Location:

Period:

24 Jan 2016 10:38:21 - 31 Jan 2016 11:36:11 (7 days 57 minutes)

Volcanoes in 100km radius:

Iliamna(19km), Redoubt(65km), Augustine(67km)

Earthquakes:

237

6 swarms found nearby.

2012

VS20120308.1(12.5km)

8 Mar

7 days 1 hours

152 earthquakes

2023

VS20230512.1(25.6km)

11 May

1 day 14 hours

29 earthquakes

VS20230605.1(18.6km)

5 Jun

1 day 19 hours

64 earthquakes

2024

VS20240224.1(20.8km)

23 Feb

23 hours

30 earthquakes

S20241201.1(23.2km)

30 Nov

3 days 6 hours

38 earthquakes

2025

VS20251205.1(19.5km)

5 Dec

2 days 15 hours

44 earthquakes

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Seismic Swarm S20160124.1: Analysis of Activity East of Pedro Bay, Alaska

Seismic swarm S20160124.1 occurred approximately 60 km east of Pedro Bay, Alaska, within a tectonically active segment of the Cook Inlet region. The swarm initiated at 10:38 on 24 January 2016 and concluded at 11:36 on 31 January 2016, spanning 168 hours and 57 minutes. During this interval, 237 earthquakes were recorded.

The first 100 events displayed consistent characteristics. Magnitudes ranged from 1.6 to 4.7, with the majority falling between 2.0 and 3.3. Depths clustered tightly around 100 km, varying from 93 km to 115 km. Notable events included a magnitude 4.7 earthquake at 14:29 on 24 January and a magnitude 4.3 event at 12:37 the same day. Early activity featured several magnitude 3+ shocks within the first two hours, followed by a gradual decline in frequency and intensity.

This swarm represents one of only two documented swarms in the region since 1 January 2000. The prior swarm occurred in 2012, highlighting the infrequent nature of such clustered seismicity east of Pedro Bay.

The broader geological setting lies along the eastern margin of the Aleutian subduction zone, where the Pacific plate descends beneath the North American plate. This convergence drives regional deformation and produces intermediate-depth earthquakes within the Wadati-Benioff zone. Depths near 100 km align with typical seismicity patterns in the subducting slab beneath the Alaska Peninsula and Cook Inlet area. Historical records indicate that the region experiences both volcanic and tectonic influences, with nearby features such as the Iliamna volcanic complex contributing to long-term crustal stress.

Analysis of the initial 100 events reveals no clear migration of hypocenters, suggesting a localized stress release within a stable depth horizon. The swarm's duration and event count provide insight into transient faulting processes at depth, distinct from typical mainshock-aftershock sequences.

Further monitoring of similar swarms could improve understanding of slab dynamics in this portion of the subduction zone.

References

SeismoSight internal swarm classification records
USGS Earthquake Catalog (historical swarm data since 2000)