Seismic Swarm S20090811.1 Near Beatty, Nevada

A seismic swarm designated S20090811.1 occurred approximately 21 km north of Beatty in Nye County, Nevada, between 02:26 on 10 August 2009 and 09:43 on 12 August 2009. Over the 55-hour duration, the sequence produced 47 earthquakes with magnitudes ranging from -0.4 to 1.5 and focal depths predominantly between 3 km and 6 km. The events clustered tightly in both space and time, characteristic of swarm behavior rather than a mainshock-aftershock sequence.

The swarm initiated with a magnitude 0.2 event at 4 km depth, followed by numerous microearthquakes of magnitude 0.5 or less. Peak activity included a magnitude 1.5 earthquake at 6 km depth on 10 August at 21:07, accompanied by several events in the 0.6–0.9 range within the same hour. Activity persisted at low levels through 11 August before tapering, with the final recorded event of magnitude 0.3 occurring at 09:43 on 12 August.

Nevada lies within the Basin and Range Province, where active extensional tectonics driven by Pacific–North American plate interaction produces abundant normal faulting. The region surrounding Beatty occupies the southern Walker Lane belt, a zone of distributed shear and extension that accommodates roughly 20 % of the relative plate motion. Historical seismicity in this area reflects both regional fault systems and local structures associated with Miocene volcanism and Basin and Range faulting.

Since 1 January 2000, six swarms have been documented in the immediate vicinity, occurring in 2002 (two swarms), 2008 (two swarms), and 2009 (two swarms). These recurrent swarms underscore the persistent low-level seismic hazard in the area, although individual events remain small and typically cause no damage.

References

• Nevada Seismological Laboratory, University of Nevada, Reno
• U.S. Geological Survey Earthquake Hazards Program
• Nevada Bureau of Mines and Geology, University of Nevada, Reno