Seismic Swarm S20081207.1: Analysis of Activity Near Pahrump, Nevada
Seismic swarm S20081207.1 was recorded 50 km NNW of Pahrump, Nevada, beginning at 18:09 on 6 December 2008 and concluding at 10:56 on 12 December 2008. Over 136 hours and 46 minutes, the sequence produced 55 earthquakes. This event aligns with patterns observed in the region since 2000, where 23 swarms have occurred, distributed across years as follows: four in 2000, seven in 2002, two in 2003, two in 2005, one in 2006, two in 2007, and five in 2008.
The swarm exhibited predominantly low-magnitude events, with values ranging from -0.6 to 1.0. The largest shock reached magnitude 1.0 on 8 December at 17:10:44. Depths clustered between 1 km and 14 km, averaging near 9 km, consistent with shallow crustal seismicity typical of the area. Early activity on 6 December featured events near 0.2 to -0.3 magnitude at depths of 6–8 km. Subsequent days showed a gradual increase in the number of detections, peaking mid-sequence with multiple events on 7–11 December. Later stages included isolated events up to magnitude 0.5, tapering off by 12 December.
This distribution reflects classic swarm characteristics: a dense cluster without a dominant mainshock, driven by fluid migration or aseismic slip along minor faults. Magnitudes remained below 2.0 throughout, indicating limited energy release and low potential for damage. Depths stayed within the upper 15 km, pointing to brittle failure in the seismogenic zone.
The Pahrump region lies within the Basin and Range Province of southern Nevada, an area shaped by Cenozoic extension that has produced numerous normal and strike-slip faults. Historical seismicity here includes recurrent small-magnitude swarms linked to ongoing tectonic adjustment. Such activity contributes to the broader understanding of crustal deformation in the western United States, where swarms serve as indicators of subsurface stress changes.
References:
SeismoSight internal swarm classification records
USGS Earthquake Catalog for regional context