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Location:
87 km S of Atka, Alaska
Period:
31 Oct 2008 14:23:02 - 1 Nov 2008 23:33:49 (1 day 9 hours 10 minutes)
Volcanoes in 100km radius:
Atka Volcanic Complex(98km), Koniuji(98km)
Earthquakes:
6
M 7.0+:
M 7.0; 101 km SW of Atka, Alaska; (30 Aug 2013) (59km from the swarm center)
30 swarms found nearby.
2008
S20080304.1(90.5km)
4 Mar
1 day 5 hours
42 earthquakes
VS20080806.1(103.9km)
5 Aug
15 days 10 hours
1433 earthquakes
S20081031.1(26.8km)
31 Oct
3 days 18 hours
94 earthquakes
2010
S20100903.1(102.6km)
3 Sep
3 days 1 hours
49 earthquakes
S20101008.1(56.6km)
8 Oct
3 days 9 hours
184 earthquakes
2011
PS20110628.1(186.9km)
27 Jun
16 hours
7 earthquakes
2013
S20130830.1(52.0km)
30 Aug
3 days 13 hours
180 earthquakes
S20130830.2(44.2km)
30 Aug
1 day 22 hours
198 earthquakes
PS20130831.1(39.5km)
31 Aug
15 hours
5 earthquakes
PS20130904.2(13.5km)
4 Sep
1 day 7 hours
11 earthquakes
4 Sep
6 days 6 hours
96 earthquakes
S20130904.1(44.9km)
4 Sep
1 day 10 hours
57 earthquakes
S20130906.1(27.1km)
5 Sep
2 days 8 hours
36 earthquakes
S20130914.2(24.8km)
14 Sep
3 days 10 hours
87 earthquakes
2014
S20140722.1(49.7km)
21 Jul
2 days 2 hours
39 earthquakes
2015
S20150904.1(36.5km)
4 Sep
1 day 9 hours
45 earthquakes
4 Sep
18 hours
5 earthquakes
5 Sep
2 days 11 hours
103 earthquakes
PS20151102.1(77.4km)
2 Nov
15 minutes
5 earthquakes
2016
S20160312.2(29.7km)
12 Mar
2 days 4 hours
52 earthquakes
S20160319.1(14.2km)
18 Mar
3 days 15 hours
59 earthquakes
PS20160319.1(22.3km)
18 Mar
15 hours
5 earthquakes
2017
PS20170509.1(184.3km)
8 May
17 hours
5 earthquakes
2019
S20191124.1(85.5km)
24 Nov
2 days 4 hours
84 earthquakes
2020
S20200214.1(52.9km)
13 Feb
1 day 6 hours
30 earthquakes
2021
S20210811.1(100.3km)
10 Aug
2 days 19 hours
224 earthquakes
2022
S20220708.1(86.8km)
8 Jul
2 days 10 hours
76 earthquakes
S20221029.1(27.0km)
28 Oct
2 days 4 hours
39 earthquakes
2024
S20241103.1(85.5km)
2 Nov
1 day 14 hours
52 earthquakes
2025
PS20250320.1(126.0km)
19 Mar
22 hours
5 earthquakes
AI-generated article — for informational and entertainment purposes only. May contain inaccuracies. Full disclaimerFound an error?

Seismic Swarm Analysis: Atka, Alaska Region (October-November 2008)

A seismic swarm designated PS20081031.1 occurred 87 km south of Atka, Alaska, from 14:23 on 31 October 2008 to 23:33 on 1 November 2008. The sequence lasted 33 hours and 10 minutes and comprised six earthquakes, with magnitudes ranging from 4.5 to 5.3 and focal depths between 36 km and 46 km.

The events unfolded as follows: a magnitude 5.1 shock at 14:23:02 on 31 October at 46 km depth; a magnitude 5.3 event at 22:10:35 on 31 October at 44 km depth; a magnitude 4.5 earthquake at 23:05:07 on 31 October at 39 km depth, immediately followed by a magnitude 5.1 shock at 23:05:15 at 40 km depth; a magnitude 5.2 event at 23:26:39 on 31 October at 37 km depth; and a final magnitude 5.0 earthquake at 23:33:49 on 1 November at 36 km depth.

This swarm represents the first of three documented swarms in the region since 1 January 2000. The area lies within the Aleutian subduction zone, where the Pacific Plate converges with the North American Plate at rates of approximately 6–7 cm per year. This tectonic setting produces frequent intermediate-depth seismicity along the Wadati-Benioff zone, consistent with the observed focal depths of 36–46 km.

The broader Aleutian arc has a long history of both swarm activity and larger mainshock-aftershock sequences driven by subduction processes. A notable subsequent event was the magnitude 7.0 earthquake on 30 August 2013, located 101 km southwest of Atka and approximately 59 km from the 2008 swarm center. Such events underscore the persistent seismic hazard in this segment of the arc.

Seismic swarms in subduction environments like this one often reflect fluid migration or stress transfer along the plate interface rather than a single mainshock. Continued monitoring by regional networks helps refine understanding of these patterns and their relation to volcanic systems on nearby islands.

References

USGS Earthquake Catalog (earthquake.usgs.gov)
Alaska Earthquake Center (www.aeic.alaska.edu)
Global CMT Catalog (www.globalcmt.org)