Overview
- This week a peer-reviewed study published in Journal of Geophysical Research: Solid Earth used a four-dimensional model fed with tree rings and radiocarbon-dated sediments to reconstruct 1,000 years of earthquakes and estimate current stress on the faults.
- The model finds stress on several southern San Andreas and San Jacinto segments now matches or exceeds any values in the past millennium, with peak estimates near 3.6 MPa on the San Jacinto–Bernardino section and about 2.8 MPa on the Mojave South San Andreas section.
- Researchers identify Cajon Pass as an 'earthquake gate' where similar, high stress on both faults makes it more likely that a rupture could jump from one system to the other and create a larger, multi-fault event.
- The authors stress the results are scenario-based and not a short-term prediction of timing or exact probabilities, and they recommend integrating these physics-driven scenarios with USGS probabilistic hazard estimates for planning.
- A joint rupture through Cajon Pass would threaten dense population centers and key infrastructure in Greater Los Angeles, San Bernardino, Riverside and the Coachella Valley, so officials and residents are urged to update emergency preparedness and infrastructure resilience plans.