San Andreas fault reaches highest stress level in 1k years
A new University of Hawaii study finds the San Andreas Fault has accumulated stress to levels not seen in at least 1,000 years, increasing the likelihood of a major earthquake in Southern California. Using ancient lake sediments to track past quakes, researchers warn the fault may be overdue for a significant rupture.
Background
- The San Andreas Fault is a major geological fault line running roughly 800 miles through California, where the Pacific and North American tectonic plates meet. It is capable of producing large, destructive earthquakes (e.g., the 1906 San Francisco earthquake).
- "Stress level" refers to the accumulation of tectonic strain (energy) along a fault. When this stress exceeds the strength of the rocks, it is released suddenly as an earthquake.
- A research team from the University of Hawaii at Mānoa used a new technique analyzing ancient earthquake records preserved in coastal sediments (e.g., off San Diego) to reconstruct a 1,000-year timeline of fault stress.
- Their findings suggest the southern section of the fault (near Los Angeles) has now built up more strain than at any point in the last millennium, meaning it is "overdue" for a major rupture. The last major earthquake on the southern San Andreas was in 1857.