VOLCANO MADNESS: [Geology2] El Mayor - Cucapah Earthquake in Baja Mexico

Sunday, October 3, 2010

[Geology2] El Mayor - Cucapah Earthquake in Baja Mexico

El Mayor - Cucapah Earthquake in Baja Mexico

September 16, 2010

Photographer: David Lynch
Summary Author: David Lynch

On Sunday April 4, 2010, a magnitude 7.2 earthquake hit in the Cucapah Mountains southwest of Mexicali. Although there were only two deaths, there was widespread damage to buildings and agriculture as a result of liquefaction and broken irrigation systems. A number of fields were tilted and significant crop failure occurred, with resulting loss of jobs for farm workers. Many roads including Highway 2, a major roadway between Mexicali and Tecate, needed immediate repair.

The epicenter was at 32.259°N, 115.287°W, and the ground was ruptured for over 60 miles (100 km) along the fault. Small, branching cracks extended northward across the US/Mexico border. Although the fault is part of the North American - Pacific plate boundary, the break was west of the heretofore accepted plate boundary - the Cerro Prieto fault. Most surprisingly of all, the number of aftershocks has been extremely high and they continue to rattle the region.

In August, a team of geologists from CICESE (Centro de Investigación Científica y de Educación Superior de Ensenada), USGS, Caltech (California Institute of Technology) and other organizations spent five days mapping and measuring the fault. Much of this was done by flying teams in by helicopter and dropping them off along the main scarp. Water and emergency supplies were also brought in since it was hot -- 115 F (46 C) by mid afternoon. In this picture, the main scarp is seen along with three geologists. Here the scarp is about five feet (1.5 m ) high, dramatically attesting to the amount of energy it took to shift that much rock along many miles. Further from the epicenter, the scarps grew smaller, in some places being only 1 in (2.5 cm) in height. Photo taken on August 10, 2010.

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