San Andreas fault reaches highest stress level in 1,000 years

Key Points:

• Recent research by University of Hawai‘i at Mānoa scientists found that tectonic stress along Southern California's San Andreas and San Jacinto fault systems has reached or exceeded the highest levels seen in the past 1,000 years.
• The study, published in the Journal of Geophysical Research: Solid Earth, highlights the potential for a large rupture involving both fault systems, which could significantly impact densely populated areas like Los Angeles and the Coachella Valley.
• Researchers identified Cajon Pass as a critical "earthquake gate" that can either block or allow ruptures to pass between the two faults, influencing the likelihood of a joint major earthquake event.
• Using a physics-based computer model fed with a millennium of geological earthquake data, the study shows the fault system is in a critically loaded state, with stress continuing to accumulate since the last major rupture over 160 years ago.
• While not predicting the timing of an earthquake, the findings provide valuable insights for refining seismic hazard assessments, infrastructure planning, and emergency preparedness in Southern California and potentially other complex fault regions worldwide.