Study finds Southern California faults at 1,000

Key Points:

• A new study led by University of Hawaii scientists reveals that the San Andreas and San Jacinto faults in Southern California have reached their highest tectonic stress levels in 1,000 years, raising concerns about a potential imminent large earthquake.
• The faults have not experienced a major earthquake in over 160 years, during which tectonic stress has continued to build, increasing the likelihood of a significant future rupture impacting densely populated areas such as Los Angeles, San Bernardino, Riverside, and the Coachella Valley.
• Researchers used a physics-based computer model combined with a 1,000-year earthquake history reconstructed from geological evidence to estimate current stress levels, finding that Cajon Pass could act as an "earthquake gate" that may allow simultaneous rupture of both fault systems.
• The study emphasizes that while it does not predict the timing of an earthquake, its findings have important implications for seismic hazard assessments, infrastructure planning, emergency preparedness, and building codes in Southern California and other regions with complex fault systems.
• Collaborators on the study include researchers from Northern Arizona University, University of Bern, U.S. Geological Survey, and University of California, San Diego, highlighting the broad scientific effort to understand earthquake risks facing millions of people.