'The big one': CA braces for massive earthquake as fault stress hits 1,000-year peak

California's fault lines are under the most amount of stress than they've experienced in 1,000 years, researchers revealed.

A new study published in the Journal of Geophysical Research, Solid Earth, cites concerns that a major earthquake might be on the horizon. There's no real way of knowing when it could happen, the experts warned.

Gizmodo reported the study on Tuesday, including a visualization from the research team of the tectonic plates in California. These plates are constantly pushing, pulling or sliding. The fault lines are where fractures in the plates accumulate pressure, and stress on those faults can build up over time.

Eventually, when the stress exceeds the friction holding the rocks together, an earthquake occurs as the fault ruptures. The more often there are little earthquakes that release the pressure, the less buildup there can be. The longer it has been since the last quake, the more energy is accumulated. All of that built-up stress energy is released as waves or vibrations that travel through the Earth, moving the ground.

“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,” said lead author Liliane Burkhard, a geophysicist and planetary geologist at the University of Bern in Switzerland, in a press release. “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."

The visualization shows the greatest stress on the fault line northeast of Los Angeles. The last major quake was a magnitude 7.9 in Fort Tejon in 1857. It remains one of the largest on record, Gizmodo recounted. Even the infamous 1994 Northridge quake didn't exceed 7.0, and it cost an estimated $49 billion, the Los Angeles Daily News reported in 2014.

Scientists are fearful that the San Andreas Fault System could move "any day now," the report said.

"Their physics-based earthquake cycle model simulates this process in three spatial dimensions over time," said Gizmodo, citing the research. The scientists put geological data of past quakes into their model, which included things like tree-ring anomalies and radiocarbon dating.

"When they ran it, the results indicated that tectonic stresses along the San Andreas and San Jacinto fault zones have reached and, in some cases, exceeded the highest levels of the last millennium," the report said.

There are two main points in the fault system where the San Andreas and San Jacinto are. Burkhard and her co-researchers called it a kind of "earthquake gate."

“The earthquake gate concept captures something important about how fault junctions work,” Burkhard said in the release. “Cajon Pass doesn’t simply block or channel earthquakes: It responds to stress conditions, and those conditions change over centuries.”

When stress builds up on both faults, it's more likely that one'll rupture at a major joint and cross both systems, the study said. That's why they fear it could be more substantial than quakes in past centuries.

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