Seismic Swarm SVS20240101.1: Analysis of Recent Activity Near West Yellowstone

Seismic swarm SVS20240101.1 occurred 29 km east-southeast of West Yellowstone, Montana, between 14:29 on 1 January 2024 and 07:15 on 3 January 2024. Over 40 hours and 45 minutes, the event sequence registered 47 earthquakes. This swarm exemplifies typical low-magnitude seismic activity in the Yellowstone region, where fluid migration and crustal stress adjustments commonly produce clustered events rather than isolated mainshocks.

Magnitudes ranged from -0.1 to 3.1, with the largest event recorded at 3.1 on 1 January at 14:41:35 UTC at a depth of 8 km. Most events clustered between magnitudes 0.0 and 2.5, reflecting the swarm's predominantly microseismic character. Depths varied from 1 km to 12 km, though the majority occurred between 7 km and 10 km, consistent with activity within the brittle upper crust overlying the Yellowstone magmatic system.

The sequence began with a rapid succession of small events on 1 January, including multiple shocks between 14:29 and 15:05. Activity continued at a lower rate through the evening and into 2 January, with isolated events persisting until the final recorded quake on 3 January. Such temporal patterns indicate episodic energy release driven by subsurface fluid movement rather than tectonic fault rupture.

The location lies within the Yellowstone Plateau, a geologically dynamic area shaped by the North American plate's passage over the Yellowstone hotspot. This hotspot has produced extensive volcanism, including three major caldera-forming eruptions over the past 2.1 million years. The most recent, approximately 631,000 years ago, formed the Yellowstone Caldera. Ongoing inflation and deflation of the underlying magma reservoir, combined with hydrothermal circulation, generate frequent earthquake swarms. Depths of 1–12 km align with the seismogenic zone above the shallow crustal magma body.

Since 2000, 85 swarms have been documented in the region. Annual counts show variability, with peaks of 10 swarms in 2022 and 7 each in 2000 and 2008. Lower activity occurred in years such as 2004, 2016, and 2017, each recording only one swarm. This long-term record underscores the persistent nature of swarm seismicity tied to the hotspot's influence.

Insights from SVS20240101.1 reinforce that swarms in this setting rarely exceed magnitude 4 and pose minimal surface hazard. Their value lies in monitoring magmatic and hydrothermal processes. Continued seismic surveillance by regional networks remains essential for tracking any evolution toward larger events or changes in volcanic unrest indicators.

References

• USGS Earthquake Catalog
• Yellowstone Volcano Observatory Annual Reports (2020–2023)