Seismic Swarm S20231102.1: Analysis of Activity Near Whites City, New Mexico

Seismic swarm S20231102.1 occurred 55 km south of Whites City, New Mexico, beginning at 19:01 on 1 November 2023 and concluding at 13:25 on 17 November 2023. Over 378 hours and 23 minutes, the swarm produced 271 earthquakes. This event represents one of only two swarms recorded in the region since 2000, following a single prior swarm in 2022.

The swarm unfolded in the Delaware Basin, a western subdivision of the larger Permian Basin. This geological province formed during the late Paleozoic era through subsidence and sedimentation within an ancient marine environment. Thick sequences of Permian-age carbonates, evaporites, and clastic rocks dominate the subsurface, reaching depths exceeding several kilometers. The basin's structural framework includes fault systems that developed during the Ancestral Rocky Mountains orogeny and later reactivation episodes.

Seismicity in southeastern New Mexico has historically remained low due to the region's intraplate setting and distance from active plate boundaries. However, the Delaware Basin has experienced increased earthquake rates in recent decades, coinciding with expanded hydrocarbon production. Depths of recorded events typically range from shallow sedimentary layers to mid-crustal levels around 5–10 km.

Examination of the first 100 events reveals predominantly low-magnitude activity. Magnitudes spanned from −0.1 to 3.4, with the majority falling between 1.0 and 2.5. Depths clustered between 4 km and 9 km, indicating a consistent mid-to-upper crustal source volume. Notable larger events included a magnitude 3.4 earthquake on 7 November at 6 km depth and several magnitude 2.9 events distributed across the initial days. Temporal clustering showed elevated rates on 2–3 November and again on 6–7 November, consistent with swarm-like behavior rather than a classic mainshock-aftershock sequence.

The limited historical record of swarms underscores the unusual nature of this sequence. Prior to 2022, no comparable clusters appear in the instrumental catalog for the immediate area. This pattern suggests episodic triggering mechanisms that warrant continued monitoring.

The geological setting features extensive salt and gypsum layers that can influence fluid migration and fault stability. Regional tectonics reflect a generally stable cratonic margin modified by far-field stresses from the Rio Grande Rift to the west.

References

• USGS Earthquake Catalog (earthquake.usgs.gov)
• New Mexico Bureau of Geology and Mineral Resources, Permian Basin studies
• SeismoSight internal swarm classification data