This research is an extension from current results by this group of determination of P-wave velocities in the earth's mantle. New emphasis will be on determination of resolution of the P-wave results and the incorporation of S-wave data. For further refinements, the ISC earthquake catalog will be relocated and special attention will be paid to subduction zones which are critical to the inversion. The 3-D map of velocities are a key indicator of mantle convection which is the primary driving force of plate tectonics and earthquake occurrence. This research is a component of the National Earthquake Hazard Reduction Program.
