Seismic Swarm S20230115.1 Near Toyah, Texas: Event Analysis and Regional Context

Seismic swarm S20230115.1 was recorded 54 km northwest of Toyah in Reeves County, Texas. The sequence began at 14:14 on 14 January 2023 and concluded at 23:36 on 19 January 2023, spanning 129 hours and 22 minutes. During this period, 72 earthquakes were detected, with magnitudes ranging from 0.0 to 2.7 and focal depths primarily between 3 km and 8 km.

The temporal distribution showed peak activity on 14 and 15 January, with multiple events exceeding magnitude 2.0. Notable shocks included a magnitude 2.7 event at 20:25 on 14 January (depth 7 km) and another magnitude 2.7 at 02:03 on 15 January (depth 6 km). Later days featured fewer but still recurrent events, such as magnitude 2.4 and 2.3 shocks on 17 January at depths of 5 km. Depths clustered around 5–8 km, consistent with shallow crustal processes. Magnitudes remained below 3.0 throughout, indicating low-level energy release without significant mainshock-aftershock pairing.

This swarm represents the second such sequence in the area since 2000, following one in 2022. The 2023 event displayed a gradual onset, sustained low-magnitude repetition, and abrupt cessation after five days, characteristic of fluid-related triggering rather than tectonic mainshock sequences.

The Toyah region lies within the western Permian Basin, specifically the Delaware Basin portion. This sedimentary province formed during the Pennsylvanian and Permian periods through subsidence and accumulation of thick carbonate and clastic deposits exceeding 3 km. Underlying Precambrian basement rocks experienced minor reactivation along inherited faults during the late Paleozoic Ouachita orogeny. Present-day seismicity in Reeves County is frequently associated with anthropogenic factors, including wastewater injection from hydrocarbon production, which can elevate pore pressure along pre-existing faults at depths of 4–8 km.

Historical records indicate sparse natural seismicity prior to extensive oil and gas development. The basin's tectonic stability has been punctuated by induced events since the mid-2000s, aligning with expanded injection volumes. Depths recorded in swarm S20230115.1 fall within the typical range for such induced activity.

Further monitoring by regional networks continues to track microseismicity in this portion of the Permian Basin to assess long-term trends.

References

USGS Earthquake Catalog
Texas Bureau of Economic Geology Permian Basin studies
SeismoSight internal swarm classification records