“It Could Be Tomorrow”: California’s Top Earthquake Expert Sounds Alarm On “The Big One”

A new peer-reviewed study found that the fault system running beneath Los Angeles and the Inland Empire is carrying more stress today than at any point in the last millennium, and that a single rupture could tear across both the San Andreas and San Jacinto faults at once.

The research, led by Dr. Liliane Burkhard of the University of Bern and published in the Journal of Geophysical Research: Solid Earth, simulated 1,000 years of earthquake cycles on the southern San Andreas and San Jacinto systems.

The flashpoint is Cajon Pass, the junction northeast of Los Angeles where the two systems meet, and where Interstate 15, freight rail lines, power corridors and the aqueducts that supply Southern California’s water all cross.

The model puts Coulomb stress at 3.6 megapascals on the San Jacinto-Bernardino segment, the highest value anywhere in the entire 1,000-year reconstruction, and 2.8 megapascals on the San Andreas Mojave South segment. Both are elevated, and both are closely aligned, the same configuration that preceded joint ruptures in the past.

Researchers caution these are modeled values that depend on the simulation’s assumptions, not direct measurements from underground. Burkhard’s team describes Cajon Pass as an “earthquake gate,” a junction that can either stop a rupture cold or let it through.

The 1857 Fort Tejon earthquake, magnitude roughly 7.9, stopped there, while the 1812 Wrightwood event is believed to have crossed both faults. A through-going rupture today, the study claimed, could reach magnitude 7.4 to 7.8. More than 160 years of slip has piled up since 1857. Caltech seismologist Lucy Jones, who helped build the widely cited magnitude-7.8 “ShakeOut” scenario, said the San Andreas is California’s longest fault and therefore capable of its largest earthquakes.

The chilling scenario projects nearly two minutes of shaking, more than 1,800 deaths, 50,000 injuries and over $200 billion in damage. “It could go another 100 years. It could be tomorrow,” Jones said in an interview with ABC7.

A 2008 USGS forecast put the 30-year odds of a magnitude-6.7 or larger quake on the southern San Andreas at 59 percent, the highest of any fault in the state. Burkhard stopped short of forecasting a date, telling Newsweek that while this does not mean an earthquake will happen tomorrow, “the system is as loaded as it has ever been in our record, and the question is not really if but when.”