Earthquake Swarm S20010308.1: Seismic Activity Near Hawthorne, Nevada in March 2001

An earthquake swarm designated S20010308.1 occurred 32 km south-southwest of Hawthorne, Nevada, between 14:21 on 7 March 2001 and 20:45 on 9 March 2001. Over 54 hours and 24 minutes, the sequence produced 47 earthquakes, providing a detailed record of clustered seismic energy release in the region.

The events exhibited magnitudes ranging from 0.3 to 3.3, with the largest shock recorded at 3.3 on 7 March at 14:43:56. Depths were predominantly shallow, concentrated between 6 km and 13 km, consistent with activity along crustal faults in the Basin and Range province. Early activity on 7 March included multiple events above magnitude 2.0 within the first hour, followed by a gradual decline in frequency and intensity through 9 March. The swarm displayed typical characteristics of fluid-influenced or fault-zone triggered sequences, with no single dominant mainshock but rather a distributed series of similar-sized events.

The Hawthorne area lies within the western Great Basin, part of the actively extending Basin and Range province. This tectonic setting features north-south trending normal faults that accommodate east-west crustal extension at rates of several millimeters per year. The location near Walker Lake places the swarm within the Walker Lane belt, a northwest-trending zone of right-lateral shear that accommodates a significant portion of Pacific-North American plate motion. Regional geology includes Quaternary alluvial deposits overlying Mesozoic basement rocks and Tertiary volcanic units, with active fault scarps visible in the Wassuk Range to the east.

Nevada maintains one of the highest levels of background seismicity in the contiguous United States due to ongoing extension. Historical records document numerous moderate events in Mineral County and adjacent areas throughout the twentieth century, including sequences associated with the same fault systems. The 2001 swarm fits within this pattern of episodic, low-to-moderate magnitude activity that rarely produces surface rupture but contributes to long-term strain release.

No damage or felt reports of significance were associated with S20010308.1, reflecting the modest magnitudes involved. Such swarms are common in the region and are monitored to improve understanding of fault interactions and potential precursors to larger events.

References
United States Geological Survey Earthquake Catalog
Nevada Seismological Laboratory Regional Reports
Basin and Range Province Tectonic Summaries, USGS Professional Papers