Researchers have reported that tectonic stress on Southern California's major San Andreas and San Jacinto fault systems has reached its highest point in the last millennium, with some sections potentially exceeding this level. The findings, published in the Journal of Geophysical Research: Solid Earth, stem from a study led by the University of Hawai'i at Mānoa.
The scientists developed a computer model that simulated stress accumulation and release over approximately 1,000 years, drawing on geological data such as radiocarbon dating and tree-ring records. This analysis estimated that the stress on the San Jacinto-Bernardino section has reached 3.6 megapascals, a pressure equivalent to the weight of two blue whales on every square meter, or over 6 billion whales when extrapolated to the fault's size.
A significant focus of the research was Cajon Pass, an intersection of the two fault systems that can act as an 'earthquake gate.' The study suggests that under certain conditions, this area could allow the San Andreas and San Jacinto faults to rupture simultaneously, a scenario that could be far more destructive than a single-fault earthquake and impact millions in the Los Angeles, San Bernardino, Riverside, and Coachella Valley areas.
The researchers stressed that their findings do not predict the timing of an earthquake but are crucial for reassessing earthquake hazards. The study's methodology could be applied globally to assess risks at complex fault intersections, potentially guiding infrastructure investment, building code updates, and emergency preparedness efforts.
