We studied the correlation between seismicity and the water table level in an abandoned coal mine (Bouches-du-Rhône, France), closed in 2003, where groundwater has been pumped out since 2010 to prevent underground flooding. Microseismicity was first felt by the population in 2010 and a strongly felt seismic swarm occurred in November 2012. The origin of the seismicity was therefore questioned, in relation to both the potential instability of old, shallow galleries that might generate damage at the surface and a local seismic hazard assessment. A temporary dense seismic network in the area allowed us to analyse the spatial distribution of the seismicity in detail. Most of the seismicity was clearly located under the mine workings, highlighting that an existing fault system crossing the mining operation was being hydraulically activated, in accordance with the known tectonic extension regime. Our analysis clearly shows a spatiotemporal relationship between seismic migration and the level of the mine aquifer between 2013 and 2017. Thus, seismicity will persist with oscillations of the mining aquifer, depending on the pumping capacities and effective rainfall. Continuous hydraulic and seismic monitoring is necessary to better understand these phenomena and assess the associated risks.

Rising groundwater in abandoned mines may result in ground movements at the surface overlying underground works. Feedbacks on several abandoned coalfields show that ground uplift is generally observed, reaching in some cases several centimetres or more. Although such ground movements, slow and associated with slight slopes, are not expected to generate surface damages, the survey of potential ground movements on abandoned coalfield is necessary, especially to confirm the end of mininginduced subsidence. The most common used method for this mission is levelling. A retro-analysis of ground movements, based on Interferometric Synthetic Aperture Radar (InSAR) technique, covering more than 20 years after mine activity ceasing, has been realised on the French abandoned coalfield of Nord-Pas de Calais. This analysis aimed to extend ground movements detection capabilities in areas not covered by levelling as well as compare InSAR analysis to levelling data for evaluating the robustness of satellite-based displacement measurements. InSAR analysis was able to highlight ground movements of a few millimetres per year, with the same order of precision than classical levelling methods. The observed ground displacement patterns expand well beyond the coalfield, indicating the influence of non-mining-induced phenomena, such as local geology and surface morphology. Our findings underline the operational capability of space-borne InSAR for monitoring abandoned coalfields.