doi.org/10.1130/GES02857.1
Credibility: 989
#Big One
Recent research indicates that a major earthquake in the northwestern United States could trigger another in California, increasing the risk of destruction
When the tectonic subduction zone beneath the Pacific Northwest shifts, the impact is intense.
An earthquake of magnitude 9 or greater in this region can cause violent tremors, tsunamis, and landslides, causing widespread devastation.
A new study published in the journal *Geosphere* suggests that this “big earthquake” could also trigger a significant earthquake in California, further increasing the danger.
“It’s hard to overstate what a magnitude 9 earthquake would be like in the Pacific Northwest,” explains Dr. Chris Goldfinger, a paleoseismologist at Oregon State University and lead author of the study.
“And the possibility of an earthquake on the San Andreas Fault right after? That sounds like something out of a movie.”
How the Pacific Coast Moves
The West Coast of the United States sits atop a complex network of tectonic plates.
North of Cape Mendocino, California, the Juan de Fuca Plate sinks beneath the North American Plate, forming a powerful subduction zone.
To the south, the Pacific and North American Plates slide against each other, causing occasional earthquakes, such as the devastating San Francisco earthquake of 1906. The idea that these two fault zones could rupture at nearly the same time poses a much greater seismic risk for the western United States.
A Chance Discovery
Scientists weren’t initially looking for this connection.
The discovery came by accident during a research expedition in 1999.
The goal was to study seafloor sediment records to understand earthquakes in the Cascadia region, but a navigational error changed everything.
A student entered the wrong latitude, and the ship ended up 90 km south of the planned position, near Cape Mendocino, in the San Andreas Fault area.
“We ended up off the coast of northern California,” Goldfinger says.
“I was pretty annoyed at first, but since we were there, I decided to collect a sample.”
When analyzing the material collected in Noyo Canyon, off the coast of California, the researchers found something unexpected.
The sediment, which covered about 3,000 years, contained several layers of turbidites-deposits formed by rapid submarine landslides.
These turbidites had an unusual characteristic: many appeared in pairs, with a layer of fine grains and a layer of coarser grains on top.
“These double turbidites intrigued us,” says Goldfinger.
A Surprising Connection
Using radiocarbon dating, scientists found that more than half of the turbidites north and south of Cape Mendocino were deposited at the same time, within the dating error.
This could not be a coincidence.
After ruling out other explanations, they concluded that the first turbidite of each pair in Noyo Canyon was caused by a large earthquake in the Cascadia zone, while the second was triggered by movement on the San Andreas Fault shortly thereafter.
Chain Hazards
The time interval between these earthquakes is not precise because the second turbidite may have erased intervening sediments.
However, in some cases, researchers have found evidence that the second deposit occurred minutes or hours after the first, suggesting that nearly the entire U.S. Pacific Coast could be hit by large earthquakes almost simultaneously.
This possibility raises concerns about preparing for such a severe event, which could cause massive damage to lives and infrastructure.
“I’m from Silicon Valley,” says Goldfinger.
“If I were there and Cascadia had an earthquake, I would drive east.
There seems to be a very high risk that the San Andreas Fault will be next.”
Published in 10/16/2025 22h44
Text adapted by AI (Grok) and translated via Google API in the English version. Images from public image libraries or credits in the caption. Information about DOI, author and institution can be found in the body of the article.
Reference article:
Original study:
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