The West Napa fault extends along the western margin of the basin that underlies much of Napa Valley. 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. The West Napa Fault runs between the valleys on the eastern edge of the mountains. The West Napa Fault is part of the huge fault zone extending outward from the San Andreas Fault, which lies about 31 miles (50 km) west of Napa Valley.The San … 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.. Mapping the exact location of the aftershocks in three dimensions will yield a picture of the actual fault plane underground. 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. 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. As Bay Area earthquake fault lines go, the West Napa Fault — tentatively identified as the source of Sunday’s magnitude-6.0 temblor — is a relative stranger. Today's earthquake was between a pair of active fault systems, the Hayward-Rodgers Creek Fault system and the Concord-Green Valley Fault system. 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 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). Parts of the West Napa Fault Zone ruptured during the Aug. 24, 2014 South Napa earthquake, they said. Napa Valley quake . Some significant faults in the region are the Calaveras, Concord-Green Valley, Greenville, Hayward, Mt. 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. Helley and Herd (1977 #509) first named the northwest to north northwest-striking zone of predominantly dextral slip faults the West Napa fault zone. 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 was more completely mapped by Fox and others (1973 #5253). (hra093) A new order from President Trump is racist, says the head of a local agency that intends to defy it 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. This was a shallow-focus … 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). Most Popular on TIME… There's a couple of faults there: the West Napa and Carneros-Franklin faults. The whole zone is about 70 km (44 mi) wide. It has been mapped as a Late Pleistocene-Holocene active fault, and is considered to be predominantly a right lateral strike-slip fault. 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. 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 causative fault of the earthquake is unknown, but the USGS said it suspected the Browns Valley section of the West Napa fault. 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. 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). 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. by Dr. Wendy Bohon. The north-northwest-striking West Napa Fault is mapped along the western margin of Napa Valley, California. 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 San Andreas Fault System is an active plate boundary comprising right-lateral strike-slip faults that runs nearly the length of California. But there is also another factor during the earthquake which can determine the zones of damage, that is the direction of the rupture itself. https://www.livescience.com/47531-what-caused-napa-earthquake.html Many faults zoned in this area were identified by … 60 miles taking this route:Take I-80 WEST, from Sacramento, to SR-12 to NAPA at EXIT 39B.Take SR-12 WEST to The relative motion on this fault is not well known but thought to be about 1 mm/yr (0.04 in/yr). 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. a strike slip fault. 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. The M=6.0 earthquake injured 120 people, three critically, and caused localized damage in Napa Valley. 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 most common usage in recent literature is West Napa fault. West Napa fault, Browns Valley section (Class A) No. 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. Pampeyan (1979 #1245) referred to this fault zone as the Napa fault. However, the fault had not been identified as being particularly hazardous prior to the quake that hit on 24 August. 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. We acquired seismic reflection, refraction, and guided-wave data along a 115-m-long profile across the known surface rupture zone of the West Napa Fault zone. The valley is located at the southernmost end of the Mayacamas Mountains and extends from the north at Calistoga to just south of Napa. 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). Diablo, Rodgers Creek, San Andreas, San Gregorio, and West Napa faults. The fault zone that ruptured in the South Napa earthquake had been previously recognized as a strand of the West Napa Fault zone . 36a Last Review Date: 2000-06-07 ... 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