Impact of past mining on public safety: seismicity in area of flooded abandoned coal Gardanne mine, France

Abstract

This paper focuses on the impact of past mining on public safety. It emphasizes the need to understand the induced seismic hazard and consequently improve the post-mining management procedures and legislations, as many mining sites are located in proximity to populated areas. Due to many challenges and complexity of the post-mining environments, induced seismic hazard nowadays remains largely unknown. However, the return experience of several post-mining sites in recent decades have shown us that the mine flooding and/or degradation of mining works can lead to the stress perturbations, inducing the seismicity and the reactivation of the surrounding geological faults. Hence, it is important to advance the seismic monitoring and research of seismicity in flooded post-mining districts. As the number of mine closures worldwide is rising, it can be expected that flooding induced reactivation of the surrounding faults becomes a more often observed phenomenon. We present in this paper the experience of the abandoned flooded coal mine of Gardanne in France, which has been experiencing post-mining seismicity problems since its closure in 2010. We show the results of a recent study of seismic multiplets and clustering of seismic events, as well as their spatio-temporal activity compared to meteorological conditions. These results provide us new insights as well as lead to raising new questions on seismic sources and triggering mechanisms.