The Concord Fault is a

geologic fault In geology, a fault is a planar fracture or discontinuity in a volume of rock across which there has been significant displacement as a result of rock-mass movements. Large faults within Earth's crust result from the action of plate tectoni ...

in the

San Francisco Bay Area The San Francisco Bay Area, often referred to as simply the Bay Area, is a populous region surrounding the San Francisco, San Pablo, and Suisun Bay estuaries in Northern California. The Bay Area is defined by the Association of Bay Area Gov ...

. The reason it is called that is 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 The West Napa Fault is a 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. It has been map ...

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.

Seismic activity

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.

Dangers

According to

USGS The United States Geological Survey (USGS), formerly simply known as the Geological Survey, is a scientific agency of the United States government. The scientists of the USGS study the landscape of the United States, its natural resources, ...

seismologists it is "the most urban fault" in the East Bay, with potential for a larger event than the

2014 South Napa earthquake The 2014 South Napa earthquake occurred in the North San Francisco Bay Area on August 24 at . At 6.0 on the moment magnitude scale and with a maximum Mercalli intensity of VIII (''Severe''), the event was the largest in the San Francisco Bay Ar ...

. 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.

References

Seismic faults of California Geology of Contra Costa County, California Concord, California Mount Diablo Geography of the San Francisco Bay Area {{tectonics-stub