9628716 Edwards The coral reefs of western Sumatra offer an opportunity to document the timing, geographic extent and vertical deformations associated with two great historical subjection zone earthquakes and their prehistoric predecessors. Living corals also display evidence for recent submergence, which perhaps represents elastic loading prior t the next great earthquake. This project is a collaborative study of the active tectonics of this subduction zone taking advantage of the details of coseismic vertical changes recorded these corals. Participants include researchers at California Institute of Technology, University of Minnesota, University of California San Diego and Santa Cruz. Results are expected to provide unusually complete information of vertical motions preceeding and caused by large earthquakes in an subduction setting.