Science & Tech · Science & Environment · 3 hrs ago
Study Finds High Stress on Southern California Faults
A study found high stress on parts of two southern California fault systems: the San Andreas and San Jacinto.
The researchers used a computer model based on records of past earthquakes and other geological evidence to examine the past 1,000 years.
The Cajon Pass is where the two fault systems come close together, and a rupture there could stop or continue from one fault to the other.
Past earthquakes behaved differently: the 1857 Fort Tejon quake did not cross the pass, while the 1812 Wrightwood quake is thought to have crossed it.
The model found stress at or near the period's highest levels on many sections, including two measured at about 3.6 and 2.8 megapascals.
A quake crossing between faults could affect a wider area, including major communities and transport and energy links, but the study does not say one will happen soon.
Researchers say the model shows possible scenarios, not when or how the next earthquake will occur, and they say the method could also be used to study fault junctions elsewhere.
A study found that stress on parts of Southern California’s San Andreas and San Jacinto fault systems reached or exceeded levels seen over the past 1,000 years.
The study focuses on Cajon Pass, where the two fault systems approach each other and a rupture could stop or continue from one fault to the other.
Researchers say the findings describe possible earthquake scenarios, not when an earthquake will happen.
The model used historical records, radiocarbon dating and tree-ring evidence to assess the faults’ past behavior.
A rupture involving both fault systems could affect communities and infrastructure in Southern California.
- Who
- A research team led by Dr. Liliane Burkhard of the University of Bern, with scientists from the University of Hawaii, the US Geological Survey and Scripps Institution of Oceanography.
- What
- A study modeled stress on parts of the San Andreas and San Jacinto fault systems and found it at or above levels seen in the past 1,000 years.
- When
- The study was published on June 3, 2026. The articles were published on October 15, 2026.
- Where
- Southern California, especially Cajon Pass, where the San Andreas and San Jacinto fault systems approach each other.
- Why
- To assess how the faults behaved in the past and what conditions could allow a rupture to stop at Cajon Pass or continue from one fault to the other.
This story does not have two clearly opposing sides.
The Wrightwood earthquake is thought to have ruptured across Cajon Pass and involved more than one fault segment.
The magnitude 7.9 Fort Tejon earthquake ruptured about 330 kilometers of the San Andreas Fault but did not cross Cajon Pass.
The study was published in Journal of Geophysical Research: Solid Earth.
The three articles were published.
- Stress period
- Past 1,000 years
- San Bernardino segment stress
- About 3.6 megapascals
- Mojave South segment stress
- 2.8 megapascals
- Earthquakes in model
- 36 of magnitude 6.4 or greater
- Study journal
- Journal of Geophysical Research: Solid Earth
- Study publication date
- June 3, 2026
3 sources
What people are saying
Cajon Pass does not simply stop or direct earthquakes.