Location:

Period:

3 Nov 2002 23:03:09 - 13 Nov 2002 20:33:54 (9 days 21 hours 30 minutes)

Volcanoes in 100km radius:

Wrangell(95km)

Earthquakes:

287

4 swarms found nearby.

2002

PS20021103.1(45.9km)

3 Nov

6 hours

10 earthquakes

S20021104.3(24.6km)

3 Nov

45 days 13 hours

1332 earthquakes

S20021106.1(5.6km)

5 Nov

23 days 19 hours

352 earthquakes

2005

S20050830.1(26.7km)

30 Aug

1 day 4 hours

33 earthquakes

AI-generated article — for informational and entertainment purposes only. May contain inaccuracies. Full disclaimerFound an error?

Seismic Swarm S20021104.8: Analysis of Activity Near Mentasta Lake, Alaska

Seismic swarm S20021104.8 was recorded 18 km east-southeast of Mentasta Lake in eastern Alaska. The sequence began at 23:03 UTC on 3 November 2002 and concluded at 20:33 UTC on 13 November 2002, spanning 237 hours and 30 minutes. During this period, 287 earthquakes were detected, with detailed parameters available for the initial 100 events.

The first event reached magnitude 4.9 at a depth of 2 km. Subsequent activity included multiple events exceeding magnitude 4.0, such as a 4.8 at 8 km depth on 5 November and several magnitude 4.0–4.2 shocks clustered within the first 48 hours. Depths remained predominantly shallow, with the majority occurring between 0 and 5 km; only a few events exceeded 10 km, the deepest reaching 19 km. Magnitudes generally declined after the initial peak, transitioning to a sustained sequence of events in the 1.6–3.9 range.

This distribution indicates a typical swarm pattern dominated by numerous smaller shocks rather than a single mainshock-aftershock sequence. The concentration of activity at shallow depths aligns with the tectonic setting of the region, where brittle failure occurs within the upper crust.

Eastern Alaska lies along the boundary between the Pacific and North American plates. The Denali Fault, a major right-lateral strike-slip structure, traverses the area and accommodates significant lateral motion. The Mentasta Lake vicinity sits near the eastern segment of this fault system, which has produced large earthquakes historically. Regional seismicity is further influenced by the broader Yakutat terrane collision and the adjacent subduction zone to the south.

The 2002 Denali Fault earthquake sequence, occurring in early November of the same year, represents the most recent major event in the immediate vicinity. Swarm S20021104.8 began on the same day as that Mw 7.9 mainshock, consistent with the heightened seismic productivity expected in the surrounding crust following large strike-slip ruptures.

Since 1 January 2000, only two swarms have been identified in the catalog for this area, with S20021104.8 being the first. The second occurred later within the same monitoring window. Such infrequent swarms underscore the episodic nature of clustered seismicity along the Denali Fault.

Data for this analysis derive from the SeismoSight internal classification system. Supporting regional context is drawn from the U.S. Geological Survey Earthquake Hazards Program and the Alaska Earthquake Center.

References
U.S. Geological Survey Earthquake Catalog
Alaska Earthquake Center Regional Reports
SeismoSight Swarm Database (internal)