The Concord Fault is a geologic fault in the San Francisco Bay Area. It is so called 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, which lies just a few miles to the north across the Suisun Bay. The fault is situated at the east of West Napa Fault and extends from Mount Diablo to the Carquinez Strait, an approximately 11 mile long distance. Like most other faults in this area, the Concord Fault is a strike-slip fault, moving approximately 2.7 to 3.6 millimeters a year.
Currently, it is considered to be under a high stress level and therefore has a higher chance of a major earthquake happening. There have been earthquakes on this fault before. On October 23, 1955, a 5.4 magnitude quake caused about 1 million dollars in damage (about 8.7 million today) and one death. The last large earthquake linked to this fault occurred over 400 years ago.
According to USGS seismologists it is "the most urban fault" in the East Bay, with potential for a larger event than the 2014 South Napa earthquake. As critical infrastructure, including refineries that process a significant portion of the state's total crude oil, and a railroad bridge, lie under it, a major earthquake from it could leave the entire northern half of the state without fuel and disrupt transmission of electricity and water to some extent across the state. One particular pumping station, if hit by a quake, would particularly damage transmission of fuel. A major earthquake there could also cause flooding, which would impact drinking quality, and a loss of electricity.
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- William A. Bryant (September 2007). "Digital Database for the Concord and Green Valley faults" (PDF). U.S. Geological Survey. Retrieved 8 May 2015.
- Galehouse, Jon S.; Lienkaemper, James J. (2003). "Inferences Drawn from Two Decades of Alinement Array Measurements of Creep on Faults in the San Francisco Bay Region" (PDF). Bulletin of the Seismological Society of America. 93 (6): 2415–2433. Bibcode:2003BuSSA..93.2415G. doi:10.1785/0120020226. Retrieved 17 May 2015.
- "Earthquake Swarm Rattles Concord Fault in East Bay".
- "Concord Fault That Saw 3.6 Magnitude Quake Has Potential To Do Major Damage To East Bay". CBS SF Bay Area. 3 May 2015. Retrieved 7 May 2015.