Detection of underground mining induced land subsidence using Differential Interferometric SAR (D-InSAR) in Jharia coalfields

Abstract

Mining induced land subsidence is very common in the areas of extensive underground coal mining which affects the overall geo-environmental scenario of the area. Jharia coalfields in Jharkhand has been experiencing land subsidence for several decades essentially due to underground mining and coal fire. Differential interferometric SAR (D-InSAR) technique has been used widely to identify and measure land subsidence. In this study, six ALOS PALSAR data pairs acquired during 2007-2008 were used to study land subsidence phenomenon in the Jharia coalfields. Two-pass D-InSAR was used in this study which uses two SAR images of the same area taken at different times to calculate the Line-of-Sight (LOS) path difference of a target point due to land displacement with the help of an external Digital Elevation Model (DEM). Well defined subsidence fringes were obtained in most of the differential interferogram pairs. The fringe areas were integrated to obtain the total subsidence affected areas during the observation period with rates of subsidence (in cm/year). The maximum subsidence rate calculated from D-InSAR processing is found to be 56.72 cm/yr and the minimum is 7.88 cm/yr. The total affected area in the study area is 7.2 sq kms. Field checks were done for confirmation of D-InSAR based subsidence results.