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USU Geologists Identify Unknown Quake Faults in Southern California

Thursday, May. 06, 2010

USU professor Susanne Janecke conducting field research

USU geology professor Susanne Janecke and her students have identified previously unknown faults near southern California's Salton Sea.

fault activity map

A new fault activity map released by the California Geological Survey includes faults identified by Janecke and her students (in the rectangle) that connect to the larger San Andreas and San Jacinto faults (indicated by the diagonal lines.)

Thanks to efforts by Utah State University geologists, along with advances in mapping technology, fault maps of California look a whole lot different than they did just 16 years ago. And the new findings indicate there may be a whole lot more shakin’ going on than previously thought.
A fault activity map released at the end of April by the California Geological Survey reveals, for the first time, faults under and near the Salton Sea in the state’s border region with Mexico. Many of these onshore faults were mapped during the past decade by USU professor Susanne Janecke and her graduate students Ben Belgarde, David Forand, Stefan Kirby and Alex Steely.
“Having these faults recognized as active in the southern California quaternary is important because they could produce future earthquakes,” Janecke says. “It’s very gratifying that our work could help many better prepare for dangerous and damaging events.”
Though relatively small, the faults, which connect the southern end of the state’s massive San Andreas Fault to the lesser known yet major San Jacinto Fault, warrant attention.
“A basic tenet of earthquake geology is that small faults cause small earthquakes and big faults cause big earthquakes,” Janecke says. “But the faults we identified are adjacent to these larger faults and could trigger tremors on the larger faults leading to significant quakes in populated areas, including the Los Angeles basin.”
Linkages between faults are important, she says, noting that in 1987 a small connector fault in the Superstition Hills southwest of the Salton Sea triggered a 6.6 magnitude quake along the San Jacinto Fault. According to the U.S. Geological Survey, the temblor caused an estimated $3 million in property damage in Imperial County.
Faults in the Salton Basin cut through mud-rich sedimentary rock and because they’re widely dispersed it’s easy for them to go unrecognized, Janecke says. But advances in mapping technology are enabling scientists to discover these faults and their connections to each other.
Faults aren’t straight, she says, but bend, step down, step up and create an intricate patchwork at varied depths.
“We have some important work to do at the faults’ branching points,” Janecke says. “The more we learn the more we discover that we need to know.”
Related links:
Contact: Susanne Janecke, 435-797-3877,
Writer: Mary-Ann Muffoletto, 435-797-3517,

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