Seismic Swarm Activity Southwest of Topaz Lake, Nevada, November 2010

A seismic swarm designated S20101116.1 occurred 6 km southwest of Topaz Lake, Nevada, between 07:58 on 15 November 2010 and 18:40 on 16 November 2010. Over this 34-hour period, 29 earthquakes were recorded. The events clustered in a compact area, with the majority exhibiting shallow focal depths ranging from surface levels to approximately 12 km. Magnitudes varied from 0.8 to a peak of 3.5, reflecting typical swarm characteristics of numerous small to moderate events without a single dominant mainshock.

The sequence began with a magnitude 2.4 event at 07:58 on 15 November, followed rapidly by larger shocks including magnitudes 3.5 and 3.2 within the first hour. Subsequent activity included multiple events of magnitude 2.0–2.8 through the afternoon and evening, with a notable cluster between 10:23 and 11:46. Activity continued at lower intensity overnight and into 16 November, featuring additional magnitude 2.1–2.8 events before concluding with a magnitude 1.8 shock at 18:40. Depths remained predominantly shallow, consistent with crustal faulting in the upper 10 km.

This swarm represents the fourth such episode in the region since 2000, with prior events recorded in 2000, 2003, and 2005. Each swarm has involved limited numbers of earthquakes, underscoring a pattern of episodic, low-to-moderate seismic unrest rather than prolonged aftershock sequences.

The Topaz Lake area lies within the Walker Lane belt of western Nevada, a zone of distributed right-lateral shear and extension that accommodates a portion of Pacific–North American plate motion. The local geology features Basin and Range-style normal faulting superimposed on older Sierra Nevada structures, creating a network of active faults capable of generating swarm-like seismicity. Historical records indicate that such swarms often occur along minor faults without producing surface rupture, driven by fluid migration or stress transfer within the crust.

Seismic monitoring in this region benefits from dense station coverage, enabling precise location of events even at low magnitudes. The 2010 swarm’s shallow depths and rapid onset align with known behavior in the central Walker Lane, where similar clusters have been documented over recent decades.

References

SeismoSight internal swarm classification S20101116.1
USGS Earthquake Hazards Program regional tectonic summaries
Nevada Seismological Laboratory historical earthquake catalogs