9725335 Grand This research is a continuation of efforts to map the three dimensional shear wave structure of the earth's mantle and produce a better seismic model for the outer core. Previously, the travel times of S, ScS, SKS, SKKS and multiple bounce S phases have been measured and inverted to obtain a 3-D model of mantle structure beneath. Long linear fast seismic anomalies interpreted to be slabs sinking to mid-mantle depths were discovered beneath the Americas. This work will extend the detailed analysis to Asian subduction zones. The core-mantle boundary layer D" will also be investigated and mapped relative to slow velocity features in the lower mantle, which may indicate the upwelling part of mantle circulation. Better analysis of the D" variations will enable the improvement of investigations of anisotropy and heterogeneity of the inner core. ***
