Nazca Plate
Chile lies above the convergent plate boundary where the Nazca Plate is subducting beneath the South American Plate, at a location where they converge at a rate of seventy millimeters a year. This quake was an oceanic interplate type, occurred in the downgoing slab of the Nazca Plate and not on the interface between the two plates. This event took place under the area of Chile, between 27° and 33° S, where the slab is nearly horizontal and there is a high degree of mechanical coupling between the plates.