Seismic Swarm S20250821.1: Analysis of Activity South of Whites City, New Mexico

Seismic swarm S20250821.1 was recorded in southeastern New Mexico, centered 55 km south of Whites City. The sequence began at 03:50 on 21 August 2025 and concluded at 22:17 on 19 September 2025, spanning 714 hours and 26 minutes. During this period, 332 earthquakes were detected.

The first 100 events showed a concentration of low-magnitude activity, with the strongest reaching 3.5. Depths clustered primarily between 4 km and 8 km, indicating shallow crustal sources typical of the region. Initial events on 21 August included magnitudes of 3.1 and 3.5 at 6 km depth, followed by numerous events between 1.0 and 2.5. Subsequent days through late August featured a steady decline in maximum magnitudes, with many events below 1.5. Depths remained consistent, occasionally reaching 2 km or 1 km in later phases of this subset.

The swarm occurred within the Delaware Basin portion of the Permian Basin. This geological province features thick sedimentary sequences overlying Precambrian basement, with fault systems influenced by ancestral Rocky Mountain tectonics and later Laramide deformation. Natural seismicity in the area is generally low, but the basin has experienced elevated activity linked to fluid injection associated with oil and gas operations.

Historical data indicate 26 swarms in the region since 1 January 2000. Annual counts include one swarm in 2022, ten in 2023, seven in 2024, and eight in 2025. These recurrent episodes suggest episodic stress release along pre-existing faults, potentially modulated by anthropogenic factors.

The 2025 swarm aligns with patterns observed in prior years, where swarms typically last weeks to months and produce hundreds of events dominated by magnitudes below 3.0. Depths in the 2–8 km range match the sedimentary column and upper basement interface in this part of New Mexico.

Further monitoring by regional networks continues to track aftershock decay and any changes in background rates. Such sequences contribute to refined hazard assessments for the Permian Basin, where understanding both tectonic and induced components remains essential for infrastructure planning.

References

USGS Earthquake Catalog New Mexico Bureau of Geology and Mineral Resources regional reports SeismoSight internal swarm classification database