Geologists are taking a closer look at an enigmatic fault line hidden in a forest in Northern California, one they suspect is still active and capable of producing earthquakes — a discovery drawing fresh attention soon after a strong quake struck the region.
Researchers are now excavating the fault in Humboldt County to learn more about its history and potential danger.
“We felt really confident but we needed to go explore by excavating it,” Mark Hemphill-Haley, professor emeritus of geology at Cal Poly Humboldt, told SFGATE. “We have since discovered that it’s a very well-presented reverse fault.”
California Geological Survey geologist Jason Patton first identified signs of the fault near Shively, California, about four years ago. Using lidar, a remote-sensing technology that maps Earth’s surface in detail, he spotted the feature from above.
Patton and Hemphill-Haley later joined forces to excavate the site, which they believe remains active based on evidence suggesting four major earthquakes have occurred there over the past 20,000 years.
Backed by funding from the U.S. Geological Survey, the team has opened a trench measuring about 30 feet across and 15 feet deep, where scientists are now collecting and analyzing data.
While the researchers were studying the trench, a magnitude 5.6 earthquake rattled nearby Mendocino County on Wednesday, causing injuries and damaging several businesses.
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Scientists say the Shively fault, however, may have the potential to generate an even more destructive earthquake.
Patton and Hemphill-Haley’s team thinks the fault could produce a magnitude 7 earthquake, more than 100 times stronger than the recent Mendocino shake according to the USGS.
Only about a dozen-and-a-half earthquakes 7.0 or above have struck California in the last century. Scientists are hopeful the additional data will prepare them for the next big one.
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But there’s concern that the Pacific Ring of Fire, which includes California and encompasses thousands of miles from the bottom tip of South America to the coast of Australia, could produce more devastating quakes.
Two Venezuela earthquakes, a magnitude 7.2 followed by a 7.5, in Venezuela, devastated the region. The country is also located along the Ring of Fire.
The U.S. Geological Survey estimated that there’s a 40% chance the death toll could climb to at least 10,000, and a 30% chance it could even top 100,000.
“High casualties and extensive damage are probable, and the disaster is likely widespread,” the USGS warned.
The California Post reached out to the geologists for further comment.