Study identifies Cajon Pass as potential “earthquake gate” amid record fault stress
Researchers modeling a millennium of seismic activity found that stress on the San Andreas and San Jacinto faults near Cajon Pass has reached historic highs, creating a potential “earthquake gate.”
An international team led by Dr. Liliane Burkhard used a four-dimensional earthquake-cycle model to reconstruct a thousand-year record of seismic activity on Southern California’s San Andreas and San Jacinto faults. Their results indicate that current stress on the San Jacinto-Bernardino segment (3.6 MPa) and the nearby Mojave South section of the San Andreas fault (2.8 MPa) are the highest observed in the simulation, creating conditions similar to those before historic joint ruptures.
The researchers term the Cajon Pass junction an “earthquake gate,” meaning it can either block or allow a rupture to cross between the two fault systems based on the stress balance. Although the study does not forecast when a quake will occur, it highlights a scenario where a combined fault rupture could impact the densely populated Los Angeles basin, San Bernardino, Riverside and the Coachella Valley. The findings aim to improve hazard assessments and emergency planning for the region’s critical transportation and energy corridors. The paper appears in the Journal of Geophysical Research: Solid Earth.
Why it matters
Record fault stress near Los Angeles raises the chance of a large, multi-fault earthquake affecting millions.
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