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]

Earthquakes

The West Napa Fault is a likely source for the magnitude 6.0 South Napa earthquake that hit Napa County on August 24, 2014.[4] Seismologists were not able to determine the exact fault on which the quake occurred, because faults are usually identified by their expression on the surface.[5]

The epicenter for the 2000 Yountville earthquake which occurred on September 3, 2000 is also near the West Napa Fault.[6]

See also

References

  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). USGS. 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
  4. ^ Perlman, David (24 August 2014). "Little-known fault suspected in Northern California quake". San Francisco Chronicle. Retrieved 25 August 2014.
  5. ^ "Which fault is it?". Seismo Blog. 24 August 2014. Retrieved 27 August 2014.
  6. ^ Courtney, Kevin (September 2, 2001). "Shake up call". Napa Valley Register. Napa, CA: Lee Enterprises, Inc.
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