An earthquake swarm designated S20200117.2 was recorded 10 km NNE of Minersville in Beaver County, Utah. The sequence began at 02:31 on 17 January 2020 and concluded at 15:51 on 20 January 2020, spanning 85 hours and 20 minutes. During this period, 46 earthquakes were registered.
The swarm exhibited a typical pattern of clustered seismic events without a single dominant mainshock. The largest event reached magnitude 3.9 at a depth of 11 km on 17 January at 02:31:11 UTC. Subsequent activity included events ranging from negative magnitudes to 2.7, with the second-highest magnitude of 2.7 recorded on 18 January at 13:05:51 at 10 km depth. Depths varied between 1 km and 15 km, indicating shallow crustal faulting.
This activity occurred within the Basin and Range Province, where extensional tectonics drive normal faulting along north-south trending structures. The region lies near the eastern margin of the Great Basin, influenced by the Intermountain Seismic Belt. Historical records document recurrent low-to-moderate seismicity in western Utah, with notable events including the 1901 magnitude 6.5 earthquake near Richfield and smaller swarms in the Mineral Mountains area during the late 20th century.
The swarm's temporal distribution showed peak activity on 17 January, with diminishing frequency over the following days. Events on 19 and 20 January were generally smaller, concluding the sequence. Depths clustered mostly between 3 km and 11 km, consistent with brittle failure in the upper crust of this extensional regime.
Such swarms are common in Utah due to fluid migration along faults and regional stress accumulation. The Minersville area has experienced similar episodic clusters linked to the regional fault network, including segments of the Beaver Valley fault zone. No damage or felt reports beyond minor shaking were associated with this swarm.
SeismoSight internal classification identifies S20200117.2 as a distinct swarm sequence based on spatiotemporal clustering criteria.