PORT ANGELES — Between 6,100 and 24,000 Clallam County residents would die within the first six weeks of a magnitude-9.0 earthquake in the Cascadia subduction zone, the Port Angeles City Council was told Tuesday.

Those who survived the initial quake and resulting tsunami would need to be ready to shelter in place for at least 30 days, according to a presentation led by former state Rep. Jim Buck.

“This is the first time in 10 years — and I’ve been working on this 10 years — that I have come out in front of a bunch of people and said what we think the casualty levels are going to be,” Buck told the City Council, department heads and about 40 audience members during a two-hour briefing on emergency preparedness.

“And the National Guard supports the numbers.”

The six-week casualty projections for Clallam County break down as follows:

• 800 to 3,000 dead from the earthquake — structural and debris strikes.

• 1,000 to 5,000 dead from the 30- to 40-foot tsunami that would inundate low-lying areas.

• 2,700 to 5,500 dead from entrapment and isolation.

• 200 to 4,000 dead among the fragile population and those with special needs like supplemental oxygen.

• 1,400 to 6,500 dead from a lack of food or water or from exposure to the elements.

“Our goal, if we work hard and do good planning, is to be on this (lower) side from a number perspective,” Clallam County Fire District No. 3 Assistant Chief Dan Orr told the council.

“The entrapment and isolation moves me, simply because, what a horrible way to go.”

After the meeting, Buck said he used age demographics and other census data to help project the loss of life.

Exactly when the earthquake strikes — and experts say it is not a matter of if, but when — will go a long way to determine the final death toll, Buck added.

The last major earthquake on the 800-mile long Cascadia subduction zone off the Northwest coast occurred on Jan. 26, 1700, scientists say.

Geologists believe there is a 10 percent chance that another 9.0 earthquake will happen in the next 50 years, Orr said.

“If we have an event, it could affect 7 million people,” Orr said of the regional impacts of a megathrust earthquake.

“Ladies and gentlemen, this has the potential of being the worst natural disaster in the history of the United States, far exceeding anything that you’re seeing on the news currently.

“The ground is going to shake so violently for five minutes that you will not be able to stand up,” Orr added.

For perspective, the 7.1 magnitude earthquake that killed more than 300 in Mexico City on Sept. 19 lasted just 20 seconds, Orr said.

The Federal Emergency Management Agency has told local planners to expect one 8.0 aftershock and up to 10 magnitude-7.0 aftershocks within the first week of a Cascadia earthquake, Orr said.

Other faults in the state, including the Lake Creek/Boundary fault south of Port Angeles, have the potential to cause significant tremblers, Orr added.

As part of the work session, Port Angeles Fire Chief Ken Dubuc briefed the council on its role after a natural disaster, the city’s Comprehensive Emergency Management Plan and a Continuity of Operations Plan that is being developed.

“Given all of the disasters and issues that have befallen several American cities and Puerto Rico, this is a very timely discussion,” said Mayor Patrick Downie, referring to recent hurricanes.

Damaged roads and bridges from a Cascadia subduction zone earthquake are expected to divide Clallam County into at least 20 “micro-islands.”

Port Angeles has two such islands separated by Peabody Creek — division N on the west and division O to the east — and eight “sub-micro islands” that would likely be separated by bridge and culvert failures.

Buck, a Joyce resident who has been highly active in countywide disaster planning, provided a Port Angeles-specific assessment of expected impacts from the Cascadia disaster in a slide presentation he titled “Detailed Ground Truth.”

Buck displayed maps of each sub-micro island depicting landslide zones, tsunami zones, liquefaction areas, bridges and culverts and historical photographs of Lincoln Street and the downtown area.

The section of Lincoln Street near the Clallam County Courthouse was built on a wooded trestle as seen in photographs from between 1914 and 1916. The canyon below the trestle was filled with loose material from railroad dump cars.

“We don’t expect Lincoln Street to survive downhill from at least Eighth Street,” Buck said.

A large section of Port Angeles — the entire area east of C Street and north of Eighth Street — is expected to experience moderate soil liquefaction in the earthquake, according to Buck’s slides.

The downtown core, which was built on fill, will experience severe liquefaction and the tsunami, Buck said.

“You can expect anything that’s built there to collapse, either through foundation failure, piling failures or just flat liquefaction,” Buck told the council.

“Seventy minutes later, the tsunami — and we think it will be in the 30- to 40-foot range — will come in and it will destroy anything that’s not already destroyed.”

Four of the 13 evacuation routes out of downtown Port Angeles — the Tumwater Street/Fifth Street bridge, the Oak Street ZigZag trail, the Laurel Street stairs and Lincoln Street — will likely be destroyed in the Cascadia earthquake, Buck said.

The Tumwater Truck Route and South Valley Street will likely be open as far as the collapsed Eighth Street bridges, Buck said.

Hill, Cedar, Cherry, First, Front, Francis and Ennis Street will likely be impassable for vehicles but open to foot traffic.

“It’s going to be basically a walk-out scenario,” Buck said.

City Councilman Dan Gase asked how people can best prepare for the Cascadia disaster.

“I think one thing that you can do before this time tomorrow night is tell 10 people what you heard here,” Buck said.

“You won’t get a briefing like this anyplace else in the state.”

Dubuc, who said he is not a “doomsday prepper,” suggested buying one item for emergency preparations every time you got to store.

“Buy a case of water, shove it under the bed,” Dubuc said.

”Buy a can of food, put it in the pantry. Buy a flashlight. Buy some batteries. Buy a little portable radio. Just one thing each time.

“That’s what I would do,” Dubuc added, “right after you check your smoke detector.”

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Reporter Rob Ollikainen can be reached at 360-452-2345, ext. 56450, or at [email protected].