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Location:
87 km SW of Delta Junction, Alaska
Period:
22 Feb 2003 11:34:09 - 24 Feb 2003 01:43:01 (1 day 14 hours 8 minutes)
Volcanoes in 100km radius:
Buzzard Creek(88km)
Earthquakes:
31
25 swarms found nearby.
2002
2 Nov
123 days 19 hours
7093 earthquakes
S20021104.2(11.4km)
3 Nov
19 days 3 hours
621 earthquakes
7 Nov
1 day 2 hours
42 earthquakes
10 Nov
1 day 16 hours
49 earthquakes
S20021113.1(27.3km)
12 Nov
1 day 14 hours
71 earthquakes
S20021124.1(16.8km)
23 Nov
16 days 18 hours
425 earthquakes
24 Nov
3 days 20 hours
81 earthquakes
25 Nov
1 day 2 hours
30 earthquakes
30 Nov
6 days 3 hours
158 earthquakes
6 Dec
20 days 21 hours
548 earthquakes
10 Dec
4 days 4 hours
122 earthquakes
18 Dec
1 day 16 hours
36 earthquakes
20 Dec
3 days 6 hours
135 earthquakes
28 Dec
9 days 5 hours
191 earthquakes
2003
1 Jan
2 days 1 hours
49 earthquakes
S20030107.1(29.1km)
6 Jan
4 days 21 hours
72 earthquakes
11 Jan
2 days 21 hours
45 earthquakes
2 Feb
3 days 0 hours
42 earthquakes
15 Mar
1 day 20 hours
37 earthquakes
S20030602.2(27.3km)
1 Jun
11 days 13 hours
108 earthquakes
S20030714.1(29.6km)
13 Jul
20 days 18 hours
166 earthquakes
9 Sep
2 days 8 hours
35 earthquakes
S20031210.1(13.8km)
9 Dec
10 days 20 hours
147 earthquakes
2004
S20040129.1(20.7km)
28 Jan
3 days 8 hours
47 earthquakes
2006
S20061005.1(10.9km)
4 Oct
16 hours
26 earthquakes
AI-generated article — for informational and entertainment purposes only. May contain inaccuracies. Full disclaimerFound an error?

Seismic Swarm Analysis: February 2003 Event Southwest of Delta Junction, Alaska

A seismic swarm occurred 87 km southwest of Delta Junction, Alaska, between 11:34 UTC on 22 February 2003 and 01:43 UTC on 24 February 2003. Over 38 hours and 8 minutes, 31 earthquakes were recorded, with magnitudes ranging from 0.9 to 2.3 and focal depths between 0 and 9 km. All events remained small, consistent with swarm behavior lacking a dominant mainshock.

The swarm location lies within central Alaska’s tectonically active interior, where ongoing Pacific Plate subduction beneath the North American Plate generates diffuse seismicity. This region also experiences strike-slip motion along the Denali Fault system, a major right-lateral structure that extends across the Alaska Range. Shallow focal depths observed during the swarm align with crustal deformation typical of the area, where brittle failure occurs in the upper 10–15 km of the crust.

Central Alaska has a well-documented history of seismic swarms. Since 1 January 2000, 18 swarms have been identified in the broader region, with notable activity in 2002 (14 swarms) and 2003 (4 swarms). The 2002 Denali Fault earthquake (magnitude 7.9) occurred months earlier and likely influenced regional stress conditions, potentially contributing to subsequent swarm activity through afterslip or fluid migration along fault networks.

Event timing showed clustering on 22–23 February, with the largest shock (magnitude 2.3) occurring at 10:25 UTC on 23 February at 1 km depth. Subsequent events decreased in frequency, culminating in a final magnitude 1.9 shock at 01:43 UTC on 24 February. Depths remained consistently shallow, suggesting activity concentrated within the upper crust rather than deeper subduction-related sources.

Such swarms are common in Alaska’s interior and typically reflect minor stress adjustments along secondary faults rather than precursors to larger events. The 2003 swarm’s modest energy release and lack of felt reports or damage are characteristic of background seismic processes in this high-strain-rate environment.

References

USGS Earthquake Hazards Program – Alaska Seismicity Overview
Alaska Earthquake Center – Regional Fault Systems and Swarm Catalog
USGS Earthquake Catalog – Event Data 2000–2003