Seismic Swarm S20190424.1 Near Beatty, Nevada: Geological Context and Event Analysis

The seismic swarm designated S20190424.1 occurred approximately 47 km east-southeast of Beatty, Nevada, within the tectonically active Basin and Range Province. This region experiences ongoing extensional deformation driven by the broader interaction between the Pacific and North American plates, particularly through the Walker Lane belt, which accommodates a significant portion of the relative plate motion via right-lateral shear and normal faulting. The area's geology features numerous Quaternary faults, volcanic fields such as Crater Flat, and shallow crustal structures that facilitate frequent microseismicity.

The swarm initiated at 09:19 on 23 April 2019 and concluded at 20:21 on 24 April 2019, spanning 35 hours and 1 minute. During this period, 46 earthquakes were recorded. Magnitudes ranged from -0.5 to 2.2, with the largest event occurring early in the sequence. Depths were predominantly shallow, concentrated between 3 km and 6 km, though a few events reached up to 10 km. The majority of events exhibited magnitudes below 0.5, characteristic of microearthquake swarms often linked to fluid migration or stress adjustments along pre-existing faults rather than a single large rupture.

Event timing showed clustering in the initial hours, followed by sporadic activity tapering toward the end of the period. Depths remained consistent in the upper crust, suggesting involvement of brittle failure in near-surface layers influenced by regional extension. No events exceeded magnitude 3.0, aligning with the low-energy nature typical of swarm sequences in this part of Nevada.

Since 1 January 2000, the region has experienced 39 documented swarms. Annual occurrences include three in 2000, seven in 2002, two in 2003, two in 2005, one in 2006, two in 2007, five in 2008, five in 2009, two in 2010, two in 2012, one in 2014, four in 2015, and three in 2016. These statistics underscore the recurrent seismic behavior driven by the area's extensional regime and proximity to volcanic and hydrothermal systems.

Such swarms contribute to understanding local seismic hazards, particularly given the region's history of monitoring associated with nearby geological repositories. Continued observation aids in distinguishing swarm patterns from foreshock sequences that might precede larger events.

References

• United States Geological Survey Earthquake Catalog (earthquake.usgs.gov)
• Nevada Seismological Laboratory regional reports
• SeismoSight internal swarm classification data