Seismic Swarm S20250101.2: Analysis of Recent Activity South of Goldfield, Nevada

A seismic swarm designated S20250101.2 was recorded 36 km south of Goldfield, Nevada, beginning at 23:50 on 31 December 2024 and concluding at 08:29 on 4 January 2025. Over 80 hours and 38 minutes, 65 earthquakes were detected. Magnitudes ranged from 0.6 to 2.5, with the largest events occurring on 1 January (M2.4), 3 January (M2.5), and 4 January (M2.5). Focal depths were predominantly shallow, between 0 and 9 km, consistent with activity along upper-crustal faults.

The sequence exhibited classic swarm characteristics: a gradual onset, multiple events of similar magnitude without a dominant mainshock, and a relatively rapid decay after peak activity on 1–3 January. Most events clustered between 4 and 7 km depth, suggesting a compact source volume likely associated with fluid migration or aseismic slip on a normal fault segment.

Regional Geological Context

Goldfield lies in Esmeralda County within the western Basin and Range Province. This extensional domain features north-trending normal faults that accommodate roughly 10–15 mm per year of east-west stretching. The swarm epicenters fall near the transition between the central Walker Lane belt—a zone of distributed dextral shear—and the Sierra Nevada–Great Valley microplate boundary. Quaternary basaltic and rhyolitic volcanic rocks, along with older sedimentary units of the Goldfield mining district, overlie the seismogenic crust.

Seismicity in this portion of Nevada is driven by ongoing tectonic extension rather than volcanic processes. Historical instrumented records show that small-magnitude swarms are common, often occurring on secondary faults subsidiary to the major range-bounding structures such as the Goldfield Hills fault system.

Historical Swarm Activity

Since 1 January 2000, seventeen swarms have been documented in the immediate region. These episodes occurred in the following years with the indicated counts: 2000 (1), 2001 (1), 2002 (1), 2006 (1), 2007 (2), 2010 (1), 2011 (2), 2012 (1), 2015 (2), 2017 (1), 2021 (1), and 2024 (3). The recurrence pattern indicates that swarm-type sequences constitute a persistent mode of strain release in the Goldfield area, typically lasting from several days to a few weeks and producing events below magnitude 3.0.

Implications

The S20250101.2 swarm reinforces the expectation of frequent, low-level seismic activity along the Nevada segment of the Walker Lane. Although individual events posed negligible hazard, the episode underscores the value of continuous monitoring for identifying changes in background rates that may precede larger earthquakes on nearby mapped faults.

References

SeismoSight internal swarm catalog S20250101.2
USGS Quaternary Fault and Fold Database of the United States
Nevada Bureau of Mines and Geology, Earthquake Hazards in Nevada (updated 2023)
USGS Earthquake Catalog, Nevada region (2000–2025)