Seismic Swarm S20240429.2: Analysis of Activity Near Prague, Oklahoma

A notable earthquake swarm, designated S20240429.2, occurred 8 km northwest of Prague, Oklahoma. The sequence began at 22:06 on 28 April 2024 and concluded at 00:25 on 5 June 2024, spanning 890 hours and 19 minutes. During this period, 969 earthquakes were recorded. Analysis of the first 100 events reveals predominantly microseismic activity. Magnitudes ranged from -2.2 to 2.4, with the majority falling between -2.0 and 0.0. Depths were shallow, concentrated between 2 km and 6 km, consistent with basement-involved faulting in the region. The largest event, magnitude 2.4, occurred on 1 May 2024 at 23:36:34. Early events on 28 April showed depths of 3–5 km and negative magnitudes, transitioning to slightly higher values and occasional positive magnitudes by late April and early May. Temporal clustering was evident, with multiple events occurring within minutes during peak periods. The Prague area lies within the Central Interior Platform of the North American craton. The local geology features Precambrian granitic basement overlain by Paleozoic sedimentary rocks, including the Hunton Limestone and Woodford Shale. The Wilzetta Fault Zone, a northeast-trending basement fault system, traverses the region and has been linked to past seismic sequences. Historical records indicate four swarms in the vicinity since 2000: one in 2011, one in 2023, and two in 2024. The 2011 swarm preceded the magnitude 5.7 Prague earthquake, which occurred on a segment of the Wilzetta Fault and caused significant damage. Oklahoma’s seismicity has been influenced by fluid injection associated with oil and gas operations, particularly wastewater disposal into deep formations near basement rocks. Regulatory measures implemented after 2015 have reduced overall rates, yet localized swarms continue to occur along pre-existing faults. Depths observed in S20240429.2 align with reactivation of these structures at 2–6 km. This swarm underscores the ongoing seismic hazard in central Oklahoma and the value of dense monitoring networks for tracking induced sequences. Continued observation will help refine understanding of fault behavior and injection-related triggering mechanisms.

References

• U.S. Geological Survey Earthquake Catalog
• Oklahoma Geological Survey Seismicity Reports
• SeismoSight Internal Swarm Classification Database