Location:

Period:

8 Jul 2006 20:48:44 - 10 Jul 2006 13:08:49 (1 day 16 hours 20 minutes)

Volcanoes in 100km radius:

Gareloi(99km)

Earthquakes:

9 swarms found nearby.

2005

PS20050614.1(94.6km)

14 Jun

14 hours

7 earthquakes

2006

S20060701.1(12.2km)

1 Jul

2 days 22 hours

170 earthquakes

PS20060708.1(24.6km)

8 Jul

9 hours

10 earthquakes

S20060708.1(19.6km)

8 Jul

3 days 22 hours

178 earthquakes

PS20060826.1(47.7km)

26 Aug

47 minutes

6 earthquakes

S20060827.1(25.4km)

26 Aug

3 days 5 hours

48 earthquakes

2007

PS20071219.1(19.5km)

19 Dec

19 hours

12 earthquakes

S20071219.2(27.6km)

19 Dec

4 days 17 hours

64 earthquakes

2020

PS20200126.1(54.9km)

26 Jan

18 hours

8 earthquakes

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Seismic Swarm S20060709.1 Near Adak, Alaska

A seismic swarm designated S20060709.1 was recorded approximately 206 km west-southwest of Adak, Alaska, in the Andreanof Islands region of the Aleutian arc. The sequence began at 20:48 UTC on 8 July 2006 and concluded at 13:08 UTC on 10 July 2006, spanning 40 hours and 20 minutes. During this period, 30 earthquakes were registered, with magnitudes ranging from 1.6 to 4.8 and focal depths between 0 and 35 km.

The swarm featured two events of magnitude 4.8, occurring at 20:48 on 8 July at 35 km depth and at 23:00 on the same day at 5 km depth. Subsequent activity included multiple events above magnitude 3.0, such as a 3.9 at 23:11 and a 3.8 at 23:11 and 01:13 the following day. Shallower events clustered around 4–7 km depth, while deeper shocks reached up to 35 km. The sequence exhibited typical swarm characteristics, with no single dominant mainshock but rather a rapid succession of comparable events distributed over two days.

The Andreanof Islands lie within the Aleutian subduction zone, where the Pacific plate converges with the North American plate at rates of approximately 6–7 cm per year. This tectonic setting produces frequent seismic activity, including both shallow crustal earthquakes and deeper events along the Wadati-Benioff zone. The region has a well-documented history of large-magnitude earthquakes, with several events exceeding magnitude 8.0 recorded in the 20th century, reflecting the high strain accumulation along the megathrust interface.

Historical swarm activity in the broader area since 2000 includes four documented swarms. One occurred in 2005, while three took place in 2006, indicating episodic clustering of seismicity that is common in subduction environments. Such swarms may arise from fluid migration, stress triggering, or aseismic slip processes, though specific causative mechanisms require detailed waveform analysis beyond basic catalog parameters.

The 2006 swarm contributed to ongoing monitoring of background seismicity levels in the central Aleutians, where earthquake rates remain elevated relative to global averages due to plate-boundary dynamics. Depths spanning crustal to upper-mantle levels align with expected patterns for the subducting slab geometry beneath the island arc.

References
USGS Earthquake Catalog (earthquake.usgs.gov)
Alaska Earthquake Information Center, University of Alaska Fairbanks
Global CMT Catalog for regional focal mechanisms
NOAA National Centers for Environmental Information tsunami and seismic archives