1,000-Year Stress Spike Hits San Andreas

Seismograph needle recording earthquake activity on paper.

A new study finds the San Andreas Fault is under the highest stress in 1,000 years — and a critical junction near Los Angeles could turn one big earthquake into two faults rupturing at once.

Story Highlights

Researchers modeled 1,000 years of earthquake history and found fault stress is now at record levels in Southern California.
The San Jacinto-Bernardino section hit 3.6 MPa of stress — the highest value seen in the entire 1,000-year simulation.
A junction called Cajon Pass could act like a gate, allowing a rupture to cross both fault systems in one massive event.
Scientists say this is not a prediction of when a quake will hit, but the system is in what they call a “critically loaded state.”

Fault Stress Hits a 1,000-Year Peak

An international research team, led by scientist Liliane Burkhard, ran a computer simulation of 1,000 years of earthquake history along the San Andreas and San Jacinto faults in Southern California. The results are striking. Stress in the earth’s crust along these faults is now higher than at any point in the past millennium. The last major rupture in this region happened more than 160 years ago, and the pressure has been building ever since.

The numbers are specific. Modeled stress on the San Jacinto-Bernardino section has reached 3.6 MPa — exceeding the highest value recorded anywhere in the 1,000-year simulation. The neighboring Mojave South section of the San Andreas Fault sits at 2.8 MPa. Both segments are highly stressed and at similar levels, which the study says is the kind of setup that has historically come before large joint ruptures. ^[4]^[7]

The “Earthquake Gate” at Cajon Pass

The study points to a spot called Cajon Pass, north of San Bernardino, as a key factor in how bad the next big quake could be. Burkhard describes it as an “earthquake gate.” Sometimes it blocks a rupture from spreading. Other times it lets the rupture pass through, connecting both fault systems into one much larger event. Right now, the stress levels on both faults are close enough in size that the gate could open. ^[7]^[8]

Burkhard put it plainly: “Not only is it concerning that the stresses are reaching historic highs, but also that the relative stress conditions between the two fault systems are approaching the range we associate with major ruptures crossing both faults simultaneously — and that is a scenario with much larger consequences for the region.” A joint rupture of both systems would be far more damaging than a single-fault event. ^[1]^[5]

What the Study Does — and Does Not — Say

The researchers are clear on one point: this is not a forecast. Burkhard states directly, “This is not a prediction of when an earthquake will happen.” No date, no countdown, no odds ratio appears in the available reporting. What the study does say is that the system is in a “critically loaded state” — meaning the conditions are serious, even if the exact timing of a rupture remains unknown. ^[2]^[6]

The San Andreas Fault and San Jacinto Fault Zone have reached their highest stress levels in 1,000 years, according to a study by researchers at the University of Hawaii at Manoa, leading scientists to wonder when California’s next “Big One” will occur. pic.twitter.com/fCoAQB5J1A

— KTLA (@KTLA) June 16, 2026

It is also worth understanding what the stress numbers actually are. The 3.6 MPa and 2.8 MPa figures come from a model built on earthquake history, not from a physical instrument stuck in the ground measuring live pressure. The Southern California Earthquake Center notes that stress estimates rely on multiple models using different data and methods. That means the findings are a well-reasoned scientific inference — not a direct readout from the fault itself. Still, the core warning is consistent across multiple news outlets and backed by the University of Bern press release: Southern California’s fault system is more loaded right now than it has been in recorded geological history. More than 70 percent of California’s population lives within 30 miles of a fault capable of serious ground shaking. ^[10]^[14] That fact alone makes this study worth taking seriously.