Skip to main content

A powerful earthquake in Alaska didn’t trigger a big tsunami — here’s why

A powerful earthquake in Alaska didn’t trigger a big tsunami — here’s why

/

‘Alaska is no stranger to these kinds of quakes’

Share this story

A map showing the location of last night’s magnitude 7.9 earthquake in the Gulf of Alaska.
A map showing the location of last night’s magnitude 7.9 earthquake in the Gulf of Alaska.
Image: USGS

Last night, a magnitude 7.9 earthquake struck southeast of Kodiak Island in the Gulf of Alaska, prompting a tsunami warning that forced people to flee to higher grounds in the middle of the night. Fortunately, the tsunami waves were less than a foot high, and the advisories were canceled a little after 4AM local time. So why was Alaska so lucky?

Powerful quakes that happen out at sea are known to cause destructive tsunamis. In 2011, a magnitude 9 earthquake in northeastern Japan triggered waves as high as 126 feet, killing nearly 20,000 people. In 2004, a similarly strong quake off the coast of Indonesia caused a tsunami that killed more than 200,000 people. Alaska also has a history of strong earthquakes: in 1964, the state experienced the most powerful quake ever recorded in the US, a 9.2 magnitude tremor followed by a tsunami that killed over 100 people.

“Alaska is no stranger to these kinds of quakes,” says Don Blakeman, a geophysicist with the US Geological Survey (USGS).

“Alaska is no stranger to these kinds of quakes.”

Earthquakes occur because the Earth’s crust is divided into plates. These plates can move smoothly against each other or become stuck. When they become stuck, they build up strain over time, until one day, the plates unstick, releasing energy that causes an earthquake. Just south of Alaska, the Pacific plate is sliding underneath the North American plate, an area called the subduction zone. That’s why the state is highly seismic, Blakeman tells The Verge.

Last night’s earthquake generated because of all the strain building up on the subduction zone, but it did not occur exactly on a fault where the Pacific Ocean seafloor is sliding under the North American plate, Blakeman says. Instead, the quake occurred a little farther out, in a place where the fault is moving horizontally. This type of quake, called a strike-slip earthquake, is less likely to trigger large tsunamis, and this is probably why Alaska only saw waves of less than a foot, according to Blakeman.

When earthquakes happen on the subduction zone itself, where one plate is pushing down while the other is going up, then high waves form. “To get a tsunami, you have to have substantial vertical movement on the seabed,” Blakeman says. Those types of earthquakes were responsible for the massive tsunamis in Japan and Indonesia.

Aftershocks in Alaska could continue for weeks or months, Blakeman says. If the quakes generate from the same zone as last night, then large tsunamis should not be expected. But because the state sits by the Pacific-North America plate boundary, it’s normal that new earthquakes will happen in the future. When and where, exactly? That’s impossible to say. Earthquakes are so complicated that scientists aren’t able to predict them — at least not yet.

“Since we can’t predict them, all we can do is be prepared,” Blakeman says.

Today’s Storystream

Feed refreshed 31 minutes ago The tablet didn’t call that play by itself

M
The Verge
Mary Beth Griggs31 minutes ago
We’re about an hour away from a space crash.

At 7:14PM ET, a NASA spacecraft is going to smash into an asteroid! Coverage of the collision — called the Double Asteroid Redirection Test — is now live.


E
Twitter
Emma RothAn hour ago
There’s a surprise in the sky tonight.

Jupiter will be about 367 million miles away from Earth this evening. While that may seem like a long way, it’s the closest it’s been to our home planet since 1963.

During this time, Jupiter will be visible to the naked eye (but binoculars can help). You can check where and when you can get a glimpse of the gas giant from this website.


Asian America learns how to hit back

The desperate, confused, righteous campaign to stop Asian hate

Esther Wang12:00 PM UTC
E
Twitter
Emma Roth7:16 PM UTC
Missing classic Mario?

One fan, who goes by the name Metroid Mike 64 on Twitter, just built a full-on 2D Mario game inside Super Mario Maker 2 complete with 40 levels and eight worlds.

