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Location:
97 km W of Adak, Alaska
Period:
22 Jun 2023 11:19:43 - 27 Jun 2023 09:02:51 (4 days 21 hours 43 minutes)
Volcanoes in 100km radius:
Takawangha(3km), Tanaga(8km), Bobrof(42km), Gareloi(52km), Kanaga(60km), Moffett(89km)
Earthquakes:
90
15 swarms found nearby.
2006
PS20060708.1(110.4km)
8 Jul
9 hours
10 earthquakes
PS20060826.1(114.8km)
26 Aug
47 minutes
6 earthquakes
2007
PS20071219.1(114.5km)
19 Dec
19 hours
12 earthquakes
2008
S20080502.3(13.4km)
2 May
10 days 5 hours
184 earthquakes
2017
23 Jan
2 days 23 hours
126 earthquakes
2018
S20180927.1(27.6km)
27 Sep
1 day 9 hours
40 earthquakes
2020
S20200122.2(16.3km)
22 Jan
10 days 13 hours
627 earthquakes
2021
S20210224.2(14.4km)
23 Feb
1 day 16 hours
34 earthquakes
2022
13 Nov
1 day 7 hours
42 earthquakes
17 Nov
7 days 23 hours
341 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
AI-generated article — for informational and entertainment purposes only. May contain inaccuracies. Full disclaimerFound an error?

Seismic Swarm VS20230623.1: Analysis of Activity West of Adak, Alaska

A seismic swarm designated VS20230623.1 occurred 97 km west of Adak, Alaska, from 11:19 UTC on 22 June 2023 to 09:02 UTC on 27 June 2023. Over 117 hours and 43 minutes, 90 earthquakes were recorded. This event aligns with the intense tectonic activity characteristic of the Aleutian Islands region.

The Aleutian arc forms part of the Pacific Ring of Fire, where the Pacific Plate subducts beneath the North American Plate at rates of approximately 6–7 cm per year. This subduction drives frequent earthquakes and volcanic eruptions along the arc. Adak lies near the Andreanof Islands segment, an area with a long history of moderate to large seismic events, including the magnitude 8.6 earthquake of 1957. Shallow crustal seismicity is common due to stresses within the overriding plate and along the plate interface.

The swarm exhibited predominantly low-magnitude events, with the largest reaching magnitude 2.5 at a depth of 7 km. Most events clustered at shallow depths of 0–7 km, consistent with upper-crustal fracturing in this subduction setting. Temporal distribution showed peak activity on 23 June, including several magnitude 2.0 events. Negative depth values in the dataset likely reflect near-surface or very shallow sources typical of swarm sequences in volcanic or tectonically active zones.

Historical records indicate 15 swarms in the region since 2000, with notable clusters in 2006 (2 swarms), 2022 (3 swarms), and 2023 (4 swarms). These swarms reflect episodic stress release along the subduction zone rather than foreshock sequences preceding a major rupture. Such patterns are well-documented in the Aleutians, where fluid migration or aseismic slip can trigger swarm behavior without leading to larger mainshocks.

This swarm provides further evidence of ongoing microseismicity in a highly active margin. Continued monitoring supports improved understanding of subduction dynamics and seismic hazard assessment for nearby communities.

References
USGS Earthquake Catalog (earthquake.usgs.gov)
Alaska Earthquake Center (earthquake.alaska.edu)
SeismoSight internal swarm classification VS20230623.1