Stress levels along two major fault lines Southern California Earthquakes have climbed to their highest levels in more than a thousand years, according to new research from the University of Hawaii at Manoa, raising new concerns about seismic risks in one of Hawaii’s most densely populated areas. USA.
The findings were published in Journal of Geophysical Research: Solid Earth This was emphasized in a press release issued by the university on June 10.
“Our results indicate that stress levels on multiple fault segments are now at or above their highest values over the past millennium, and that large-scale outright ruptures involving both fault systems could occur in the region,” lead author Liliane Burkhard said in a statement.
How did scientists come to this conclusion?
The researchers built a physics-based computer model that simulates how pressure builds up and is released along the San Andreas and San Jacinto fault systems, including the key intersection between the two regions, Cajon Pass, which is located 63 miles northeast of the San Andreas fault system. Los AngelesEvery people.
To build the model, the scientists used 1,000 years of earthquake history gleaned from geological evidence, including radiocarbon dating and tree-ring records. They then used the model to estimate how much stress had accumulated on the fault today.
The study found that there have been 36 earthquakes of magnitude 6.4 or above in the Los Angeles area over the past 1,000 years. These include the 1857 magnitude 7.9 Fort Tejon earthquake, the last major earthquake to occur in the region. Today, approximately 13 million people live in the Los Angeles area.
“Currently, pressures in the region are at historically high levels, and more than 160 years have passed since the last major rupture, and the system is under critical load,” Burkhard said.
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How the Cajon Pass could affect future earthquakes
One of the study’s most important findings involves Cajon Pass, which the researchers say can act as an “earthquake gate,” sometimes blocking large ruptures from crossing both fault systems and sometimes allowing them to pass, thus involving both faults in a single event.
“The conditions that determine whether the Cajon Pass ‘seismic door’ opens or remains closed appear to be related to how well the stress levels on the two fault systems align with each other at the time of rupture,” Burkhard explained.
The study found that pressures normally released by large earthquakes instead continued to increase to what the researchers called “unprecedented levels.” Simultaneous rupture of the San Andreas and San Jacinto faults could be far more destructive than a single fault event, affecting densely populated areas including Los Angeles, San Bernardino, Riverside and the Coachella Valley.
The San Andreas Fault is the major boundary between the Pacific and North American plates and stretches for about 650 miles. Other faults include the Hayward Fault, which branches off it, According to ABC7 News.
Why scientists say these findings are still important
Scientists say the research is not about predicting when earthquakes will strike, but about improving understanding of the risks faced by millions of people.
“This is not a prediction of when an earthquake will occur,” Burkhard said. “However, studies like this make important contributions to national and global earthquake hazard research because we are using rigorous quantitative science to better understand the risks faced by millions of people.”
The researchers believe the findings will help improve earthquake hazard assessment, emergency preparedness and infrastructure planning.
