Monitoring residual mining subsidence of Nord/Pas-de-Calais coal basin from differential and Persistent Scatterer Interferometry (Northern France)

Both differential SAR Interferometry (DInSAR) and Persistent Scatterer Interferometry (PSI) are used to estimate surface displacement of the Nord/Pas-de-Calais coal basin during a 15-year period (1992-2007) after the end of 270 years of mining exploitation. On the results issued from ERS and Envisat data processing, even if the area undergoes high temporal decorrelation due to the high amount of field crops, present residual deformation are well detected. Those deformations show low amplitude with a maximum rate of more than 1 cm/year during a period of 5 to 7 years after the end of the mining exploitation (1992-1999). Then decrease up to stability, prevails, depending on the area. The deformation field obtained by differential and Persistent Scatterer Interferometry shows good agreement with the traditional methods of levelling comparison focused on specific sites. The recent displacements, revealed by DInSAR and PSI within a wider area, lead us to propose various natural (geology and neotectonics) or/and anthropic origins.