Seismic Swarm S20110411.1 Near Hawthorne, Nevada

A notable earthquake swarm designated S20110411.1 occurred 19 km south-southwest of Hawthorne, Nevada. The sequence began at 22:57 on 10 April 2011 and concluded at 05:11 on 13 April 2011, spanning 54 hours and 14 minutes. During this period, 104 earthquakes were recorded.

Analysis of the first 100 events reveals predominantly shallow focal depths between 0 and 17 km, with the majority clustered around 3–6 km. Magnitudes ranged from 0.6 to 4.1, with the largest event (magnitude 4.1) occurring at 00:22 on 11 April 2011 at a depth of 4 km. Several other notable shocks reached magnitudes of 3.9, 3.5, and 3.1 early in the sequence. Activity showed a rapid initial onset followed by a gradual decline, typical of swarm behavior where no single mainshock dominates.

The Hawthorne region lies in western Nevada’s Basin and Range Province, an area shaped by ongoing crustal extension. Normal faulting accommodates east-west stretching, producing a landscape of alternating mountain ranges and valleys. The site is situated near the northern Walker Lane, a zone of distributed shear that transfers motion between the Pacific and North American plates. This tectonic setting produces frequent small earthquakes and occasional swarms.

Historical records since 1 January 2000 document four prior swarms in the immediate area. These occurred in 2001 (one event) and 2006 (three events). Such episodic clustering underscores the region’s tendency toward swarm-type seismicity rather than isolated large events.

Seismic swarms in this part of Nevada are commonly linked to fluid migration along faults or minor magmatic processes at depth, though definitive source mechanisms require further geophysical study. Depths recorded during S20110411.1 are consistent with brittle failure in the upper crust, where temperatures permit stick-slip behavior.

Monitoring by regional networks continues to improve understanding of strain accumulation along Walker Lane structures. The 2011 swarm contributed valuable data on short-term clustering patterns that inform probabilistic hazard assessments for Mineral County and surrounding communities.

• SeismoSight internal swarm classification S20110411.1
• USGS Earthquake Catalog (regional Nevada events)