This research is a continuation of highly successful seismic body wave investigations of the earth's mantle. Efforts now will be directed towards the upper 300 km and lower 300 km (D" layer) of the earth's mantle, regions that appear to have the most lateral variation in seismic velocities. This information is critical to resolution of models of convection in the mantle, the major driving force for plate tectonics and earthquakes. D" will be investigated by means of precursory arrivals to the PKP phase along with constraints from other core phases such as ScS, Sdiff, SKS, etc. The upper 300 km of the mantle around the Hawaiian Hotspot will be investigated with multiple bounce S-wave techniques. The lithosphere beneath portions of the U.S. and Canada will be investigated by means of Pn and Sn phases.
