Monitoring of ground deformation in Liulin district, China using InSAR approaches

Coalbed methane (CBM) exploration generally refers to a technique that extracts natural gas from coal beds. The development of CBM in Liulin, China, has experienced a significantly growth period during the past two decades. Previous research mainly focused on the coal geological background or CBM technique itself, while time series InSAR (TS-InSAR) technique was conducted in this work to study the potential land deformation induced by CBM extraction from 2003 to 2011. In total, 21 ALOS-1 PALSAR images (acquired from 22 December 2006 to 2 January 2011) and 14 ENVISAT ASAR scenes (captured between 29 October 2003 and 7 November 2007) were used. The TS-InSAR outcome revealed that the annual deformation rates were ranging from 15 to -40 mm yr(-1) over the study region. Then the time series deformation evolutions were analysed over 8 CBM sites (No. 4 coal seam) out of 20, and the subsidence rates between 1.9 and -6.5 mm yr(-1) were derived. In addition, the average subsidence rate and standard deviation among these eight measurements were -3.0 and 2.6 mm yr(-1) respectively, suggesting that these CBM extraction sites were quite stable and no obvious subsidence had been observed during this eight-year period.