Analysis of 5 years of continuous monitoring (2021-2026) of the Lacq induced seismicity (Southwestern France)

Summary Understanding induced seismicity is a critical challenge for seismic risk mitigation, particularly in Europe where geo-resource exploitation increasingly occurs in densely populated areas. The Lacq site in southwestern France represents one of the most significant and long-lasting cases of induced seismicity in Western Europe. Despite decades of observations, the characterization of Lacq seismicity remains limited by insufficient instrumentation and monitoring, leading to poorly constrained earthquake locations and uncertainties regarding whether seismic events occur within or below the reservoir. In this study, we present a high-resolution seismicity catalog covering a five-year period (2021–2026), representing the most comprehensive dataset available for the Lacq area. To achieve this, a temporary seismic network was deployed through a collaboration between GFZ (Potsdam), OMP (Toulouse), and UPPA (Pau). Event detection and location were performed using two independent approaches: a detailed manual picking and relocation workflow, and a fully automated deep-learning-based method. Combined with the use of a pre-existing local 3D velocity model, this dual approach significantly reduces location uncertainties and improves the robustness and completeness of the catalog. The resulting dataset constitutes a valuable resource for future studies.