Newly Discovered Faults on Mount Hood Could Trigger a Massive Portland Earthquake

According to geologists, the quake “would be strong enough to knock you off your feet.”

Hiking near Mount Hood (Joe Michael Riedl)

Geologists have discovered new faults on Mount Hood that could trigger a highly destructive earthquake in the Portland area.

The faults are separate from the Cascadia subduction zone, which for nearly a decade scientists have warned could cause a massive earthquake dubbed The Big One.

According to a release from Portland State University and the Oregon Department of Geology and Mineral Industries (DOGAMI) there is an "extensive network of geologic faults extending north and south of Mt. Hood," that could "generate large earthquakes and may pose a significant hazard to surrounding communities, critical infrastructure, and even the city of Portland."

Researchers predict that the faults could trigger a 7.2 magnitude earthquake, which would be larger than the Loma Prieta earthquake that did severe damage to the San Francisco Bay Area in 1989. As well, today's release notes, the Mt. Hood faults are nearer to Portland than the Loma Prieta epicenter was to San Francisco.

San Francisco after the 1989 Loma Prieta earthquake. (U.S. Geological Survey/Flickr)

"This would be a crustal earthquake as opposed to the Cascadia subduction zone earthquake Portland has been bracing for," PSU's assistant professor of geology, Ashley Streig, says. "Subduction zone quakes are deeper below the surface, they last longer—as long as seven minutes—but they are lower in amplitude. The kind of quake we would get from Mt. Hood would be shorter—20 seconds to less than a minute—and would be strong enough to knock you off your feet."

The Mt. Hood fault network also spans the Columbia River, meaning rail lines in the Columbia Gorge and the Bonneville Dam power plant could be damaged.

Streig says the earthquake would jeopardize Hood River, Odell, Parkdale, White Salmon, Stevenson, Cascade Locks and Government Camp. In the Portland metro area, Streig says, residents would "experience strong ground motions and could suffer liquefaction damage along waterfront areas."

The discovery of the faults is doubly alarming considering recent news that Portland is lagging behind in efforts by West Coast cities to install early earthquake warning systems.  

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