Seismic Swarm S20140619.1 Near Cold Springs, Nevada

Seismic swarm S20140619.1 was recorded 3 km southeast of Cold Springs, Nevada. The sequence began at 04:35 on 19 June 2014 and concluded at 22:09 on 20 June 2014, lasting 41 hours and 34 minutes. During this period, 115 earthquakes were detected.

Analysis of the first 100 events reveals consistently low magnitudes, ranging from -0.9 to 1.1. Depths remained shallow, predominantly between 0 km and 9 km, with the majority clustered between 3 km and 6 km. Early activity featured events of magnitude -0.4 at depths of 5–6 km, followed by scattered positive magnitudes up to 0.5 within the first hour. Subsequent events showed intermittent peaks, including a magnitude 0.9 at 4 km depth and a magnitude 1.1 at 5 km depth near the sequence’s later stages. The pattern indicates a diffuse distribution without a dominant mainshock, characteristic of swarm behavior driven by fluid migration or localized stress adjustments rather than classic aftershock decay.

The Cold Springs area lies in the western Basin and Range Province of Nevada, a region defined by active crustal extension since the Miocene. This tectonic setting produces north-south trending normal faults that accommodate east-west stretching at rates of approximately 1 cm per year. The swarm location falls within the northern Walker Lane belt, a transitional zone of dextral shear linking the San Andreas fault system to the east with the Basin and Range interior. Quaternary fault mapping by the U.S. Geological Survey documents multiple active structures nearby, including segments of the Petersen Mountain fault system capable of producing moderate earthquakes.

Nevada experiences elevated background seismicity owing to this extensional regime. Since 2000, the state has recorded 18 swarms in the Cold Springs vicinity according to SeismoSight internal classification. Prior episodes occurred in 2008 (6 swarms), 2010 (1 swarm), 2012 (1 swarm), 2013 (8 swarms), and 2014 (2 swarms). These recurrent swarms align with regional observations that small-magnitude clusters often occur without producing surface rupture or larger triggered events.

No damage or felt reports were associated with swarm S20140619.1, consistent with its microseismic character. Continued monitoring by regional networks remains essential given the area’s proximity to the Reno–Sparks metropolitan corridor.

References

• U.S. Geological Survey, Quaternary Fault and Fold Database of the United States (updated 2023).
• Nevada Seismological Laboratory, University of Nevada, Reno, regional earthquake catalog.
• SeismoSight internal swarm classification records.