This research involves a search for lithosphere and mantle downwelling beneath the Hindu Kush, Burma Arc, and southern Tibet by means of a residual sphere approach and 3-D finite difference calculation for theoretical travel times. Data will be collected from WWSSN, Canadian network and digital (IRIS/GSN, GEOSCOPE and GDSN) network data for earthquakes extending from the Hindu Kush eastward to Burma. Determination of differential residual spheres for pairs of events on the order of 400 km apart should test for the existence of a major downwelling proposed in the region by other scientists. For each group of differential spheres, indications of deep high velocity anomalies will be forward modeled using the finite difference scheme. The methods and results developed will have application to seismically active areas of proposed downwelling in the U.S. This research is a component of the National Earthquake Hazard Reduction Program.
