Seismic Swarm S20090726.2: Analysis of Activity Near Beatty, Nevada

Seismic swarm S20090726.2 was recorded in the area 47 km east-southeast of Beatty, Nevada. The sequence began at 13:00 on 25 July 2009 and concluded at 07:04 on 24 August 2009, spanning 714 hours and 3 minutes. During this period, 381 earthquakes were detected.

Analysis of the first 100 events shows predominantly low-magnitude activity. Magnitudes ranged from -0.9 to 1.1, with the majority falling between -0.6 and 0.5. Depths were concentrated between 1 km and 11 km, most commonly 7–10 km. The sequence opened with events near magnitude -0.6 at 10 km depth and remained at low levels through the initial hours. Scattered positive magnitudes appeared later, including peaks of 0.9 on 26 July and 1.1 on 29 July, both at approximately 9 km depth. Depth variations were modest, with occasional shallower events near 1–5 km interspersed among the dominant mid-crustal activity.

This swarm occurred within the Basin and Range province of southwestern Nevada, a region shaped by Cenozoic crustal extension. The local geology features normal faulting and right-lateral shear associated with the Walker Lane tectonic belt. Historical volcanic centers, including the Timber Mountain caldera complex to the northeast, have influenced the crustal structure and may contribute to fluid migration that triggers swarm-type seismicity.

Earthquake swarms are recurrent in this portion of Nye County. Records since 2000 document 28 such swarms, distributed across multiple years with varying event counts. The 2009 activity fits this established pattern of episodic, low-magnitude clustering rather than mainshock-aftershock sequences.

Ongoing monitoring by regional seismic networks continues to track activity in the area. The combination of extensional tectonics and possible hydrothermal influences sustains the potential for similar swarms in the future.

References

USGS Earthquake Hazards Program – Nevada Seismicity
Nevada Bureau of Mines and Geology – Regional Geologic Maps
SeismoSight internal swarm classification records