Study says stress on Southern California fault systems is at its highest level in 1,000 years
The Facts
- A new study reports that stress on Southern California's San Andreas and San Jacinto fault systems has reached, and in some areas exceeded, the highest levels seen in the past 1,000 years.
- The research says the fault system is under high long-term stress but is not showing signs of an imminent rupture.
- Researchers say the current stress state could support large earthquakes, including events that rupture across multiple fault segments or fault systems.
- The study was published in the Journal of Geophysical Research: Solid Earth.
- The findings are relevant to major population centers in Southern California because the faults run near densely populated areas including parts of the Inland Empire and the Los Angeles region.
- Several reports on the study identify Cajon Pass, where the San Andreas and San Jacinto systems meet, as an area of focus for understanding whether a rupture could transfer between the faults.
How left and right are reading this
- Both agree
- A fault system can be under historically extreme long-term stress without showing signs of an imminent rupture, yet still pose a serious public-safety concern because that stress could support large earthquakes near major Southern California population centers.
- They split on
- Less a disagreement than a question of emphasis: the public-safety exposure created by long-horizon seismic risk near dense communities, versus the need to pair that warning with discipline about what the study does not say about imminent rupture.
Context
Does this study mean a major earthquake is about to happen?
No. The reports say researchers are not identifying signs of an imminent rupture and are not predicting when the next large earthquake will occur; instead, they say the fault system is in a high-stress state that raises long-term concern USA Today,Yahoo,Yahoo.
Why do scientists care about both the San Andreas and San Jacinto faults together?
The study says stress is building across multiple segments, and several reports say a rupture could potentially jump between the San Andreas and San Jacinto systems, producing a larger multi-fault earthquake USA Today,Daily Press,Cool Down.
Why does this matter for residents?
The faults pass near heavily populated parts of Southern California, so the findings are being framed as important for hazard assessment and earthquake preparedness for millions of people in the region Yahoo,Yahoo,Daily Press.
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