Seismic Discrimination of Natural and Anthropogenic Events Near Atlanta, Georgia, USA

Xu Si, Michael Snook, Yunyi Qian, Zhigang Peng , Chang Ding, Karl Lang, Martha Cary Eppes, Sidao Ni

Distinguishing small earthquakes from anthropogenic seismic sources is important for accurate fault characterization and seismic hazard assessment, yet remains challenging in regions with sparse seismic networks and frequent quarry activities. Around Atlanta, Georgia, only a small number of local natural earthquakes and one operator-confirmed quarry blast in July 2026 are reported in regional USGS catalogs in recent years. Here we use three cataloged earthquakes and the 2026 quarry blast as references to search 14 years of continuous seismic and pressure records at a nearby permanent station N4.Y52A. Based on a machine-learning-assisted workflow, we identify 2,181 impulsive events with clear seismic arrivals, associated pressure disturbances, and reliable particle-motion measurements. Most of them occur during weekday working hours and exhibit repeated source-distance and directional patterns that correspond to known quarry areas, indicating that the detected population is dominated by quarry-blast activity. The search also recovers smaller earthquake candidates and short event sequences with more ambiguous origins, demonstrating that waveform similarity or occurrence time alone cannot determine source type. As an independent case study, we reassess signals previously associated with a 17 July 2023 spontaneous rock exfoliation event at Arabia Mountain. The previously associated regional signal is more consistent with quarry activity, whereas subsequent exfoliation events in 2024 produced highly localized signals recorded only by a near-source dense array but not clearly at N4.Y52A. These results demonstrate that improved seismic detection must be accompanied by independent seismic, acoustic, spatial, and direct observational constraints for reliable source identification.