Location:

Period:

4 Sep 2013 02:32:30 - 5 Sep 2013 10:09:26 (1 day 7 hours 36 minutes)

Volcanoes in 100km radius:

Koniuji(89km), Atka Volcanic Complex(98km), Kasatochi(99km)

Earthquakes:

M 7.0+:

M 7.0; 101 km SW of Atka, Alaska; (30 Aug 2013) (45km from the swarm center)

30 swarms found nearby.

2008

S20080304.1(95.2km)

4 Mar

1 day 5 hours

42 earthquakes

VS20080806.1(92.7km)

5 Aug

15 days 10 hours

1433 earthquakes

S20081031.1(37.0km)

31 Oct

3 days 18 hours

94 earthquakes

PS20081031.1(13.5km)

31 Oct

1 day 9 hours

6 earthquakes

2010

S20100903.1(89.2km)

3 Sep

3 days 1 hours

49 earthquakes

S20101008.1(45.9km)

8 Oct

3 days 9 hours

184 earthquakes

2011

PS20110628.1(198.9km)

27 Jun

16 hours

7 earthquakes

2013

S20130830.1(41.7km)

30 Aug

3 days 13 hours

180 earthquakes

S20130830.2(37.0km)

30 Aug

1 day 22 hours

198 earthquakes

PS20130831.1(26.2km)

31 Aug

15 hours

5 earthquakes

S20130905.1(16.1km)

4 Sep

6 days 6 hours

96 earthquakes

S20130904.1(34.1km)

4 Sep

1 day 10 hours

57 earthquakes

S20130906.1(37.9km)

5 Sep

2 days 8 hours

36 earthquakes

S20130914.2(11.4km)

14 Sep

3 days 10 hours

87 earthquakes

2014

S20140722.1(41.8km)

21 Jul

2 days 2 hours

39 earthquakes

2015

S20150904.1(27.8km)

4 Sep

1 day 9 hours

45 earthquakes

PS20150905.1(19.8km)

4 Sep

18 hours

5 earthquakes

S20150905.1(16.6km)

5 Sep

2 days 11 hours

103 earthquakes

PS20151102.1(90.0km)

2 Nov

15 minutes

5 earthquakes

2016

S20160312.2(43.0km)

12 Mar

2 days 4 hours

52 earthquakes

S20160319.1(25.7km)

18 Mar

3 days 15 hours

59 earthquakes

PS20160319.1(34.8km)

18 Mar

15 hours

5 earthquakes

2017

PS20170509.1(172.7km)

8 May

17 hours

5 earthquakes

2019

S20191124.1(73.2km)

24 Nov

2 days 4 hours

84 earthquakes

2020

S20200214.1(45.3km)

13 Feb

1 day 6 hours

30 earthquakes

2021

S20210811.1(100.2km)

10 Aug

2 days 19 hours

224 earthquakes

2022

S20220708.1(79.9km)

8 Jul

2 days 10 hours

76 earthquakes

S20221029.1(36.5km)

28 Oct

2 days 4 hours

39 earthquakes

2024

S20241103.1(72.6km)

2 Nov

1 day 14 hours

52 earthquakes

2025

PS20250320.1(114.6km)

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: PS20130904.2 Near Atka, Alaska

A seismic swarm designated PS20130904.2 occurred 91 km south-southwest of Atka, Alaska, beginning at 02:32 on 4 September 2013 and concluding at 10:09 on 5 September 2013. Over the 31-hour-and-36-minute period, 11 earthquakes were recorded. The sequence unfolded within the tectonically active Aleutian subduction zone, where the Pacific Plate converges with and subducts beneath the North American Plate at rates of approximately 6–7 cm per year. This interaction generates frequent seismic events and volcanic activity throughout the Aleutian Islands.

The largest event reached magnitude 6.5 at a depth of 20 km on 4 September 2013 at 02:32:30. Subsequent shocks included a magnitude 5.8 at 26 km depth (04:16:30), a magnitude 5.2 at 11 km (05:15:52), a magnitude 2.2 at 29 km (06:07:55), a magnitude 5.7 at 21 km (06:16:49), a magnitude 6.0 at 17 km (06:27:03), a magnitude 5.2 at 30 km (06:54:15), a magnitude 5.0 at 10 km (18:57:25), a magnitude 5.6 at 20 km (05:43:39 on 5 September), a magnitude 5.0 at 25 km (09:34:22), and a magnitude 5.1 at 25 km (10:09:26). Depths ranged from 10 to 30 km, consistent with intermediate-depth seismicity along the subducting slab.

This swarm followed closely after a magnitude 7.0 earthquake on 30 August 2013 located 101 km southwest of Atka, approximately 45 km from the swarm centroid. Regional historical records since 1 January 2000 document 10 prior swarms, occurring in 2008 (four events), 2010 (two events), 2011 (one event), and 2013 (three events). Such episodic clustering reflects stress redistribution along the megathrust and associated crustal faults in the central Aleutians.

Atka Island itself lies within a chain of volcanic islands built atop the subduction-related magmatic arc. The local geology features andesitic stratovolcanoes and fault systems that accommodate both convergence and lateral shear. Earthquake swarms in this setting often precede or accompany volcanic unrest, although no immediate eruptive activity was linked to the 2013 sequence.

USGS Earthquake Catalog
Alaska Earthquake Center regional bulletins
Tectonic summaries of the Aleutian subduction zone (USGS Professional Papers)