Poster of the Oaxaca, Mexico Earthquake of 20 March 2012 - Magnitude 7.4

Tectonic Summary

The March 20, 2012 earthquake occurred as a result of thrust-faulting on or near the plate boundary interface between the Cocos and North America plates. The focal mechanism and depth of the earthquake are consistent with its occurrence on the subduction zone interface between these plates, approximately 100 km northeast of the Middle America Trench, where the Cocos plate begins its decent into the mantle beneath Mexico. In the region of this earthquake, the Cocos plate moves approximately northeastwards at a rate of 60 mm/yr.

Historically, there have been several significant earthquakes along the southern coast of Mexico. In 1932, a magnitude 7.9 thrust earthquake struck in the region of Jalisco, several hundred kilometers to the northwest of todays event. On October 9, 1995 a magnitude 7.9 earthquake struck in the Colima-Jalisco region, killing at least 49 people and leaving 1,000 homeless. The most deadly nearby earthquake occurred in the Michoacan region 470 km to the northwest of todays event, 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. More recently, a 2003 M7.6 Colima, Mexico earthquake 640 km to the northwest of todays event killed 29 people, destroyed more than 2,000 homes and left more than 10,000 homeless.

Earthquake Report

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