Guerrero, Mexico Earthquake

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Posting Date: January 2, 2004, 12:30:00 PM

A strong earthquake struck Guerrero, Mexico on Thursday, January 1, 2004, at about 5:30 p.m. local time (23:30 UTC). The U. S. Geological Survey (USGS) initially estimated the moment magnitude to be 5.7, but later revised the magnitude upward to 6.0, with a focal depth of about 8 miles (13 km). The quake was felt across western and central Mexico from Acapulco to the capital, Mexico City, some 185 miles (130 km) to the east. It was centered about 25 miles (40 km) east of the resort city of Zihuatanejo, and about 70 miles (115 km) east-southeast of Lazaro Cardenas in the Mexican state of Michoacan. This earthquake occurred along the plate boundary zone where the Cocos plate subducts under the South American plate at a rate of about 47 mm/yr. The earthquake focal mechanism indicates that it was a typical subduction thrust event occurring at the plate interface. Seismicity along this part of the plate boundary is very active. Some of the largest historic earthquakes, such as the 1985 Mexico City M 8.1, the 1995 M 8.0 Manzanillo, and the 2003 M 7.8 Colima earthquake, all occured within 186 miles (300 km) distance of the current event. There were no immediate reports of damage or injury in Mexico City, but buildings were reported to have swayed and there were some power outages. In Guerrero state, minor damage such as cracks in walls were reported.

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Posting Date: January 2, 2004, 12:30:00 PM