West Napa Fault

The reported epicenter of the 2014 South Napa earthquake was located beneath the Napa Valley Marina

The West Napa Fault is a 57 km (35 mi) long geologic fault in Napa County, in the North Bay region of the San Francisco Bay Area in northern California. It is believed to be the northern extension of the Calaveras Fault in the East Bay region.

It has been mapped as a Late Pleistocene-Holocene active fault, and is considered to be predominantly a right lateral strike-slip fault.[1] The fault was discovered in 1976 by Gene Boudreau, a ground water drilling specialist from Sebastopol.[2] In 2023 there was data showing that the West Napa Fault is actually nine miles longer than previously known.[3]

  1. ^ Wesling, John R.; Hanson, Kathryn L. (2008). "Mapping of the West Napa Fault zone for input into the Northern California Quaternary Fault Database" (PDF). United States Geological Survey. Retrieved 25 August 2014.
  2. ^ Jensen, Peter (August 31, 2014). "A lesser fault line blamed for Sunday's earthquake". Napa Valley Register. Napa, CA: Lee Enterprises, Inc. Retrieved August 31, 2014.
  3. ^ Fault line that caused 2014 Napa quake longer, potentially stronger than previously thought: USGS, ABC7 News San Francisco, 26 December 2023