Seismic Swarm S20140120.1: Analysis of Activity Near Spanish Springs, Nevada
Seismic swarm S20140120.1 was recorded beginning at 06:59 on 19 January 2014 and concluding at 10:53 on 22 January 2014. The events were centered 2 km northeast of Spanish Springs, Nevada. Over the 75-hour-and-54-minute duration, a total of 91 earthquakes were detected.
The swarm exhibited typical characteristics of clustered microseismicity, with event magnitudes ranging from -0.6 to 2.4. Depths were predominantly between 7 km and 13 km, consistent with shallow crustal faulting in the region. The largest event reached magnitude 2.4 at 07:31 on 20 January 2014. Activity showed temporal clustering, with peak rates on 20 January, followed by a gradual decline through 22 January. Smaller events dominated the sequence, reflecting the low-energy release typical of swarm behavior rather than a mainshock-aftershock pattern.
Spanish Springs lies within the northern Basin and Range province, where extensional tectonics drive normal faulting along north-south trending structures. The area forms part of the Walker Lane belt, a zone of distributed right-lateral shear that accommodates approximately 20 percent of the Pacific-North American plate boundary motion. This tectonic setting produces frequent small-magnitude earthquakes and episodic swarms. Historical records indicate elevated swarm activity in the vicinity, with 16 documented swarms since 1 January 2000. These include six events in 2008, one in 2012, eight in 2013, and the present swarm in 2014.
Such swarms are commonly linked to fluid migration or aseismic slip on pre-existing faults within the extensional regime. Depths observed in S20140120.1 align with the brittle-ductile transition zone in this portion of the crust. No surface rupture or significant damage was associated with the sequence, consistent with the modest energy release.
Ongoing monitoring by regional seismic networks continues to track microseismicity in the Spanish Springs area, contributing to refined hazard assessments for the Reno metropolitan region. The 2014 swarm underscores the persistent seismic productivity of the Walker Lane transition zone.
References
SeismoSight internal swarm catalog
USGS Earthquake Catalog
Nevada Seismological Laboratory regional reports