This project will analyze a set of OBH seismic data collected off the margin of central Chile where the aseismic Juan Fernandez Ridge is being subducted. Velocity structure will be determined along two transects normal to the coast and in a grid sited over a possible buried seamount under the Valparaiso Basin. The data will be used to (1) test whether there is a seamount and if so whether it acts as an "asperity" which may have served as a focus for the 1985 earthquake and (2) determine the 3D shape and velocity structure of the accretionary wedge and lithosphere to constrain sediment porosity and elasticity of the subducting plate.
