Location:

Period:

14 Jan 2020 16:51:44 - 16 Jan 2020 04:27:00 (1 day 11 hours 35 minutes)

Volcanoes in 100km radius:

Denison(4km), Steller(8km), Kukak(10km), Snowy Mountain(13km), Katmai(29km), Griggs(33km), Kaguyak(35km), Trident(39km), Novarupta(40km), Mageik(49km), Martin(56km), Fourpeaked(62km), Douglas(74km), Unnamed(80km)

Earthquakes:

10 swarms found nearby.

2002

S20020715.1(18.6km)

14 Jul

1 day 0 hours

27 earthquakes

2016

VS20161015.1(16.6km)

14 Oct

10 hours

26 earthquakes

2019

VS20190820.1(18.9km)

20 Aug

1 day 22 hours

61 earthquakes

2020

S20200126.1(23.3km)

25 Jan

3 days 12 hours

54 earthquakes

S20200223.2(10.1km)

23 Feb

1 day 0 hours

26 earthquakes

VS20200814.1(19.5km)

14 Aug

3 days 14 hours

68 earthquakes

2022

VS20220825.1(29.1km)

24 Aug

4 days 10 hours

146 earthquakes

2023

VS20230331.1(27.0km)

30 Mar

1 day 12 hours

25 earthquakes

2024

VS20240310.1(15.8km)

10 Mar

8 hours

24 earthquakes

S20241004.1(19.4km)

3 Oct

2 days 16 hours

46 earthquakes

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Seismic Swarm VS20200115.1: Analysis of Activity North of Karluk, Alaska

The seismic swarm designated VS20200115.1 occurred approximately 80 km north of Karluk on Kodiak Island, Alaska. Registered between 16:51 on 14 January 2020 and 04:27 on 16 January 2020, the sequence lasted 35 hours and 35 minutes and included 81 earthquakes. This event represents the fourth swarm documented in the region since 2000, following earlier episodes in 2002, 2016, and 2019.

Kodiak Island lies within the Aleutian subduction zone, where the Pacific Plate converges with and subducts beneath the North American Plate. Convergence rates average 6–7 cm per year, generating intense crustal stress and frequent seismicity. The swarm location aligns with the shallow forearc region north of the island, where fault systems accommodate both plate-boundary slip and local crustal deformation. Depths recorded during the swarm ranged primarily between 0 and 10 km, consistent with activity in the upper crust above the subducting slab.

Magnitudes remained low throughout the sequence, with the largest event reaching 2.4. Most events clustered between 0.0 and 1.7, and several registered negative magnitudes, indicating microseismicity. Temporal distribution showed the highest rate of events during the morning and early afternoon of 15 January, with a gradual decline thereafter. Depths exhibited modest variation, typically stabilizing between 4 and 7 km during peak activity.

Such swarms are characteristic of the Kodiak region and often reflect fluid migration or stress redistribution along pre-existing faults rather than immediate foreshock activity preceding a larger mainshock. Historical records confirm that previous swarms in 2002, 2016, and 2019 displayed similar patterns of numerous small-magnitude events over short durations. The 1964 Great Alaska Earthquake, which ruptured a portion of the subduction interface near Kodiak, remains the dominant historical benchmark, having produced widespread uplift and triggered long-term aftershock sequences across the island.

Ongoing monitoring by regional seismic networks continues to track background rates in this tectonically active zone. The VS20200115.1 swarm fits within the established pattern of episodic, low-magnitude clustering that does not necessarily signal an imminent large earthquake. Continued observation supports improved understanding of stress accumulation along the Aleutian megathrust and associated crustal structures.

References

SeismoSight internal swarm classification records
USGS Earthquake Catalog (general regional tectonics)
Alaska Earthquake Center historical summaries