How West Coast residents should prepare for the threat of a tsunami

·National Reporter and Producer
·7 min read

When most people hear the word “tsunami,” they may imagine a massive wave, but that’s actually a misconception that researchers in Washington state are trying to correct. Since the state’s coastline is at risk of being hit with a devastating tsunami following an earthquake of magnitude 7.5, the state is trying to educate the public about what it actually would be like.

The Washington State Department of Natural Resources released a wave simulation study in July and shared a bit of startling news: a tsunami in Puget Sound could engulf Seattle’s shoreline, leaving it under more than 20 feet of water within minutes.

Several videos released along with the study illustrate how an earthquake-triggered tsunami would most likely cause water to inundate the coastal areas around Seattle. From land, a tsunami functions and looks more like a storm surge from a hurricane than a tidal wave.

The waterfront, the Space Needle and the downtown skyline of Seattle.
The waterfront, the Space Needle and the downtown skyline of Seattle in 2015. (George Rose/Getty Images)

“That’s been something that these videos, I hope, help kind of pull the curtain back on and help educate not only the public, but also the emergency managers and anyone who’s interested in tsunamis to understand how they behave geographically over time,” Daniel Eungard, a geologist with the Washington Geological Survey who helped conduct the study, told Yahoo News.

All it takes is a few feet of water on the mainland to devastate a community, according to experts.

“Tsunamis are an unusual series of powerful, moving and extensive increases of water that can be expected following a locally felt earthquake — or something as far away as a South Pacific island volcano,” Dave Snider, tsunami warning coordinator for the National Oceanic and Atmospheric Administration, told Yahoo News.

In the U.S. there are over 90 million people living in coastal counties, including more than 30 million on the West Coast. While tsunamis big enough to flood North America are rare, the data from the Washington study concludes that tsunami waves could reach the shoreline in fewer than three minutes in many areas of western Seattle, including parts of Bainbridge Island, Elliott Bay and Alki Point. The tsunami inundation and strong currents have the potential to continue for more than three hours from the start of the earthquake, according to the simulation.

A slide from the wave simulation study explains tsunami wave amplitude and tsunami inundation depth.
A slide from the Washington State Department of Natural Resources’ wave simulation study. (Washington State Department of Natural Resources via YouTube)

The West Coast is considered to be at a high to very high risk for these phenomena because of tectonic plates that meet in this part of the country. Large earthquakes in these areas can cause the seafloor to rise and spark a tsunami. According to the National Weather Service, the U.S.’s most damaging tsunami was caused by the Great Alaska Earthquake of 1964, which was a magnitude 9.2. A 7.5 earthquake striking in the area is very unlikely in any given year, but it is possible.

“Although the chances of this happening in our lifetime is low, it’s important for families to get prepared now,” said Maximilian Dixon, the hazards and outreach program supervisor for the Washington Emergency Management Division.

“The ground shaking will be your warning that a tsunami may be on the way,” Dixon said. “Make sure you know where the closest high ground is and the quickest route to get there.”

Tsunamis are caused by underwater disturbances such as earthquakes, landslides or volcanic eruptions that push water upward and outward toward the coast. The water rises, sometimes violently, rushing inland, causing flooding and potential disaster.

Deeper in the ocean, tsunami waves have the ability to travel as fast as jetliners. However, they look much different closer to shore.

A famous illustration of an ocean wave by Japanese artist Hokusai.
“The Great Wave off Kanagawa,” a 19th century woodblock print by Hokusai. (Metropolitan Museum of Art via WikiCommons)

“A tsunami is more like storm surge from a hurricane rather than a breaking ocean wave you surf; however, icons and visualizations often portray a tsunami as an idealized surf wave — including artwork such as ‘The Great Wave off Kanagawa,’” Snider said.

Tsunamis can be extremely deadly if sparked by a massive earthquake. In 2004 a tsunami in the Indian Ocean pummeled multiple nations in Asia and caused at least 225,000 deaths along with massive destruction. It was a magnitude 9.1 quake off the coast of the Indonesian island of Sumatra.

