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In the next 50 years, there is a one-in-10 chance of a generation-defining disaster striking the Northwest. A magnitude 9.0 earthquake along the Cascadia Subduction Zone is predicted to cripple the coast, kill thousands and topple roads, buildings and bridges.

This, by now, should be common knowledge for residents of Cascadia, the area stretching from Northern California to Vancouver, British Columbia.

The New Yorker magazine this month ran a long piece on the havoc such an earthquake could cause, with warnings of high walls of water and that “everything west of Interstate 5 will be toast.”

Well, hold on now.

As The Daily News reported in January and many times before, such an earthquake will be deadly and devastating. But it’s something to prepare for, not panic about.

“Like having airbags, we need to do something to prepare,” said Bill Steele, seismology lab coordinator at the University of Washington. “So it doesn’t become an economic disaster as well as an earthquake disaster.”

That means knowing what’s coming as well as knowing what to do when the big one hits.

In Longview and Kelso, Steele predicts two minutes of moderate ground shaking and maybe four or five minutes of shaking in total. It will be the length, not the intensity, of the 9.0 quake that will cause the most damage.

“That gives lots of time for poorly built structures to break, for liquefiable soils to liquefy,” he said. “So that could amplify damage to certain areas susceptible to that kind of hazard.”

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Soil liquefaction occurs when water-logged sand in the ground shakes and shifts “like cereal does in the box to settle down to a much smaller volume,” Steele said.

Liquefaction would be especially damaging at alluvial areas along the river, such as the Port of Longview. It could also split utility lines and sewer pipes and cause uneven foundations throughout the area.

Other than that risk, Steele said neighborhoods and communities will largely remain intact but could become “islands,” cut off from services and supplies. For the majority of people, that will be the real hazard.

“Prepare to be on your own from anywhere from three days to two weeks, without being able to go to the store, pick up medications, potentially without electricity or water,” said Jennifer Engkraf, a coordinator with the Cowlitz County Department of Emergency Management. “Make sure you have a pretty stout survival kit at home and another in your car.”

The real killer will be the tsunami that accompanies the earthquake. While images of giant waves come to mind, it is more of a surge of quickly rising water, as in a flash flood.

Little effect of the tsunami will be felt this far inland, but those in coastal communities need to have an evacuation plan ready — knowing there is about 15 minutes from the start of the shaking to get to higher ground, probably without a vehicle. Most people on the Long Beach Peninsula won’t have time to reach high ground, which is why authorities are planning to build earthquake-resistant evacuation sites. Construction is some years off, though.

Though it may seem dire — and an earthquake could very well be imminent — it could be worse.

“We still have one third of the risk that Californians live with,” Steele said.

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Contact Daily News reporter Brooks Johnson at 360-577-7828 or bjohnson@tdn.com.

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