7.5-magnitude “shaker” prompts tsunami warning from Aleutians to Kenai Peninsula

Screenshot from U.S. Tsunami Warning Center on Oct. 19, 2020 showing the areas under tsunami alert.

Residents of coastal Alaska, from Sand Point to Kodiak, scrambled for higher ground and motored boats into deeper water Monday afternoon after a magnitude 7.5 earthquake hit near Sand Point and triggered a tsunami warning. 

Large waves did not appear, but life in the communities was disrupted by the emergency. 

Residents from Unalaska to the Kenai Peninsula reported to the USGS that they’d felt the earthquake. The National Weather Service downgraded the warning to an advisory toward the end of the afternoon.

Raynelle Gardner, who works at the Sand Point School, said residents felt the violent shaking of the first quake. She hadn’t felt any aftershocks because she had been driving, but as she spoke on the phone, she watched the Alaska Earthquake Center website as it ticked off one that rippled through the area. 

In the first hour after the quake, the center reported ten aftershocks, including seven of magnitude 5 or greater. The largest was a magnitude 5.9 at 1:45 p.m.

The Sand Point School is the evacuation point for the eastern Aleutian fishing community of just under 1,000 people.

Austin Roof teaches there and is also general manager at the community’s radio station, KSDP-AM. 

“The community mostly evacuated to high ground, so it’s hard to tell if any tsunami came,” Roof said. “The last earthquake, there was a small, one-foot tsunami that did happen, so it would have been really hard to tell if that had happened from where we were.” 

The National Tsunami Warning Center reported that a small tsunami, measured at two feet, had reached Sand Point at 2:25 p.m., and a smaller wave in King Cove.  

Roof said this isn’t the first time they’ve been through the drill this year. 

“I guess from the last earthquake we’re all kind of ready for it,” he said. “So it is what it is.”

The “last earthquake” Roof is talking about was another major earthquake that struck near Sand Point on July 22. Today’s earthquake was about 50 miles southwest of that earthquake. According to Alaska’s Earthquake Center, Monday’s earthquake could be an aftershock of that quake. 

People look ouut towards the water from a parking lot on a bluff
Evacuees watch the boats evacuate from Kodiak harbors at Deadman’s Curve on Oct. 19, 2020. (Maggie Wall/KMXT)

The July earthquake damaged and closed both city docks in Sand Point. It damaged the road to the harbor as well. 

Just south of Sand Point, Cold Bay was also under a tsunami warning. Former mayor Candace Nielsen remembered the July earthquake all too well. She said Monday’s quake felt different. 

“The earthquake — it was pretty significant. My house was rattling pretty hard,” she said.  “It didn’t seem as roll-y as the last one. It was kind of more of a shaker then — the last time, it felt like we were on a wave. And this time, it was just kind of vibrating, roughly.”

Nielsen said Cold Bay’s tsunami warning sirens did not go off. 

She found out about tsunami warning through a King Cove Nixle alert on her phone and by monitoring the Tsunami Warning Center’s Facebook page. 

“We were surprised. But we’re happy to have one another and be together. And I think mostly just okay. We’ve been having aftershocks. We were all together during the last big earthquake. And so it’s kind of like, ‘okay, you know, here we go again. We’ve done that before.’”

State Seismologist Mike West said the two earthquakes are definitely related. And in this part of the world, it’s not surprising to get earthquakes — even of that large magnitude — relatively often. 

It’s one of the world’s major tectonic plate boundaries, where each year the Pacific Plate shoves a few inches under the North American plate that Alaska sits on. 

“We build up a whole lot of strain,” West said. “In some sense, yes, we anticipate, we are almost never surprised by a magnitude 7 earthquake — most anywhere along that boundary.” 

And while it’s not exactly routine, residents of coastal communities know what to do when they feel an earthquake. 

“We know to grab our important stuff and grab the dog and whatever and where to go,” said Kodiak resident Maggie Wall. “We’ve been through it. We’ve had a lot of practice runs.”

Wall said she felt the earthquake from her home about 12 miles outside of town. She works at the public radio station, KMXT.

As Kodiak’s new tsunami warning sirens blared all around her, Wall drove into town. 

“There were not very many people on the road,” she said. But, coming up to an area known as Dead Man’s Curve along the coastal highway she found a group of people who had been in the airport. 

Airport staff told them to evacuate, shooed them all out and locked the doors, Wall said. 

Further along that highway, she saw some boats evacuating as well, motoring out into deeper water — though the vast majority stayed in the harbor. 

Most people headed for higher ground near the town’s high school. When Wall got there, she said there were “lots of people milling around.”

The tsunami warning was downgraded to an advisory a few hours after it was issued. 

And it’s not the first time this year that’s happened. For the last few years, residents on the coast have felt the quake, gone running for the high ground and waited for a large, destructive wave that ultimately hasn’t appeared. 

That routine is something that State Seismologist Mike West worries about. 

“We’ve had four tsunami warnings in Alaska since 2018. And none of them happened to generate a deadly tsunami,” he said. 

He thinks Alaskans may be lulled into a false sense of security.  

“I would strongly caution people not to try and second guess and do their own education about whether or not maybe a large tsunami is coming. That’s what the warning means,” he said. “There really shouldn’t be any questions remaining when the warnings are issued.”

One other note about Monday’s quake is that it happened near an area that West said scientists had been speculating about for decades. 

“The plates are locked together and they’re pushing together. They build up a couple of inches, couple of inches and then eventually it ruptures in an earthquake,” West said. 

And that process of earthquakes relieving pressure happens all across the Aleutians and southern Alaska. It happens in patches along the plate boundary — on one end and then the other. Then maybe one in the middle. 

From the 1930s to the 1960s, through a series of huge earthquakes, West said almost the entirety of the Aleutians and southern Alaska ruptured and readjusted in one way or another — and there were a lot of destructive earthquakes that came out of that, including the 1964 earthquake. 

But while all of those earthquakes were happening, there were two places where they didn’t. One is near Yakutat, and the other was the Shumagin Islands, where Sand Point is located. 

West said they called it the “Shumagin Gap.” And scientists were essentially waiting for it to crack. 

And sure enough, the earthquake that happened in July ruptured that gap. It was the largest earthquake on the planet so far this year. 

West said a lot of the scientific community has been debating lately about that massive earthquake and the Shumagin Gap.  

“Well, did the whole gap rupture? Did just a little bit of it rupture? Maybe there’s still a little piece that hasn’t ruptured. It’s a tricky place,” he said. 

But West said he doesn’t think Monday’s earthquake fits neatly into the picture of the Shumagin Gap resettling. Most of the big earthquakes in this area happen as the tectonic plates grind past each other. But Monday’s earthquake didn’t happen along that boundary — rather, it happened inside the Pacific plate. It’s the same kind of conditions that created the 2018 earthquake that struck Anchorage. 

And West said a 7.5 earthquake is nothing to sneer at. 

“You know, these are massive earthquakes and we talk about them very casually,” he said. “It turns out in Alaska, the vast majority of our earthquakes happen far away from people, far away from significant infrastructure … so I do think we get lulled into this idea, ‘oh (a magnitude) 7.5 that’s probably not a big deal. That’s probably not a tsunami.’ I do think we dodge a bullet more often than most people just because of our expanse. ”

This is a breaking news story that has been updated.

Rashah McChesney, Ian Dickson of KTOO and Hope McKenney of KUCB contributed to this report.