Pacific Northwest earthquake ‘the big one’ could set off ‘the bigger one,’ study finds
Oct 10, 2025, 5:24 PM | Updated: 5:25 pm
Mud is seen on land that was under the Salton Sea a few years ago on January 1, 2019 near Calipatria, California, United States. Scientists believe that the southern portion of the San Andreas Fault will inevitably give birth to a massive earthquake, bigger than any that has occurred in Southern California in modern history. (Photo: David McNew, Getty Images for Lumix)
(Photo: David McNew, Getty Images for Lumix)
Most in the Pacific Northwest have heard of “the big one,” a potentially massive earthquake that could shake the region.
A new study found “the big one” could set off “the bigger one,” triggering California’s San Andreas fault and leading to a monumental disaster, The Guardian reported Thursday.
“If they both went off together, then you’ve got potentially San Francisco, Portland, Seattle, and Vancouver all in an emergency situation in a compressed timeframe,” Dr. Chris Goldfinger, the study’s lead author and a marine geologist and geophysicist, told The Guardian.
Goldfinger told Science that if the Cascadia fault zone went off, he would take that as a clear warning for San Andreas.
He explained the two fault zones run for more than 1,000 kilometers along the Pacific coast, but they create earthquakes differently.
His team looked at around 100 sediment cores drilled near the Triple Junction, where both the Cascadia and San Andreas fault zones end.
Their breakthrough was discovering that a recurring “upside down” pattern was actually the result of two earthquakes occurring within minutes of each other, not just one.
The study is evidence that the two faults do interact, Amanda Thomas, a geophysicist at the University of California Davis, told Science. The knowledge could help California better prepare for a major earthquake if one strikes in Washington.
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Pacific Northwest earthquake, ‘the big one,’ could create tsunami
A magnitude 9 earthquake in the Pacific Northwest has the potential to produce a tsunami wave of up to 80 feet, knocking out coastal communities within 30 minutes, according to The Guardian.
“Our preparedness level is poor,” Goldfinger told the media outlet. “We have a long way to go, and all these areas were built on top of ticking time bombs.”
Ben Deci, the senior media officer for the California Earthquake Authority, recommended getting earthquake insurance, strengthening homes, and remembering to drop, cover, and hold on when shaking starts.
Use MyNorthwest’s Earthquake Tracker to stay updated in real-time.
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