Mt. Hood Faults Could Cause Major Quake

mount hood mt

Researchers from Portland State University and the Oregon Department of Geology and Mineral Industries (DOGAMI) have discovered an extensive network of active geologic faults extending north and south of Mt. Hood. They say the faults could generate large earthquakes and may pose a significant hazard to surrounding communities, critical infrastructure, and even the city of Portland.

Ian Madin of DOGAMI and Ashley Streig, assistant professor of geology at PSU, discovered the fault network after analyzing recent high-tech imaging of the area. They followed up their analysis by conducting field research in the area to verify the mapped fault traces.

The faults potentially could trigger a 7.2 magnitude quake -- larger in size than the 1989 Loma Prieta earthquake that seriously damaged the San Francisco Bay Area. The Mt. Hood faults are closer to Portland than the Loma Prieta epicenter was to San Francisco, which means it could be even more damaging, Streig said.

“This would be a crustal earthquake as opposed to the Cascadia subduction zone earthquake Portland has been bracing for,” Streig said. “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 fault networks are north, south and southwest of Mt. Hood. The north fault network extends to the Columbia River. Streig says a large earthquake along this fault could have implications for infrastructure including rail lines in the Columbia Gorge and power generation at Bonneville Dam.

In addition, the Mt. Hood faults pose a serious seismic hazard to the cities of Hood River, Odell, Parkdale, White Salmon, Stevenson, Cascade Locks, Government Camp and the Villages at Mount Hood, according to Streig and Madin’s ongoing research. The Portland metro would experience strong ground motions and could suffer liquefaction damage along waterfront areas, Streig says.

Source: Portland State University

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