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Location:
93 km W of Adak, Alaska
Period:
17 Nov 2022 18:45:39 - 25 Nov 2022 18:27:00 (7 days 23 hours 41 minutes)
Volcanoes in 100km radius:
Takawangha(4km), Tanaga(13km), Bobrof(35km), Kanaga(53km), Gareloi(58km), Moffett(82km)
Earthquakes:
341
12 swarms found nearby.
2008
S20080502.1(27.9km)
2 May
19 days 15 hours
1079 earthquakes
2 May
10 days 5 hours
184 earthquakes
2017
23 Jan
2 days 23 hours
126 earthquakes
2020
22 Jan
10 days 13 hours
627 earthquakes
2021
23 Feb
1 day 16 hours
34 earthquakes
2022
13 Nov
1 day 7 hours
42 earthquakes
12 Dec
10 days 11 hours
186 earthquakes
2023
10 Feb
2 days 6 hours
71 earthquakes
17 Feb
6 days 13 hours
309 earthquakes
28 Feb
1 day 15 hours
114 earthquakes
4 Mar
57 days 17 hours
4231 earthquakes
22 Jun
4 days 21 hours
90 earthquakes
AI-generated article — for informational and entertainment purposes only. May contain inaccuracies. Full disclaimerFound an error?

Seismic Swarm VS20221118.1: Analysis of Activity West of Adak, Alaska

Seismic swarm VS20221118.1 was recorded 93 km west of Adak, Alaska, in the central Aleutian Islands. The sequence began at 18:45 UTC on 17 November 2022 and concluded at 18:27 UTC on 25 November 2022, spanning 191 hours and 41 minutes. During this interval, 341 earthquakes were registered.

Analysis of the first 100 events reveals predominantly low-magnitude activity. Magnitudes ranged from 0.3 to 4.1, with the majority below 2.0. The largest event reached magnitude 4.1 at a depth of 9 km on 19 November 2022 at 09:42 UTC. Depths were consistently shallow, typically between 0 km and 12 km, indicating activity within the upper crust. A notable cluster occurred on 18 November between 16:51 and 17:21 UTC, featuring events up to magnitude 3.2. Subsequent elevated activity on 19 November included multiple events above magnitude 2.0 within a short time window.

This swarm aligns with the established pattern of episodic seismicity in the region. Since 1 January 2000, six prior swarms have been documented in the same area: two in 2008, and one each in 2017, 2020, 2021, and 2022.

The location lies within the Aleutian subduction zone, where the Pacific plate converges with and subducts beneath the North American plate. Convergence rates average 6–7 cm per year, generating frequent earthquakes along the megathrust interface and within the overriding plate. The central Aleutians host both tectonic and volcanic seismicity, with Adak situated near the Andreanof Islands segment. Historical large events in the broader region include the 1957 magnitude 8.6 Andreanof Islands earthquake and the 1965 magnitude 8.7 Rat Islands earthquake, underscoring the zone’s capacity for great earthquakes. Shallow swarm activity such as VS20221118.1 may reflect stress transfer along local faults or fluid migration associated with nearby volcanic systems.

The swarm’s short duration and modest magnitudes suggest a localized release of accumulated strain rather than a precursor to a major rupture. Continued monitoring remains essential given the Aleutian arc’s overall high seismic hazard.

References SeismoSight internal swarm classification VS20221118.1 USGS Earthquake Catalog (regional tectonic framework) Alaska Earthquake Center (Aleutian arc seismicity summaries)