Seismic Swarm S20220329.1 Near West Yellowstone, Montana
Seismic swarm S20220329.1 occurred 18 km northeast of West Yellowstone, Montana, within the Yellowstone volcanic region. The sequence began at 17:21 on 28 March 2022 and concluded at 06:09 on 31 March 2022, registering 117 earthquakes over 60 hours and 48 minutes. Analysis of the first 100 events reveals magnitudes ranging from -1.4 to 2.5, with the majority between 0.0 and 1.3. Depths clustered primarily between 2 km and 10 km, consistent with shallow crustal activity typical of the area.
The Yellowstone region lies above a continental hotspot, where the North American plate overrides a mantle plume. This setting produces the Yellowstone Caldera, formed by massive eruptions approximately 2.1 million, 1.3 million, and 640,000 years ago. Ongoing magmatic and hydrothermal processes drive frequent seismicity, including both isolated events and swarms. Earthquake swarms in this locale often result from fluid migration or stress changes within the volcanic system rather than tectonic fault rupture alone.
Historical records maintained by SeismoSight indicate 91 swarms in the region since 1 January 2000. Annual counts show variability: 10 swarms in 2000, 5 in 2001, 6 in 2002, 3 in 2003, 2 in 2004, 1 in 2005, 5 in 2006, 3 in 2007, 7 in 2008, 5 in 2009, 1 in 2010, 1 in 2011, 7 in 2013, 8 in 2014, 3 in 2015, 1 in 2016, 5 in 2017, 3 in 2018, 3 in 2019, 5 in 2020, and 7 in 2021. These patterns underscore the recurrent nature of swarm activity linked to the underlying volcanic and hydrothermal dynamics.
Magnitudes in swarm S20220329.1 remained low, with only a few events exceeding 2.0. Such characteristics align with previously documented swarms that pose minimal surface hazard yet provide valuable data on subsurface fluid movement. Depths averaging around 6–8 km suggest involvement of the brittle-ductile transition zone influenced by elevated geothermal gradients.
Continued monitoring by the Yellowstone Volcano Observatory supports ongoing assessment of seismic trends. Swarm S20220329.1 contributes to the long-term dataset used to refine models of caldera unrest and potential precursors to larger volcanic episodes.
References
SeismoSight internal swarm classification records.
Yellowstone Volcano Observatory geological summaries.