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Location:
57 km SE of West Yellowstone, Montana
Period:
4 Sep 2015 08:26:39 - 4 Sep 2015 13:00:55 (4 hours 34 minutes)
Volcanoes in 100km radius:
None
Earthquakes:
24
32 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
5 Dec
1 day 6 hours
39 earthquakes
2004
31 Aug
1 day 10 hours
27 earthquakes
2006
18 Mar
12 hours
28 earthquakes
5 Apr
16 hours
77 earthquakes
2008
23 Nov
1 day 15 hours
66 earthquakes
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
15 Apr
17 hours
30 earthquakes
23 Jun
5 hours
29 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
12 Feb
11 hours
36 earthquakes
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
12 Feb
7 hours
25 earthquakes
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 SVS20150904.1: A Detailed Examination of Activity Southeast of West Yellowstone

On September 4, 2015, a seismic swarm designated SVS20150904.1 was recorded 57 km southeast of West Yellowstone, Montana. The sequence began at 08:26 and concluded at 13:00, spanning 4 hours and 34 minutes. During this interval, 24 earthquakes were detected, with magnitudes ranging from 0.0 to 1.4 and focal depths between 2 km and 8 km. The events clustered tightly in both time and space, characteristic of swarm behavior where no single mainshock dominates.

The sequence opened with low-magnitude events near 7 km depth. Successive shocks maintained shallow depths, with several registering at 4–6 km. Peak magnitudes of 1.4 occurred at 09:25, 11:55, and 11:55, all at depths of 4–6 km. Activity tapered after 11:55, ending with a 0.9 magnitude event at 13:00 and 7 km depth. Depths remained consistently within the upper crust, consistent with hydrothermal and tectonic processes in the region.

This swarm reflects typical seismicity patterns in the Yellowstone volcanic field. The area lies above a continental hotspot that has produced extensive rhyolitic volcanism and a large caldera system. Crustal extension, combined with fluid migration from the underlying magmatic system, generates frequent small earthquakes. Depths of 2–8 km align with the brittle-ductile transition zone influenced by elevated geothermal gradients.

Since 2000, 18 swarms have occurred in the same locale. Documented episodes took place in 2002 (five swarms), 2004 (one), 2006 (two), 2008 (two), 2009 (three), 2010 (one), 2011 (one), and 2013 (three). These recurrent swarms illustrate ongoing crustal adjustment without escalation to larger tectonic events.

The 2015 swarm fits established patterns of short-duration, low-magnitude clustering. Such sequences rarely produce felt shaking beyond the immediate vicinity and serve as indicators of subsurface fluid dynamics rather than precursors to volcanic unrest. Continuous monitoring by regional seismic networks supports timely assessment of any deviations from baseline activity.

References

USGS Earthquake Hazards Program – Yellowstone Region Catalog
Yellowstone Volcano Observatory Annual Reports (2015)
Montana Bureau of Mines and Geology – Seismic Monitoring Summaries