‘Double-Fault’ Earthquake Would Devastate California: San Andreas-San Jacinto Jolt Could Kill Hundreds

A massive “double-fault” earthquake could strike Southern California, igniting fires, killing hundreds and unleashing destruction across parts of the state, according to a recent study that offers a bleak picture for population centers along the faults. The study suggests that an earthquake along the San Jacinto fault could continue to the San Andreas fault, creating the sort of severe earthquake that many have long feared, the Los Angeles Times reported Thursday.

While the San Andreas fault has produced powerful earthquakes — and could potentially create a stronger earthquake on its own than the magnitude 7.5 earthquake envisioned in the study — it sits further from major population centers. If it were to join with the San Jacinto fault, it could strike a number of communities, including in San Bernardino, Colton, Moreno Valley, Redlands, Lomo Linda, Hemet and San Jacinto, among other areas. To those on the ground, it would feel like a single quake, Science Alert reported.

The study was published by Julian Lozos, a geophysics professor at Cal State Northridge, who wrote it as part of his doctoral research at Stanford University and the U.S. Geological Survey. According to his theory, a devastating magnitude 7.5 earthquake that killed 40 people in 1812 resulted from a similar scenario.

Some seismologists think multi-fault quakes have already been happening in California and could be more calamitous, despite potentially being weaker.

"Combination earthquakes aren’t necessarily more powerful than single-fault ones, but they do travel in different ways," Jesse Emspak wrote in Smithsonian. "Instead of zipping relatively neatly along the fault line under San Bernardino, a multi-fault earthquake — even a less powerful one than the 1812 temblor — could jump right across a very densely populated region, causing even more damage than anything the San Andreas could produce alone."

Much of California is considered to be at strong risk to an earthquake. Scientists believe the state will be rocked by a powerful earthquake within the next three decades. The U.S. Geological Survey has set the chance of a magnitude 6.7 jolt at 95 percent in northern California and about 93 percent in southern California.