Seismic Swarm S20230314.1 Near Deep Springs, California

A seismic swarm designated S20230314.1 was recorded 15 km north of Deep Springs, California, beginning at 13:20 UTC on 13 March 2023 and concluding at 09:14 UTC on 17 March 2023. Over the 91-hour 53-minute period, 75 earthquakes were detected, with magnitudes ranging from 0.6 to 3.8. Depths varied from surface levels to 13 km, consistent with shallow crustal activity typical of the Basin and Range province.

The sequence featured several events of magnitude 3.0 or greater, including two at 3.8 on 14 March. Activity peaked during the first 48 hours, with frequent events between magnitudes 1.5 and 2.8 occurring at intervals of minutes to hours. Later stages showed reduced frequency and lower magnitudes, tapering to isolated smaller shocks by 17 March. Depths remained predominantly under 10 km, indicating brittle failure within the upper crust.

The Deep Springs region lies within the western Basin and Range extensional province, characterized by normal faulting and distributed deformation. This tectonic setting results from ongoing east-west extension linked to the broader Pacific-North America plate boundary. Nearby structures include the White Mountains fault zone and elements of the Eastern California Shear Zone, which accommodate right-lateral shear and contribute to moderate seismicity. Historical records document recurrent small-to-moderate earthquakes driven by these active faults.

Since 2000, only one prior swarm has been identified in the immediate area, occurring in 2020. This low recurrence rate aligns with the diffuse nature of Basin and Range seismicity, where swarms often reflect fluid migration or stress triggering along minor faults rather than mainshock-aftershock sequences on major structures.

The March 2023 swarm provides a clear example of clustered, low-magnitude activity without a dominant mainshock. Such patterns are common in extensional regimes and typically do not indicate elevated long-term hazard beyond background levels. Monitoring by regional networks continues to track any subsequent activity in this tectonically active corridor.

References

USGS Earthquake Hazards Program – Basin and Range Province overview
California Geological Survey – Active Faults of Inyo County
Nevada Seismological Laboratory – Regional Seismicity Summaries