This Quiet Fault in Southern California Hadn't Moved in 500 Years. Now It's Slipping.

livescience.com | 10/18/2019 | Nicoletta Lanese - Staff Writer
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A series of major earthquakes shook Southern California in July and placed strain on a nearby fault that has been quiet for about 500 years, according to a new study.

And that once-quiescent fault could trigger a magnitude 7.8 temblor, the authors noted.

Garlock - Fault - Boundary - Mojave - Desert

The Garlock fault traces the northern boundary of the Mojave Desert and extends about 186 miles (300 kilometers) across Southern California. The July quakes, collectively known as the Ridgecrest earthquake sequence, rattled the earth when ruptures occurred along several small faults in the region and stopped just a few miles from Garlock. The nearby disruption triggered movement along the fault, scientists reported Oct. 17 in the journal Science. Since July, the fault has slipped about 0.8 inches (2 centimeters) at the surface.

The Ridgecrest sequence not only set the Garlock fault in motion, it has also shaken up our idea of how major earthquakes typically occur, the authors said.

Earthquake - Sequences - History - Sheds - Light

"It ended up being one of the best-documented earthquake sequences in history and sheds light on how these types of events occur," study co-author Zachary Ross, an assistant professor of geophysics at Caltech, said in a statement. "It's going to force people to think hard about how we quantify seismic hazard and whether our approach to defining faults needs to change."

The most powerful shaking during the Ridgecrest sequence took place about 124 miles (200 km) north of Los Angeles, according to the statement. The event began July 4 with a magnitude 6.4 foreshock; the even-larger mainshock came about 34 hours later at a...
(Excerpt) Read more at: livescience.com
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