Location:

Period:

13 Oct 2006 05:21:02 - 13 Oct 2006 14:00:45 (8 hours 39 minutes)

Volcanoes in 100km radius:

Uratman(62km), Prevo Peak(62km), Zavaritzki Caldera(70km), Ketoi(74km), Milna(80km), Ushishur(87km), Srednii(95km)

Earthquakes:

M 7.0+:

M 8.3; 2006 Kuril Islands Earthquake; (15 Nov 2006) (36km from the swarm center)

10 swarms found nearby.

2003

PS20031231.1(105.3km)

30 Dec

1 day 20 hours

8 earthquakes

2005

PS20051024.1(84.0km)

23 Oct

16 hours

5 earthquakes

2006

PS20060930.1(32.0km)

30 Sep

19 hours

15 earthquakes

PS20061108.1(108.1km)

8 Nov

18 hours

7 earthquakes

PS20061115.1(172.4km)

15 Nov

2 days 17 hours

53 earthquakes

PS20061115.3(40.6km)

15 Nov

19 hours

11 earthquakes

PS20061120.1(94.2km)

19 Nov

1 day 1 hours

7 earthquakes

2007

PS20070113.2(136.4km)

13 Jan

7 hours

8 earthquakes

2008

PS20080303.1(29.3km)

3 Mar

6 hours

5 earthquakes

2012

PS20120714.1(155.7km)

13 Jul

20 hours

6 earthquakes

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Seismic Swarm Activity in the Kuril Islands: October 2006

The Kuril Islands form a volcanic island arc along the northwestern Pacific Ocean, marking the boundary where the Pacific Plate subducts beneath the Okhotsk Plate at rates of approximately 8–9 cm per year. This tectonic setting produces intense seismicity, with frequent earthquakes occurring at varying depths along the Wadati-Benioff zone. The region experiences both shallow crustal events and deeper intraslab earthquakes, contributing to its classification as one of the most active segments of the Pacific Ring of Fire.

On 13 October 2006, a seismic swarm designated PS20061013.1 was recorded in the Kuril Islands. The sequence began at 05:21 UTC and concluded by 14:00 UTC, encompassing five earthquakes over 8 hours and 39 minutes. Event parameters included a magnitude 5.0 earthquake at 28 km depth at 05:21:02, followed by a magnitude 5.9 event at 4 km depth at 13:47:39. Subsequent shocks registered magnitudes 5.1 (10 km depth), 5.0 (80 km depth), and 4.1 (10 km depth), concluding at 14:00:45. Such swarms represent clusters of seismicity without a dominant mainshock, often linked to fluid migration or stress redistribution within the subduction interface.

This activity aligns with the area's established pattern of episodic swarm occurrences. Since 1 January 2000, three swarms have been documented in the Kuril Islands, with prior episodes in 2003 and 2005. The October 2006 swarm preceded the magnitude 8.3 Kuril Islands earthquake of 15 November 2006 by roughly one month, with the mainshock epicenter located 36 km from the swarm centroid. The 2006 mainshock ruptured a substantial portion of the megathrust, highlighting the potential for swarm events to occur within broader seismic cycles.

Geological records indicate that the Kuril subduction zone has hosted multiple great earthquakes historically, driven by the accumulation and release of strain along the trench. Depths ranging from shallow (under 30 km) to intermediate (up to 80 km) in the swarm data reflect the complex geometry of the descending slab. These characteristics underscore the importance of continuous monitoring for understanding precursory patterns in subduction environments.

References

SeismoSight internal swarm classification data (PS20061013.1)
USGS Earthquake Catalog for Kuril Islands region (2000–2006 events)