A large earthquake off the coast of Alaska could send a tsunami that reaches all the way into Puget Sound. That’s according to a new model from state experts looking at how that would likely unfold.
A summary of the project shows that water levels could rise two feet in Seattle, four feet all the way south in Olympia, and as high as 24 feet at Westport along the coast.
The model illustrates the impact of a massive 9.2 magnitude earthquake off the coast of Alaska. State agencies based the model, in part, on a deadly 1964 earthquake that sent a tsunami to Washington State.
The new scenario shows how a powerful earthquake, along the Alaska-Aleutian subduction zone, would likely push high waves down along Washington’s Coast and into Puget Sound.
“It shows that even for that distant event, this is something that all of Washington will experience,” said Elyssa Tappero, Tsunami Program Manager with the Washington State Emergency Management Division.
We often hear about the potential for earthquakes from the Cascadia Subduction Zone, off the Washington State coast. But Tappero points out, “While something on our Cascadia subduction zone can do a lot of damage, here, they don’t happen as frequently. What we do get frequently are distant tsunamis coming from somewhere else in the Pacific Ocean.”
Tsunamis are generated by underwater earthquakes. Harold Tobin, Director of the Pacific NW Seismic Network, explains, “In the simplest terms, when an earthquake happens under the sea it tends to suddenly lift up the seabed… and when it pushes up, that pushes the water up.”
The water disperses in waves. “It’s really a lot like the whole Pacific Ocean is one big pond and the ripples in the pond from somebody dropping a stone in it.”
Tobin stressed, “The fact is, that without any earthquake here, we can still have a tsunami that arrives from somewhere else. So that’s why the warnings are critically important.”
In the scenario presented in the new state model, it takes about 3.5 hours for the first high waves to reach the Washington Coast, giving people time to evacuate.
The state has 122 tsunami sirens located on the coast and other vulnerable areas. Tappero says you would also get a tsunami warning on your smartphone, using the same system that sends out Amber Alerts.