Science
Cascadia subduction zone beneath northern Oregon is shallower than previously estimated, study finds
New seismic analysis indicates a future megathrust earthquake could cause stronger ground shaking along the northern Oregon coast than prior models predicted.
The short version
- A seismic analysis reveals the Juan de Fuca plate interface is roughly 20 kilometers deep near the northern Oregon coast—about 5 kilometers shallower than past estimates.
- The shallower depth could increase shaking intensity along the northern Oregon coast by 9% to 17% during a future Cascadia megathrust earthquake.
- Researchers also documented a deep sedimentary basin beneath Tillamook, Oregon, which can trap and amplify seismic waves.
- Scientists plan to analyze the dataset further to assess seismic risk for the Tualatin Basin near Portland.
Key facts
- Data gathered from 192 temporary nodal seismometers deployed between Tillamook and Portland in 2021 and 2022, alongside offshore seismic data, indicates the Juan de Fuca plate interface is around 20 kilometers deep near the northern Oregon coastline.[ScienceDaily]
- U.S. Geological Survey seismologist Erin Wirth presented the findings at the 2026 Seismological Society of America Annual Meeting.[ScienceDaily]
- The updated plate depth could elevate estimated peak ground acceleration along northern Oregon's coast by approximately 9% to 17% in a future megathrust event.[ScienceDaily]
- Researchers direct-mapped a deep sedimentary basin under Tillamook, Oregon, which can cause seismic energy to linger and increase ground shaking.[ScienceDaily]
What remains uncertain
- The precise extent to which the Tualatin Basin near Portland will amplify ground shaking remains under investigation using the collected seismic dataset.[ScienceDaily]
Sources
- The next Cascadia megaquake could hit Oregon harder than expectedScienceDaily - Science