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Study: Baja earthquake sign of a bigger one to come?

A study by the Jet Propulsion Laboratory shows that the Baja earthquake in April acted in unexpected ways. It also could set off another major quake in three to 30 years.

By Staff writer / December 16, 2010

Men stand next to cracks on a street in Mexicali, Mexico, on April 5, after a powerful earthquake struck. The quake shook buildings in Mexico, California, and Arizona.

Guillermo Arias/AP/file

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When an earthquake fault ruptured in Baja California last Easter Sunday, seismologists knew first and foremost that it was a big one. At magnitude 7.2, it was the most powerful quake on the fault in 120 years.

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After months of study, however, seismologists say the quake has become one for the text books.

Not only has it displayed highly unusual traits in its own right, it has revealed the existence of several previously unknown faults on both sides of the California-Mexico border.

And it has triggered movement on several faults in southern California, including three of the region's mightiest: the San Andreas, San Jacinto, and Elsinore faults.

One experimental model run at NASA's Jet Propulsion Laboratory in Pasadena, Calif., suggests that if the past 100,000 years of seismic history in California is any guide, the Baja quake may have shifted stress patterns along faults to the north in ways that could touch off a large quake on one of the Big Three within three to 30 years.

Indeed, the research team conducting the study notes that the shift in strain in the Earth's crust after the Baja quake may have touched off a magnitude 5.4 earthquake in July on the San Jacinto fault at Collins Valley, west of the Salton Sea.

"This earthquake was a special event," said John Fletcher, a seismologist at the Center for Scientific Research and Higher Education in Ensenada, Mexico, on Baja California's west coast.

The fault in question, the Laguna Salada, is part of a series of generally northwest trending faults that mark the boundary between the Pacific and North American plates, two large segments of Earth's crust. The various faults along the boundary run up the Gulf of California, then pass through the Colorado River Delta to crease and crinkle the Earth's surface inland of the California coast. A drive from Los Angeles east to Barstow, in the Mojave Desert, spans 115 miles and bridges the two plates.

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