US west coast faults could trigger catastrophic back-to-back earthquakes, study finds | West Coast
Warnings of the threat of a “major earthquake” – a devastating earthquake that could devastate cities – have been raising fears on the US west coast for decades. But a high-magnitude earthquake in the Pacific Northwest could trigger a second quake along California’s San Andreas fault, leading to an unprecedented disaster, according to a new study.
Researchers say the “bigger one” may have the potential to wreak havoc up and down the coast at the same time.
Lead author Dr. D., a marine geologist and geophysicist. “We can expect an earthquake just on one of the faults to deplete the entire country’s resources to respond to it,” Chris Goldfinger said. “If the two go out together, then potentially San Francisco, Portland, Seattle and Vancouver are all left in an emergency situation in a compressed time frame.”
According to the research published on September 29, the Cascadia subduction zone, which alone can produce a magnitude 9 earthquake, has caused tremors on the San Andreas fault in the past.
The findings come after decades of confusing and difficult-to-explain data, Goldfinger said.
Researchers examining deep-sea sediment cores containing thousands of years of geological history scanned the layers left behind from ancient earthquakes. Goldfinger said they thought the submarine landslide deposits were caused by San Andreas earthquakes, but “they were different from what we usually see.”
“We realized it wasn’t one deposit,” he added, “it was two.”
The patterns, studied by graduate students for decades, led to a lightbulb moment around 2017 when scientists realized there was evidence of synchronicity between the Cascadia subduction zone and the San Andreas fault.
By analyzing sandy structures within turbidites, which are layers of sedimentary deposits, scientists were able to determine that some fractures occurred only hours, sometimes even minutes, apart. According to the research, there was evidence of 18 synchronized earthquakes in the last 3000 years.
The findings show that these back-to-back earthquakes are not the exception, but occur in the majority of cases.
The most recent event they uncovered was linked to a massive tremor that sent a tsunami sweeping the Pacific in 1700. Archaeological artifacts show that the houses of the Cowichan people living on Vancouver Island were destroyed in the 9 magnitude earthquake. also caused landslides and serious collapsesall remain in the geological record.
Researchers have now found that a second earthquake of up to magnitude 7.9 likely hit Northern California shortly after the first quake.
Experts have long hypothesized that the faults could be linked, but this study provides the largest amount of evidence of significant dangers that have the potential to affect millions of people.
In one scenario, a magnitude 9 earthquake along the Cascadia subduction zone fault has the potential to produce an initial tsunami wave of up to 25 meters that would hit coastal communities within 30 minutes after shaking begins. Drawn by federal emergency managers Their analysis found that the earthquake’s impact would span more than 140,000 square miles, affecting people in three provinces and parts of Canada, and that the ensuing tsunami would reach 27 countries and 17 tribes.
According to a similar analysis A 7.8 magnitude earthquake occurred in Southern San AndreasParts of California could shake for more than two minutes, causing more than 1,800 deaths, 50,000 injuries and $200 billion in damage, causing “serious, prolonged disruption.”
According to experts, major earthquakes on these faults occur approximately every 200 years.
Together, these events will cause unprecedented destruction. But there is a silver lining for Goldfinger: Cascadia’s eruption could serve as a natural early warning system, giving people who might be affected by the San Andreas earthquake more time to prepare, he said.
This breakthrough in science, although fraught with frightening consequences, provides researchers with greater insight to help them adapt and respond when disasters occur.
“Our level of preparedness is poor,” Goldfinger said. “We have a long way to go, and all these areas are built on ticking time bombs.”
The study also keeps the dangers fresh in the minds of emergency managers and those living in the places most at risk. Although it is uncertain when the next major earthquake will occur, there is still time to prepare.
“Get earthquake insurance. Explore options for retrofitting homes built to old standards,” Ben Deci, senior media officer for the California Earthquake Authority, said in an emailed response. “Know what to do when the shaking starts: let go, cover and hold on.”
“Environmental risks are interconnected at many levels,” he added. “Understanding this could be an important first step towards inspiring people to participate in a resilience ecosystem.”
