Seismic Swarm SVS20130416.1 Near West Yellowstone, Montana
Seismic swarm SVS20130416.1 occurred approximately 50 km southeast of West Yellowstone, Montana, within a tectonically active region influenced by the Yellowstone hotspot. The event sequence began at 17:40 on 15 April 2013 and concluded at 11:30 on 16 April 2013, spanning 17 hours and 49 minutes. During this period, 30 earthquakes were recorded, with magnitudes ranging from -0.2 to 2.9 and focal depths primarily between 1 and 15 km. These shallow depths are consistent with activity in the upper crust of the Yellowstone volcanic system.
The sequence exhibited typical swarm characteristics, featuring numerous events of similar magnitude without a dominant mainshock. Notable activity included a magnitude 2.9 earthquake at 09:46:48 on 16 April at 4 km depth, alongside several events between 1.0 and 2.4. Smaller events, including negative magnitudes, reflect the sensitivity of modern seismic networks in detecting microseismicity. Such swarms often arise from fluid migration or stress adjustments along faults in volcanic terrains.
This location lies along the margins of the Yellowstone Caldera, formed by massive eruptions 2.1 million, 1.3 million, and 640,000 years ago. The caldera remains a dynamic volcanic field driven by a mantle plume, resulting in elevated heat flow, hydrothermal features, and frequent seismicity. The Intermountain Seismic Belt, which encompasses this area, experiences ongoing tectonic extension that interacts with magmatic processes to produce earthquake clusters.
Historical records indicate 15 swarms in the region since 2000, occurring in 2002 (4 swarms), 2006 (3), 2008 (2), 2009 (3), 2010 (1), 2011 (1), and 2013 (1). These recurrent episodes underscore the persistent seismic vitality of the Yellowstone area, where swarms serve as indicators of subsurface changes without necessarily signaling imminent volcanic activity.
Monitoring by networks such as the Yellowstone Volcano Observatory continues to track these patterns, contributing to assessments of regional hazard. The 2013 swarm aligns with established behavior in this geologically complex zone.
References
- United States Geological Survey Earthquake Catalog
- Yellowstone Volcano Observatory reports
- SeismoSight internal swarm classification data