Cajon Pass at 1,000-year stress peak could fuel a bigger San Andreas–San Jacinto quake
A new study finds southern portions of the San Andreas and adjacent San Jacinto faults are at their highest 1,000-year stress level, with the Cajon Pass acting as an “earthquake gate” that could allow a large rupture to cascade between faults. If triggered, a joint rupture could reach magnitude about 7.4–7.8 and affect Los Angeles, San Bernardino, Riverside, and the Coachella Valley; officials are urged to prepare for multi-fault earthquakes rather than a single-fault event.