Seismic Swarm Near Hawthorne, Nevada: April 2014 Event

The region surrounding Hawthorne, Nevada, lies within the Basin and Range Province, an area shaped by extensional tectonics that produces numerous normal faults. Western Nevada, including Mineral County, sits at the eastern margin of the Walker Lane belt, a zone of distributed shear that absorbs a portion of the relative motion between the Pacific and North American plates. This tectonic setting generates frequent small-magnitude earthquakes and occasional earthquake swarms.

SeismoSight recorded swarm S20140421.1 beginning at 14:11 on 20 April 2014 and concluding at 21:02 on 21 April 2014, 16 km east-northeast of Hawthorne. Over the 30-hour, 51-minute period the network detected 28 events. Magnitudes ranged from –0.1 to 3.1, with the largest shock occurring at 15:35 on 20 April at a focal depth of 6 km. Most events clustered between 5 km and 10 km depth, consistent with brittle failure in the upper crust of this portion of the Walker Lane.

The sequence displayed classic swarm characteristics: a rapid onset, lack of a single dominant mainshock-aftershock pattern, and a gradual decay in activity. Twenty-one events were recorded on 20 April and seven on 21 April. The majority of events remained below magnitude 1.0, although four shocks reached or exceeded magnitude 1.4. Depths showed modest variation, with the shallowest event at 0 km and the deepest at 10 km.

Historical records maintained by SeismoSight indicate five swarms have occurred in the same source area since 1 January 2000. Three swarms took place in 2011, one in 2012, and the present sequence in 2014. This recurrence suggests persistent, localized stress release along favorably oriented faults within the Walker Lane.

The 2014 swarm did not produce reported damage or felt reports beyond the immediate vicinity, consistent with the modest magnitudes and rural setting. Continued seismic monitoring remains important because the Walker Lane accommodates approximately 10–15 mm per year of right-lateral shear, sustaining the potential for larger earthquakes elsewhere in the belt.

References

USGS Earthquake Hazards Program
Nevada Seismological Laboratory, University of Nevada, Reno
Nevada Bureau of Mines and Geology, Geological Survey of Nevada