![2014 South Napa Earthquake epicenter](https://upload.wikimedia.org/wikipedia/commons/3/3d/2014_South_Napa_Earthquake_epicenter.jpg)
The West Napa Fault is a long
geologic fault
In geology, a fault is a planar fracture or discontinuity in a volume of rock across which there has been significant displacement as a result of rock-mass movements. Large faults within Earth's crust result from the action of plate tectonic ...
in
Napa County
Napa County () is a county north of San Pablo Bay located in the northern portion of the U.S. state of California. As of the 2020 census, the population was 138,019. The county seat is the City of Napa. Napa County was one of the original co ...
, in the
North Bay region of the
San Francisco Bay Area
The San Francisco Bay Area, often referred to as simply the Bay Area, is a populous region surrounding the San Francisco, San Pablo, and Suisun Bay estuaries in Northern California. The Bay Area is defined by the Association of Bay Area Go ...
in northern
California
California is a U.S. state, state in the Western United States, located along the West Coast of the United States, Pacific Coast. With nearly 39.2million residents across a total area of approximately , it is the List of states and territori ...
. It is believed to be the northern extension of the
Calaveras Fault
The Calaveras Fault is a major branch of the San Andreas Fault System that is located in northern California in the San Francisco Bay Area. Activity on the different segments of the fault includes moderate and large earthquakes as well as aseismi ...
in the
East Bay
The East Bay is the eastern region of the San Francisco Bay Area and includes cities along the eastern shores of the San Francisco Bay and San Pablo Bay. The region has grown to include inland communities in Alameda and Contra Costa countie ...
region.
It has been mapped as a
Late Pleistocene
The Late Pleistocene is an unofficial Age (geology), age in the international geologic timescale in chronostratigraphy, also known as Upper Pleistocene from a Stratigraphy, stratigraphic perspective. It is intended to be the fourth division of ...
-
Holocene
The Holocene ( ) is the current geological epoch. It began approximately 11,650 cal years Before Present (), after the Last Glacial Period, which concluded with the Holocene glacial retreat. The Holocene and the preceding Pleistocene togethe ...
active fault
An active fault is a fault that is likely to become the source of another earthquake sometime in the future. Geologists commonly consider faults to be active if there has been movement observed or evidence of seismic activity during the last 10,0 ...
, and is considered to be predominantly a
right lateral strike-slip fault. The fault was discovered in 1976 by Gene Boudreau, a ground water drilling specialist from
Sebastopol
Sevastopol (; uk, Севасто́поль, Sevastópolʹ, ; gkm, Σεβαστούπολις, Sevastoúpolis, ; crh, Акъя́р, Aqyár, ), sometimes written Sebastopol, is the largest city in Crimea, and a major port on the Black Sea ...
.
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. 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.
The epicenter for the
2000 Yountville earthquake which occurred on September 3, 2000 is also near the West Napa Fault.
See also
*
Green Valley Fault
Green is the color between cyan and yellow on the visible spectrum. It is evoked by light which has a dominant wavelength of roughly 495570 Nanometre, nm. In subtractive color systems, used in painting and color printing, it is created by ...
— ''northern extension of the East Bay
Concord Fault
The Concord Fault is a geologic fault in the San Francisco Bay Area. The reason it is called that is because it is located under the city of Concord. It is connected to, and considered to be part of, the same fault zone as the Green Valley fault, ...
''.
*
*
References
{{Quaternary Footer
Seismic faults of California
Geology of Napa County, California
Napa, California
Strike-slip faults
Late Pleistocene
Pleistocene California
Quaternary California
Holocene North America