Seismic Swarm S20240806.1: Analysis of Recent Activity Near Prague, Oklahoma

Seismic swarm S20240806.1 occurred 8 km west-northwest of Prague, Oklahoma, beginning at 04:56 on 5 August 2024 and concluding at 18:49 on 13 August 2024. Over 205 hours and 52 minutes, the event sequence produced 84 earthquakes, with magnitudes ranging from -1.7 to 1.8 and focal depths predominantly between 3 and 7 km. The swarm exhibited typical characteristics of clustered microseismicity, featuring numerous events below magnitude 0.0 alongside a modest number of events exceeding magnitude 0.5.

The temporal distribution showed peak activity on 6 August, with 19 recorded events concentrated in the early morning hours. Magnitudes remained low throughout, with the largest event (M1.8) occurring on 9 August at 23:42:46 UTC at a depth of 5 km. Depths clustered around 4–6 km, consistent with shallow crustal faulting in the region. Negative-magnitude detections indicate a high-resolution monitoring network capable of capturing microearthquakes, reflecting the dense instrumentation deployed in central Oklahoma.

Geologically, the Prague area lies within Lincoln County on the Cherokee Platform, part of the stable cratonic interior of North America. The basement consists of Precambrian granite and rhyolite overlain by Paleozoic sedimentary strata, including the Arbuckle Group, which serves as a primary target for wastewater disposal. Regional fault systems, such as the Wilzetta Fault Zone, provide preexisting planes of weakness that can be reactivated by pore-pressure changes. Historical seismicity in Oklahoma remained low prior to 2009 but increased sharply thereafter, coinciding with expanded oil-and-gas operations and associated fluid injection.

Since 1 January 2000, seven swarms have been documented in the immediate vicinity, occurring in 2011 (1 swarm), 2023 (1 swarm), and 2024 (5 swarms). The 2011 sequence included the M5.7 Prague earthquake, which caused significant damage and was linked to nearby injection wells. Subsequent swarms have been smaller in both magnitude and event count, suggesting a possible modulation of stress release through ongoing fluid management practices.

This latest swarm aligns with the pattern of induced seismicity observed across central Oklahoma, where cumulative wastewater injection volumes correlate with elevated earthquake rates. Depths of 3–7 km place events within the crystalline basement or basal sedimentary section, where critically stressed faults are most susceptible to triggering. No events exceeded magnitude 2.0, indicating limited energy release compared with earlier sequences.

Continued monitoring by regional networks remains essential for tracking any evolution in swarm behavior. The data underscore the value of high-resolution catalogs in distinguishing natural from anthropogenic signals and informing mitigation strategies in areas of active resource development.

References

SeismoSight internal swarm classification S20240806.1 (2024).
Oklahoma Geological Survey, Earthquake Catalog (through 2024).
U.S. Geological Survey, Earthquake Hazards Program, Central and Eastern U.S. Seismicity.
Ellsworth, W. L. (2013). Injection-induced earthquakes. Science, 341(6142).