This research is to study the detailed P- and S-wave velocity crust and upper mantle structures under Tibet along a nearly N-S profile across the Plateau. In cooperation with the Institute of Geophysics, State Seismological Bureau of the Peoples' Republic of China, the deployment of 10 or more PASSCAL seismic systems for 12 months will be done recording teleseisms, regional events in central and eastern Asia, and local seismicity in the Tibetan Plateau. The Tibetan Plateau is a first order topographic feature on Earth; it represents an "end member" in the global tectonics in terms of the intensity of collisional tectonics. This cooperative research program between the U.S. and Chinese scientists will involve equal sharing of funding and data. This research is a component of the National Earthquake Hazard Reduction Program.