9404809 Chen This research is a collaboration between the University of Illinois and Purdue University to analyze short-period and broad- band seismic waveform data from the northwestern Pacific. Because of the complex tectonic setting and major subduction zones in the area, pronounced variation in lithospheric and upper mantle structure is expected near this margin. Using high-resolution seismic waveform data, a detailed study of such variation can place additional constraints on mantle dynamics and mineral physics. Using high-quality seismic data from the broad-band networks, the proposed work complements existing long-period and travel time studies in this region. ***