The next Cascadia megaquake could hit Oregon harder than expected
New seismic analysis reveals that the Juan de Fuca tectonic plate is shallower than previously thought, potentially increasing earthquake shaking intensity in northern Oregon. Researchers also identified a deep sedimentary basin near Tillamook that could further amplify ground motion.
Why it matters
Improved understanding of subduction zone depth and local geology allows for more accurate disaster preparedness and building codes in the Pacific Northwest.
A new seismic analysis of the Juan de Fuca tectonic plate beneath northern Oregon suggests the subducting slab lies closer to the surface than scientists previously believed. The finding could affect estimates of how strongly the region might shake during a future Cascadia megathrust earthquake.
The Juan de Fuca plate is being forced beneath the North American plate, creating the Cascadia subduction zone along the Pacific Northwest. This fault system has produced devastating magnitude 9 earthquakes in the past.
"We estimate that the slab interface is about 20 kilometers [deep] near the coastline, which is about 5 kilometers shallower than previous estimates," said Erin Wirth, a seismologist with the U.S. Geological Survey who presented the results at the 2026 SSA Annual Meeting.
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