Study Finds Stress on Southern California Faults at Millennial Highs
Researchers report that tectonic stress on the San Andreas and San Jacinto fault systems has reached levels not seen in at least 1,000 years, heightening concerns about a potential large earthquake.
A new study published in the AGU Journal indicates that stress beneath Southern California’s San Andreas and San Jacinto fault systems has risen to the highest levels in at least a millennium. Using geological evidence, radiocarbon dating, historical records and computer simulations of stress accumulation, researchers reconstructed roughly 1,000 years of seismic activity and found that current stress levels are exceptionally high.
The analysis highlights Cajon Pass, where the two faults intersect, as a critical zone that could determine whether a rupture remains on a single fault or spreads across multiple systems. Similar stress levels on both faults may facilitate the transfer of rupture between them, potentially affecting a broad region that includes Los Angeles, San Bernardino, Riverside and the Coachella Valley.
While the timing of a major earthquake cannot be predicted, the study underscores that geological conditions conducive to a large event are becoming more apparent. The findings serve as a reminder of the ongoing seismic risk in a densely populated area with extensive infrastructure.
"The stress levels on the San Andreas and San Jacuto faults have become more similar, creating conditions that may make it easier for an earthquake to jump between the two systems," the researchers said.