Seismic Swarm S20110715.1 Near Hawthorne, Nevada

Seismic swarm S20110715.1 occurred 12 km southwest of Hawthorne, Nevada, in Mineral County. The sequence began at 14:24 on 14 July 2011 and concluded at 05:17 on 17 July 2011, spanning 62 hours and 53 minutes. During this period, 34 earthquakes were recorded, with magnitudes ranging from 0.8 to 2.9 and focal depths between 0 and 3 km. The largest event, magnitude 2.9, took place at 00:14 on 15 July.

The swarm exhibited a typical pattern of clustered, low-magnitude events without a single dominant mainshock. Activity peaked in the early hours of 15 July, with multiple events occurring within minutes of each other. Shallow depths indicate that rupture occurred within the uppermost crust, consistent with fluid-driven or fault-zone processes common in swarm sequences.

The Hawthorne area lies in the western Basin and Range Province, within the Walker Lane tectonic belt. This region accommodates northwest-directed dextral shear between the Pacific and North American plates, resulting in a network of active normal and strike-slip faults. Extension rates average 1 cm per year, producing frequent small earthquakes and episodic swarms. The local geology features Quaternary alluvium overlying Tertiary volcanic and sedimentary rocks, with mapped faults including strands of the Wassuk Range fault system to the west.

Historical records since 2000 document eight swarms in the immediate vicinity. These occurred in 2001 (one swarm), 2006 (three swarms), and 2011 (four swarms, including S20110715.1). Such recurrent activity reflects ongoing tectonic strain and possible hydrothermal fluid involvement along pre-existing fractures.

No damage or felt reports of significance were associated with this swarm, reflecting the small magnitudes involved. Continued monitoring remains important given the region’s position in a seismically active corridor.

References

USGS Earthquake Hazards Program – Nevada Seismicity
Nevada Bureau of Mines and Geology – Walker Lane Tectonic Summary