Expert breaks down WA tsunami threat, Seattle Fault earthquake risks
Analyzing tsunami threat in WA, Seattle Fault earthquake risks
An expert at the pacific Northwest Seismic Network says the recent 8.8-magnitude earthquake that struck off the coast of Russia is a mirror image of what could happen in Seattle, also known as "The Big One."
SEATTLE - A tsunami advisory was eventually canceled for parts of Washington following an 8.8-magnitude earthquake near Russia on Tuesday evening. Now, many people are wondering how much warning time they would have if a similar earthquake were to strike closer to home – and what to do if a tsunami were imminent.
Dr. Harold Tobin, director of the Pacific Northwest Seismic Network, joined Good Day Seattle Wednesday morning to discuss with FOX 13 meteorologist Abby Acone what a major earthquake and potential tsunami could mean for the region.
FOX 13's Abby Acone:
"This [earthquake] happened in Russia, and we had many hours of a heads-up. But if ‘the big one’ happens off the Cascadia Subduction Zone, off our coast, a tsunami could be very imminent afterward. What does that hypothetical look like?"
What would happen if an 8.8M earthquake struck the Cascadia Subduction Zone?
Dr. Harold Tobin:
"Yeah, this earthquake is kind of a mirror image of the Cascadia Subduction Zone on the other side of the Pacific," said Dr. Harold Tobin. "It's also a subduction zone. It's the same kind of earthquake that the Cascadia could be – 8.8 – it could very easily be the kind of scale we're at. And the nearby coast was affected by up to something like, you know, 25 or 30 feet high tsunami surges [which were] very damaging in Kamchatka, Russia.
"So Cascadia would be similar if the earthquake happened here. And then the tsunami arrival time, after the earthquake at the coastline, is only a matter of – depending on where you are – anywhere from 10 to 30 minutes or so. Just a very short period of time for people to actually evacuate from the hazard zone."
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Tsunami advisory canceled for Washington coast
A tsunami advisory issued for parts of Washington remains in effect on Wednesday morning.
FOX 13's Abby Acone:
"So we have alerts that would be sent out to your phone, lots of work going around with the Shake App, and then sirens, emergency plans along the coast. Do you think we have all the infrastructure in place for these coastal communities if ‘the big one’ happens?
Is western WA prepared for a major earthquake or tsunami?
Dr. Harold Tobin:
"Well, unfortunately, we absolutely don't have all the infrastructure in place," said Dr. Tobin. "There are many regions where actually evacuating would be really challenging. You can imagine the immediate gridlock and bottlenecks in some places. There are parts of our coastal communities where evacuation to higher ground really isn't possible.
"We need those – what are called "vertical evacuation structures" – fortified buildings or even special-purpose towers that people can go up instead of away in order to get away from the tsunami. We're just beginning to be able to have that equipment and infrastructure here in Washington state, and we have a long way to go, unfortunately.
"I will say, though, that the earthquake itself is the best advance warning. All those alerts you mentioned are important features, but if you feel very strong shaking, and you're by the sea at the coast, it's important to move to higher ground."
(The Washington Emergency Management Division)
FOX 13's Abby Acone:
"Something that isn't talked about maybe often enough in the media is that the Seattle Fault here would be more devastating for us than if a big one were to go off along subduction zone. Is that right? And what would those impacts look like?
Would the Seattle Fault be more dangerous than the Cascadia Subduction Zone?
Dr. Harold Tobin:
"Yeah, here in Seattle and in the population centers in Puget Sound, the faults like the Seattle Fault – and there's another called the Tacoma Fault – have less frequent earthquakes, but they really are sort of worst case event scenario," said Dr. Harold Tobin.
"The shaking will be very strong for a Seattle Fault earthquake. And it could potentially produce a localized tsunami inside the Sound, which would have really damaging effects along the shoreline. Fortunately, those events seem to be quite rare: the last one was apparently more than 1,000 years ago. But there's the possibility of a future Seattle Fault event. And that's another thing we need to prepare for."
FOX 13's Abby Acone:
"If a Seattle Fault earthquake were to happen, what do people need to do in the city? How far away would they need to get for higher ground?
What should I do if a Seattle Fault earthquake happens?
Dr. Harold Tobin:
"Yeah I mean, first of all, number one: drop, cover and hold on," said Dr. Tobin. "You know, the shaking will be strong, and we want people to make themselves safe during the actual earthquake shaking.
"In a scenario like that, then the tsunami would actually arrive very quickly because, of course, Elliott Bay and the Sound is a pretty enclosed small area. What it means is get to whatever you can 30 feet above the water line. It doesn't mean the whole city has to go to the top of the hill.
"Fortunately, we have a lot of hills, we have a lot of topography in Seattle, we can get to higher ground. But 30 feet above sea level, 100 feet above the sea level is a reasonable, truly safe distance. And for many of us, that's only a few blocks inland, away from the water's edge."
Tsunami alerts across WA Pacific Coast
Tsunamis advisories are in effect across the Washington coast and even into northern California after a powerful 8.8-magnitude earthquake struck near Russia. Dr. Harold Tobin joins Good Day Seattle to talk more about these advisories and what may happen if a sizeable earthquake were to strike closer to home.
The Source: Information in this story comes from a live TV interview on Good Day Seattle with Dr. Harold Tobin, director of the Pacific Northwest Seismic Network.
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