Seismic Swarm S20020104.1: Geological Context and Event Analysis Near Beatty, Nevada
Seismic swarm S20020104.1 occurred 45 km east-southeast of Beatty, Nevada, in the southwestern Great Basin. The sequence began at 19:52 on 3 January 2002 and concluded at 20:56 on 6 January 2002, encompassing 61 earthquakes over 73 hours and 3 minutes. Magnitudes remained very low, ranging from -0.2 to 1.6, with the majority clustered between 6 km and 9 km depth. A notable concentration of events took place on 4 January between 12:23 and 14:54, during which 28 earthquakes were recorded within a two-hour window, all at depths of 6–8 km.
The swarm unfolded in a region shaped by ongoing extensional tectonics of the Basin and Range Province. Beatty lies near the transition between the Walker Lane belt and the central Nevada seismic belt, where distributed normal and strike-slip faulting accommodates Pacific–North America plate motion. The local geology features Quaternary alluvial fans overlying Miocene volcanic and sedimentary rocks, with active faults associated with the Bare Mountain and Fluorspar Canyon systems. These structures have produced recurrent low-level seismicity, consistent with the five swarms documented since 1 January 2000, the earliest of which occurred in 2000.
Event depths indicate activity within the brittle upper crust, typical for the area’s geothermal gradient and fault architecture. The tight spatiotemporal clustering, small magnitudes, and absence of a dominant mainshock align with fluid-driven swarm behavior commonly observed along range-front faults in the southwestern Nevada volcanic field. No surface rupture or significant damage was associated with the sequence.
Continued monitoring of such swarms contributes to refined seismic hazard assessments for nearby infrastructure corridors and supports understanding of strain accumulation across the Death Valley–Walker Lane transition zone.
References
- USGS Earthquake Catalog (ANSS Comprehensive Catalog)
- Nevada Seismological Laboratory swarm records
- SeismoSight internal swarm classification S20020104.1