研究期間：10302~10312;The Longitudal Valley in East Taiwan is the collision suture zone between the Philippine Sea Plat and the Eurasia Plate. The abundant seismic activity in the valley demonstrates different behaviors between the North and South segments. Furthermore, whether there is a west-dipping Central Range Fault in the valley remains an open question. Some areas in the longitudal valley possess potentials for geothermal explorations. In this proposal, we plan to conduct a tomographic study to invert high resolution crustal velocity structures in the Longitudal Valley using P and S arrival times as recorded by strong motion stations in the area deployed by Central Weather Bureau over the past decade or so. The resulting velocity structures can be used to correlate with the N-S different seismic behaviors, to detect the potential existence of the Central Range Fault, and to determine the suitable sites for geothermal explorations. We expect that fulfillment of the project will significantly help understand the seismotectonics of the Longitudal Valley for a better prediction on potential zones of future earthquakes for hazard mitigation.