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Location:
89 km SW of Delta Junction, Alaska
Period:
11 Jan 2003 12:45:07 - 14 Jan 2003 10:34:32 (2 days 21 hours 49 minutes)
Volcanoes in 100km radius:
Buzzard Creek(93km)
Earthquakes:
45
21 swarms found nearby.
2002
2 Nov
123 days 19 hours
7093 earthquakes
S20021104.2(15.8km)
3 Nov
19 days 3 hours
621 earthquakes
S20021108.1(13.1km)
7 Nov
1 day 2 hours
42 earthquakes
10 Nov
1 day 16 hours
49 earthquakes
S20021124.1(12.5km)
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
2 Feb
3 days 0 hours
42 earthquakes
22 Feb
1 day 14 hours
31 earthquakes
15 Mar
1 day 20 hours
37 earthquakes
9 Sep
2 days 8 hours
35 earthquakes
9 Dec
10 days 20 hours
147 earthquakes
2004
S20040129.1(16.1km)
28 Jan
3 days 8 hours
47 earthquakes
2006
4 Oct
16 hours
26 earthquakes
AI-generated article — for informational and entertainment purposes only. May contain inaccuracies. Full disclaimerFound an error?

Seismic Swarm S20030112.1 Near Delta Junction, Alaska

Seismic swarm S20030112.1 occurred approximately 89 km southwest of Delta Junction in interior Alaska. The sequence began at 12:45 on 11 January 2003 and concluded at 10:34 on 14 January 2003, spanning 69 hours and 49 minutes. During this interval, 45 earthquakes were recorded, with magnitudes ranging from 1.0 to 2.9 and focal depths predominantly between 0 and 7 km.

The events clustered in the first two days, with peak activity on 11 and 12 January. Notable shocks included a magnitude 2.8 event at 20:32 on 11 January at 3 km depth and a magnitude 2.9 event at 04:38 on 12 January at 4 km depth. Later activity tapered, with the final two events on 14 January registering magnitudes 1.2 and 1.1 at depths of 4 km and 6 km, respectively. Depths remained consistently shallow, consistent with activity along upper-crustal structures.

This swarm represents the sole sequence recorded in 2003 within the regional catalog maintained since 2000. Historical data indicate 14 swarms in total during this period, including 13 swarms in 2002. Such episodic clustering suggests recurrent stress release along pre-existing faults without progression to a mainshock-aftershock sequence.

The swarm location lies within the Yukon-Tanana terrane of interior Alaska, a region dominated by right-lateral strike-slip faulting associated with the Denali Fault system. The Denali Fault, a major intracontinental structure extending over 2,000 km, accommodates much of the Pacific-North America plate motion transferred inland from the subduction zone. Local geology features metamorphic rocks of Paleozoic to Mesozoic age intruded by Cretaceous granites, overlain by Quaternary glacial and alluvial deposits. Seismicity in this area typically reflects reactivation of secondary faults splaying from the main Denali trace.

Interior Alaska experiences moderate background seismicity driven by far-field stresses from the Aleutian subduction zone and ongoing convergence along the Denali system. The shallow depths observed in swarm S20030112.1 align with the brittle upper crust, where strain accumulates and releases in discrete clusters. No volcanic sources are implicated, as the nearest Holocene volcanoes lie more than 200 km to the south in the Wrangell Mountains.

References

  • USGS Earthquake Catalog (earthquake.usgs.gov)
  • Alaska Earthquake Center, University of Alaska Fairbanks
  • Denali Fault System tectonic summaries, Geological Society of America
  • SeismoSight internal swarm classification records