Seismic Swarm SVS20010203.1: Analysis of Activity Near West Yellowstone, Montana

On 3 February 2001, a seismic swarm designated SVS20010203.1 was recorded 32 km east-southeast of West Yellowstone, Montana. The sequence began at 00:58 UTC and concluded at 16:04 UTC, encompassing 26 earthquakes over 15 hours and 6 minutes. This event occurred within the seismically active Yellowstone region, part of the Yellowstone Caldera system driven by a mantle hotspot beneath the North American plate.

The Yellowstone area experiences frequent earthquake swarms due to its underlying volcanic and hydrothermal framework. The caldera formed through massive eruptions approximately 2.1 million, 1.3 million, and 640,000 years ago, leaving a large magma reservoir that influences crustal stress and fluid migration. Swarms in this zone often result from movement of hydrothermal fluids or minor magmatic adjustments rather than direct volcanic eruption. Depths of recorded events typically range from 2 to 11 km, aligning with the brittle-ductile transition zone in the upper crust.

Event magnitudes in SVS20010203.1 remained low, with the largest reaching 2.1 and many registering below 1.0. Depths clustered between 2 and 11 km, showing a concentration around 5–8 km. Notable events included a magnitude 1.6 at 8 km depth at 15:02 and the peak magnitude 2.1 at 6 km depth at 15:48. Negative or near-zero magnitudes reflect the sensitive detection thresholds of regional networks monitoring the Yellowstone volcanic field.

Such swarms contribute to ongoing monitoring of the broader volcanic system. Historical records since 2000 indicate 10 swarms in the area, with nine occurring in 2000 and this event marking the sole swarm of 2001. These patterns underscore the persistent low-level seismicity characteristic of the region, where fluid-driven processes sustain episodic activity without leading to significant surface deformation.

Seismic data from the swarm provide insight into localized stress release. Events showed variable timing, with clusters in the early morning and afternoon hours. Depths suggest activity within the seismogenic crust overlying the magma chamber, consistent with established models of Yellowstone's tectonic-volcanic interaction.

References

• USGS Earthquake Hazards Program: Yellowstone Seismic Activity Reports (2001 data)
• Yellowstone Volcano Observatory Geological Summaries
• SeismoSight Internal Swarm Classification SVS20010203.1