Seismic Swarm S20160130.1 Near Mina, Nevada: Geological Context and Event Analysis
The seismic swarm designated S20160130.1 occurred approximately 23 km west-northwest of Mina in Mineral County, Nevada. It began at 00:45 UTC on 30 January 2016 and concluded at 08:39 UTC on 31 January 2016, spanning 31 hours and 53 minutes. During this interval, 28 earthquakes were recorded, with magnitudes ranging from 0.0 to 2.8 and focal depths predominantly between 2 and 4 km, though several events reached depths of 7–9 km. The largest event, a magnitude 2.8 earthquake, initiated the sequence, followed by numerous smaller aftershocks that exhibited a typical swarm pattern of clustered, low-magnitude activity without a dominant mainshock.
This swarm aligns with the broader tectonic framework of western Nevada, situated in the Basin and Range Province. The region experiences active crustal extension driven by normal faulting along north- to northwest-striking faults. Heat flow is elevated due to thinned lithosphere, contributing to frequent microseismicity. The Mina area specifically lies near the southern margin of the Walker Lane belt, a northwest-trending zone of right-lateral shear that accommodates a portion of the Pacific–North American plate boundary deformation. Historical records indicate that similar swarm activity has been documented in this corridor, often linked to fluid migration or aseismic slip on pre-existing faults.
Since 1 January 2000, 14 swarms have been identified in the immediate vicinity. These occurred in 2006 (1 swarm), 2011 (4 swarms), 2012 (1 swarm), 2014 (4 swarms), and 2015 (4 swarms). The 2016 event fits within this episodic pattern, underscoring the area's persistent low-level seismic productivity. Depths remained shallow throughout, consistent with brittle failure in the upper crust where temperatures permit stick-slip behavior.
Seismic swarms in extensional regimes like the Basin and Range commonly reflect distributed strain rather than single-fault rupture. The 2016 sequence displayed a gradual decay in event rate after the initial peak, with most activity concentrated in the first 12 hours. Magnitudes stayed below 3.0, producing no reported damage or felt reports beyond the immediate epicentral zone. Ongoing monitoring by regional networks continues to track background rates, providing data for refined hazard assessments in this sparsely populated portion of Nevada.
References
- USGS Earthquake Catalog (earthquake.usgs.gov)
- Nevada Seismological Laboratory, University of Nevada, Reno
- Nevada Bureau of Mines and Geology, Geological Survey of Nevada