It has been mapped as a
Late Pleistocene-
Holoceneactive 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]