San Andreas Fault Reaches Unprecedented Stress, Heightening Quake Fears

WHO:

Live Science - Liliane Burkhard, a planetary geologist at the University of Bern in Switzerland and at the University of Hawaii at Manoa, stated, "Our results show that stress levels on multiple fault segments are now at or above the highest values seen in the past millennium."

ABC7 Los Angeles - Scientist Liliane Burkhard from the University of Hawaii at Manoa conducted the study.

WHAT:

ABC7 Los Angeles - The study indicates that the stress levels on the Mojave South segment are estimated at 2.8, the North San Bernardino segment at 1.8, and the San Jacinto Bernardino segment at 3.6, making the San Jacinto segment the most heavily loaded portion of the Cajon Pass fault junction.

Live Science - The study indicates that the San Andreas and San Jacinto faults have caused 36 earthquakes with magnitudes of 6.4 or above in the past 1,000 years.

Live Science - The last "big one" was a magnitude 7.9 event in 1857, when a 205-mile (330 kilometers) segment of the San Andreas fault slipped horizontally.

ABC7 Los Angeles - The study indicates that the Cajon Pass may sometimes block large ruptures from crossing between the faults, and at other times, it may allow them to pass through and involve both systems in a single event.

ABC7 Los Angeles - The study outlines implications for seismic hazard assessments in one of the nation's most populated and infrastructure-critical regions.

ABC7 Los Angeles - The study indicates that the Cajon Pass could cause a joint rupture of both faults simultaneously.

ABC7 Los Angeles - The stress along the San Andreas and San Jacinto faults has reached the highest levels in 1,000 years.

ABC7 Los Angeles - The study indicates that the region may be capable of a large through-going rupture involving both fault systems.

ABC7 Los Angeles - The Cajon Pass may act as an "earthquake gate," affecting the potential for large ruptures.

WHERE:

ABC7 Los Angeles - The study focuses on the San Andreas and San Jacinto faults in Southern California, including densely populated areas such as Los Angeles, San Bernardino, Riverside, and the Coachella Valley.

WHEN:

ABC7 Los Angeles - The study references more than 160 years since the last major rupture.

WHY:

ABC7 Los Angeles - The study suggests that stress normally released in large earthquakes has continued to grow to unprecedented levels.

HOW:

FOX Weather - Researchers used computer simulations of the last 1,000 years of rupture history to estimate how stress builds up in critical fault segments and impacts surrounding areas over time.

Live Science - Researchers used observations such as tree-ring records and age data from sediments that have been displaced to reconstruct Southern California's earthquake history.

ABC7 Los Angeles - Researchers estimated how much stress has built up by feeding the simulation 1,000 years' worth of earthquake history from the region.

ABC7 Los Angeles - Researchers designed a physics-based model that simulates the stress build-up on the two fault systems, including at the Cajon Pass.

ABC7 Los Angeles - Researchers designed a physics-based model that simulates the stress build-up on the two fault systems, using 1,000 years of earthquake history from the region.

(UPDATED June 17, 2026 04:21 UTC)

A new study reveals that the San Jacinto Bernardino segment of the Cajon Pass fault junction is under the most stress, with levels estimated at 3.6, compared to 2.8 for the Mojave South segment and 1.8 for the North San Bernardino segment. Researchers utilized computer simulations that analyzed the last 1,000 years of rupture history to understand how stress accumulates in these critical fault segments. This research provides valuable insights into the seismic risks that could affect surrounding areas over time.

(UPDATED June 16, 2026 20:06 UTC)

A new study reveals that stress levels on multiple fault segments in Southern California are now at or above the highest values seen in the past millennium, according to Liliane Burkhard, a planetary geologist at the University of Bern and the University of Hawaii at Manoa. The research highlights that the San Andreas and San Jacinto faults have been responsible for 36 earthquakes with magnitudes of 6.4 or above in the last thousand years, with the most significant event being a magnitude 7.9 earthquake in 1857. To reconstruct this earthquake history, researchers utilized tree-ring records and age data from displaced sediments.

(UPDATED June 16, 2026 18:31 UTC)

A new study suggests that the Cajon Pass could play a dual role in seismic activity, sometimes blocking large ruptures from crossing between faults, while at other times allowing them to merge into a single event. Researchers conducted their analysis by simulating the stress buildup in the area, utilizing a thousand years of earthquake history to inform their findings. This research could have significant implications for understanding earthquake dynamics in the region.

(UPDATED June 16, 2026 08:52 UTC)

A new study has significant implications for seismic hazard assessments in one of the nation's most populated and infrastructure-critical regions. Researchers have developed a physics-based model that simulates the stress build-up on two fault systems, indicating that the Cajon Pass could potentially cause a joint rupture of both faults simultaneously. This research highlights the importance of understanding seismic risks in areas where millions of people live and work.

(UPDATED June 16, 2026 06:53 UTC)

A new study led by scientist Liliane Burkhard from the University of Hawaii at Manoa reveals that stress along the San Andreas and San Jacinto faults has reached the highest levels in a millennium, indicating a potential for a large rupture involving both fault systems. This research highlights the Cajon Pass as a possible "earthquake gate," which could influence the likelihood of significant seismic events in densely populated areas of Southern California, including Los Angeles and the Coachella Valley. The study, which utilizes a physics-based model to analyze 1,000 years of earthquake history, suggests that stress typically released during major earthquakes has continued to accumulate, with over 160 years passing since the last major rupture.