Location:

Period:

24 Dec 2002 09:28:08 - 30 Dec 2002 00:40:18 (5 days 15 hours 12 minutes)

Volcanoes in 100km radius:

Buzzard Creek(60km)

Earthquakes:

113

14 swarms found nearby.

2002

S20021023.2(14.2km)

23 Oct

1 day 18 hours

37 earthquakes

S20021103.1(28.6km)

2 Nov

123 days 19 hours

7093 earthquakes

S20021104.2(21.4km)

3 Nov

19 days 3 hours

621 earthquakes

S20021108.1(25.4km)

7 Nov

1 day 2 hours

42 earthquakes

S20021110.1(5.8km)

9 Nov

1 day 17 hours

53 earthquakes

S20021113.1(18.6km)

12 Nov

1 day 14 hours

71 earthquakes

S20021126.1(28.7km)

25 Nov

1 day 2 hours

30 earthquakes

S20021227.1(17.8km)

26 Dec

7 days 19 hours

98 earthquakes

2003

S20030107.1(17.1km)

6 Jan

4 days 21 hours

72 earthquakes

S20030307.1(22.0km)

6 Mar

26 days 8 hours

396 earthquakes

S20030403.1(20.1km)

2 Apr

23 days 4 hours

248 earthquakes

S20030602.2(13.5km)

1 Jun

11 days 13 hours

108 earthquakes

S20030714.1(16.0km)

13 Jul

20 days 18 hours

166 earthquakes

S20030807.1(11.8km)

7 Aug

6 days 18 hours

95 earthquakes

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Seismic Swarm S20021225.1: Analysis of Activity East of Cantwell, Alaska

Seismic swarm S20021225.1 was recorded 60 km east of Cantwell, Alaska, beginning at 09:28 on 24 December 2002 and concluding at 00:40 on 30 December 2002. Over 135 hours and 12 minutes, 113 earthquakes were detected. Analysis of the first 100 events reveals predominantly low-magnitude activity consistent with swarm behavior rather than a mainshock-aftershock sequence.

Event magnitudes ranged from 0.7 to 2.6, with the majority below 1.5. Depths were shallow, concentrated between 0 and 17 km, indicating activity within the upper crust. Temporal distribution showed clustering in the initial 48 hours, followed by a gradual decline, with sporadic bursts on 26–28 December. Notable events included a 2.6 magnitude shock at 10:49 on 24 December (depth 8 km) and a 2.5 magnitude event at 15:41 the same day (depth 2 km). Later peaks featured magnitudes of 2.2 and 2.4 on 28 December.

This swarm represents the earliest recorded since 2000 in the region, with six additional swarms occurring afterward through the present. Such sequences highlight episodic, non-destructive seismicity typical of the area.

Regional Geological Context

Cantwell lies within the central Alaska Range, where the Denali Fault system dominates the tectonic framework. The fault accommodates right-lateral strike-slip motion driven by oblique convergence between the Pacific and North American plates. The Pacific Plate subducts along the Aleutian megathrust to the south, transferring stress northward and producing distributed crustal deformation across central Alaska.

Crustal structure in the vicinity includes Paleozoic to Mesozoic sedimentary and volcanic rocks accreted during terrane assembly, intruded by younger granitic bodies. Quaternary glaciation has sculpted the landscape, leaving thick surficial deposits that can influence local ground motion. Seismicity here reflects both far-field plate-boundary forces and local fault interactions along splays of the Denali system.

Historical Seismicity

Instrumental records document frequent small-magnitude events along the Denali Fault. The 3 November 2002 Denali Fault earthquake (Mw 7.9) occurred approximately one month prior, rupturing segments east of the swarm location and triggering widespread aftershocks. Post-2002 monitoring by regional networks has improved detection of low-magnitude swarms, underscoring the fault’s capacity for clustered activity without large mainshocks.

References

Alaska Earthquake Center, University of Alaska Fairbanks
U.S. Geological Survey Earthquake Hazards Program
Denali Fault System tectonic summaries, USGS Professional Papers