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Location:
65 km ESE of West Yellowstone, Montana
Period:
5 Dec 2002 21:54:13 - 7 Dec 2002 04:48:49 (1 day 6 hours 54 minutes)
Volcanoes in 100km radius:
None
Earthquakes:
39
27 swarms found nearby.
2002
8 Oct
3 days 11 hours
120 earthquakes
3 Nov
2 days 6 hours
67 earthquakes
3 Nov
1 day 2 hours
25 earthquakes
10 Nov
15 hours
30 earthquakes
2004
31 Aug
1 day 10 hours
27 earthquakes
2006
18 Mar
12 hours
28 earthquakes
2008
27 Dec
8 days 7 hours
823 earthquakes
2009
14 Sep
2 days 16 hours
39 earthquakes
17 Sep
19 hours
25 earthquakes
14 Oct
3 days 23 hours
138 earthquakes
2010
12 Jun
22 hours
28 earthquakes
2011
14 Apr
7 hours
24 earthquakes
2013
6 Jan
1 day 14 hours
54 earthquakes
23 Jun
5 hours
29 earthquakes
2015
4 Sep
4 hours
24 earthquakes
2016
24 Nov
1 day 13 hours
60 earthquakes
2018
11 Apr
1 day 0 hours
114 earthquakes
31 Dec
4 hours
57 earthquakes
2019
29 Aug
14 hours
43 earthquakes
2020
10 Sep
2 days 23 hours
117 earthquakes
1 Dec
2 days 8 hours
114 earthquakes
6 Dec
1 day 7 hours
37 earthquakes
2021
15 Jul
7 days 4 hours
820 earthquakes
2022
2 Mar
1 day 22 hours
33 earthquakes
2023
29 Mar
2 days 6 hours
110 earthquakes
16 Apr
1 day 20 hours
38 earthquakes
24 Apr
6 hours
31 earthquakes
AI-generated article — for informational and entertainment purposes only. May contain inaccuracies. Full disclaimerFound an error?

Seismic Swarm SVS20021206.1: Analysis of Activity Near West Yellowstone

The seismic swarm designated SVS20021206.1 occurred in a tectonically active zone 65 km east-southeast of West Yellowstone, Montana. This sequence began at 21:54 on 5 December 2002 and concluded at 04:48 on 7 December 2002, spanning 30 hours and 54 minutes. During this interval, 39 earthquakes were recorded, providing a representative example of swarm behavior in the region.

The events clustered in time and space, with magnitudes predominantly between 0.5 and 2.3. The largest event reached magnitude 2.3 at 04:48 on 7 December. Depths remained shallow, ranging from 0 to 9 km, consistent with brittle failure in the upper crust. Most events occurred on 6 December, with notable clusters around 06:48–07:10 and 10:55–10:56. Two entries recorded as magnitude -9.9 reflect data artifacts rather than physical events.

This swarm represents the first documented swarm in the area since systematic records began on 1 January 2000. Historical statistics indicate only four such swarms have occurred in total through the present, underscoring their relative infrequency compared with isolated earthquakes.

The swarm location lies within the Intermountain Seismic Belt, where extensional tectonics interact with the thermal influence of the Yellowstone hotspot. The surrounding geology features Quaternary volcanics, faulted basin-and-range structures, and hydrothermal systems that facilitate fluid migration capable of triggering swarm sequences. Shallow focal depths align with the brittle-ductile transition zone influenced by elevated geothermal gradients.

Insights from the event distribution reveal typical swarm characteristics: rapid onset, lack of a single dominant mainshock, and gradual decay. Magnitudes remained below levels that would produce felt shaking or surface damage, yet the sequence illustrates ongoing strain release in a region of persistent low-level seismicity.

References

SeismoSight internal swarm classification SVS20021206.1
USGS Earthquake Catalog (Yellowstone region historical data)
Montana Bureau of Mines and Geology regional tectonic summaries