Magnitude 6.5 Earthquake Rattles Alaska's Aleutian Islands

A powerful magnitude 6.5 earthquake struck off Alaska's remote Aleutian Islands early Thursday. The tremor occurred roughly 103 miles west of Nikolski at a depth of 69 miles. Officials confirmed there is no tsunami threat, and no major damage or casualties were reported. Here's what officials have reported so far.

Magnitude 6.5 earthquake struck off Aleutian Islands

Deep-Focus Earthquake Strikes Near Nikolski

A strong magnitude 6.5 earthquake struck off Alaska's isolated Aleutian Islands early Thursday morning, the U.S. Geological Survey (USGS) reported.

Read more: Earthquake Magnitude Scale

The epicenter was located roughly 103 miles west of Nikolski, a small community on Umnak Island.

The quake was relatively deep, occurring about 69 miles below the surface.

Shortly after the earthquake, the National Tsunami Warning Center issued an assessment stating that an earthquake had occurred but that a tsunami was not expected.

Early estimates were slightly different. The center initially measured the event at magnitude 6.3 and placed it about 45 miles northeast of Amukta Pass. 

As additional seismic data became available, the USGS revised the earthquake's magnitude and location, ultimately listing it as magnitude 6.5 at a depth of about 69 miles.

The USGS PAGER system assigned the event a green alert, indicating a very low estimated likelihood of significant casualties or economic losses.

No major damage or deaths had been reported in the immediate aftermath.

Data from the U.S. Census Bureau shows around 8,700 residents live scattered across the broader Aleutian territory.

By Thursday afternoon, the USGS "Did You Feel It?" platform logged just six user reports from Atka, Unalaska, and Adak. 

These locations sit 144 to 245 miles from the epicenter, with residents describing signs of this earthquake is only faint vibrations. 

Stay prepared with live severe weather alerts, wind conditions for Unalaska!

Initial assessments from the National Tsunami Warning Center pegged the quake at magnitude 6.3, located 45 miles northeast of Amukta Pass. 

Officials noted those early figures were subject to revision. The USGS later finalized the parameters at magnitude 6.5 with a 69-mile depth. 

A strong magnitude 6.5 earthquake hit near Alaska’s Chagulak Island on Thursday (Source: KTUU)

Earthquake Follows Recent Nikolski Seismic Activity

Thursday's earthquake occurred after a period of heightened seismic activity near Nikolski.

On Sept. 3, a magnitude 6.3 earthquake struck about 57 miles south of Nikolski at a much shallower depth of roughly six miles, according to the Alaska Earthquake Center.

That earlier earthquake was followed by numerous smaller tremors.

Scientists described the sequence as the "Nikolski Swarm," reflecting the concentration of earthquakes around the area.

Thursday's event was different in both location and depth.

It occurred farther west and nearly 69 miles beneath the Earth's surface, making it considerably deeper than the Sept. 3 earthquake.

(Related: What causes an earthquake?)

Why Alaska Experiences Frequent Earthquakes

The Aleutian Islands form part of one of the world's most active seismic zones. 

Along the Aleutian Arc, the Pacific Plate moves beneath the North American Plate in a process known as subduction. 

This constant movement creates intense geological stress and produces frequent earthquakes across Alaska.

According to the Alaska Earthquake Center, Alaska experiences thousands of earthquakes each year, ranging from small tremors to powerful events capable of causing widespread damage and tsunamis.

Alaska’s notable seismic events in 2025 (Source: Alaska Earthquake Center)

The region has recorded some of the largest earthquakes in U.S. history. 

A magnitude 8.6 earthquake struck the Andreanof Islands in 1957, while a magnitude 8.7 earthquake hit near the Rat Islands in 1965.

Alaska also has a long history of earthquake-generated tsunamis. 

The magnitude 9.2 Great Alaska Earthquake in 1964 produced destructive tsunami waves and other ground effects that killed 122 people. 

In 1958, an earthquake-triggered rockslide at Lituya Bay generated a wave reaching about 1,720 feet, killing five people.

Thursday's magnitude 6.5 earthquake was much weaker than these historic events, and authorities reported no tsunami threat. 

Still, the latest tremor highlights the persistent seismic activity along Alaska's Aleutian Arc.

References

1. FOX Weather

2. USA Today

3. NTD News