Analysis of ground subsidence in coal mining area using SAR interferometry

This study presents the application of interferometric synthetic aperture radar (InSAR), small baseline subset (SBAS) algorithm and GIS for subsidence analysis in a mining area located at Gangwon-do, Korea. Several mining areas at the Samchuk coalfield had operating coalmines until 2002-2003. Ground deformation has occurred as a form of subsidence due to the continuous mining activity or the collapse of residual cavities. Twenty-three scenes from a JERS-1 satellite acquired from 1992 to 1998 are used to detect the ground movement by means of the differential InSAR process. Distinctive phase variations induced by subsidence were observed in several interferograms. The SBAS algorithm was applied for a detailed analysis. As a result, it was confirmed that deformation was occurring between September 21, 1992 and September 30, 1998 and attained 22 cm at the most significantly subsiding site. The mean and standard deviation of RMS error were 2.0 cm and 0.78 cm, respectively, showing the level of the error due to the used digital elevation model, unwrapping and atmospheric effect. The SBAS-derived cumulative subsidence map was validated with the underground workings and geological maps in order to find the spatial relations and subsiding mechanism. From the spatial comparison with these data, it was shown that the subsidence has taken place above excavations and fault lines.