PORTLAND, OR — Here’s one more thing to worry about. People living in the Portland area already have several potential natural disasters to worry about. There’s the possibility that Mt. Saint Helens could erupt again. There’s the possibility of a tsunami wiping out much of the coast.
And, of course, the possibility of “The Big One” is ever-present. The region has had 9.0 earthquakes on a regular basis over the centuries. And we’re overdue.
On top of all that, scientists from Portland State University and the state’s Department of Geology and Mineral Industries announced on Monday that they’ve discovered “an extensive network of active geologic faults extending north and south of Mt. Hood.”
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While faults themselves may not necessarily be overly threatening, the newly discovered network “could generate large earthquakes and may pose a significant hazard to surrounding communities, critical infrastructure, and even the city of Portland.”
The networks — discovered by Ian Madin from DOGAMI and Ashley Streig from Portland State — run north, south, and southwest under Hood.
If they were to cause an earthquake, it could be one of 7.2 magnitude, which is more powerful than the 1989 quake that damaged San Francisco. The scientists also point out that the faults under Hood are closer to Portland than the epicenter of the 1989 quake was to San Francisco.
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That quake killed 67 people and caused more than $5 billion in damage.
“The Big One,” as the hypothetical earthquake is known, could be even worse, Madin and Streig say.
The fault line running north ends at the Columbia River. The scientists say if it goes that way, it will damage not only Portland, but Cascade Locks, Hood River, Odell, Parkdale, White Salmon, Stevenson, Government Camp and the Villages at Mount Hood as well. It could also damage rail lines, roads and other infrastructure into the Gorge.
Bonneville Dam would also be at risk.
“This would be a crustal earthquake as opposed to the Cascadia subduction zone earthquake Portland has been bracing for,” Streig said in a press release. “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.”
Another concern, they say, is liquefaction by waterfront areas (think Portland, which straddles the Willamette). Liquefaction is what caused towns in Indonesia to be wiped out when an earthquake struck there late last month.
Photo via Oregon Mount Hood Territory.