Seismic Swarm S20240118.1: Analysis of Activity Near Pahrump, Nevada

On 18 January 2024, a seismic swarm designated S20240118.1 was recorded approximately 51 km north-northwest of Pahrump, Nevada. The sequence began at 11:10 local time and concluded at 19:45, encompassing 51 earthquakes over a duration of 8 hours and 35 minutes. All events occurred at shallow depths between 4 and 7 km, with magnitudes ranging from -0.3 to 1.7. The largest event, magnitude 1.7, took place at 14:59, while several smaller shocks clustered between 13:35 and 15:00, highlighting a brief period of elevated activity.

The swarm exhibited typical characteristics of low-magnitude, shallow seismicity. Early events remained below magnitude 0.0 until a notable increase around 13:39, when magnitudes reached 0.6 and subsequently 1.2. Activity persisted with frequent events of magnitude 0.0 to 0.2 through the afternoon, tapering after 16:00. Depths remained consistent, predominantly at 5–6 km, suggesting a localized source volume within the upper crust.

This region lies within the Basin and Range Province of southern Nevada, an area defined by extensional tectonics driven by northwest-directed shear along the Walker Lane belt. Normal and strike-slip faults accommodate ongoing crustal stretching, producing frequent small earthquakes and occasional swarms. The Pahrump Valley sits near the transition between the Sierra Nevada and the extended Basin and Range, where Quaternary faulting contributes to the observed seismicity. Historical patterns indicate that such swarms are common in this tectonic setting, often linked to fluid migration or minor stress adjustments along pre-existing faults rather than large mainshock-aftershock sequences.

Since 1 January 2000, 45 swarms have been documented in the area. Annual counts include five in 2000, seven in 2002, two each in 2003 and 2005, one in 2006, two in 2007, six in 2008, four in 2009, three in 2010, one each in 2012 and 2014, three in 2015, four in 2016, one in 2019, two in 2022, and one in 2023. These statistics underscore the recurrent nature of swarm activity, with peaks in the early 2000s and mid-2010s.

The 2024 swarm aligns with this established pattern, reinforcing the value of continuous monitoring for understanding regional strain accumulation. No damage or felt reports were associated with the events, consistent with their small magnitudes and depths.

References

SeismoSight internal swarm classification records.
USGS Earthquake Catalog for regional tectonic context.
Nevada Bureau of Mines and Geology, Basin and Range Province reports.