Southern California fault systems capable of magnitude 7.3 earthquakes

In 1933, the fault system featured a 6.4 magnitude quake near Long Beach, killing 115 people.
By Brooks Hays   |   March 7, 2017 at 2:22 PM

March 7 (UPI) -- New analysis of coastal fault systems in Southern California suggest the region is capable of a magnitude 7.3 earthquake.

Until now, scientists thought the Newport-Inglewood and Rose Canyon faults were separate, but the latest research -- published in the Journal of Geophysical Research -- showed the two systems, running from Los Angeles to San Diego, are connected.

Analysis of the fault system suggests a rupture on land could produce magnitude 7.3 earthquakes, while an combination offshore-onshore fault slip could yield magnitude 7.4 earthquakes.

"This system is mostly offshore but never more than four miles from the San Diego, Orange County and Los Angeles County coast," Valerie Sahakian, a former Scripps researcher, now a postdoctoral fellow with the U.S. Geological Survey, said in a news release. "Even if you have a high 5 or low 6 magnitude earthquake, it can still have a major impact on those regions, which are some of the most densely populated in California."

Scientists use sonar imaging to map the system's fault lines and to analyze the system's "stopovers," gaps where the faults are horizontally offset. The researchers determined none of the four gaps are large enough to ensure a future earthquake remains localized.

The study offered researchers a new understanding of the system's potential. In 1933, the fault system featured a 6.4 magnitude quake near Long Beach, killing 115 people. Scientists say more work is needed to explore the risks a Newport-Inglewood and Rose Canyon system quake would pose coastal cities like Tijuana and Los Angeles.

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