California fault zone could trigger devastating magnitude 7.8 earthquake, says study

The Palos Verdes fault zone runs 70 miles along the coast of Los Angeles

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A fault zone which runs 70 miles along the coast of Los Angeles has the potential to trigger an earthquake with a magnitude as strong as 7.8, according to a study.

Scientists say that the Palos Verdes fault zone, which runs deep beneath the Palos Verdes Peninsula, could produce a quake as big as the more famous San Andreas Fault.

Harvard University scientists say in the study that they now believe that the fault, which runs from Santa Monica Bay down to Dana Point, is an interconnected fault line.

It had previously been thought that it was a network of smaller faults. And earlier estimates had estimated that it could only generate up to a magnitude 7.4 earthquake.

While that seems like just a marginal difference, the US Geological Survey says a magnitude 7.8 quake produces four times the energy of a 7.4.

In a worst-case scenario a quake could combine the destructive qualities of the 1994 Northridge earthquake, and 2019 Ridgecrest earthquake, said John H Shaw, a professor of structural and economic geology at Harvard University and one of three authors of the study.

“Historically, this fault has been seen as a segmented fault — lots of little pieces,” he said.

“This seemed like a structure that wasn’t going to rupture in one big earthquake.”

More than 50 active faults run under LA County, and the majority move 1 millimetre or less annually.

The last time the region was struck by a quake as strong as a magnitude 7.8 was in 1857.