San Andreas Fault Under Highest Stress in 1,000 Years: Study

Stress along the San Andreas and San Jacinto faults in Southern California has reached its highest levels in 1,000 years, according to groundbreaking research from the University of Hawaii at Manoa.

The study sheds light on potential implications for seismic hazard assessments in a region that is both densely populated and home to critical infrastructure.

Liliane Burkhard, a scientist involved in the study, notes that "the region may be capable of a large through-going rupture involving both fault systems." Additionally, the researchers have found that Cajon Pass could act as an 'earthquake gate,' sometimes blocking or allowing large ruptures to pass through.

The researchers have designed a physics-based model to simulate the stress buildup on the two fault systems, including at the Cajon Pass. By feeding the simulation with 1,000 years' worth of earthquake history, they estimated the amount of stress that has built up over time.

The study discovered that stress normally released in large earthquakes has continued to grow to unprecedented levels. This stress is being held back by the Cajon Pass, which could lead to a joint rupture of both faults simultaneously. Densely populated areas, including Los Angeles, San Bernardino, Riverside, and the Coachella Valley, will be severely affected.

The San Andreas Fault serves as the primary boundary between the Pacific and North American plates, stretching approximately 650 miles and branching off into other faults, including the Hayward Fault.