Location:

Period:

15 Apr 2008 23:31:18 - 19 Apr 2008 05:57:08 (3 days 6 hours 25 minutes)

Volcanoes in 100km radius:

Gareloi(9km), Tanaga(51km), Takawangha(60km), Bobrof(99km)

Earthquakes:

12 swarms found nearby.

2006

PS20060708.1(66.0km)

8 Jul

9 hours

10 earthquakes

PS20060826.1(61.1km)

26 Aug

47 minutes

6 earthquakes

2007

PS20071219.1(70.9km)

19 Dec

19 hours

12 earthquakes

2008

S20080301.2(24.4km)

1 Mar

3 days 4 hours

82 earthquakes

S20080416.1(8.5km)

15 Apr

8 days 6 hours

286 earthquakes

2013

S20130121.1(29.7km)

21 Jan

3 days 11 hours

62 earthquakes

2017

S20170501.2(21.5km)

30 Apr

23 days 10 hours

1627 earthquakes

S20170508.1(30.0km)

7 May

3 days 10 hours

165 earthquakes

S20170508.2(19.0km)

8 May

3 days 22 hours

59 earthquakes

S20170527.1(28.9km)

26 May

18 days 7 hours

298 earthquakes

2020

PS20200126.1(96.9km)

26 Jan

18 hours

8 earthquakes

2026

S20260617.2(10.1km)

16 Jun

1 day 5 hours

26 earthquakes

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

Seismic Swarm VS20080416.1: Analysis of Activity West of Adak, Alaska

Seismic swarm VS20080416.1 occurred approximately 142 km west of Adak in the Aleutian Islands, Alaska. The sequence began at 23:31 UTC on 15 April 2008 and concluded at 05:57 UTC on 19 April 2008, spanning 78 hours and 25 minutes. During this interval, 89 earthquakes were recorded, with magnitudes ranging from 1.8 to 4.5 and focal depths predominantly between 0 and 12 km.

The swarm exhibited typical characteristics of clustered seismic activity in a subduction setting. Initial events on 15 April included magnitudes of 3.3, 2.7, and a peak of 4.2 at shallow depths of 2–9 km. Activity intensified overnight, with notable events such as a 4.5 magnitude quake at 01:18 on 16 April and a 4.3 at 01:23, both at depths under 6 km. Subsequent days featured recurring events around 2.0–3.3 magnitude, including a 4.0 on 16 April at 08:46 and a 4.4 on 17 April at 07:13 (depth 24 km). The sequence tapered with smaller events through 19 April.

This pattern reflects fluid migration or stress transfer along faults within the overriding plate or near the subduction interface. Depths remained largely crustal, consistent with volcanic-arc seismicity rather than deeper intraslab events.

The Aleutian Islands form part of the Pacific Ring of Fire, where the Pacific Plate converges with the North American Plate at rates of approximately 6–7 cm per year. This oblique subduction generates the Aleutian Arc, a chain of active volcanoes and frequent earthquakes. The region west of Adak lies near the Andreanof Islands segment, known for both swarm activity and larger megathrust events.

Historically, the area has recorded multiple seismic swarms since 2000, with five documented episodes. These occurred in 2006 (two swarms), 2007 (one swarm), and 2008 (two swarms, including VS20080416.1). Such swarms often precede or accompany volcanic unrest but do not always culminate in larger mainshocks.

Seismic monitoring in the Aleutians relies on networks operated by the Alaska Earthquake Center and the U.S. Geological Survey. Data from these sources confirm the high background seismicity, with thousands of events annually across the arc.

References

Alaska Earthquake Center catalog records
U.S. Geological Survey earthquake data archive
SeismoSight internal swarm classification database