Seismic Swarm SVS20161125.1 Near West Yellowstone, Montana
Seismic swarm SVS20161125.1 was recorded 48 km southeast of West Yellowstone, Montana, beginning at 13:32 on 24 November 2016 and concluding at 02:36 on 26 November 2016. Over 37 hours and 3 minutes, 60 earthquakes were detected. Magnitudes ranged from 0.4 to 2.8, with the largest event occurring at 05:47 on 25 November. Depths were predominantly shallow, concentrated between 1 km and 8 km, though isolated events reached 19 km. The sequence exhibited typical swarm characteristics, featuring numerous small-magnitude events clustered in time without a single dominant mainshock.
This activity aligns with the tectonic and volcanic setting of the Yellowstone Plateau. The area sits within the eastern portion of the Yellowstone caldera, formed by massive rhyolitic eruptions approximately 2.1 million, 1.3 million, and 0.63 million years ago. Ongoing crustal deformation, hydrothermal fluid circulation, and regional extension associated with the Basin and Range province contribute to frequent seismicity. Earthquake swarms in this region often result from migrating fluids or aseismic slip that triggers brittle failure at shallow depths.
Historical records since 2000 indicate 24 prior swarms in the vicinity, with notable occurrences in 2002 (5 swarms), 2006 (3), 2008 (4), 2013 (5), and single events in 2010, 2011, 2014, and 2015. These episodes underscore the persistent low-level seismic unrest characteristic of the Yellowstone volcanic field, where swarms can last from hours to weeks and rarely exceed magnitude 4.
The November 2016 swarm remained well below thresholds that would indicate magmatic intrusion or heightened volcanic hazard. Such events provide valuable data for monitoring subsurface stress changes and refining models of hydrothermal system dynamics. Continued seismic surveillance by regional networks supports timely assessment of any evolving activity.
References
USGS Earthquake Hazards Program – Yellowstone Seismicity
Yellowstone Volcano Observatory Annual Reports (2016–2023)
SeismoSight internal swarm classification SVS20161125.1