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Interesting article...
Can the Pacific Northwest prepare for the cataclysmic quake that's coming?
Americans have long dreaded the "Big One," a magnitude 8.0 earthquake along California's San Andreas Fault that could one day kill thousands of people and cause billions of dollars in damage. The Big One, though, is a mere mini-me compared with the cataclysm forming beneath the Pacific Northwest.
Roughly 100 miles off the West Coast, running from Mendocino, California, to Canada’s Vancouver Island, lurks the Cascadia Subduction Zone, where the Juan de Fuca Plate is sliding beneath the North American Plate, creating the conditions for a megathrust quake 30 times stronger than the worst-case scenario along the notorious San Andreas, and 1,000 times stronger than the earthquake that killed 100,000 Haitians in 2010. Shockwaves will unleash more destructive force against the United States and Canada than anything short of nuclear war, a giant asteroid strike, or a civilization-threatening super-volcano.
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The megathrust quake could strike at any time. Not even the most hardcore adrenaline junkies will want to be anywhere near when it does. "It will be," says Andrew Phelps, director of the Oregon Office of Emergency Management, "the worst natural disaster in American history."
When it happens, the earth will slip by roughly 60 feet along a rupture zone more than 600 miles long, unzipping the sea floor at roughly two miles per second and convulsing the West Coast for as long as five minutes. Bridges will fall. Wet soil will liquefy. Brick and masonry buildings will shatter. Skyscrapers built before modern earthquake codes may topple. City centers in Portland, Seattle, and Vancouver will be buried beneath glass shards and rubble. Everything underground—water mains, natural gas pipes—will be crushed. Land that has bulged upward from tectonic pressure for the past 300 or so years will collapse to baseline, permanently altering the topography and plunging low-lying coastal areas into the ocean. The inland Cascade Mountains will knock the knees out from under the earthquake, but numerous landslides will occur, especially on roads built with a "cut and fill" method, where flat slabs get cut out of rock walls and smoothed over with soft fill. Just a few minutes after the quake finally stops, the second hammer blow will strike. Tsunami waves up to 50 feet high will rip the face of the coastal region clean off the map, pulverizing everything and killing everyone in their path.
More at link
https://www.city-journal.org/pacific-earthquakes/
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