South American Plate
In this area, the Nazca Plate is subducting beneath the South American Plate. This earthquake occurred at the plate interface and is associated with the subduction of the 1.5 km high Nazca Ridge beneath the South American plate. This was a complex event, and there were at least two larger events occurring between 18 and 30 seconds after the onset. This earthquake may have ruptured part of the rupture zone of the earthquake of August 24, 1942.