Seismic Swarm SVS20220212.1: Analysis of Activity Southeast of West Yellowstone

On 12 February 2022, a seismic swarm designated SVS20220212.1 was recorded 34 km southeast of West Yellowstone, Montana. The sequence began at 06:26 and concluded at 13:47, encompassing 25 earthquakes within a span of 7 hours and 21 minutes. Magnitudes ranged from 0.0 to 2.7, with the largest event occurring at 09:42. Focal depths remained shallow, primarily between 0 and 5 km, consistent with activity in the upper crust of the region.

The swarm exhibited typical characteristics of clustered, low-magnitude seismicity. Multiple events clustered within minutes of one another, such as the paired occurrences at 06:49 and 09:42, reflecting rapid stress release along small fault segments. Depths showed a concentration in the 1–4 km interval, indicating brittle failure near the surface rather than deeper magmatic processes. No events exceeded magnitude 3.0, underscoring the swarm’s modest energy release compared with tectonic mainshock-aftershock sequences.

This episode fits within a broader pattern of swarm activity documented since 2000. A total of 45 swarms have been identified in the area, with notable concentrations in 2002 and 2006 (six each), 2009 and 2020 (four each), and 2013, 2019, and 2021 (four, two, and four respectively). Earlier years such as 2000, 2010, 2012, 2014–2018 recorded one to three swarms annually, illustrating episodic rather than continuous clustering.

The location lies within the Yellowstone volcanic system, where the crust experiences elevated temperatures and fluid circulation driven by underlying magmatic reservoirs. Earthquake swarms here commonly arise from hydrothermal fluid migration or minor adjustments along pre-existing fractures within the caldera margin and adjacent zones. Historical monitoring by the U.S. Geological Survey has established that such sequences rarely precede larger eruptions but serve as indicators of the dynamic stress field in this tectonically active setting.

Ongoing instrumentation in the region, including dense seismic networks operated by the University of Utah and the Yellowstone Volcano Observatory, continues to refine detection thresholds and improve real-time characterization of these events. The February 2022 swarm, like its predecessors, remained confined to small magnitudes and shallow depths, posing negligible hazard beyond localized ground shaking detectable only by sensitive instruments.

References

• U.S. Geological Survey Earthquake Catalog (earthquake.usgs.gov)
• Yellowstone Volcano Observatory annual reports (usgs.gov/yvo)