Experts warn Cajon Pass could unleash a massive quake across two fault systems

Cajon Pass, a heavily used mountain route north of Los Angeles, sits at the junction of the San Andreas and San Jacinto fault systems and is described by scientists as a potential "earthquake gate" that could either block or transmit a large rupture. Studies show that simultaneous stress increases on both faults have previously allowed ruptures to spread through the pass, raising the possibility of a magnitude-7.5 earthquake in the region.

The corridor supports about 160,000 vehicles each day and hosts rail lines, power grids, fiber-optic cables, aqueducts and high-pressure gas pipelines, meaning a major quake could cause widespread disruption beyond the immediate fault zone. Earlier modeling forecasts over 1,800 deaths, 50,000 injuries and roughly $200 billion in damage for a 7.8-magnitude event, with additional hazards such as landslides blocking roads and destroying infrastructure.

California officials acknowledge the vulnerability and have created a task force to coordinate recovery, while utilities like Southern California Edison and SoCalGas have invested hundreds of millions in seismic hardening and safety valves. Despite these measures, seismologists caution that the next large quake is inevitable, though its exact timing remains unknown.