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Major Quake Threat Looms Over Hayward Fault

SAN FRANCISCO (CBS SF) – Like a sportsbook at a Nevada casino, the U.S. Geological Survey has posted a list of probabilities for a major quake rocking a Bay Area fault line in the next 30 years.

The 2014 Working Group on California Earthquake Probabilities used information from recent earthquakes, improved mapping of active faults and a new model for estimating earthquake probabilities to come up with the predictions.

The group concluded that there is a 72 percent probability (or likelihood) of at least one earthquake of magnitude 6.7 or greater striking somewhere in the San Francisco Bay region before 2043.

For a 6.0 quake, the chances rose to near certainty at 98 percent.

The USGS scientists ranked the Hayward Fault that runs up the spine of the populated East Bay as the biggest threat in the region for a magnitude 6.7 or greater quake with a 33 percent probability of it occurring some time before 2043.

The southern end of the Calaveras Fault that runs near Morgan Hill, Salinas and Watsonville ranked second at 26 percent.

The infamous San Andres Fault, the culprit in the deadly 1906 San Francisco and 1989 Loma Prieta earthquakes, ranks third at 22 percent.

A surprise to some local residents is the Concord/Green Valley Fault system which has the fourth highest probability in the region at 16 percent.

The Green Valley fault runs between the cities of Napa and Fairfield and lies near key dams and aqueducts northeast of San Francisco and a major quake of 6.7 or above could disrupt the water supply to the region.

The fault was believed to have last ruptured sometime in the 1600s.

Meanwhile, the Concord fault runs through the heavily populated areas of Concord, Walnut Creek and Martinez.

The scientists did not include a prediction for the West Napa Fault and the less well-known Carneros-Franklin Fault that were at the site of the damaging 2014 Napa quake.

The little-known Maacama Fault -- a right-lateral strike-slip fault that lies north of Santa Rosa and extends as far north as Ukiah – is the next highest rated with a probability of 8 percent on its southern end.

The final quake ranking was the San Gregorio Fault at a 6 percent chance. The fault runs up the San Mateo coast through Half Moon Bay and all the way to Southern Marin County.

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