Historic Earthquakes: Tectonic Summary
Magnitude 6.8 NEAR THE COAST OF CENTRAL CHILE
2003 June 20 13:30:38 UTC
This earthquake occurred in the Chilean subduction zone, in which the dominant tectonic process is the subduction and underthrusting of the Nazca plate to the east beneath the South American plate at a rate of about 8 cm/yr. The currently available location and moment-tensor of the earthquake imply that the shock occurred as a sudden slippage on the thrust-fault boundary between the plates. The hypocenter of this event is located within a segment of the plate boundary that was ruptured in 1943 by a magnitude 7.9 earthquake.