Moho dip and crustal anisotropy in northwestern Nevada from teleseismic receiver functions

Receiver functions are derived from teleseismic waves recorded during the 1988 to 1989 PASSCAL Basin and Range passive-source seismic experiment in northwestern Nevada. A velocity model involving both a planar dipping Moho and crustal anisotropy is needed to explain the radial and tangential motions of the observed P-S conversions. An arrival-time difference often observed between radial and tangential Moho P-S conversions suggests an anisotropic crust. The P-S conversions are large and indicate a major discontinuity under the area. The particle motion directions for most of the tangential components change sign between South American events and events from the other two source areas (Japan and Tonga regions), providing good evidence for a Moho dipping approximately to the north. Also, the P-S conversions from the Moho follow direct P arrivals by about 3.2 sec under the southern part of the array, 3.4 sec under the southern central part of the array, and 3.7 sec under the northern part of the array, indicating a Moho that varies in depth from about 26 to 31 km. A velocity model with the Moho dipping similar to 9 degrees in a nearly northerly direction and an anisotropic crust with a split time of similar to 0.25 sec and a fast axis of similar to 130 degrees best explain these observations.