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A "megathrust" earthquake and tsunami would devastate the Northwest United States, a geologic region of the Pacific Ocean's "Ring of Fire" called the Cascadia Subduction Zone, where major tectonic plates collide.
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Written, narrated and produced by Bryce Plank
Video editing and effects by Robin West
Research by Juliet Saunders
Video based on this article:
www.newyorker.com/magazine/201...
Music:
All This - Scoring Action by Kevin MacLeod is licensed under a Creative Commons Attribution license (creativecommons.org/licenses/...)
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Decisions by Kevin MacLeod is licensed under a Creative Commons Attribution license (creativecommons.org/licenses/...)
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Seattle timelapse courtesy of KZbinr Edward Aites:
• TIMELAPSE SEATTLE in HD
When you think of the big earthquake that will devastate the Western U.S., you probably assume it will hit California. But the massive one we’re supposedly long overdue for will actually hit the Pacific Northwest, devastating Seattle and much of 700 coastal miles from Vancouver to NorCal’s Mendocino Cape.
This area lies on the Cascadia subduction zone. The Cascades are the volcanic mountain range that run parallel to the fault, some 100 miles inland, and are formed by the Juan De Fuca tectonic plate colliding with, and sliding underneath, the North American plate. This geological battle will eventually result in the weaker North American plate buckling violently as it gives way to the mounting pressure, dropping several meters in a few seconds.
This will cause a 9.2 magnitude megathrust earthquake that will last around 4 minutes and will be 30 times more powerful than anything California’s San Andreas fault can produce.
What happens after that is truly terrifying.
Since the event will happen in the ocean, it will send a tsunami, a wall of water more than 15 meters high, rushing back toward coastal areas like Puget Sound and the heavily populated Seattle area. As it washes ashore it will destroy everything in its path.
The catastrophic tsunami triggered by the 2011 Tōhoku 9.0 earthquake in Japan was responsible for the vast majority of the 18,000+ deaths suffered in that disaster. And Japan even had an early warning system that sensed the initial tremor and automatically activated to save countless lives by shutting down power plants and railways, and performing various other vital services before the full quake and tsunami struck.
The Pacific Northwest has no such early warning system.
In fact, three years ago the citizens of Seaside, Oregon rejected a plan that would’ve raised their taxes in order to move three schools out of the tsunami inundation zone. [Show clip of devastated school administrator describing why that’s such a mistake.]
The voters came to their senses this November and funded a version of the plan, but the story is representative of the lack of awareness those living in the Cascadia Subduction Zone have about the uncertain ground they actually live on.
Part of the reason why the region seems to be in a complete state of denial is because the Juan De Fuca plate hasn’t caused an earthquake in 317 years. It’s a sleeping giant that’s 75 years overdue for an awakening.
To get a sense for how destructive a 9.2 quake would be, we need look no further than the 1964 Great Alaskan Earthquake of the same magnitude that sent tsunami’s rippling throughout the pacific, one of which killed 12 people in Crescent City, California, some 1,600 miles away from the quake’s epicenter.
The biggest problem is that seismology was in its infancy when much of the Pacific Northwest was built, so Portland - for example - didn’t have a seismic building code until 1974. More than a million structures in the region would collapse or be irreparably damaged by a megathrust quake, three thousand of them schools. Other critical infrastructure that will either collapse or be greatly compromised will be half of all highway bridges, fifteen of the seventeen bridges spanning Portland's two rivers, two thirds of all railways and airports, one-third of all fire stations, half of all police stations, and two-thirds of all hospitals.
There will also be land liquefaction, a phenomenon whereby partially saturated soil loses strength and stiffness. Not only does 15 percent of Seattle lie on land vulnerable to liquefaction, but so does Oregon’s Critical Infrastructure hub where miles of gas lines converge.
megaquake