Mapping accumulated mine subsidence using small stack of SAR differential interferograms in the Southern coalfield of New South Wales, Australia

The Southern Coalfield is located in the Sydney Basin, in the state of New South Wales (NSW), Australia. The coal seams of the Southern Coalfield contain high quality, hard coking coals which are mostly used for steel production. This paper describes an approach developed to study the subsidence associated with underground coal mining activity in the West Cliff colliery in the Southern Coalfield of NSW using multiple SAR differential interferograms. Accumulated subsidence maps have been derived using the approach within the study area. Results obtained by processing ten (10) ALOS PALSAR images showed that the land surface had subsided by more than 700 mm in the area of West Cliff colliery longwall 32 during the period of image acquisitions, June 2007 to October 2008. The results have been compared with deformation predicted by modelling as well as with the available GPS field survey data. High correlation has been observed between the DInSAR-derived subsidence results and the predicted mining-induced deformation. By comparing the DInSAR-measured subsidence with the GPS-derived results between September 2007 and March 2008, the magnitude and trend of the deformation has been confirmed. The absolute differences range from 0 to 45 mm, with a standard deviation of 8 mm and an average absolute difference of 12 mm.