Monitoring a Large and Complex Land Subsidence in Coal Mining Areas with a Small-baseline Interferogram Stacking Technique

China is the world’s largest coal-producing country and mining-related land subsidence happens almost in every coal mining area. In north-west China, land subsidence in coal mining areas is mainly caused by underground mining activities and uncontrolled burnings of subsurface coal seam. As Hoffmann (2004) reported, burning coal-seams can result in extensive subsidence of several meters and typical large deformation rate due to volume change of the burning coal and thermal effects in the adjacent rock mass. Because of rather low coherence due to high deformation rate, it is difficult for a classical Differential InSAR (D-InSAR) approach applied to C-band ERS-1/2 or Envisat ASAR data, such as 2-pass or 3-pass DInSAR, to measure mining-related land subsidence in this case. The recently developed Persistent Scatterer InSAR (PSInSAR) technique enhances the capacity to measure ground displacement than previously feasible and allows highly accurate measurements of deformation that occurs at individual, phase-dependent radar targets called permanent or persistent scatterers (PS). However, identification and interpretation of PS points are still a challenge in such coal mining areas with a large and complex deformation.