California could be due for a major earthquake in the near future, according to concerning new models based on data comprising 1,000 years of quake activity on the West Coast.
According to recent findings, tectonic stress has quietly been building in California to levels not seen since the last major earthquake in the region, which bore a magnitude of 7.9 and struck the West Coast nearly 170 years ago.
That event, known as the Fort Tejon earthquake, affected the greater Los Angeles area, and since the time of those historic rumblings, researchers have grown increasingly concerned about a period of seismic silence that could point to the likelihood of an event of similar magnitude at some point in the future.
The potentially concerning new forecast was detailed in a recent study by an international team of researchers led by Dr. Liliane Burkhard of the Division of Space Research and Planetary Sciences (WP) at the Physics Institute of the University of Bern, which focused on historic earthquake data as a means of gauging current stress loading at Cajon Pass.
The study, published in the Journal of Geophysical Research: Solid Earth, indicates tectonic stress levels that are now believed to exceed the highest seen during the years the team surveyed.
The “Earthquake Gate” at Cajon Pass
The researchers aimed to investigate stress that has slowly built along the San Andreas and San Jacinto faults and incorporated what they likened to an “earthquake gate” at Cajon Pass, which, in their models, functioned like a point of control that governed the size of earthquakes and whether they could spread to both systems.
For their research, they used a four-dimensional earthquake cycle model that allowed them to replicate certain processes both in spatial dimensions and across time.
Using a millennium of reconstructed earthquake data from the region based on geological information such as radiocarbon dates, unusual events recorded in dendrochronological data (i.e., information obtained from tree rings), and historical information sources, the team gave this to the model they devised.
Dr. Burkhard said the team’s simulation offered them a unique opportunity to better understand the ways stresses in the fault system build up over long periods of several centuries.
“By running the earthquake history of Southern California as a simulation, we can estimate the extent to which the fault system is already under stress today,” Dr. Burkhard said. The results of those simulations weren’t particularly promising either: according to Burkhard, current stress levels in the region are the highest they have been in 1,000 years, based on the data.
Concerning New Earthquake Data
The team also identified significant new information regarding the function of the so-called “earthquake gate” at Cajon Pass.
“The earthquake gate concept captures something important about how fault junctions work,” Burkhard said in a recent statement. “Cajon Pass doesn’t simply block or channel earthquakes: It responds to stress conditions, and those conditions change over centuries.”
Not only this, but Burkhard and her team also determined that a key element to these quakes involves not only the level of stress that accumulates at a single fault, but perhaps more significantly, the way stress between two systems can align. This is because, as the stress across a pair of faults rises together over longer periods, this appears to be most conducive to a large joint rupture comparable to the 1857 Fort Tejon earthquake.
Conversely, if stress levels are not in concert as they evolve, the team determined that this causes quakes that probably will not propagate beyond the junction.
In short, a more severe earthquake event today would entail a joint rupture that crosses the Cajon Pass, as opposed to one constrained either to the San Andreas or the San Jacinto Fault alone. Should such an event occur, it would likely impact one of the largest population centers, as well as a crucial infrastructure system that supplies energy and transportation to surrounding areas.
For Burkhard, “The question of when and how the next major earthquake will occur in this region is one of the most pressing problems in applied geoscience.” Based on the team’s findings, they say that their new modeling hopes to provide a much more complete picture of the science behind the factors that could lead to a major quake—conditions that could apply equally to other parts of the world as they do to California.
Burkhard adds that her team’s study is not intended merely as a prediction for when the next major earthquake could potentially occur, but also as a means of preparing for future quakes and mitigating their effects.
“What we can say is that the system is critically stressed and that physics-based models like ours give a clearer picture of the range of scenarios we should be prepared for,” Burkhard says. “This information is important for hazard assessment, infrastructure planning, and emergency preparedness.”
The team’s study, “Cajon Pass and the Southern San Andreas Fault System: Earthquake Cycle Stress Accumulation and Present‐Day Loading,” appeared in the Journal of Geophysical Research: Solid Earth.
Micah Hanks is the Editor-in-Chief and Co-Founder of The Debrief. A longtime reporter on science, defense, and technology with a focus on space and astronomy, he can be reached at micah@thedebrief.org. Follow him on X @MicahHanks, and at micahhanks.com.
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