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. 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. 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. Diablo, Rodgers Creek, San Andreas, San Gregorio, and West Napa faults. (hra093) Parts of the West Napa Fault Zone ruptured during the Aug. 24, 2014 South Napa earthquake, they said. 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. by Dr. Wendy Bohon. 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). 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 has identified to have the potential capacity to generate a 6.8 to 7.1 magnitude earthquake (Napa County, BDR, 2005). However, the fault had not been identified as being particularly hazardous prior to the quake that hit on 24 August. The San Andreas Fault System is an active plate boundary comprising right-lateral strike-slip faults that runs nearly the length of California. The fault zone that ruptured in the South Napa earthquake had been previously recognized as a strand of the West Napa Fault zone . 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). 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. Most Popular on TIME… Today's earthquake was between a pair of active fault systems, the Hayward-Rodgers Creek Fault system and the Concord-Green Valley Fault system. 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 … Mapping the exact location of the aftershocks in three dimensions will yield a picture of the actual fault plane underground. 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.. 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 most common usage in recent literature is West Napa fault. 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). 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. 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