Detection of coal-mining-induced subsidence and mapping of the resulting deformation using time series of ALOS-PALSAR data

Land subsidence caused by extracted void collapses due to coal mining activities is a major geohazard in northern China. Differential SAR interferometry (DInSAR) has been adopted as an effective tool for coal mining subsidence detection and deformation mapping. However, previous studies were mostly focused on the derivation of linear deformation rates in coal mines, while the spatial-temporal pattern of coal mining subsidence and its interaction with the fault systems have rarely been investigated. In this study, ALOS-PALSAR images acquired from 19 June 2007 to 12 November 2010 were analysed with DInSAR and small baselines subset (SBAS) techniques to characterize the distribution and magnitude of subsidence in central Henan province, which is one of the leading coal producers in China. More than 40 funnel-shaped subsidence areas distributed within the coalfields have been detected in both Dengfeng and Xinmi. The maximum annual mean deformation can be as high as 8 cm in the line-of-sight (LOS) direction. Deformation maps were generated in the study area, showing an extended subsidence of 2009 compared with that of 2007. We also analysed the deformation profiles perpendicular to the faults, and found an asymmetric subsidence pattern along the profiles. Such a pattern may be an indicator of local fault activities, and it may help understanding of coal mine subsidence near faults.