Seismic Swarm S20200516.1: Analysis of Activity Near Mina, Nevada

The seismic swarm designated S20200516.1 occurred 37 km southeast of Mina, Nevada, in a tectonically active portion of the western Basin and Range province. This region experiences distributed extensional deformation along normal faults, with additional influence from the Walker Lane shear zone that accommodates right-lateral motion between the Pacific and North American plates. Such settings commonly produce earthquake swarms rather than mainshock-aftershock sequences. The swarm initiated at 11:11 on 15 May 2020 and concluded at 22:39 on 16 June 2020, spanning 779 hours and 28 minutes. During this interval, 1150 earthquakes were recorded. Analysis of the first 100 events reveals predominantly shallow focal depths between 0 and 20 km, with the majority occurring at 5 km or less. Magnitudes ranged from 0.9 to 4.3, clustering between 1.5 and 3.0; notable events included multiple shocks of 3.5–3.6 and a peak magnitude of 4.3 on 17 May 2020. Early activity featured several events above magnitude 3.0 within the first 24 hours, followed by a gradual decline in both rate and size. Historical records indicate nine comparable swarms in the same area since 1 January 2000. These occurred in 2000 (one swarm), 2003 (two swarms), 2013 (two swarms), 2014 (one swarm), and 2020 (three swarms, including the present sequence). The recurrence underscores persistent strain accumulation and release along local fault networks. Overall, swarm S20200516.1 exemplifies typical background seismicity in this portion of Nevada, where low-to-moderate magnitude events occur in clusters without producing significant surface rupture.

References

SeismoSight internal swarm classification S20200516.1 USGS Earthquake Catalog (regional tectonics of Mina, Nevada area)