAVE PROFILING OF THE LITHOSPHERE BENEATH THE MOJAVE DESERT USING TERRASCOPE DATA

We have applied surface wave analysis to the Mojave Desert in southern California to extract the regional lithosphere velocity structure. Seismograms from teleseismic sources recorded by the TERRAscope stations, a recently established network of broadband instruments, were used to determine the phase velocity dispersion data of Rayleigh waves for wave paths crossing the Mojave Desert. An inversion analysis on the dispersion data for each path gave the shear wave velocity structure beneath the path. Inversion results show that there is a low-velocity layer at the middle and lower crust, which is particularly pronounced for paths traversing the western part of the Mojave Desert. This low-velocity layer at the midcrust may reflect the existence of a transition zone from the brittle to the ductile regimes, where there is an absence of earthquake occurrence.