Seismic Swarm S20050622.1: Analysis of Activity Near Beatty, Nevada

The region 37 km east-northeast of Beatty, Nevada, lies within the Basin and Range Province, where active extensional tectonics drive normal faulting along north-south trending structures. This setting produces frequent microseismicity and occasional earthquake swarms, particularly near the transition to the Walker Lane shear zone. Historical records document multiple seismic swarms in the area since 2000, consistent with fluid migration or aseismic slip triggering clustered events at depths of 6–14 km. Swarm S20050622.1 began at 20:47 UTC on 22 June 2005 and concluded at 14:17 UTC on 25 June 2005, spanning 65 hours and 29 minutes. A total of 137 earthquakes were recorded during this interval. Analysis of the first 100 events reveals predominantly low-magnitude activity, with values ranging from –1.0 to 1.1. The majority of magnitudes fell between –0.6 and 0.4, reflecting a microseismic character typical of swarm sequences. Depths clustered tightly around 7–9 km, with isolated events reaching 14 km or as shallow as 0 km. Temporal distribution shows an initial burst of activity within the first hours, followed by episodic bursts through 23 and 24 June. Several events of magnitude 1.0–1.1 occurred amid numerous negative-magnitude detections, indicating a high rate of small events without a single dominant mainshock. This pattern aligns with swarm behavior driven by distributed strain rather than classic aftershock decay. Prior to this swarm, three additional swarms had been identified in the region since 1 January 2000, occurring in 2000 (one swarm) and 2002 (two swarms). The 2005 sequence adds to this record of episodic clustered seismicity in southwestern Nevada.

References

• Nevada Seismological Laboratory, University of Nevada, Reno. Regional earthquake catalog and swarm documentation.
• USGS Earthquake Hazards Program. Tectonic framework of the Basin and Range Province.