San Francisco is expected to be hit with a 6.7 magnitude or higher earthquake before 2032, according to the US Geological Survey (USGS). But USGS scientists just discovered that two fault lines in the area are connected, which could make a Bay Area earthquake much worse. The Rodgers Creek and Hayward fault lines are linked, which means they could rupture together and San Francisco could be rocked with a 7.4 magnitude earthquake.

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Four USGS scientists found that the Hayward fault, which runs beneath neighborhoods east of San Francisco, and the Rodgers Creek fault, which runs through wine county, are linked. The two connect under the San Pablo Bay, north of the city, and together run 118 miles. If the fault lines rupture together, it could result in an earthquake that releases five times as much energy than if the Hayward fault ruptured on its own.

Related: NASA experts say California’s next big earthquake could happen in less than three years

Even worse, such an earthquake could come soon – there’s usually 140 years between earthquakes on the Hayward fault, but the last quake along the line was 148 years ago in 1868, when a 6.8 magnitude quake killed 30 people. A earthquake along both fault lines could result in a quake over five times more powerful than a 1989 earthquake along the San Andreas fault. More than 60 people died then, and a portion of the San Francisco – Oakland Bay Bridge collapsed.

USGS geophysicist and study lead writer Janet Watt told New Scientist, “The concerning thing with the Hayward and Rodgers Creek faults is that they’ve accumulated enough stress to be released in a major earthquake. They’re, in a sense, primed.” The journal Science Advances published the scientists’ research online this week.

What can Bay Area residents do to get ready? University of California, Berkeley fault researcher Roland B├╝rgmann told New Scientist it’s important to be prepared “at all levels” – from resilient construction techniques to early warning systems to having your own supplies ready if an earthquake occurs.

+ Science Advances

Via New Scientist and

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