Location:

Period:

31 Jan 2025 07:08:35 - 4 Apr 2025 17:07:19 (63 days 9 hours 58 minutes)

Volcanoes in 100km radius:

Spurr(14km), Hayes(52km), Redoubt(80km)

Earthquakes:

1115

15 swarms found nearby.

2021

S20210614.1(24.3km)

14 Jun

2 hours

37 earthquakes

2022

VS20221203.1(18.4km)

2 Dec

1 day 16 hours

40 earthquakes

2024

VS20240220.1(11.5km)

19 Feb

1 day 7 hours

27 earthquakes

S20240303.1(19.0km)

2 Mar

4 days 4 hours

89 earthquakes

VS20240308.1(11.5km)

7 Mar

4 days 5 hours

48 earthquakes

VS20240426.1(15.6km)

25 Apr

3 days 17 hours

68 earthquakes

VS20240519.1(11.6km)

18 May

3 days 19 hours

80 earthquakes

VS20241008.1(16.1km)

7 Oct

4 days 19 hours

110 earthquakes

VS20241028.1(14.8km)

27 Oct

2 days 13 hours

56 earthquakes

VS20241102.1(17.2km)

1 Nov

3 days 22 hours

85 earthquakes

VS20241123.1(18.0km)

22 Nov

2 days 17 hours

49 earthquakes

VS20241130.1(5.0km)

30 Nov

53 days 4 hours

1155 earthquakes

2025

VS20250507.1(13.6km)

6 May

25 days 14 hours

387 earthquakes

S20250630.1(19.5km)

29 Jun

7 days 9 hours

78 earthquakes

VS20250717.1(19.4km)

16 Jul

9 days 3 hours

170 earthquakes

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Seismic Swarm VS20250201.1: Analysis of Activity Near Tyonek, Alaska

Earthquake swarm VS20250201.1 was recorded in the Cook Inlet region of south-central Alaska, centered approximately 64 km west-northwest of Tyonek. The sequence began at 07:08 UTC on 31 January 2025 and concluded at 17:07 UTC on 4 April 2025, spanning 1521 hours and 58 minutes. During this interval, 1115 earthquakes were detected.

Analysis of the first 100 events reveals predominantly low-magnitude seismicity. Magnitudes ranged from -1.5 to 1.4, with the majority falling between -1.2 and 0.5. Depths were mostly shallow, concentrated between 0 and 6 km, although isolated events reached 22 km, 25 km, and one deeper event at 118 km. The initial event registered magnitude -0.6 at 3 km depth, followed by rapid succession of similar micro-earthquakes. Activity showed clustering in time, with multiple events occurring within minutes on several occasions during late January and early February 2025.

This swarm occurred within the tectonically active margin where the Pacific plate subducts beneath the North American plate along the Aleutian megathrust. The Cook Inlet basin lies above this convergent boundary, resulting in frequent crustal and intraslab seismicity. Regional geology features a complex assemblage of accreted terranes, sedimentary basins, and Quaternary volcanic centers. Historical records indicate elevated swarm activity in recent years, with 12 documented swarms since 2000. These include single swarms in both 2021 and 2022, followed by ten swarms in 2024 alone.

Such swarms are characteristic of the region and may reflect fluid migration, stress redistribution along faults, or minor volcanic influences associated with the nearby arc volcanoes. Magnitudes remained well below levels that produce felt shaking or damage at the surface. Continued monitoring by regional seismic networks supports improved understanding of swarm recurrence and their relationship to larger tectonic events.

References

Alaska Earthquake Center, University of Alaska Fairbanks
U.S. Geological Survey Earthquake Hazards Program
SeismoSight internal swarm classification records