Cascadia quake may create 'emergency situation' in other West Coast fault zone, study warns
The so-called “Big One” or Cascadia Subduction Zone earthquake expected to trigger disruptive quakes throughout the West Coast could cause more damage than previously estimated if it sets off quakes in the nearby San Andreas Fault Zone, according to a recent study.
Chris Goldfinger, a marine geologist at Oregon State University and lead author of the Sept. 29 study published in the journal Geosphere, made the findings with an international team of researchers after scouring deep-sea sediment cores going back thousands of years. The Cascadia Subduction Zone earthquake last hit the coasts of Oregon, Washington and California in 1700, with an estimated magnitude of 9.0. It produces major earthquakes roughly every 300 to 500 years.
Scientists compared sediment deposits created by underwater landslides from earthquakes within the Cascadia Subduction Zone with sediment layers from the San Andreas fault system, which extends throughout California and sits on the boundary between the North American and Pacific tectonic plates. They found the deposits were formed at similar times and had similar structural characteristics, indicating that quakes in the Cascadia Subduction Zone triggered quakes in the San Andreas Fault System.
“We could expect that an earthquake on one of the faults alone would draw down the resources of the whole country to respond to it,” Goldfinger said in an Oct. 6 news release. “And 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.”
https://washingtonstatestandard.com/2025/10/14/repub/cascadia-quake-may-create-emergency-situation-in-other-west-coast-fault-zone-study-warns/
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