Overview
- A peer-reviewed, physics-based reconstruction of the past 1,000 years shows southern segments of the San Andreas and parts of the San Jacinto fault system are at or above stress levels not seen in the last millennium.
- The team reports specific stress estimates, including 3.6 megapascals on the San Jacinto Bernardino segment and 2.8 megapascals on the Mojave South section of the San Andreas, and finds a current stress difference of about 0.8 MPa that past models linked to through-ruptures.
- Researchers identify Cajon Pass as an "earthquake gate" that can either stop or transmit ruptures, and they say a joint rupture crossing the pass could reach roughly magnitude 7.4 to 7.8 and affect Los Angeles-area corridors, highways, rail lines, and energy infrastructure.
- Authors and outside experts urge city managers and emergency planners to treat these quantified joint-rupture scenarios as realistic planning cases and to prioritize resilience for roads, rails, utilities, and dense population centers.
- The paper is a scenario-driven hazard tool rather than a short-term forecast; it complements existing probabilistic USGS assessments, carries model uncertainties tied to input records and rupture behavior, and does not specify when a quake will occur.