The San Andreas just hit its highest stress level in 1,000 years. Here’s what that means for facilities in Southern California.

A new study from the University of Hawaiʻi at Mānoa found that tectonic stress along the San Andreas and San Jacinto fault systems in Southern California has reached its highest level in 1,000 years. The research, published in the Journal of Geophysical Research: Solid Earth, does not predict when an earthquake will strike. What it does say is more useful for anyone responsible for a building or a campus in the region: the system is, in the researchers’ words, “critically loaded,” and it has been more than 160 years since the last major rupture.

For facility operators in Los Angeles, San Bernardino, Riverside, and the Coachella Valley, the takeaway is not panic. It is planning. Here is what the study found and what it changes about how organizations should think about seismic readiness.

What the researchers actually measured

The team, led by Liliane Burkhard, built a physics-based model that simulates how stress accumulates across the San Andreas and San Jacinto faults, including the area around Cajon Pass where the two systems meet. They fed the model 1,000 years of regional earthquake history and used it to estimate how much stress has built up over time.

The result: stress that is normally released in large earthquakes has continued to grow to unprecedented levels. Multiple fault segments now sit at or above the highest values seen in the past millennium. By 2025 the model estimates Coulomb stress as high as 3.6 MPa on the San Jacinto–San Bernardino segment and 2.8 MPa on the Mojave South segment, with the fastest accumulation north of Cajon Pass.

One finding stands out for risk planning. Burkhard’s team identified Cajon Pass as a potential “earthquake gate.” Sometimes the pass blocks a large rupture from crossing between the two fault systems. Other times it lets the rupture through, allowing both systems to fail in a single event. A joint rupture of that kind would affect a far larger and more densely populated area than a single-fault event. This builds on earlier research showing that major West Coast faults may be more interconnected than once assumed, a theme we covered in our look at how the Cascadia and San Andreas systems could be linked.

Why “critically loaded” is not the same as “imminent”

It is worth being precise here, because the headlines are not. A 1,000-year stress high does not mean an earthquake is overdue or scheduled. Faults do not run on timers. Burkhard was direct about this: “This is not a prediction of when an earthquake will happen.”

What the study does is sharpen the hazard picture. The San Andreas is the primary boundary between the Pacific and North American plates and runs roughly 650 miles through California. The USGS Earthquake Hazards Program has long flagged Southern California as one of the highest-risk seismic regions in the country. This research adds quantitative weight to that assessment and narrows the uncertainty around where the most strained segments are.

For an operations or safety leader, that distinction matters. You cannot act on a date that does not exist. You can act on a credible, peer-reviewed signal that the regional hazard is elevated and that a multi-fault rupture is physically plausible.

What this changes for facility operators

The practical implication is straightforward. If your buildings, equipment, or people sit in the affected corridor, the cost of being unprepared just went up, and the case for automated protection got stronger.

A few things worth reviewing this quarter:

Know your warning window. Earthquake early warning works because the data signal from a quake travels faster than the damaging shaking. Depending on your distance from the epicenter, that can mean several seconds to tens of seconds of advance notice. The federal ShakeAlert system provides that signal across California, Oregon, and Washington.

Decide what those seconds should trigger. Warning time only protects you if something happens with it. That is the gap automated systems close. The same few seconds can open fire station bay doors, pause an assembly line, bring elevators to the nearest floor, isolate gas lines, or alert a surgical team before the shaking arrives. Manual reaction alone leaves most of that value on the table.

Pressure-test your most vulnerable operations. Hospitals are a clear example. California’s hospital seismic compliance deadline in 2030 is already forcing this conversation, but the same logic applies to manufacturers handling hazardous materials, schools, and any operation where a few seconds of automated response changes the outcome.

The bottom line

The University of Hawaiʻi study does not tell anyone to evacuate. It tells facility operators in Southern California that the ground they build on is more strained than it has been in a thousand years, and that a rupture involving both major fault systems is within the realm of the possible. The organizations that treat this as a planning signal, rather than a news cycle, are the ones that will have automated safeguards already in place when the warning comes.

If you want to understand how earthquake early warning connects to automated protection for your specific facility, see our solutions overview.

Sources: Burkhard et al., “Cajon Pass and the Southern San Andreas Fault System: Earthquake Cycle Stress Accumulation and Present-Day Loading,” Journal of Geophysical Research: Solid Earth (2026); University of Hawaiʻi News (June 10, 2026).

 

Related story from ABC7: