Three years of mining subsidence monitored by SAR interferometry, near Gardanne, France

Differential interferogram images derived from repeat-pass spaceborne Synthetic Aperture Radar (SAR) systems give the possibility to map surface deformations of small spatial extent and to monitor their spatiotemporal evolution. A slow and local phenomenon of subsidence caused by underground coal mining has been observed near Gardanne, France, from images acquired by both European ERS-1/2 satellites between 1992 and 1995. Interferometric monitoring revealed the migration of the subsidence halo caused by the advance of the coal working face. Comparison with field leveling data has shown that the amount of effective land subsidence is similar. The analysis and interpretation of the observed movements take into account the structural characteristics of the sedimentary basin, the micro-seismic activity of the region and the geometry of the underground workings. Such an application of SAR interferometry, under normal conditions of observation and at different periods, opens up wide application prospects, not only for research goal but also for industrial use.