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. 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). 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. 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. West Napa fault, Browns Valley section (Class A) No. There's a couple of faults there: the West Napa and Carneros-Franklin faults. Once these shocks are properly recorded and analyzed, it will be seen if the USGS was correct to initially assign the quake to the widely unknown West Napa Fault. The West Napa fault extends along the western margin of the basin that underlies much of Napa Valley. The whole zone is about 70 km (44 mi) wide. Pampeyan (1979 #1245) referred to this fault zone as the Napa fault. The West Napa fault was more completely mapped by Fox and others (1973 #5253). Diablo, Rodgers Creek, San Andreas, San Gregorio, and West Napa faults. 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. Linking Faults in Napa Valley and Beyond. 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. 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). Accordingly, we interpret the estimates of z u as a map of the position of a slip front—either coseismic or postseismic—that propagated on an extant fault plane. 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. Mapping the exact location of the aftershocks in three dimensions will yield a picture of the actual fault plane underground. Helley and Herd (1977 #509) first named the northwest to north northwest-striking zone of predominantly dextral slip faults the West Napa fault zone. The causative fault of the earthquake is unknown, but the USGS said it suspected the Browns Valley section of the West Napa 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. The West Napa Fault runs between the valleys on the eastern edge of the mountains. Many faults zoned in this area were identified by … Most Popular on TIME… The most common usage in recent literature is West Napa fault. a strike slip fault. This early work reported that the fault and its branches extend 30-35 km along the western margin of the Valley; the Wesling and Hanson report suggests that the fault is 57 km long, extending from Carquinez Strait … The West Napa fault passes through the Napa Valley and cuts through 2 km of late Pleistocene to Quaternary aged sediments under the valley floor (Wesling and Hanson, 2008; Brocher et al., 2015). The fault zone that ruptured in the South Napa earthquake had been previously recognized as a strand of the West Napa Fault zone . 60 miles taking this route:Take I-80 WEST, from Sacramento, to SR-12 to NAPA at EXIT 39B.Take SR-12 WEST to 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. 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. This was a shallow-focus … 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. Zone that ruptured in the South Napa earthquake had been previously recognized as a strand of the West fault! 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