Tag Archives: earthquake

Varying Frost

Map by AlaskaWx

I found this map fascinating. There is almost a month differential across the Fairbanks Borough on the date of the first freeze this fall. I was in the August 18 Camp, which my zucchini never really recovered from.

Many of the recording areas with “After Sept 14”, will fall today, the 15th, as we are expected to drop into the Blue Zone by morning. My place was at 23F on Tuesday morning.

Officially, the Fairbanks Airport is on a decent streak of 135 days above freezing. Which is the fourth longest since recording began. 144 days is the record, which happened in 1974.

There was a 4.9 magnitude earthquake just east of Fairbanks on Monday night, just before 10pm. The cabin went through a decent shake.


Atka Volcanic Complex

Earthquake activity on Atka Island

The southern portion of Atka Island is older than the north, with some volcanic rock dating back 5 million years. The active northern part of the island once had one large cone, which was lost in a large eruption, and is now peppered with several smaller volcanos.

A volcanic complex can have several vents, and a widely varying composition of lava. Seismic activity within a complex can be difficult to pinpoint the source of the activity. Which vent is rumbling now? Some of those smaller vents have developed into stratovolcanoes.

Korovin Volcano has been very active in recent times, while Mount Kliuchef last erupted in 1812. The Atka Complex recently was elevated to a Level Yellow, due to seismic activity on the island. Interestingly, the swarm of activity is not near the known suspects, but several kilometers the the west and southwest, and approximately 10 miles from the community of Atka.

Source: AVO


Shaking in Chignik

The 8.2 magnitude earthquake and the 140 aftershocks

At around 10:30 on Wednesday night, the alarm bells went off, and people across Alaska’s southern coast made a bee-line for higher ground. An 8.2 magnitude earthquake struck the interface between the subducting Pacific and overriding North American plates. This interface is known as the Aleutian Megathrust,and it is a very active seismic region. In fact, a 7.6 magnitude earthquake hit the area almost a year ago exactly.

Wave action

A tsunami warning was immediately issued for coastal communities, but luckily incoming waves never reached heights over a 1/4 meter, and the warning was lifted a little over two hours later.

This was the first 8.0+ earthquake to hit the United States in 50 years. In the 12 hours after the initial quake, the area received 140 aftershocks, with the largest being a 6.1. In 1938, the same area experienced an 8.3 magnitude shaker.

NWS Priority Warnings Chart

Interestingly, Tsunami Warning is Priority #1 on the National Weather Service priority list. One would hope that Nuclear Power Plant Meltdown is higher on a different agency’s list.


The Good Friday Earthquake

Aerial view of Anchorage’s Park Strip the day after the 9.2 quake; Photo from the University of Alaska Archives

Saturday, March 27 was the 57th Anniversary of the 1964 Good Friday Earthquake that hit south-central Alaska. The 9.2 magnitude earthquake struck at 5:36 pm AST, and the earth shook for the next 4 minutes and 28 seconds. Witnesses say that the earth roared like a freight train for that entire time.

The epicenter was 78 miles from Anchorage in Prince William Sound. It was a relatively shallow quake, with a depth of roughly 15 miles. 131 people were killed due to the earthquake, with 122 of the deaths due to the resulting tsunamis.

Downtown Anchorage after the 1964 earthquake; Photo from the University of Alaska Archives

Seward, Kodiak, Valdez, Chenega, were all hit by tsunamis. Shoup Bay was hit by the largest tsunami with a wave height of 220 feet.

In the first 24 hours after the main shaker, there were 11 aftershocks over 6.0, with another nine over the following three weeks. Thousands of aftershocks hit the area over the next year.


Alaska Jökulhlaup

A large glacial dam gave way in Southeast Alaska this summer. Known by its Icelandic term: jökulhlaup, the power of this sudden release of pent up water can be incredibly destructive.

The terminus of Lituya Glacier; Photo credit: NPS/J. Capra

Desolation Lake, which sits above the Lituya Glacier in Desolation Valley, collects meltwater from both the Desolation and Fairweather Glaciers. That meltwater is normally blocked by the Lituya Glacier, forming the roughly four square mile lake.

The water level suddenly dropped 200 feet.

A commercial fisherman, Jim Moore, along with his two grandsons, tried to enter Lituya Bay to fish for Chinooks in August. They should have been riding the tide into the bay, but the unusually muddy water was moving outward, and it was filled with trees and other debris. The bay was also filled with small icebergs. Moore managed to bring some of the ancient ice onboard for his coolers, then left the bay, instead of fighting the dangerous current.

Lituya Glacier terminus and delta; Satellite image credit: USGS

It is one of the largest jökulhlaups known to have occurred in Alaska. The water found a path under the Lituya Glacier, causing a rush that would have rivaled the hourly discharge of the Amazon River. It would have lasted for several days.*

Lituya Bay has a history. In 1958, an earthquake triggered a landslide that started one of the largest known tsunamis at over 1700 feet.

*NPS Geologist, Michael Loso


Whole Lotta Shakin’

The Alaska Earthquake Center reported 50,289 earthquakes in the state of Alaska for 2019. That did not break the record that was set in 2018, but it’s enough for the year to come in second place.

In the video above, each frame is a day, in a time-lapse of 2019 earthquakes. Pretty amazing to see it in this form. Kudos to AEC.


Denali Fault Quake

Photo credit: Daily News-Miner

This week is the 17 year anniversary of the 2002 Denali Earthquake. At a magnitude of 7.9, to date, it is the largest quake I have personally experienced.

