M7.2 Baja California, Mexico Earthquake
A large earthquake occurred on Sunday, April 4, 2010 in Mexico just south of the California, US border (see figure). Nearly 1 million people were exposed to shaking of a very strong intensity, and the earthquake has been reported to be felt over a vast area of Mexico and the US, throughout southern California, and as far as Las Vegas, Nevada. Damage and loss, however, are expected to be focused in the epicentral region.
EQECAT estimates total economic damage from this event will not exceed $1 billion, and insured losses will not exceed $300 million. Most of the economic damage will have occurred in Mexico.
M7.2 Mexicalli Earthquake Intensity - April 4, 2010
Source: U.S. Geological Survey (USGS)
Although damage will have occurred in both Mexico and the US, the community of Mexicali is the largest urban area affected by this event, and damage there is expected to be widespread. The largest US city affected by the earthquake is El Centro, California, although significantly less damage is expected there than in Mexicali, due both to lower-intensity ground shaking and less-vulnerable structures.
The ground shaking experienced in Mexicali was of an intensity typically associated with moderate-to-heavy damage in vulnerable structures such as unreinforced masonry. Structures with greater earthquake resistance may have experienced slight to moderate damage. The intensity of shaking that occurred in El Centro and other US locations is below the threshold typically associated with structural damage.
This earthquake ruptured on the Laguna Salada fault, whose last major earthquake occurred in 1892, to the northwest of yesterday's rupture. Another historic earthquake that affected the region was the 1940 Imperial Valley (US) earthquake (M6.9), which caused strong shaking in the US cities of El Centro and Brawley. Buildings damaged in 1940 will have been repaired or replaced, and highly-vulnerable buildings were not reconstructed in the El Centro region.
However, border cities such as Mexicali had not experienced shaking as severe as from yesterday's quake for nearly 100 years. Consequently, many buildings in Mexicali will have been at risk to major damage, particularly older commercial and residential structures, and particularly those built of unreinforced masonry. Unreinforced masonry buildings have consistently demonstrated vulnerability to damage from earthquakes.
EQECAT will continue to monitor this event and provide updates as necessary.
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