CONSTRAINTS ON CRUSTAL STRUCTURE AND COMPLEX MOHO TOPOGRAPHY BENEATH PINYON FLAT, CALIFORNIA, FROM TELESEISMIC RECEIVER FUNCTIONS

We use teleseismic P waves recorded at Pinon Flat Observatory (PFO) to constrain the three-dimensional crustal and upper-mantle velocity str ucture beneath the station. By forward modeling radial receiver functi on waveforms, we construct one-dimensional crustal model that includes a significant shear-velocity inversion at 9 km in depth. Arrivals on the tangential components indicate dip of at least the uppermost disco ntinuity. Complicated Moho topography, deepening to the northwest of P FO, is suggested by azimuthal dependence of travel times and amplitude s of the receiver functions and travel times of crustal P-wave reverbe rations. Although fine details cannot be resolved, each of those sets of observations plus mislocation vectors provide strong indications of abrupt Moho topography, possible including step offsets of several ki lometers. This is not only consistent with gravity data in implying Ai ry isostasy with compensation at Moho depth but extends that model to a much finer length scale than had been resolved.