On 23 October 2002, the Denali Fault released a magnitude 6.7 quake. That would be a foreshock of what was to come on November 3.

Highway Shift; Richardson Highway, circa 2002

After the 6.7, I remember the Alaska Earthquake Center saying that the Denali Fault was capable of producing an 8.0. Sure enough, the fault came very close.

I was at an intersection in my ’66 Chevy C-20. All of a sudden, the truck was lurching all over the place, and I found it hard to stay on the brake pedal. There were two university students in the next lane, the passenger rolled down his window and asked what the hell was happening. I said, “Earthquake”. He then promptly hit the driver on the arm and said, “I told you it was an earthquake”.

The light changed, I drove on, but had to stop at the next light. The earth was still shaking. An elderly couple had been walking on the sidewalk, and the wife fell to the concrete, the husband was struggling to stay upright by hugging a signpost. Then the shaking was over. I rolled down the other window, to see if the couple was all right. They were, and I headed home to see if there was any damage.

The quake had ruptured 205 miles of earth along three different, yet connected faults in Interior Alaska. It was the largest ever recorded in Alaska’s Interior. It was the largest inland quake North America had seen in almost 150 years.

Both the Parks & Richardson Highways saw major damage. The Trans-Alaska Pipeline moved sideways 18 feet, and rose 5 feet. The engineers had designed for the fault, and the pipeline behaved exactly as it was designed to behave. Although, it did come within two feet of its sideways movement limit.

The Denali Earthquake was felt as far away as Louisiana.

Previously, the largest earthquake Fairbanks had experienced was a magnitude 7.3 in 1937.


Cabin Life

Spent some more time out at the lake last week. I did do some work to the place, but mainly wanted to get out and enjoy some autumn solitude.

It was quiet out there, rarely did I see more than one other boat on the water, and we seemed to do a little dance where we kept the same distance between ourselves, as we fished various areas of the lake.

I did experience my first earthquake out there. It’s an interesting feeling as the wave flows through the cabin. The quake was centered down in the Willow area, so I’m a bit surprised I felt one from that distance, but after checking their website, the Alaska Earthquake Center had it rated at a 5.2.

No fox were to be seen on this week, but there were swans. One night, I ventured out to the end of the dock past dusk. Two white blobs were visible, and with the binoculars, I could clearly see that they were trumpeter swans. One swan had its head buried under a wing, but the other was at full alert, with head held high. The lookout was not looking in my direction, but I knew it was fully aware of my presence just the same. A further inspection brought two more swans into view.

By morning, I had 13 trumpeters just past the reeds from the dock. I watched them for much of the morning. None of them seemed to be too worried about me. When they paddled off, if a boat cut across the lake, they came back to where I was sitting.

Not a bad way to spend an autumn week.

A foggy morning


55 Years Ago: Great Alaska Earthquake

Yesterday, March 27, was the anniversary of the Great Alaska Earthquake. The 9.2 magnitude quake, also known as the Good Friday Earthquake, is still the largest earthquake to hit North America, and the second largest to ever be recorded.

“We ran out of the building, and hung onto the wire mesh fence across the street. The road looked like waves in the ocean. All of the air police trucks looked like they were dancing as they were bouncing up and down.” — Airman stationed at Elmendorf AFB, Anchorage

The 1964 Earthquake and the resulting tsunamis took at least 139 lives. The earth shook for 4 minutes and 38 seconds from the main quake alone. Girdwood and Portage sank eight feet; portions of Kodiak rose over thirty feet. Seward burned; Valdez, Whittier and Chenega were destroyed, wiped off the face of the earth by the giant waves. A 75 ton locomotive was carried 300 feet by the waves in Seward, as 14 oil tankers and 40 railcars went up in flames. The tsunami that hit the WWII port of Whittier was 40′ high.


Alaska Railroad tracks near Turnagain Arm, south of Anchorage; March 28, 1964; Photo credit: USGS


2018 Earthquake Review


Alaska: 2018 Seismicity; Color coded by depth, Notable events labeled

The Alaska Earthquake Center at the University of Alaska – Fairbanks, has done their annual year in review for 2018. We set a record for earthquakes within the state, with over 55,000 events during 2018. That blows past the previous record of 42,989 set in 2017. The next highest number occurred in 2014 with 40,686 quakes. We had so many earthquakes in 2018 that AEC is still counting to get a specific number.

It needs to be noted, that much of the increase in numbers is due to advancing detection techniques, as well as additional recording stations. The purpose of this post, is not to imply that Alaska is about to break off from the Yukon, but to show how seismically active Alaska is.

The two largest earthquakes have set off thousands of aftershocks. The 7.9 magnitude quake in the Gulf of Alaska was the largest, followed by the now rated 7.1 near Anchorage in November.

We also had a couple of “swarms” in the northern part of the state, in the Brooks Range & on the North Slope, that lasted for months, and accounted for over 17,000 events.

The surprise earthquake of the year, happened near Kaktovik, on Alaska’s north coast. The 6.4 mainshock and 6.0 aftershock, were by far the largest ever recorded north of the Brooks Range.

On Saturday, March 9, a sudden jolt went through the cabin as I worked about the place, while listening to Minnesota hockey swarm the Michigan Wolverines. Sure enough, a 3.7 magnitude quake had occurred roughly 15-20 miles from the cabin.

A very special thanks to the Alaska Earthquake Center for the above graph and earthquake information.