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Special Report: Preparing for the next major earthquake and tsunami

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FLORENCE, Ore. -- We all know western Oregon has potential for earthquakes and tsunamis, but with our busy lives, it can be easy to forget that we live in an area prone to natural disasters.

Off the Oregon coast, the Cascadia Subduction Zone is a ticking time bomb, according to OSU Marine Geologist Chris Goldfinger.

"The Juan De Fuca plate subducts under North America," he said. "We're sitting at a 10 to 15% chance of a magnitude 9 event, which doesn't sound like a lot, but Japan was sitting at 20% chance in 2011 when they had their tsunami."

Off the Oregon coast there are several fault lines, such as the Blanco Transform Fault, the Juan De Fuca Ridge, the Gorda Ridge, and the Cascadia Subduction Zone. All of these faults, except for the Cascadia Subduction Zone, will produce earthquakes but not tsunamis. This is because they either slide past one another, or they spread apart.

What makes the Cascadia Subduction Zone of concern is the fact that it converges with the North American Plate. The oceanic crust is denser and subducts under the North American Plate. As it does, friction is created. Eventually one day it will release and displace tons of ocean water, creating a massive tsunami.

Goldfinger said the wave would be about 40 to 60 feet high and travel up to 500 mph out at sea. As it gets closer to the shore, it will slow down to speeds of 20 to 30 mph. The shaking from the earthquake would last up to five minutes, then 15 to 20 minutes later the wave would arrive to the coast. Downtown Florence would be inundated with water, and the effects of the wave would travel as far up the Siuslaw River as Mapleton. He said it would take 40 to 60 minutes for Mapleton to see flooding.

Pedro Lomonaco, a researcher at the Hindale Wave Research Lab in Corvallis, said our infrastructure will not be able to handle an earthquake followed by a tsunami.

"What happens when you have a building that is elevated, the space under the structure would allow water to go through," Lomonaco said.

He added that the reason why our infrastructure can't handle an earthquake is because our homes and bridges were built before the theory of plate tectonics was even discovered. We would have to retrofit our infrastructure to get everything ready.

In towns like Florence, emergency managers are well aware of the dangers of a catastrophic earthquake.

"We are planning for a Cascadia Subduction Zone earthquake. We make sure we have staff that are trained to assess buildings after an earthquake," said Megan Messmer, the Assistant City Manager of Florence. "We have annual meetings to educate people on the dangers. Our newspapers have tsunami evacuation information in them, and we had a grant program that allowed us to put blue lines on the road so people know when they are leaving a tsunami hazard zone."

She said if the big one happens, evacuate by foot, not by car. Many deaths happen when people evacuate by car. The most important thing is to have a gameplan of what to do to get to higher ground in the event of a tsunami.

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