This research will investigate upper mantle stratification in the vicinity of subducting slabs by means of stacked seismograms that reveal underside reflections from discontinuities. A systematic analysis will be made of earthquake records for deep and intermediate depth events in the circum-Pacific subduction zones using broadband digital data as well as WWSSN and LRSM analog data. This will provide constraints on the character of mantle discontinuities in the thermally perturbed mantle near subducting slabs and back-arc basins. Variations in depth and impedance contrasts for P and S wave reflectors will then be interpreted in terms of thermal and petrological models for upper mantle layering near subduction zones.
