Location:

Period:

11 Aug 2010 08:16:38 - 13 Aug 2010 06:42:54 (1 day 22 hours 26 minutes)

Volcanoes in 100km radius:

Tana(60km), Vsevidof(66km), Kagamil(67km), Cleveland(70km), Recheschnoi(73km), Uliaga(77km), Herbert(78km), Carlisle(80km)

Earthquakes:

8 swarms found nearby.

2006

S20060510.1(24.4km)

10 May

3 days 7 hours

56 earthquakes

2007

PS20071227.1(54.7km)

26 Dec

17 hours

7 earthquakes

2010

S20100718.1(20.1km)

17 Jul

56 days 16 hours

2676 earthquakes

S20100719.1(4.0km)

18 Jul

17 days 10 hours

390 earthquakes

S20100815.1(6.4km)

14 Aug

1 day 7 hours

34 earthquakes

2015

PS20150727.1(40.3km)

27 Jul

3 hours

8 earthquakes

2017

S20170810.1(20.6km)

9 Aug

2 days 7 hours

32 earthquakes

2022

PS20220111.1(65.6km)

11 Jan

3 hours

8 earthquakes

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Seismic Swarm S20100812.1: Analysis of Earthquake Activity Near Nikolski, Alaska

Seismic swarm S20100812.1 occurred approximately 31 km south-southwest of Nikolski, Alaska, in the central Aleutian Islands. The sequence began at 08:16 on 11 August 2010 and concluded at 06:42 on 13 August 2010, spanning 46 hours and 26 minutes. During this period, 41 earthquakes were recorded, with magnitudes ranging from 1.6 to 2.8 and focal depths predominantly between 0 and 13 km.

The swarm exhibited typical characteristics of clustered seismic activity, featuring a rapid onset followed by sustained low-to-moderate magnitude events without a single dominant mainshock. Initial events on 11 August included magnitudes of 1.8 at 3 km depth and 2.0 at 1 km depth, progressing to a peak magnitude of 2.7 at 4 km depth later that evening. Activity continued into 12 August with events such as a 2.8 magnitude quake at 6 km depth and several shallower occurrences near 0–2 km. The sequence tapered off on 13 August with final events of 2.1 and 2.6 magnitude at depths of 6 km and 7 km, respectively.

This swarm took place within the tectonically active Aleutian subduction zone, where the Pacific Plate converges with and subducts beneath the North American Plate at rates of approximately 6–7 cm per year. The central Aleutians, including the region around Umnak Island near Nikolski, experience frequent seismicity due to this oblique subduction, which generates both interplate thrust events and intraslab earthquakes. Shallow depths observed in the swarm align with crustal deformation above the plate interface.

Historically, the Nikolski area has recorded multiple seismic swarms since 2000, totaling four documented episodes. Prior swarms occurred in 2006 (one event cluster) and 2007 (one event cluster), with two additional swarms in 2010. These episodes reflect episodic stress release along the subduction margin, often associated with fluid migration or localized fault activation rather than large-scale rupture.

The Aleutian Islands form part of the Pacific Ring of Fire, characterized by active volcanism and high seismicity. Nikolski lies near Umnak Island, home to stratovolcanoes such as Mount Vsevidof and Mount Recheshnoi. Regional geology includes accreted terranes and volcanic arcs shaped by millions of years of subduction, contributing to the observed earthquake patterns.

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

This analysis underscores the importance of continuous monitoring in subduction environments to better understand swarm dynamics and their relation to broader tectonic processes.