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7.2 Mexicali earthquake made 2 other California faults riskier

July 2, 2010 |  8:06 am

Mexicali quake

Preliminary analysis shows that the 7.2 Mexicali earthquake in April placed more pressure on at least two Southern California fault lines: the Elsinore and the San Jacinto.

The Elsinore fault runs through portions of San Diego County, including near Julian, as well as through Temecula and Lake Elsinore in Riverside County; the San Jacinto fault runs near cities such as Hemet, Loma Linda and San Bernardino.

Scientists say earthquakes now are more likely on those two faults, but because so little is known about them, it's hard to calculate the risks.

Experts say the larger question is whether the temblor made quakes more likely along more dangerous fault lines, such as the Whittier — which produced the deadly 1987 Whittier Narrows quake — and the San Andreas.

Scientists are particularly interested in the Whittier fault because it's connected to the Elsinore and runs under heavily populated areas.

On Thursday, NASA flew a specially equipped Gulfstream III jet over the quake zone, looking for signs of Earth rupture that could help experts understand how the various faults are connected.

There are several key clues scientists were looking for during the nearly six-hour research flight, which covered such seismically active areas as the Salton Sea and U.S.-Mexico border as well as the San Diego coast. If data show slipping along the northern edges of the Mexican fault that triggered the 7.2 quake, that would suggest that pressure is being placed on faults in Southern California.

If they don't see significant slippage, it could suggest that the fault has stabilized and there is less risk to faults in California. The flight, one of several planned, produced photos and data that scientists will analyze.

Read more scientists seeking clue to the Mexicali quake here.

-- Hector Becerra

Photo: A passenger photographs a huge crack in a Mexican road near Mexicali left by the 7.2 earthquake in April, the largest quake in the region in years. JPL scientists are studying data from the quake, trying to learn how — or if — the quake affected other faults; credit: Don Bartletti / Los Angeles Times