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.
When it’s all over, flooding and road destruction will trap more than a million people, leaving
them without access to electricity as fires burn all around them.
It will be far worse than the most damaging natural disaster thus far in American history,
Hurricane Katrina.
So the next time you hear about America’s desperately needed infrastructure investment,
understand that it’s not only about repairing the many potholes we’re constantly avoiding
on our roads, it’s also about protecting our cities and towns from the effects of natural
disasters--precautions that could be the difference between life and death for thousands of people.
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Until tomorrow, for TDC, I’m Bryce Plank.