This research is a continuation of an investigation of the upper-mantle transition-zone structure in and around subducting slabs around the Philippine Sea, Japan Sea, Yellow Sea, East China Sea and Bohai Sea. In the Japan region, the stagnant, or flattened, slab appears to be smaller than earlier tomographic studies would suggest. Lateral variations within the transition zone appear to be substantial. These results were obtained by means of 1-D modeling, and therefore are somewhat limited. The current research will utilize a 2-D finite difference scheme to improve the modeling. The work is carried out in collaboration with scientists at the Earthquake Research Institute (ERI) at the University of Tokyo. This short-wave-length work will be combined with the large-scale results from the University of Tokyo to provide a more accurate upper mantle transition zone model for the western Pacific. These results will be important for the constraint of vertical convection models across the transition zone boundaries.
