Seismic Swarm S20070124.1: Analysis of Activity Near Goldfield, Nevada

A seismic swarm designated S20070124.1 was recorded 34 km south-southeast of Goldfield, Nevada, between 11:30 on 24 January 2007 and 03:00 on 27 January 2007. Over 63 hours and 30 minutes, the sequence produced 85 earthquakes. The events occurred within the Basin and Range Province, where regional extension along normal faults drives ongoing seismic activity. Goldfield lies in Esmeralda County, an area historically shaped by mining and situated amid Quaternary fault systems that accommodate crustal stretching.

The swarm began with a magnitude 4.1 event at 6 km depth. Subsequent activity included multiple events exceeding magnitude 2.0, such as a 3.3 at 6 km depth roughly 35 minutes later and a 3.0 at 6 km depth about 45 minutes after that. Depths throughout the sequence ranged from surface level to 18 km, with the majority clustered between 4 km and 8 km. Later notable shocks reached magnitude 2.9 at 5 km depth and 2.8 at 6 km depth on 26 January. The pattern showed a rapid initial burst followed by a gradual decline, typical of swarm behavior where no single mainshock dominates.

Geologically, the region features Basin and Range normal faulting superimposed on older volcanic and sedimentary rocks. Goldfield itself developed around early twentieth-century epithermal gold deposits linked to Miocene volcanism. Modern seismicity reflects continued extension rates of several millimeters per year across the province. The swarm location aligns with known zones of distributed faulting southeast of the town, where small-magnitude events frequently occur without producing surface rupture.

Historical records since 2000 indicate four prior swarms in the immediate area, occurring in 2000, 2001, 2002, and 2006. Each consisted of a single documented swarm episode, suggesting recurrent but infrequent clustered activity. Such sequences differ from aftershock series by lacking a clear triggering mainshock and instead reflecting fluid migration or aseismic slip along faults.

The 2007 swarm contributed to the regional catalog by highlighting persistent low-level deformation. Depths predominantly in the upper crust are consistent with brittle failure in the seismogenic zone, while occasional deeper events point to possible involvement of transitional crustal layers. No damage or felt reports beyond the immediate vicinity were associated with the largest shocks.

Continued monitoring in this portion of Nevada remains important given the broader tectonic framework. The documented swarm underscores the value of dense seismic networks in capturing transient clusters that illuminate fault mechanics and strain accumulation patterns.