Location:

Period:

4 Nov 2002 13:08:20 - 21 Nov 2002 12:16:11 (16 days 23 hours 7 minutes)

Volcanoes in 100km radius:

Buzzard Creek(67km)

Earthquakes:

418

14 swarms found nearby.

2002

S20021023.1(1.6km)

23 Oct

12 days 6 hours

727 earthquakes

S20021024.1(2.6km)

23 Oct

10 days 5 hours

183 earthquakes

S20021023.2(20.8km)

23 Oct

1 day 18 hours

37 earthquakes

S20021108.2(6.6km)

8 Nov

1 day 9 hours

133 earthquakes

S20021110.1(27.2km)

9 Nov

1 day 17 hours

53 earthquakes

S20021113.1(29.8km)

12 Nov

1 day 14 hours

71 earthquakes

S20021118.1(2.6km)

17 Nov

3 days 1 hours

69 earthquakes

S20021227.1(15.5km)

26 Dec

7 days 19 hours

98 earthquakes

2003

S20030107.1(27.7km)

6 Jan

4 days 21 hours

72 earthquakes

S20030307.1(11.9km)

6 Mar

26 days 8 hours

396 earthquakes

S20030403.1(23.4km)

2 Apr

23 days 4 hours

248 earthquakes

S20030602.2(29.5km)

1 Jun

11 days 13 hours

108 earthquakes

S20030714.1(27.1km)

13 Jul

20 days 18 hours

166 earthquakes

S20030807.1(23.4km)

7 Aug

6 days 18 hours

95 earthquakes

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Seismic Swarm S20021105.2: Geological Context and Event Analysis Near Cantwell, Alaska

Seismic swarm S20021105.2 occurred approximately 63 km east-northeast of Cantwell, Alaska, within the rugged terrain of the Alaska Range. The sequence began at 13:08 UTC on 4 November 2002 and concluded at 12:16 UTC on 21 November 2002, spanning 407 hours and registering 418 earthquakes. This activity unfolded in a region defined by intense tectonic deformation along the Denali Fault system, a major right-lateral strike-slip structure that accommodates part of the oblique convergence between the Pacific and North American plates.

The Alaska Range lies within the Pacific Ring of Fire, where ongoing subduction and transform faulting produce frequent seismicity. The Denali Fault, extending over 2,000 km, has hosted significant historical ruptures, including the magnitude 7.9 Denali earthquake of 3 November 2002, whose aftershock zone overlaps the swarm location. Crustal depths in the area typically range from 0 to 20 km, consistent with shallow brittle failure in the upper crust. Rock types include metamorphic complexes and sedimentary units deformed by Cenozoic orogenesis, with permafrost and glacial cover influencing surface wave propagation but not directly affecting hypocentral determinations.

Analysis of the first 100 events reveals a rapid onset of moderate-magnitude activity. The initial event measured magnitude 1.8 at 5 km depth, followed within minutes by a magnitude 2.0 shock at 2 km. Magnitudes peaked at 4.2 on 5 November at 7 km depth, accompanied by several events exceeding magnitude 3.0 within the first 24 hours. Depths clustered between 0 and 17 km, with a notable concentration in the 1–10 km range, indicating shallow crustal fracturing. Temporal distribution showed highest rates on 4–6 November, declining thereafter, characteristic of swarm behavior rather than a classic mainshock-aftershock sequence.

This swarm represents the earliest documented in the regional catalog since 2000, highlighting episodic unrest along the fault. Such sequences often reflect fluid migration or stress triggering in a structurally complex zone. Continued monitoring remains essential given the proximity to critical infrastructure and the fault's capacity for large-magnitude events.

References

USGS Earthquake Catalog
Alaska Earthquake Center Regional Reports
Denali Fault Tectonic Summaries (USGS)