A University of Iowa-led study has found that a series of Southern California earthquakes last summer increased stress on the Garlock Fault, a major earthquake fault line that has been dormant for at least a century.
The researchers used satellite imagery and seismic instruments to map the effects of the Ridgecrest earthquakes, a sequence that began with a magnitude 6.4 foreshock in the Mojave Desert on July 4 before a magnitude 7.1 earthquake that struck the next day. In all, there were more than 100,000 aftershocks stemming from the twin earthquakes.
The analysis by Bill Barnhart, a geodesist at Iowa, and researchers at the U.S. Geological Survey showed the Ridgecrest earthquakes and aftershocks caused “aseismic creep” along a 12- to 16-mile section of the Garlock Fault, which runs east to west for 185 miles from the San Andreas Fault to Death Valley, and perpendicular to the Ridgecrest earthquake region.
“The aseismic creep tells us the Garlock Fault is sensitive to stress changes, and that stresses increased across only a limited area of the fault,” says Barnhart, assistant professor in the UI Department of Earth and Environmental Sciences and corresponding author on the study, published in the journal Geophysical Research Letters.
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