Earthquake Swarm S20230313.1 Near West Yellowstone, Montana

Earthquake swarm S20230313.1 was recorded 5 km east-southeast of West Yellowstone, Montana. The sequence began at 01:36 on 13 March 2023 and concluded at 20:24 on 14 March 2023, spanning 42 hours and 48 minutes. During this interval, 136 earthquakes were detected. The swarm occurred within the Yellowstone volcanic plateau, a region shaped by repeated caldera-forming eruptions over the past 2.1 million years. The most recent major event, approximately 631,000 years ago, created the present Yellowstone Caldera. Ongoing magmatic and hydrothermal processes drive frequent seismicity, with earthquakes typically occurring at depths of 5–12 km as brittle failure responds to fluid migration and crustal stress changes. Analysis of the first 100 events shows magnitudes ranging from –0.2 to 2.6, with the majority below 1.0. Depths clustered between 5 km and 11 km, consistent with the shallow crustal regime beneath the caldera margin. The largest events (magnitudes 2.4–2.6) occurred between 17:03 and 18:31 on 13 March, followed by a gradual decline in both rate and size. No events exceeded magnitude 3.0, and the sequence displayed the classic swarm pattern of numerous small events without a single dominant mainshock. Historical records indicate persistent swarm activity in this sector. Since 1 January 2000, 85 swarms have been documented in the broader Yellowstone region. Annual counts vary, with notable activity in 2000 (9 swarms), 2008 (7), 2013 (7), 2014 (6), 2022 (7), and lower counts in intervening years. This 2023 swarm represents the sole event recorded to date in that calendar year. Such sequences are common manifestations of the dynamic Yellowstone system, where hydrothermal fluids and minor magmatic movement episodically perturb the crust. Continued monitoring remains essential for distinguishing routine swarm behavior from any potential escalation linked to deeper volcanic processes.

References

SeismoSight internal swarm classification S20230313.1
USGS Earthquake Hazards Program – Yellowstone seismic monitoring reports
Smith RB, Jordan M, et al. (2009) Geodynamics of the Yellowstone hotspot and mantle plume. Journal of Volcanology and Geothermal Research