LOS ANGELES, CA — Scientists are sounding the alarm with a new study that indicates some of California's ancient fault lines are experiencing more stress than in more than 1,000 years, and say a major earthquake could be around the corner.
The study was published in the Journal of Geophysical Research: Solid Earth on June 3.
Researchers at the University of Bern in Switzerland modeled 1,000 years of earthquake history on the San Andreas and San Jacinto fault systems and found more pressure on the plates than ever before, and that a "critical fault junction" on the outskirts of Los Angeles could be the deciding factor in just how big the region's next major earthquake is.
The study indicates that the Earth's plates move in constant motion. Fractures in the plates are where pressure starts to accumulate and trigger more activity.
Scientists are concerned it could trigger a major earthquake more powerful than anything California has seen in more than a century.
"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."
—Liliane Burkhard, lead author of "Cajon Pass and the Southern San Andreas Fault System: Earthquake Cycle Stress Accumulation and Present-Day Loading"
"Our results provide a clearer, physics-based picture of the current stress state of the fault system, and the framework we developed is not just applicable to California, but also for other complex fault junctions worldwide," Burkhard said in a news release.
The last major earthquake (a quake greater than 7.0) to strike the greater Los Angeles area was the magnitude 7.9 Fort Tejon earthquake in 1857, which left Southern California with a surface rupture scar 217 miles long, according to Caltech.
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The researchers said there is a junction in Southern California between the San Andreas and San Jacinto faults, which they call an "earthquake gate," that could essentially either block a large rupture between the two systems— or allow for the two systems to interact when the stress on them becomes similar, setting off a massive quake.
This junction lies in the Cajon Pass.
"The earthquake gate concept captures something important about how fault junctions work," Burkhard said.
"Cajon Pass doesn’t simply block or channel earthquakes: It responds to stress conditions, and those conditions change over centuries," she added.
The study indicated that when stress of a similar size percolates on both fault lines, a major joint will likely experience a rupture that crosses both fault systems.
According to researchers, the San Jacinto-Bernardino section of the San Jacinto Fault is currently showing the highest modeled stress level seen in the 1,000-year simulation, reaching 3.6 megapascals. Nearby, the Mojave South section of the San Andreas Fault is also under elevated stress at 2.8 megapascals.
Because both fault segments are highly stressed and at similar levels, researchers say the system is in a configuration that has historically been linked to joint ruptures— meaning, the "earthquake gate" is more poised to allow a quake through both systems at the same time than to block it from crossing.
But despite the ominous data, Burkhard cautioned there is no timetable for when Southern California will experience a major earthquake.
"The study is not a prediction of when an earthquake will occur. 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. This information is important for hazard assessment, infrastructure planning and emergency preparedness."
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