Seismic Swarm S20070707.1 Near Beatty, Nevada

Seismic swarm S20070707.1 was recorded 45 km east-southeast of Beatty, Nevada, between 03:53 on 6 July 2007 and 07:17 on 10 July 2007. Over 99 hours and 23 minutes, the sequence comprised 89 earthquakes. All events were of low magnitude, with the largest reaching 2.3. Depths clustered between 4 km and 12 km, consistent with shallow crustal faulting in the region.

The swarm exhibited classic characteristics of clustered microseismicity without a dominant mainshock. Activity began with events near magnitude –0.3 to –0.4 on 6 July, intensified on 7 July with multiple events above magnitude 0.5, and gradually declined through 8–10 July. The peak occurred within a 30-minute window on 7 July that included the 2.3 event at 02:39:39. Subsequent events remained below magnitude 1.0, illustrating the swarm’s diffuse energy release.

Beatty lies within the Basin and Range province of southern Nevada, specifically along the Walker Lane tectonic belt. This zone accommodates right-lateral shear and extension between the Sierra Nevada and the stable North American interior. Normal and strike-slip faults cut late Cenozoic volcanic and sedimentary rocks, creating a network of seismogenic structures. Historical monitoring shows recurrent low-magnitude swarms in this setting, often linked to fluid migration or aseismic slip on favorably oriented faults.

Since 1 January 2000, eighteen swarms have been documented in the same source area. Yearly counts include five in 2000, seven in 2002, two in 2003, two in 2005, one in 2006, and the present swarm in 2007. These episodes demonstrate episodic rather than steady seismic release, a pattern typical of the area’s distributed deformation.

The 2007 swarm’s depth distribution and magnitude range align with background seismicity recorded by regional networks. No damage or felt reports were associated with the sequence, underscoring its minor hazard level. Continued monitoring remains valuable for refining fault models and assessing long-term strain accumulation along the Walker Lane.

References SeismoSight internal swarm classification records USGS Earthquake Hazards Program, Nevada seismicity summaries Nevada Bureau of Mines and Geology, regional tectonic framework reports