Location:

Period:

13 Jul 2003 18:18:05 - 3 Aug 2003 12:25:32 (20 days 18 hours 7 minutes)

Volcanoes in 100km radius:

Buzzard Creek(73km)

Earthquakes:

166

M 7.0+:

M 7.9; 2002 Denali Fault, Alaska Earthquake; (3 Nov 2002) (12km from the swarm center)

21 swarms found nearby.

2002

S20021023.1(28.4km)

23 Oct

12 days 6 hours

727 earthquakes

S20021024.1(29.4km)

23 Oct

10 days 5 hours

183 earthquakes

S20021023.2(8.1km)

23 Oct

1 day 18 hours

37 earthquakes

S20021103.1(27.0km)

2 Nov

123 days 19 hours

7093 earthquakes

S20021104.2(18.3km)

3 Nov

19 days 3 hours

621 earthquakes

S20021105.2(27.1km)

4 Nov

16 days 23 hours

418 earthquakes

S20021108.1(20.7km)

7 Nov

1 day 2 hours

42 earthquakes

S20021110.1(12.9km)

9 Nov

1 day 17 hours

53 earthquakes

S20021113.1(3.8km)

12 Nov

1 day 14 hours

71 earthquakes

S20021118.1(28.7km)

17 Nov

3 days 1 hours

69 earthquakes

S20021126.1(27.3km)

25 Nov

1 day 2 hours

30 earthquakes

S20021201.1(29.8km)

30 Nov

6 days 3 hours

158 earthquakes

S20021225.1(16.0km)

24 Dec

5 days 15 hours

113 earthquakes

S20021227.1(13.6km)

26 Dec

7 days 19 hours

98 earthquakes

2003

S20030101.1(26.6km)

1 Jan

2 days 1 hours

49 earthquakes

S20030107.1(1.3km)

6 Jan

4 days 21 hours

72 earthquakes

S20030223.2(29.6km)

22 Feb

1 day 14 hours

31 earthquakes

S20030307.1(15.5km)

6 Mar

26 days 8 hours

396 earthquakes

S20030403.1(5.2km)

2 Apr

23 days 4 hours

248 earthquakes

S20030602.2(3.3km)

1 Jun

11 days 13 hours

108 earthquakes

S20030807.1(7.4km)

7 Aug

6 days 18 hours

95 earthquakes

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Seismic Swarm S20030714.1 Near Cantwell, Alaska: Geological Context and Event Analysis

Seismic swarm S20030714.1 occurred approximately 88 km east of Cantwell, Alaska, along the Denali Fault system. The swarm initiated at 18:18 on 13 July 2003 and concluded at 12:25 on 3 August 2003, spanning 498 hours and 7 minutes. During this period, 166 earthquakes were recorded. This activity took place in a region of intense tectonic deformation driven by the collision between the Pacific and North American plates.

The Denali Fault is a major right-lateral strike-slip structure extending over 2,000 km across central Alaska. It accommodates significant lateral displacement and has produced large historical earthquakes. The 2002 Denali Fault earthquake, magnitude 7.9 on 3 November 2002, occurred only 12 km from the swarm center, highlighting the area's persistent seismic hazard. Post-mainshock stress redistribution likely contributed to subsequent swarm activity.

Analysis of the first 100 events reveals a sequence dominated by low to moderate magnitudes. The largest event reached magnitude 4.5 at a depth of 5 km on 14 July 2003 at 15:50:48. Other notable events included magnitudes 3.6, 3.2, and 2.9, with the majority falling between 1.0 and 2.5. Focal depths ranged primarily from 0 to 22 km, indicating shallow crustal fracturing consistent with strike-slip faulting. Temporal clustering was evident, with heightened activity on 14–15 July and 20–22 July.

Since 1 January 2000, twenty seismic swarms have been documented in the region. Prior swarms occurred in 2002 (14 events) and 2003 (6 events), underscoring recurring episodic behavior along the fault. These swarms typically feature numerous small events without a single dominant mainshock, distinguishing them from aftershock sequences.

The swarm's characteristics align with known patterns of fault-zone fluid migration and stress triggering following major events such as the 2002 Denali earthquake. Depths under 10 km predominated in early events, suggesting initial rupture within the upper brittle crust.

References

SeismoSight internal classification data for swarm S20030714.1
USGS Earthquake Hazards Program records on Denali Fault activity