If you hadn’t heard of the West Napa Fault before Sunday morning’s 6.0 shaker, you’re not alone.
Even though a magnitude 5.0 earthquake occurred along that same fault in Yountville in 2000, few locals – and few geologists, for that matter – have given it much thought.
And yet, on Sunday at 3:20 a.m., it appears to have hosted the Bay Area’s most powerful earthquake in 25 years.
“Those faults are not very well known,” said Diane Moore, a research geologist with the U.S. Geological Survey in Menlo Park, referring to a complex web of North Bay fault lines that includes the West Napa Fault. As a result, she said, there are no strong estimates on the likelihood of quakes occurring near the region.
“If you look at the probability elements for the area, that is not even included on it,” she said.