Earthquake swarm SW of Adak Islands, Alaska
An earthquake swarm has been occurring southwest of Adak Islands, Alaska, since December 8, 2024, beginning with M6.3 at a depth of 18 km (11 miles). The swarm includes multiple significant earthquakes, including two M6.3 events, an M6.1, and numerous aftershocks up to M5.8.
Earthquakes SW of Adak Island, Alaska - December 8 - 9, 2024. Image credit: TW/SAM, Google
The swarm is located about 100 km (62 miles) SSW of Adak, Alaska, U.S., and 1 540 km (957 miles) ESE Klyuchi, Kamchatka, Russia.
The initial M6.3 quake was followed by 7 aftershocks with magnitudes from 3.8 to 5.8 and another M6.3 at 00:15 UTC in the same location. Several moderately strong aftershocks followed over the next 20 minutes before M6.1 at 00:38 UTC.
Moderately strong aftershocks are still being registered, with the latest being M5.1 at 05:56 UTC.
“This is not a typical mainshock-aftershock sequence; it is a swarm—a cluster of several earthquakes of about the same magnitude,” said Elisabeth Nadin of the Alaska Earthquake Center at the University of Alaska.
“Although today’s swarm includes several significant earthquakes, the chances that they are forerunners of something larger is statistically quite low,” said Michael West, Alaska Earthquake Center director and state seismologist.
“Swarms of moderately large earthquakes are common in the Aleutians and do not necessarily portend anything more substantial,” West said. “However, because this area has been in, or on the edge, of numerous large historical earthquakes, we are keeping close watch on it.”
The recent swarm of large earthquakes occurring at the subduction interface between the Pacific and North American plates is considered a fairly typical seismic event for this region. These earthquakes are taking place along the Aleutian subduction zone, where the Pacific plate is descending beneath the North American plate.
Seismological analysis of the larger earthquakes in the swarm reveals that all were caused by thrust motion along the subduction zone. This type of fault motion is characteristic of the convergent boundary dynamics between the two tectonic plates.
Earthquake swarms of this nature in the Aleutian subduction zone are relatively common, occurring on average every few years.
A similar swarm was recorded in May 2024, approximately 550 km (350 miles) to the east of the current events.
These swarms can result from uneven strain accumulation along specific sections of the subduction interface, leading to multiple smaller earthquakes rather than a single, large rupture. Typically, strain in subduction zones is released through a single major earthquake followed by numerous aftershocks.
References:
1 Earthquake swarm emerges southwest of Adak Island – UAF/Alaska Earthquake Center – December 8, 2024
2 M6.3 earthquake Andreanof Islands, Alaska – USGS – December 8, 2024
3 M6.3 earthquake Andreanof Islands, Alaska – EMSC – December 8, 2024
Teo Blašković founded The Watchers in 2011 and edited it until 2026, covering seismic and volcanic activity, extreme weather, space weather and near-Earth objects. Articles on this page are his archive.
