Seismic Swarm S20100212.2: Analysis of Activity Near Beatty, Nevada

Seismic swarm S20100212.2 occurred approximately 49 km east-southeast of Beatty, Nevada, from 00:49 UTC on 12 February 2010 to 09:08 UTC on 19 February 2010. Over 176 hours and 18 minutes, the swarm produced 89 earthquakes, with magnitudes ranging from -0.5 to 0.8 and focal depths predominantly between 0 and 11 km.

The events clustered tightly in time and space, exhibiting the characteristic pattern of a seismic swarm: numerous small-magnitude earthquakes without a distinct mainshock-aftershock sequence. The largest event reached magnitude 0.8 at 02:47 UTC on 13 February at 8 km depth. Depths remained shallow throughout, consistent with activity within the brittle upper crust.

Regional Geological Setting

Beatty lies within the Basin and Range Province of southwestern Nevada, a region shaped by extensional tectonics since the Miocene. Normal faulting accommodates east-west crustal stretching, producing north-south trending mountain ranges and valleys. The area sits near the transition to the Walker Lane shear zone, where dextral strike-slip motion contributes to regional deformation.

The local geology features Paleozoic sedimentary rocks overlain by Tertiary volcanic deposits associated with the Southwestern Nevada Volcanic Field. Timber Mountain and Black Mountain calderas record major Miocene eruptions that influenced the present-day fault network. Ongoing extension along range-front faults sustains low to moderate seismicity.

Historical Swarm Context

Instrumental records since 2000 document 31 swarms in the same vicinity. Annual counts vary: five in 2000, seven in 2002, two each in 2003 and 2005, one in 2006, two in 2007, seven in 2008, four in 2009, and one in 2010. This recurrence indicates persistent, episodic strain release rather than isolated tectonic events.

Interpretation and Implications

The February 2010 swarm reflects fluid migration or aseismic slip along favorably oriented faults within the extensional regime. Shallow depths and low magnitudes suggest limited rupture areas and minimal surface deformation potential. No damage or felt reports were associated with the sequence.

Continued monitoring of the Beatty area remains important for understanding how swarm activity interacts with the broader fault system. Such episodes contribute to long-term seismic hazard assessments in this tectonically active portion of the Basin and Range.

References

USGS Earthquake Catalog (earthquake.usgs.gov)
Nevada Seismological Laboratory, University of Nevada, Reno
USGS Professional Paper 1516: Geology of the Southwestern Nevada Volcanic Field