North America has two tsunami warning centers tasked with tracking and sounding the alarm in the event of underwater earthquakes that could cause a tsunami on the West Coast. One covers Hawaii and the U.S. Pacific territories, and one covers the rest of the country and Canada. These centers alert local authorities when residents may need to evacuate vulnerable areas.

At 6:09 a.m. on Jan. 15, the National Weather Service issued a tsunami advisory for the entire West Coast because of a volcano that erupted in the Pacific Ocean.

Two surfers stand in water, watching the waves come in.
Surfers in Manhattan Beach, Calif., take advantage of the increased swell after a magnitude 8.9 earthquake hit Japan. (Axel Koester/Corbis via Getty Images)

Many residents in coastal communities from Southern California to Oregon and Washington heard sirens but had no clue what they were for until the news came out — a potential threat from tsunami conditions.

“I was pretty shocked frankly, and as a resident of Seattle, quite shocked,” said Hilary Franz, Washington’s commissioner of public lands.

At the time, a Seattle resident tweeted: “I live in Seattle and I did not receive a tsunami advisory alert on my phone yesterday, @USGS_ShakeAlert? Why is that, @waEMD? Does 3rd and Pike have a tsunami alert siren installed yet? Can we get on that please? Thanks! Thank you for your service.”

“In Southern California, we don’t do much because typically the tsunami is hours and hours away and it’s much more of an issue typically in Northern California and Alaska and along the coast there, so we are fairly blasé about a tsunami warning,” said Los Angeles County resident Susan Heller.

In California there’s a Tsunami Preparedness Week, and several areas along the coast have signs reading “Tsunami hazard zone: In case of earthquake go to high ground or inland.”

A tsunami hazard sign reads: Tsunami hazard zone. In case of earthquake go to high ground or inland.
A tsunami hazard sign near the Balboa Pier in Newport Beach, Calif., on Jan. 15. (Mark Rightmire/MediaNews Group/Orange County Register via Getty Images)

Snider added that California’s emergency services and the National Weather Service work together advising local communities on potential tsunami risks. They also have a warning plan in place but urge residents to have their own plan to evacuate inland or to higher ground.

However, that could be problematic for people who live near the coast and who aren’t near high ground. Many of these areas could be difficult to quickly evacuate, especially if the warning created a traffic jam.

According to the city of Santa Monica, Calif., most buildings cannot withstand the impact from these strong tsunami waves. So the best option is to evacuate inland. If that’s not possible, the city says, upper stories of some strong and tall buildings would provide limited protection. That could be important for vulnerable populations or individuals without transportation who may not be able to get inland. A tsunami could arrive within minutes or hours later. Swift evacuation might also be extremely difficult for people with disabilities, highlighting the need for preparation.

Some scientists and geologists believe climate change plays a role in these potentially devastating disasters, but mostly in Alaska, where melting glaciers are a real threat.

Harriman Glacier near Whittier, Alaska.
Harriman Glacier near Whittier, Alaska. (Education Images/Universal Images Group via Getty Images)

“As global warming continues to thaw glaciers and permafrost, landslide-created tsunamis are emerging as a greater threat — not just in Alaska, but in places like British Columbia and Norway,” said Woods Hole Research Center scientist Anna Liljedahl in a 2020 statement released by the state of Alaska.

In the same statement, geologist Steve Masterman said data showed that a glacier retreating from the Barry Arm could release tons of rock into the Harriman Fjord (east of Anchorage), triggering a significant tsunami.

“The most noteworthy of these tsunamis was in 1958, when a landslide entered the Lituya Bay Fiord in Glacier Bay and generated a wave that went 1,700 feet up the opposite side of the fiord,” said Masterman, who retired this year as state geologist and director of the Alaska Division of Geological & Geophysical Surveys.

“The most recent was at Southeast Alaska’s Taan Glacier in 2015, where a wave went 600 feet up the opposite wall of the glacial valley,” he added.