An Alaska Earthquake Center map of all the earthquakes that happened in the year 2020, including the epicenter of a magnitude 6.1 earthquake that happened May 30, 2021. (Courtesy Image / Ned Rozell)

Alaska Science Forum: Alaska earthquake stirs many

The beat goes on.

By Ned Rozell

I just so happened to be stretched out on good ol’ Mother Earth the other night when an earthquake happened.

On a Memorial Day overnight canoe trip, a friend and I had dragged our boats onto the gravel of a little island on the Chena River.

After mosquitoes chased us into our tents and we’d all fallen asleep, my dog and I woke to the sound of splashes. A moose strolled by upriver, right past the tent. A few moments later, the ground swayed as if we were strung in a hammock.

During that earthen wave, I looked outside through the screen and saw a young willow, skinny as a whip and belt high. It quivered, the local expression of an underground release 400 miles away from our island and 25 miles beneath the ground surface.

That spot, just east of Talkeetna, was the epicenter of a magnitude 6.1 earthquake felt over much of Alaska.

On the Alaska Earthquake Center’s website, someone reported feeling the shake in Circle on the Yukon River, 270 miles away from Talkeetna. People also mentioned feeling the earthquake in Kotzebue, 530 miles away, as well as Unalaska Island, 900 miles away.

Though it was the highlight of my weekend, earthquakes happen all the time in Alaska. Technicians at the earthquake center, using devices buried all over the state, record an earthquake about every 15 minutes. In one recent year, they detected 54,000 earthquakes. That’s about 150 per day.

A moose walks past a tent in the upper Chena River near Fairbanks as Cora the dog watches. (Courtesy Photo / Ned Rozell)

A moose walks past a tent in the upper Chena River near Fairbanks as Cora the dog watches. (Courtesy Photo / Ned Rozell)

Why so many?

Many of Alaska’s earthquakes are the result of immense sheets of our planet grinding past one another, in fits and starts.

The Pacific Plate is the underwater landmass that includes the seafloor of the entire Pacific Ocean. Due to the oozing of molten rock within the center of the planet, that colossus creeps at the speed fingernails grow toward mainland Alaska, which sits on what seismologists call the North American Plate.

Beneath the southern coast of Alaska, the dense oceanic rocks of the Pacific Plate plunge beneath the lighter rocks of the North American Plate.

Giant earthquakes can happen at this plate boundary if the masses release their stuttering grip somewhat close to the ground surface. An example of this was the magnitude 9.2 earthquake epicentered in Prince William Sound in 1964. The rupture happened just 15 miles beneath the ocean floor.

The motion of the Pacific Plate has molded the face of Alaska, giving rise to mountains as well as pulling apart river valleys. As plate motion kneads the landmass of this giant peninsula, sometimes sutures across Alaska’s skin help relieve the stress.

One of these slices in the state is the Denali Fault, the trace of which is visible from satellite within a frown of Alaska Range mountains in the center of the state. Within that arc is a trench, often filled with glacier ice, where many earthquakes happen. Part of the Denali Fault slipped in 2002 to rattle us with a 7.9 earthquake.

Of the 6.1 earthquake many Alaskans felt the other night, State Seismologist Mike West said it was “not a surprise in the least.” But it was interesting enough to him that he wrote a detailed report on it, concluding that “like most earthquakes, there is something to learn here if we are willing to pay attention.”

• Since the late 1970s, the University of Alaska Fairbanks’ Geophysical Institute has provided this column free in cooperation with the UAF research community. Ned Rozell ned.rozell@alaska.edu is a science writer for the Geophysical Institute.

More in News

It's a police car until you look closely and see the details don't quite match. (Juneau Empire File / Michael Penn)
Police calls for Friday, June 18, 2021

This report contains public information from law enforcement and public safety agencies.

A former Juneau chiropractor who was indicted for multiple sexual assault charges in April was charged with more assaults in early June. (Michael S. Lockett / Juneau Empire)
Former chiropractor faces additional sexual assault charges

The former Juneau resident was indicted for five more felony charges early in June.

Interior Secretary Deb Haaland appears before the Senate Appropriations Committee, at the Capitol in Washington, Wednesday, June 16, 2021. (AP Photo/J. Scott Applewhite)
Senators press Interior Secretary Haaland on oil lease pause

Murkowski said she was flabbergasted that Haaland did not address the court ruling.

I have flies with barbell eyes, jig heads, cone heads, bead heads and no heads. I have flies with stinger hooks that trail and long-shanked salmon hooks that don’t. I have red, pink, salmon, fuchsia, cerise, purple, orange, flesh, green, olive, chartreuse, white and black flies made of feathers, chenille, hackle, marabou, flashabou and silicone. (Jeff Lund / For the Juneau Empire)
I Went to the Woods: One good fish

Three is the magic number.

This undated electron microscope image made available by the U.S. National Institutes of Health in February 2020 shows the Novel Coronavirus SARS-CoV-2, yellow, emerging from the surface of cells, blue/pink, cultured in the lab. Also known as 2019-nCoV, the virus causes COVID-19. THE CANADIAN PRESS/AP, NIAID-RML
COVID at a glance for Wednesday, June 16

The most recent state and local figures.

In this July 13, 2007, file photo, workers with the Pebble Mine project test drill in the Bristol Bay region of Alaska, near the village of Iliamma. (AP Photo / Al Grillo)
Appeals court panel orders review of EPA decision in Alaska

Review concerns decision to withdraw proposed restrictions on large-scale mining near Bristol Bay.

A recently released map by the National Telecommunications and Information Administration shows the vast areas of low data speeds and access by broadband users across Alaska and the rest of the U.S. (Screenshot)
White House laying groundwork for improved internet infrastructure

In Alaska, providers are looking at their own improvments to access.

Louisiana Attorney General Jeff Landry speaks in front of the U.S. Supreme Court in Washington. The Biden administration’s suspension of new oil and gas leases on federal land and water was blocked Tuesday, June 15, 2021, by a federal judge in Louisiana. U.S. District Judge Terry Doughty’s ruling came in a lawsuit filed in March by Louisiana’s Republican attorney general, Jeff Landry and officials in 12 other states. Doughty’s ruling granting a preliminary injunction to those states said his order applies nationwide. (AP Photo / Manuel Balce Ceneta, File)
Federal judge blocks Biden’s pause on new oil, gas leases

The decision is a blow to Biden’s efforts to rapidly transition the nation away from fossil fuels.

It's a police car until you look closely and see the details don't quite match. (Juneau Empire File / Michael Penn)
Police calls for Wednesday, June 16, 2021

This report contains public information from law enforcement and public safety agencies.

Most Read