POLARIZATION TOMOGRAPHY FOR P-WAVE VELOCITY STRUCTURE IN SOUTHERN CALIFORNIA

We develop a tomographic inversion method that uses teleseismic P wave polarization data to obtain velocity structure. Polarization inversio n has some intrinsic advantages over travel Lime inversion: It is not influenced by source location and origin time errors; it is not sensit ive to deep mantle velocity structure and can be used iteratively to i mprove the tomographic result. Polarization inversion is more sensitiv e to near-station velocity structure and to velocity gradient and is c omplementary to travel time inversion in this sense. The method is app lied to California Institute of Technology-U.S. Geological Servey sout hern California array data. The result is generally consistent with pr evious work and also reveals that the high-velocity feature beneath th e Transverse Ranges is bounded between 40 and 200 km depths and possib ly has a second small piece at about 300 km depth. The slow velocity a nomaly under the Salton Trough is limited to shallow depths, less than about 60 km.