Cascadia Subduction Zone

Found an interesting article on the above:

Safe in the Sound?

That obligatory article that’s going to scare the bejesus out of you about the possibility of an earthquake in the South Sound

By Nikki Talotta on April 20, 2011

Do you know, according to the Pacific Northwest Seismic Network, there have been more than 35 earthquakes in Washington state just in the last two weeks?

Do you know we live near one of the most hazardous faults in the world?

Do you know this particular fault line – the Cascadia Subduction Zone – is aching to release a megathrust earthquake?

Now, imagine this fault ruptures and a 9.0 magnitude earthquake violently shakes the Pacific Northwest.

“It would be like a freakishly monstrous catapult that hurls 75,000 square miles of rock, the margin of a continent, as much as 65 feet,” says Patrick Pringle, associate professor of Earth Sciences at Centralia College, national author and overall geo-enthusiast.

In Olympia, the Capitol building would sway, shake and essentially sink into the soft ground that holds the Capitol campus. The quaking would last three minutes or longer, perhaps the scariest three minutes of a lifetime. In the aftermath there would be struggle to contact friends and family. Transportation and technical communications would come to a halt.

In Tacoma, homes would be knocked into the Narrows by earthquake induced landslides; the ground would liquefy near the Tacoma flatlands, and historical buildings would crack, strain and crumble.

In the wake of Japan’s devastating earthquakes, this scenario is not difficult to imagine.

“The Cascadia Subduction Zone is almost a mirror image of the one in Japan,” says Pringle.

A subduction zone, where oceanic plates collide with colossal continental plates, essentially slipping a new slab of crust under an old one, puts tremendous strain on the Earth’s surface between quakes, explains Pringle.

Running from Vancouver Island to Northern California, the Cascadia Subduction Zone is 700 miles long.

You can follow the trail of volcanoes through the Pacific Northwest to get an idea of where these plates collide. (Glacier Peak and Mounts Baker, Rainier, St. Helens, Hood, etc.) This chain of volcanoes, which Pringle refers to as “sleeping giants,” due to their mild – but possibly explosive –  nature, are part of the Ring of Fire, a spread of more than 450 volcanoes along coastal waters which include Japan, Indonesia, Russia, Chile and other geographically unstable parts of the world.

The Northwest is no stranger to the Earth’s power. The Mount St. Helens  eruption, mudslides, lahars, fires and floods have all scarred our landscape, forever changing history.

Most notable, perhaps, is the megathrust earthquake that shook the West Coast in the year 1700. Although there was no formal recordkeeping in the region then, oral legends from local tribes describe tragic experiences caused by the great tectonic disturbance. Evidence from carbon dating, sediment left by tsunamis and studies of tree rings, all point to a grim past. In Japan, there is even documentation on rice paper of the country experiencing tsunami waves likely resulting from a massive earthquake in the Cascadia Subduction Zone during the same time.

The fact that the Pacific Northwest is ripe for ruin is not breaking news. The Earth’s timeline places a major earthquake in this region every 250 to 1000 years, with an average of one every 500 years.

The last megathrust was over 300 years ago. Basic math shows us the odds are not in our favor.

Since science is not fiction, when we experience the “big one,” results will be catastrophic.

With the possibility of thousands dead or missing, people will be a main concern. But post-quake financial realities would soon hit as well, like months of clean up and repair, and billions of dollars in damages. The Nisqually earthquake in 2001 (magnitude 6.8) caused almost $2 billion in damages; imagine the damage a 9.0 mega thrust would cause. The agency EQE International, which specializes in risk management, estimates more than $800 billion in damages.

Forget post-quake costs; with an already tight state budget, will we have the means to realistically finance preventive education programs, pay to seismically retrofit structures for safety (have you seen all the old bridges over Interstate 5?) and adequately fund scientists and engineers?

Patrick Pringle tells me that while he was working for the state Division of Geology the budget was cut by nearly 42 percent during the 2003-05 fiscal years.

“They cut the entire geological hazard section except for one researcher,” he recalls.

“I’m afraid of seeing the baby get thrown out with the bathwater once again,” Pringle says of the dwindling state funds, “because many of the state scientists have had to rely on grants to do their important work.”

Part of the problem is it often takes a major disaster to stir up concern, a shake and wake, if you will.

“A lot of us tend to forget about earthquakes, the last one here was 10 years ago,” says Tacoma Community Relations Manager Rob McNair-Huff, who, together with his wife Natalie, wrote Washington Disasters: True Stories of Tragedy and Survival, highlighting 22 natural disasters that have rocked this region.

The husband and wife team recently presented their book at the Tacoma Art Museum, with an afterparty of earthquake preparedness tips and kits.

It’s important that these types of gatherings, education and resources are available to the community.

“With a small budget, we need to use tools like social media; accounts on Facebook and Twitter,” says McNair-Huff. “And in the event of an emergency, we can use these for real-time outreach.”

In the opinion of this bartender/writer, you might even make it a little fun –  host an earthquake/disaster preparedness party and serve drinks like martinis (shaken, not stirred), Rainiers and mudslides. And for a non-alcoholic alternative try earthquake milkshakes with chunks of rocky road.

And then talk. Talk about evacuation routes and designate meeting places. Talk about resources. Talk about survival techniques. Talk about basic first aid. And talk about how to educate even more.

Because, we can never be too sure.

“You just wait,” assures Pringle, “there is a chance we’re going to experience a major earthquake in the next few decades.”

http://www.weeklyvolcano.com/mudroom/special-report/2011/04/imagine-Cascadia-Subduction-Zone-ruptures-9-magnitude-earthquake-violently-shakes-Pacific-Northwest/

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