Coquimbo, Chile Earthquake

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Posting Date: June 20, 2003, 12:30:00 PM

A strong earthquake struck Chile at 9:30 a.m. EDT on Friday, June 20, 2003. The moment magnitude of the quake was 6.8, according to the U.S. Geological Survey. The epicenter was located near the coast of central Chile, about 40 miles (65 km) south of Coquimbo, 175 miles (280 km) north of Valparaiso, and about 205 miles (335 km) north northwest of the capital, Santiago. Focal depth is estimated at about 21 miles (34 km). The earthquake rattled buildings in Buenos Aires, Argentina, across the Andes Mountains. The epicenter is located along the Chilean trench, where the Nazca plate subducts eastward, under the South American plate, at a rate of over 8 cm/yr. This earthquake is a typical subduction thrust event, generated by the Chilean subduction zone system. Major earthquakes have occurred in this zone frequently, with earthquakes greater than magnitude 8 occurring, on average, every decade. The largest historical earthquake ever reported, the 1960 M 9.4 Chile earthquake, which caused a rupture of about 1000 km of the subduction zone, occurred about 500 km south of the current event. In a narrower area, within 300 km of the current event, 6 earthquakes of magnitude 8.0 or greater have occurred since the 18th century. One of them, the 1985 M8.0 Valparaiso earthquake, caused extensive loss of life and damage. There were no reports of injuries, deaths, or major damage an hour after the quake, but schools were evacuated and electrical power was disrupted. While no damage reports have yet been received for the earthquake, AIR seismologists currently expect insured losses to be minimal. AIR will continue to monitor events in the area and will post additional information as necessary.

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Posting Date: June 20, 2003, 12:30:00 PM