Scientists are raising alarms that California may soon experience an earthquake similar to a recent quake. According to a new study, the seismic pressures on California’s two major fault lines are currently at their highest level in the past 1,000 years.

Published in Geophysical Research Journal, this new paper emphasizes the unpredictability of earthquake occurrences. However, it reveals that the Southern San Andreas and San Jacinto faults are under unprecedented stress, a condition termed “critical load.”

The last major earthquake of similar magnitude in California was the devastating 7.9 magnitude San Francisco earthquake on April 18, 1906, which claimed nearly 3,000 lives and brought widespread destruction to the Bay Area.

This catastrophic event released a significant amount of energy, affecting the northern segment of the San Andreas fault, while the southern fault systems examined in this study remained unaffected.

Since earthquakes in one section of the fault network do not relieve pressure in others, researchers indicate that strain has been building in the southern segments for decades, if not centuries.

Key Findings from the Research

Geologists, led by Lillian Burkhardt from the University of Hawaii at Manoa, utilized computer simulations to model significant seismic activities over the past millennium. Their findings indicate that California is experiencing its highest stress levels, thereby increasing the chances of an earthquake.

The model highlights a critical junction, or “earthquake gate,” located at Cajon Pass near San Bernardino, just northeast of Los Angeles. Burkhardt’s team notes that this junction could determine whether a rupture remains confined to one fault or propagates across multiple faults.

According to the model, the “gate” opens based on the matching stress levels of the two faults, both of which are currently under considerable pressure. A rupture that extends across both faults would be far more destructive than one occurring on a single fault, posing significant risks to Los Angeles, San Bernardino, Riverside, and the Coachella Valley, among the most densely populated areas in the United States.

Modern building codes have strengthened structures to withstand significantly more shaking compared to those built in 1906; however, a failure at a critical joint may still lead to catastrophic outcomes.

Expert Opinions

Bill McGuire, Emeritus Professor of Geophysics and Climate Hazards at University College London, who was not involved in this research, stated in an interview with BBC Science Focus, “Significant earthquakes are possible in both northern California (San Francisco and the Bay Area) and southern California (Los Angeles).” He highlights the importance of these new insights into earthquake risks.

McGuire further noted, “The concept that junctions like Cajon Pass function as ‘earthquake gates’ influencing whether one or multiple faults rupture is significant and has vital implications for future earthquake risk assessments.” He emphasized that the current stress levels on these faults being at historic highs is crucial for predicting when the next major event may occur in the Los Angeles region.

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