California Faults Face Record Stress, Raising Earthquake Risks

WHO:

Science Daily - Researchers from the University of Bern, Switzerland, and other institutions, including Northern Arizona University, the US Geological Survey, and the University of California, San Diego.

ScienceAlert - Liliane Burkhard, lead author and geophysicist from the University of Bern.

WHAT:

Science Daily - Southern California's major fault system is under the highest stress levels in the last 1,000 years.

ScienceAlert - Tectonic pressure in the San Andreas and San Jacinto fault lines is described as "unusually high."

ScienceAlert - Stress levels on multiple fault segments are at or above the highest values seen in the past millennium.

ScienceAlert - The estimated pressure is 2.8 MPa on the Mojave South segment and 3.6 MPa on the San Jacinto Bernardino segment.

ScienceAlert - The last major rupture in the area occurred over 160 years ago.

WHERE:

Science Daily - The Cajon Pass, where the San Andreas and San Jacinto faults meet, is located just northeast of Los Angeles.

ScienceAlert - Densely populated areas affected include Los Angeles County, Ventura County, Orange County, San Diego County, the Palm Springs–Indio metropolitan area, and Tijuana.

WHEN:

ScienceAlert - The study is published in the Journal of Geophysical Research: Solid Earth, in 2026.

WHY:

ScienceAlert - The accumulation of stress in the fault lines raises concerns about an imminent large earthquake that could cause major damage to Southern California.

ScienceAlert - The study aims to contribute to national and global earthquake hazard research to better understand the risk facing millions of people.

HOW:

ScienceAlert - Researchers designed a physics-based computer model to analyze the history of fault lines in the region and simulate scenarios based on 1,000 years of earthquake history data.

ScienceAlert - The model indicates that the conditions at Cajon Pass determine whether the "earthquake gate" opens or remains closed during a rupture event.

(UPDATED June 18, 2026 18:04 UTC)

Researchers from the University of Bern and other institutions have found that Southern California's major fault system is experiencing the highest stress levels in the last millennium, particularly along the San Andreas and San Jacinto fault lines. The study, published in the Journal of Geophysical Research: Solid Earth in 2026, indicates that the pressure on these fault segments raises concerns about an imminent large earthquake that could significantly impact densely populated areas like Los Angeles and San Diego. Using a physics-based computer model, the researchers analyzed a thousand years of earthquake history to better understand the risks facing millions of people in the region.