As if California needed more bad news – amidst a drought of unprecedented proportions, new research has revealed the state could be in for a massively destructive earthquake. We reported last month that seismologists expect a megaquake in California’s future, and now a further discovery makes that news even more terrifying. According to, seismologists from UC Berkeley have now proven that the Hayward Fault, east of San Francisco, is actually a branch of the Calaveras Fault that runs east of San Jose – which means both could eventually rupture together and create a much larger earthquake than previously expected.

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At 43 miles long, the Hayward Fault is already known as one of the most dangerous in the country because it travels through densely populated areas, but the news that it’s connected to the Calaveras Fault adds a whole new dimension to the earthquake potential of the fault.

“The maximum earthquake on a fault is proportional to its length, so by having the two directly connected, we can have a rupture propagating across from one to the other, making a larger quake,” lead researcher Estelle Chaussard, a postdoctoral fellow in the Berkeley Seismological Laboratory, told “People have been looking for evidence of this for a long time, but only now do we have the data to prove it.”

Related: The next California earthquake could be caused by human-made drought

The U.S Geological Survey updated its seismic hazards in March, estimating a 14.3 percent likelihood of a magnitude 6.7 or higher earthquake on the Hayward Fault in the next 30 years, and a 7.4 percent chance on Calaveras. These estimates were based on the assumption that the two faults are independent systems, according to Now with the news they’re connected, the energy released in a simultaneous fault rupture would be 2.5 times greater.

“A rupture from Richmond to Gilroy would produce about a 7.3 magnitude quake, but it would be even greater if the rupture extended south to Hollister, where the Calaveras Fault meets the San Andreas Fault,” Chaussard said.


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