Historic Earthquakes: Tectonic Summary

Magnitude 7.6 COLIMA, MEXICO
2003 January 22 02:06:34 UTC

This shallow earthquake occurred in a seismically active zone near the coast of central Mexico. The earthquake occurred near the juncture of three tectonic plates: the North American Plate to the north-east, the Rivera Plate to the north-west, and the Cocos Plate to the south. Both the Rivera Plate and the Cocos Plate are being consumed beneath the North American Plate. The slower subducting Rivera Plate is moving north-west at about 2 cm per year relative to the the North American Plate and the faster Cocos plate is moving in a similar direction at a rate of about 4.5 cm per year.

There have been several significant earthquakes near the recent event. In 1932, a magnitude 8.4 thrust earthquake struck about 100 km to the north-north-west. More recently, on October 9, 1995 a magnitude 8.0 earthquake struck about 50 km to the north-west killing at least 49 people and leaving 1,000 homeless. The most deadly earthquake in the region occurred about 170 km to the south-east on September 19, 1985. This magnitude 8.0 earthquake killed at least 9,500 people, injured about 30,000, and left 100,000 people homeless.