This research will support analysis of seismic data from two past deployments of the PANDA seismic array along the eastern margin of the central Andes. The goal is to determine 1) the crustal thickening across the eastern margin of the central Andean plateau; 2) the seismic wave velocities within, and the continuity of, the subducted Nazca plate; and 3) the depths of mantle transition zone discontinuities near 400 km and 650 km near the subducted Nazca plate. It is anticipated that this research will provide new constraints on mechanisms of earthquakes and uplift in the central Andean plateau, and on the thermal structure of the subducted plate and adjacent mantle. This research is a component of the National Earthquake Hazard Reduction Program.