Napa Valley quake . The 2000 quake was attributed to the West Napa Fault, but initially USGS scientists believed it was an unmapped, undiscovered fault system that was responsible. The West Napa fault system is a relatively minor strike-slip fault in the Contra Costa shear zone, which transfers slip be-tweentheNorthernCalaveras,WestNapa,andConcordfaults (Unruh and Kelson, 2002a,b; Kelson et al., 2004, 2005; Wes-ling and Hanson, 2008; Brossyet al., 2010). 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.. West Napa fault, Browns Valley section (Class A) No. Napa lies exactly in the axis - or "along the strike" as seismologists call it - of the West Napa Fault, the assumed origin of Sunday's quake. The West Napa Fault and its branches were first mapped by Weaver (1949), and subsequent work extended from the 1970's into the 1990's (references in the article cited). The San Andreas Fault System is an active plate boundary comprising right-lateral strike-slip faults that runs nearly the length of California. However, the fault had not been identified as being particularly hazardous prior to the quake that hit on 24 August. The relative motion on this fault is not well known but thought to be about 1 mm/yr (0.04 in/yr). This earthquake nucleated ~11km beneath Napa Valley on or near the West Napa fault, which is itself one a series of subparallel right-lateral strike-slip faults that comprise the San Andreas fault system. The West Napa Fault runs between the valleys on the eastern edge of the mountains. The epicenter of the 2000 M L 5.2 Yountville earthquake occurred 5 km west of the surface trace of the West Napa Fault as defined by Helley and Herd (1977), and thus the source of the earthquake was assigned to an unmapped fault. On 24 August 2014, the M 6.0 South Napa earthquake shook much of the San Francisco Bay area, leading to significant damage in the Napa Valley. We separately acquired P- and S-wave data at every station using multiple hammer hits, which were edited and stacked into individual shot gathers in the lab. Our seismic survey was designed to image a strand of the West Napa Fault Zone (WNFZ), which ruptured during the 24 August 2014 Mw 6.0 South Napa Earthquake. Some significant faults in the region are the Calaveras, Concord-Green Valley, Greenville, Hayward, Mt. by Dr. Wendy Bohon. The north-northwest-striking West Napa Fault is mapped along the western margin of Napa Valley, California. Our seismic survey was designed to image a strand of the West Napa Fault Zone (WNFZ), which ruptured during the 24 August 2014 Mw 6.0 South Napa Earthquake. Helley and Herd (1977 #509) first named the northwest to north northwest-striking zone of predominantly dextral slip faults the West Napa fault zone. It has been mapped as a Late Pleistocene-Holocene active fault, and is considered to be predominantly a right lateral strike-slip fault. In November 2016, the U.S. Geological Survey acquired high-resolution P- and S-wave seismic data across the surface trace of the West Napa Fault zone at Saintsbury Winery in Napa, California. New state maps show the locations of the West Napa Fault and associated faults in greater detail than ever before in such places as western city of Napa neighborhoods. There's a couple of faults there: the West Napa and Carneros-Franklin faults. 60 miles taking this route:Take I-80 WEST, from Sacramento, to SR-12 to NAPA at EXIT 39B.Take SR-12 WEST to Diablo, Rodgers Creek, San Andreas, San Gregorio, and West Napa faults. The West Napa fault extends along the western margin of the basin that underlies much of Napa Valley. Parts of the West Napa Fault Zone ruptured during the Aug. 24, 2014 South Napa earthquake, they said. The most common usage in recent literature is West Napa fault. The West Napa fault was more completely mapped by Fox and others (1973 #5253). Mapping the exact location of the aftershocks in three dimensions will yield a picture of the actual fault plane underground. a strike slip fault. The 2014 Mw 6.0 South Napa earthquake occurred on the West Napa Fault Zone (WNFZ) and caused damage in and around the City of Napa. The valley is located at the southernmost end of the Mayacamas Mountains and extends from the north at Calistoga to just south of Napa. Although the northern deep anomaly appears to cross the West Napa fault without apparent offset, the shallow wavelength, medium wavelength, and unfiltered magnetic data indicate that the apparent continuity of the deep magnetic anomaly across the West Napa fault separates two distinct magnetic sources. Most Popular on TIME… It clearly confirms that part of the West Napa Fault system was responsible for the 6.0 earthquake that rocked California’s wine-producing region. (hra093) The West Napa Fault has identified to have the potential capacity to generate a 6.8 to 7.1 magnitude earthquake (Napa County, BDR, 2005). But there is also another factor during the earthquake which can determine the zones of damage, that is the direction of the rupture itself. Linking Faults in Napa Valley and Beyond. https://www.livescience.com/47531-what-caused-napa-earthquake.html In October 2016, we acquired high-resolution P- and S-wave seismic data along a 120-m-long, SW-NE-trending profile in Napa, California. Pampeyan (1979 #1245) referred to this fault zone as the Napa fault. 36a Last Review Date: 2000-06-07 ... Bryant, W.A., 1982, West Napa fault zone and Soda Creek (East Napa) fault, Napa County: California Division of Mines and Geology Fault Evaluation Report FER-129, microfiche copy in Division of Mines and Geology Open-File Report 90-10, 18 p., scale 1:24,000. As noted in Table 4.10-3, there are four faults (West Napa, Hunting Creek, Green Valley and Cordelia) that are of concern to Napa County. The whole zone is about 70 km (44 mi) wide. The causative fault of the earthquake is unknown, but the USGS said it suspected the Browns Valley section of the West Napa fault. 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