'Earthquake Gate' May Be Only Thing to Block the Big One

Southern California's most infamous faults are carrying more strain than they have in a millennium, scientists say. A new study in the Journal of Geophysical Research: Solid Earth finds that the San Andreas and San Jacinto systems are in a "critically loaded" state, with stress on several segments now matching or exceeding the highest levels seen over the last 1,000 years, per the Guardian. That raises the possibility of a rare, large earthquake that could rip through both fault systems in a single event. Using a computer model with a millennium of seismic history fed into it, University of Hawaii at Manoa scientists found that stress has built up steadily to "unprecedented levels" during the more than 160 years since the last major rupture in the region, per a release.

The research points to Cajon Pass, northeast of Los Angeles, as a key wild card. This junction between the two faults may act as an "earthquake gate," either stopping a rupture from jumping faults or allowing for a joint break with regionwide consequences. The study doesn't forecast timing, but lead author Liliane Burkhard says it puts into sharper view what planners should expect: a highly stressed system capable of producing scenarios that Californians need to be ready for.