The Cigéo project, led by the French National Radioactive Waste Management Agency (Andra), involves the future disposal of high-level and long-lived radioactive waste in a deep geological repository. The site is located between the departments of Meuse and Haute-Marne in north-eastern France. In order to better monitor local seismicity and enhance the discrimination between natural and anthropogenic seismic events in the vicinity (<40 km) of the future Cigéo site, a dedicated network of four seismic stations – known as the Réseau d'Ecoute Sismique (RES) – was installed in 2002 and has been operated since then by the French Alternative Energies and Atomic Energy Commission (CEA). Over the past 60 years, the CEA has recorded 268 natural seismic events within a 90 km radius of the Cigéo site, with the largest reaching a local magnitude (ML) of 3.9. The closest recorded earthquake occurred about 20 km from the site, with a magnitude of ML 1.7. Historical and early instrumental records indicated that seismic activity in this region was low, a finding confirmed following the implementation of the RES network which significantly improved the detection and location of small earthquakes and identification of numerous quarry explosions in this region. This enhancement has finally increased the number of seismic events processed annually with more than 1,000 quarry blasts detected annually and allowed to reduce the completeness local magnitude down to approximately ML 1.5. We highlight the improvements in terms of event location and hypocentral depth accuracy provided by the RES network by comparing the median primary and secondary azimuthal gaps and the dimensions of the error ellipses before and after its deployment. Furthermore, we relocate the entire catalogue using a 3D location algorithm along with a 3D global velocity model to obtain more reliable estimates of event locations and hypocentre depth and to better quantify the uncertainties.
Mazet-Roux et al. (2026) studied this question.