DAVIS (CBS SF) — The next earthquake in the Napa Valley could be much stronger than the magnitude 6 quake that shook the region in August, according to preliminary research from the University of California at Davis.
A team of geologists and graduate students found that the West Napa Fault line is about 45 miles long. Scientists say that’s larger than previously thought and capable of producing a magnitude 7 earthquake, which has 31 times the energy release of a magnitude 6 quake.
A statement released by UC Davis Friday said that while scientists do not predict when such a quake might occur, “geological evidence along the fault suggests it might happen every 1,000 to 2,000 year.”
The Napa quake produced California’s first surface-rupturing earthquake in more than 20 years, which was important for researchers to study using new technology.
Since August 24th, the fault that produced the quake has continued moving several inches. U.S. Geological Survey geophysicist Ken Hudnut said the creep or “afterslip” is slow movement and should not produce any aftershocks.
Hudnut said scientists expect two to six inches of additional fault movement over the next three years for that part of the west Napa fault system that goes directly through the Brown’s Valley neighborhood.
Graduate students Chad Trexler and Alex Morelan rushed to Napa in the hours following the earthquake to quickly photograph broken sidewalks, roads and curbs.
Then using smartphones, text messages, Twitter and Google Earth, they were able to create the first publicly available online map of where the fault broke to the surface.
“Twenty years is not long geologically speaking, but in terms of technology, it’s huge,” Trexler said. “Everyone wants to know where the fault broke for things like infrastructure repair and emergency response. The quicker you can get that up, the better.”
The class used the data to compare this year’s earthquake to one that occurred in nearby Yountville in 2000 and found they were on the same fault, also affirming that a small portion of that fault ruptured twice in the in past 15 years.
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