Seismic Swarm S20130213.1 Near Mina, Nevada: Geological Context and Event Analysis

The seismic swarm S20130213.1 began at 21:23 on 12 February 2013 and ended at 03:09 on 24 February 2013. Centered 39 km south of Mina, Nevada, the sequence lasted 269 hours and 45 minutes and produced 345 earthquakes.

This activity took place in western Nevada’s Walker Lane belt, a zone of distributed dextral shear and normal faulting that accommodates part of the Pacific–North America plate motion. The region lies within the Basin and Range province, where Miocene-to-present crustal extension has created a landscape of north-trending ranges and valleys bounded by active faults. Mina itself sits near the intersection of several Quaternary faults capable of producing moderate earthquakes, consistent with the swarm’s shallow focal depths.

The first 100 events illustrate a classic swarm pattern: an abrupt onset followed by numerous smaller aftershocks without a single dominant mainshock. The largest event reached magnitude 5.1 at 00:10:14 on 13 February at 7 km depth. Additional notable shocks included magnitudes 3.7 (twice), 3.5 (twice), 3.4, 3.3, and 3.1, all occurring within the first 24 hours and concentrated between 6 km and 11 km depth. The majority of events ranged from magnitude 0.9 to 2.6 and clustered between 5 km and 11 km, although a few occurred at depths of 0–4 km, suggesting possible involvement of shallower crustal structures.

Temporal distribution shows peak rates in the first six hours after the magnitude-5.1 shock, followed by a gradual decline punctuated by occasional magnitude-3+ events. Depths remained stable throughout, indicating a compact source volume typical of fluid-driven or aseismic-slip-triggered swarms in the Walker Lane.

Since 1 January 2000 the same area has hosted nine documented swarms. These occurred in 2000 (six swarms), 2003 (two swarms), and 2013 (one swarm), underscoring the recurrent nature of clustered seismicity along this portion of the plate-boundary deformation zone.

Collectively, the 2013 sequence and its historical precedents highlight the persistent seismic hazard posed by distributed faulting in western Nevada and the value of dense monitoring for understanding swarm mechanics in transtensional regimes.

References

SeismoSight internal swarm classification S20130213.1
USGS Quaternary Fault and Fold Database of the United States
Nevada Bureau of Mines and Geology seismic-hazard reports