Editor's Note: This story was first published in June 2016

CAMP MURRAY, Wash. - It's being called the largest exercise of any kind in Washington state history, and it's all about getting ready for what scientists say is coming: a magnitude 9 earthquake and ensuing tsunami.

For decades, evidence has built about the impact of what a magnitude 9 earthquake will have along the Cascadia Subduction Zone, a fault line that runs from Cape Mendicino, California, up past Oregon, Washington and along the western shore of Vancouver Island, British Columbia, Canada.

In total, the exercise involves multiple states, Washington, Oregon and the Canadian province of British Columbia. Some 20,000 people will be involved, from civilian first responders to active duty elements of the U.S. Army, Navy, and Coast Guard.

And the idea, says Lt. Col. Clay Braun of the Washington Military Department, is to test the response as much as they can. To find the holes and patch them for the time when the real earthquake hits.

Braun has led the planning for the exercise for two and a half years. The scenario isn't pretty. The projections are than 8,400 people could be killed in Washington state alone in the first earthquake and tsunami; another 12,000 injured. Six thousand could die in Oregon, numbers that could go higher as the days and weeks drag on.

"The initial step is that first responders in the entire affected area try to do their job. But they will be immediately overwhelmed," said Braun.

The idea is that immediately after the shaking stops, the word goes out across the country.

"So we're already reaching out to other states to provide mutual aid through compacts, and start mobilize assets as soon as possible,” said Braun. “And we're pre-coordinating, where these people need to be. Where they need to go. They have pre-assigned missions.”

READ: Interactive Map: Washington State Seismic Hazards Catalog

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