M7.0 - SANTIAGO DEL ESTERO, ARGENTINA

Tectonic Summary

This major earthquake occurred within the subducted lithosphere of the oceanic Nazca plate. At the latitude of the earthquake, the Nazca plate moves east relative to the South America plate at a rate of about 7 cm per year. It is overridden by the South America plate at the Peru-Chile trench, west of the Chilean coast, and sinks into the earth's mantle beneath South America. This earthquake occurred as normal faulting within a segment of the subducted plate that has produced frequent earthquakes with focal depths of 500 km to 625 km beneath the earth's surface. In the past quarter century, two other shocks of magnitude 7 or larger have occurred in the segment of subducted Nazca plate that lies beneath northern Argentina.

Earthquakes that have focal depths greater than 300 km are commonly termed "deep-focus" earthquakes. Deep-focus earthquakes cause less damage on the ground surface above their foci than is the case with similar magnitude shallow-focus earthquakes, but large deep-focus earthquakes may be felt at great distance from their epicenters. The largest recorded deep-focus earthquake had a magnitude of 8.2, occurring within the subducted Nazca plate beneath Bolivia in June 1994.

Earthquake Information for South America