Mining-induced subsidence and fault reactivation due to open pit lignite mining in the Hambach region, North Rhine-Westphalia, Germany: Insights from Sentinel-1 based European Ground Motion Service (EGMS) and field surveys

With an operating area of 4,380 ha producing approximately 40 million tons per year  of lignite , the Hambach mine is the largest open pit mine in Germany. To extract the lignite in open-cast mining, the groundwater level needs to be lowered down to below the deepest point of the open pit mine. This leads  to major changes in the aquifer conditions which may result in land subsidence that can affect the safety of built-up structures with significant socio-economic impacts. In this study we perform a regional analysis of ground surface deformation in the Hambach mining area using interferometric observations from the Copernicus Sentinel-1 satellite. We present results from our validation investigation,  where results provided by German and European Ground Motion Services are compared with those obtained from our local surveys using high-resolution TerraSAR-X SAR data. We further investigate the correlation between InSAR measurement points, in-situ observations, and damages to infrastructures, and show evidence for several cases of fault reactivation and damages to infrastructures within the area undergoing mining related subsidence. Fault reactivation has resulted in the formation of fault scarps (offsets > 1 m), with detrimental impacts on existing structures. Finally, we integrate between results from InSAR measurement points with open source geospatial data to create maps that support hazard, exposure and risk assessment related to subsidence at regional scale in the Hambach region.