Add The California Post on Google A crucial Southern California corridor sits above two major fault lines where scientists say tectonic stress has reached its highest level in 1,000 years — raising fears of the devastation that could follow the region’s next major earthquake.
Cajon Pass — a heavily traveled route through the San Bernardino and San Gabriel Mountains north of Los Angeles — lies where the San Andreas and San Jacinto fault systems meet.
Scientists have described the area as a potential “earthquake gate,” meaning it could either prevent a large rupture from spreading between the two faults or allow a rupture to tear through both systems and produce a much larger earthquake, according to National Geographic.
“We all know the San Andreas fault is loaded. It’s ready to go. For years the scientific community has been saying so,” Ken Hudnut, who helped the U.S. Geological Survey develop seismic resiliency initiatives for California, told National Geographic.
Researchers found that during previous periods when stress increased simultaneously along the faults, Cajon Pass allowed ruptures to spread through both systems.
The findings don’t predict when the next big earthquake will happen, but they suggest that a future event at this junction could reach about magnitude 7.5.
“We are primed to have another one in our generation,” study lead author Liliane Burkhard, a geophysicist at the University of Bern, told the magazine.
The threat is highly significant because Cajon Pass is packed with infrastructure connecting Southern California to the rest of the region.
An average of about 160,000 vehicles travel through the corridor each day, while rail lines, power infrastructure, fiber optic cables, aqueducts and high-pressure natural gas pipelines also cross the area.
A major rupture along the southern San Andreas could therefore cause damage far beyond buildings near the fault.
Previous earthquake modeling has projected that a magnitude 7.8 event could kill more than 1,800 people, injure 50,000 and cause about $200 billion in damage.
The 2008 ShakeOut Scenario also projected severe consequences at Cajon Pass, including destroyed rail lines, damaged highways, severed fiber optic connections and ruptured gas infrastructure.
Earthquake-triggered landslides could bring down transmission towers and bury other critical lines, while an estimated 75,000 cubic meters of debris could block roads through the pass.
“This earthquake’s inevitable. We just don’t know exactly when,” former USGS seismologist Lucy Jones told National Geographic, warning that “any sort of lifeline crossing the fault will be cut off.”
California officials acknowledged the corridor’s vulnerability, saying that losing access through Cajon Pass could significantly disrupt transportation, supply chains, communications, and power systems.
The California Governor’s Office of Emergency Services said a task force has been established to coordinate government and private-sector efforts to restore critical infrastructure following a disaster.
Utilities have also taken steps to strengthen their systems.
Southern California Edison said it invested roughly $300 million in seismic hardening between 2016 and 2025, while SoCalGas said it has installed automated and fault-isolation valves around transmission pipelines in Cajon Pass.
Scientists still can’t say when Southern California’s next major earthquake will strike, but Jones said the location of the danger is a no-brainer.
“We know exactly where this will happen,” she said. “That’s the thing that’s frustrating.”
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