Looking at the gameplay shared on Twitter is enough to make me want to break out my SNES, or at least buy Super Mario Maker 2 so I can play this epic retro revamp.


R
External Link
Russell Brandom7:13 PM UTC
The US might still force TikTok into a data security deal with Oracle.

The New York Times says the White House is still working on TikTok’s Trump-era data security deal, which has been in a weird limbo for nearly two years now. The terms are basically the same: Oracle plays babysitter but the app doesn’t get banned. Maybe it will happen now, though?


R
Youtube
Richard Lawler6:54 PM UTC
Don’t miss this dive into Guillermo del Toro’s stop-motion Pinocchio flick.

Andrew Webster and Charles Pulliam-Moore covered Netflix’s Tudum reveals (yes, it’s going to keep using that brand name) over the weekend as the streamer showed off things that haven’t been canceled yet.

Beyond The Way of the Househusband season two news and timing information about two The Witcher projects, you should make time for this incredible behind-the-scenes video showing the process of making Pinocchio.


R
External Link
Russell Brandom4:29 PM UTC
Edward Snowden has been granted Russian citizenship.

The NSA whistleblower has been living in Russia for the 9 years — first as a refugee, then on a series of temporary residency permits. He applied for Russian citizenship in November 2020, but has said he won’t renounce his status as a U.S. citizen.


E
External Link
Emma Roth4:13 PM UTC
Netflix’s gaming bet gets even bigger.

Even though fewer than one percent of Netflix subscribers have tried its mobile games, Netflix just opened up another studio in Finland after acquiring the Helsinki-based Next Games earlier this year.

The former vice president of Zynga Games, Marko Lastikka, will serve as the studio director. His track record includes working on SimCity BuildIt for EA and FarmVille 3.


A
External Link
Andrew J. Hawkins3:37 PM UTC
Vietnam’s EV aspirant is giving big Potemkin village vibes

Idle equipment, absent workers, deserted villages, an empty swimming pool. VinFast is Vietnam’s answer to Tesla, with the goal of making 1 million EVs in the next 5-6 years to sell to customers US, Canada and Europe. With these lofty goals, the company invited a bunch of social media influencers, as well as some auto journalists, on a “a four-day, multicity extravaganza” that seemed more weird than convincing, according to Bloomberg.


J
James Vincent3:17 PM UTC
Today, 39 years ago, the world didn’t end.

And it’s thanks to one man: Stanislav Petrov, a USSR military officer who, on September 26th, 1983, took the decision not to launch a retaliatory nuclear attack against the US. Petrov correctly guessed that satellite readings showing inbound nukes were faulty, and so likely saved the world from nuclear war. As journalist Tom Chivers put it on Twitter, “Happy Stanislav Petrov Day to those who celebrate!” Read more about Petrov’s life here.


Soviet Colonel who prevented 1983 nuclear response
Photo by Scott Peterson/Getty Images
J
The Verge
James Vincent3:03 PM UTC
Deepfakes were made for Disney.

You might have seen the news this weekend that the voice of James Earl Jones is being cloned using AI so his performance as Darth Vader in Star Wars can live on forever.

Reading the story, it struck me how perfect deepfakes are for Disney — a company that profits from original characters, fans' nostalgia, and an uncanny ability to twist copyright law to its liking. And now, with deepfakes, Disney’s most iconic performances will live on forever, ensuring the magic never dies.


E
External Link
Elizabeth Lopatto2:41 PM UTC
Hurricane Fiona ratcheted up tensions about crypto bros in Puerto Rico.

“An official emergency has been declared, which means in the tax program, your physical presence time is suspended,” a crypto investor posted on TikTok. “So I am headed out of the island.” Perhaps predictably, locals are furious.


R
The Verge
Richard Lawler2:09 PM UTC
Teen hacking suspect linked to GTA 6 leak and Uber security breach charged in London.

City of London police tweeted Saturday that the teenager arrested on suspicion of hacking has been charged with “two counts of breach of bail conditions and two counts of computer misuse.”

They haven’t confirmed any connection with the GTA 6 leak or Uber hack, but the details line up with those incidents, as well as a suspect arrested this spring for the Lapsus$ breaches.