Twenty-foot waves cresting off Westport. Swift and dangerous currents coursing through Hood Canal. Tsunami water pushing down to Olympia and up to Washington's northern border with Canada.
For the first time, state researchers have modeled the impact of a tsunami sparked by a magnitude 9.2 quake along the Alaska-Aleutian subduction zone, and they've found some surprises.
The modeling, released as a joint project between the Washington Emergency Management Department, the state Department of Natural Resources and others, is a first-of-its kind project.
That's because so much of the state's tsunami preparation involves the Cascadia Subduction Zone, said Elyssa Tappero, of the Washington State Military Department.
A large quake and tsunami from the Cascadia subduction zone — which is found 70 or more miles off Washington's coast — could lead to more than 14,000 deaths, nearly 1 million displaced people and $81 billion in damage, according to a 2016 Seattle Times analysis.
The Cascadia Subduction Zone is the department's top priority, because it’s going to be so devastating, but there’s also a much smaller chance of it happening in our lifetimes,” said Tappero, the department's tsunami program manager.
"A large, distant tsunami, like one from Alaska, is much more likely to happen in our lifetimes,” she added. “Alaska has large underwater earthquakes pretty frequently. Once you start paying attention, you notice how often those happen."
The new tsunami modeling was based on Alaska's 1964 Good Friday earthquake, which killed 131 people and ripped houseboats in Seattle from their Lake Union moorings. For the modeling, researchers moved the epicenter of that quake closer to Kodiak Island, which would create the strongest wave effect toward Washington.
In those scenarios, the first modeled wave arrives off the Washington coast just over 3 1/2 hours after the earthquake's start, according to a summary of the project. The largest offshore waves occur near Westport, in Grays Harbor County, which could exceed 20 feet, with Grays Harbor itself and nearby Willapa Bay getting inundated.
A map of the modeled waves shows the first massive pulse of water would arrive at La Push, on the Washington coast three hours and thirty minutes after the hypothetical quake. At four hours, it reaches Port Angeles, Seattle gets it at five hours and forty minutes. Seven hours after the quake, the deluge hits Olympia.
Along Hood Canal, waters would likely swell 3 feet near Bangor and 4 feet near Hoodsport — but surge to 14 feet at the channel's endpoint at Lynch Cove, near Belfair. Bays near Port Townsend and Eastsound also would see outsized waves.
Activity from the tsunami may last for more than 24 hours, and the first wave may not be the biggest or bring the most flooding.
"This tsunami wave also propagates into the Strait of Juan de Fuca and adjacent inner waterways, eventually reaching both Olympia in the south Sound and the Washington-Canadian Border in Whatcom County," according to a summary of the project. "
The model shows risk for Washington’s inner waterways from fast currents brought by the tsunami. Places "such as the San Juan Islands, Guemes Channel, Port Gamble, and Hood Canal should expect hazardous current speeds" that could especially threaten people on the water and maritime infrastructure.
"We do actually see some interesting and significant impacts on the inner coast and Puget Sound, and that’s not something we expected," Tappero said.
If an earthquake occurs in the much closer Cascadia Subduction Zone, residents on the outer coast would have much less time to evacuate, perhaps just 10 to 20 minutes. Since 2016, some communities have built what are called vertical evacuation structures, to provide people a safe place above the waves. At least 58 such evacuation structures are needed in key areas, and perhaps more than 80, to protect about 175,000 Washingtonians who live in tsunami inundation zones, according to state officials.
Tappero urged people to go to the Military Department's website on emergency notifications — mil.wa.gov/alerts — to find out how to receive notifications and learn more about preparedness.
Additionally, people can check their smartphones to make sure government alerts are on. The same alert system that delivers Amber Alerts on phones will deliver tsunami alerts, she said. Tappero also recommended people get NOAA radios, which she said can be programmed to give off an alert in the event of a tsunami, kind of like an alarm clock.
When it comes to an Alaskan tsunami, "understanding what that looks like for Washington, especially based on where along our coastline you are, can really help dispel some of the fears that we see," Tappero said. And help people prepare.”
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