Location:

Period:

18 Mar 2016 09:38:06 - 19 Mar 2016 01:35:12 (15 hours 57 minutes)

Volcanoes in 100km radius:

Atka Volcanic Complex(91km)

Earthquakes:

M 7.0+:

M 7.0; 101 km SW of Atka, Alaska; (30 Aug 2013) (80km from the swarm center)

27 swarms found nearby.

2008

S20080304.1(76.9km)

4 Mar

1 day 5 hours

42 earthquakes

S20081031.1(30.8km)

31 Oct

3 days 18 hours

94 earthquakes

PS20081031.1(22.3km)

31 Oct

1 day 9 hours

6 earthquakes

2010

S20101008.1(78.7km)

8 Oct

3 days 9 hours

184 earthquakes

2011

PS20110628.1(164.6km)

27 Jun

16 hours

7 earthquakes

2013

S20130830.1(74.1km)

30 Aug

3 days 13 hours

180 earthquakes

S20130830.2(65.2km)

30 Aug

1 day 22 hours

198 earthquakes

PS20130831.1(61.0km)

31 Aug

15 hours

5 earthquakes

PS20130904.2(34.8km)

4 Sep

1 day 7 hours

11 earthquakes

S20130905.1(28.3km)

4 Sep

6 days 6 hours

96 earthquakes

S20130904.1(67.2km)

4 Sep

1 day 10 hours

57 earthquakes

S20130906.1(29.2km)

5 Sep

2 days 8 hours

36 earthquakes

S20130914.2(46.0km)

14 Sep

3 days 10 hours

87 earthquakes

2014

S20140722.1(70.9km)

21 Jul

2 days 2 hours

39 earthquakes

2015

S20150904.1(58.4km)

4 Sep

1 day 9 hours

45 earthquakes

PS20150905.1(24.4km)

4 Sep

18 hours

5 earthquakes

S20150905.1(26.0km)

5 Sep

2 days 11 hours

103 earthquakes

PS20151102.1(55.3km)

2 Nov

15 minutes

5 earthquakes

2016

S20160312.2(19.0km)

12 Mar

2 days 4 hours

52 earthquakes

S20160319.1(22.1km)

18 Mar

3 days 15 hours

59 earthquakes

2019

S20191124.1(107.7km)

24 Nov

2 days 4 hours

84 earthquakes

2020

S20200214.1(73.9km)

13 Feb

1 day 6 hours

30 earthquakes

2021

S20210811.1(93.8km)

10 Aug

2 days 19 hours

224 earthquakes

2022

S20220708.1(92.3km)

8 Jul

2 days 10 hours

76 earthquakes

S20221029.1(32.2km)

28 Oct

2 days 4 hours

39 earthquakes

2024

S20241103.1(107.4km)

2 Nov

1 day 14 hours

52 earthquakes

2025

PS20250320.1(148.2km)

19 Mar

22 hours

5 earthquakes

AI-generated article — for informational and entertainment purposes only. May contain inaccuracies. Full disclaimerFound an error?

Seismic Swarm PS20160319.1: Analysis of Activity South of Atka, Alaska

The seismic swarm designated PS20160319.1 occurred 75 km south of Atka, Alaska, in the central Aleutian Islands. It began at 09:38 on 18 March 2016 and concluded at 01:35 on 19 March 2016, spanning 15 hours and 57 minutes. Five earthquakes were recorded during this interval, with magnitudes ranging from 2.5 to 6.0 and focal depths between 10 km and 50 km.

The sequence opened with two closely spaced events on 18 March at 09:38:06 (M 5.1 at 10 km depth) and 09:38:12 (M 5.0 at 50 km depth). Activity resumed early on 19 March with an M 5.0 event at 01:22:16 (10 km depth), followed by an M 2.5 shock at 01:26:55 (10 km depth) and a culminating M 6.0 earthquake at 01:35:12 (17 km depth). These events illustrate typical swarm characteristics, featuring clustered moderate-magnitude shaking without a single dominant mainshock.

The Aleutian arc lies within the Pacific Ring of Fire at the convergent boundary where the Pacific Plate subducts northwestward beneath the North American Plate at rates of approximately 6–7 cm per year. This tectonic setting produces frequent earthquakes and active volcanism, including nearby Atka and Korovin volcanoes. Atka Island itself sits on the overriding plate, where crustal stresses from subduction generate both shallow crustal and intermediate-depth seismicity.

Historical records maintained by SeismoSight indicate 20 swarms in the region since 1 January 2000. These occurred in the following years and counts: 2008 (3), 2010 (1), 2011 (1), 2013 (8), 2014 (1), 2015 (4), and 2016 (2). The 2013 swarm count was the highest in the period, coinciding with elevated regional strain. A notable M 7.0 earthquake struck on 30 August 2013 approximately 101 km southwest of Atka and 80 km from the PS20160319.1 swarm center, underscoring the persistent seismic hazard along this segment of the arc.

Such swarms contribute to ongoing monitoring efforts that help distinguish background seismicity from potential precursors to larger events or volcanic unrest. Depths in the 10–50 km range align with both the megathrust interface and overlying crustal faults characteristic of the central Aleutians.

USGS Earthquake Catalog
Alaska Earthquake Center regional reports
SeismoSight internal swarm classification database