Earthquake swarm with ‘significant’ quakes rocks Alaska’s Aleutian Islands

Seismologists are monitoring an earthquake swarm that is continuing to develop off Alaska‘s Aleutian Island chain and includes several stronger quakes.

According to the U.S. Geological Survey (USGS), the first magnitude 6.3 earthquake occurred just before 11 a.m. local time on Sunday in the Pacific Ocean about 70 miles southwest of Adak, Alaska, at a depth of about 11 miles. Within the hour, at least six aftershocks with magnitudes no greater than 5.8 were recorded. 

Then, a few hours later, two more significant quakes of magnitude 6 or greater struck within 20 minutes of each other. According to the University of Alaska Fairbanks Alaska Earthquake Center, this is not a typical aftershock sequence following a main earthquake but a swarm, or a cluster of earthquakes near the same magnitude.

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“Swarms of moderately large earthquakes are common in the Aleutians and do not necessarily portend anything more substantial,” Alaska Earthquake Center Director and State Seismologist Michael West said. “Because this area has been in, or on the edge, of numerous large historical earthquakes, we are keeping close watch on it.”

This map by the Alaska Earthquake Center shows earthquakes recorded between Dec. 4 and Dec. 8, 2024, including the swarm southwest of Adak Island on Dec. 8 in red.

(Alaska Earthquake Center)

The earthquake center said because of the “unusually high number” of moderately-sized earthquakes, its seismologists continue to keep an eye on the region. More aftershocks of magnitudes 5 and below are forecast to continue in the weeks ahead. 

On Monday, the USGS recorded several more quakes off the coast of Adak.

No Tsunami Watches or Warnings were issued because of the earthquakes over the weekend. 

The Aleutian Islands are where the Pacific Plate subducts into the mantle beneath the North American Plate. This region is considered seismically active, with thousands of earthquakes each year.