Seismic Swarm S20070623.1 Near Beatty, Nevada: Analysis and Regional Context

Seismic swarm S20070623.1 occurred 44 km east-southeast of Beatty, Nevada, beginning at 09:26 on 23 June 2007 and concluding at 15:53 on 24 June 2007. Over this 30-hour, 26-minute interval, 40 earthquakes were recorded. Magnitudes ranged from -0.8 to 0.5, with the majority falling between -0.5 and -0.3. Focal depths clustered predominantly between 9 km and 11 km, though a few events reached as shallow as 0 km or as deep as 12 km.

The sequence displayed typical swarm characteristics: no single dominant mainshock, a rapid onset followed by sustained low-level activity, and a gradual decline in event rate. Early events on 23 June clustered tightly in both time and magnitude, while later activity on 24 June became more sporadic. Depths remained stable overall, suggesting a consistent source volume within the upper crust.

The Beatty region lies within the Basin and Range province of southern Nevada, where east-west crustal extension produces north-south trending normal faults and horst-and-graben topography. The area also forms part of the Walker Lane shear zone, accommodating dextral shear between the Pacific and North American plates. Nearby structures include segments of the Furnace Creek and Death Valley fault systems, which have produced moderate historical earthquakes. The local geology features Paleozoic sedimentary rocks overlain by Tertiary volcanic deposits associated with the Timber Mountain caldera complex, approximately 30 km to the northeast. These volcanic units contribute to elevated heat flow and fractured rock that can facilitate fluid migration and swarm activity.

Since 1 January 2000, seventeen swarms have been documented in the immediate vicinity. Prior episodes occurred in 2000 (five swarms), 2002 (seven swarms), 2003 (two swarms), 2005 (two swarms), and 2006 (one swarm). This recurrence pattern indicates persistent, low-level strain release along favorably oriented faults, possibly modulated by hydrothermal fluids or magmatic processes at depth.

The 2007 swarm fits within this established background of episodic microseismicity. Its maximum magnitude of 0.5 and limited spatial extent align with previous events that have not escalated into larger mainshock-aftershock sequences. Continued monitoring remains important given the proximity of critical infrastructure and the historical potential for larger earthquakes on regional faults.

References

• U.S. Geological Survey Earthquake Hazards Program, Nevada Seismicity
• Nevada Bureau of Mines and Geology, Regional Geologic Maps
• SeismoSight internal swarm classification records