High Tectonic Stress in Southern California

 

San Andreas Fault 

The San Andreas fault and a neighboring fault in Southern California have reached their highest levels of tectonic stress in 1,000 years, and a rupture at one fault could propagate to the other, researchers found.

The results of a study published in the Journal of Geophysical Research: Solid Earth, suggest the San Andreas and San Jacinto faults are primed for an Earth-shattering rupture, which may involve the earthquake gate at Cajon Pass opening to unleash more destruction than a single-fault event would on its own.

Cajon Pass, where the San Andreas and San Jacinto faults connect, is an "earthquake gate" that can facilitate the spread of ruptures.

The San Andreas and San Jacinto faults have caused 36 earthquakes with magnitudes of 6.4 or above in the past 1,000 years. Southern California's last "big one" was a magnitude 7.9 event in 1857, when a 205-mile (330 kilometers) segment of the San Andreas fault slipped horizontally between Parkfield and Cajon Pass. That rupture did not propagate through Cajon Pass, but a similar megaquake in 1812 did, suggesting this could happen again in what is now a much more built-up and densely populated environment, according to the study.

Read more here: 'The system is critically stressed': San Andreas and San Jacinto faults scarily close to major earthquake, study finds | Live Science