Detecting coal fires in China using differential interferometric synthetic aperture radar (InSAR)

Abstract

In this study we investigate the feasibility of detecting subsurface in subsurface coal deposits through InSAR observations of surface displacements. Uncontrolled burning of subsurface coal seams have been reported from different locations around the world. In northern China alone, more than 10 Million tons of coal are estimated to burn every year, with massive implications for the economy and ecology. In fighting these fires and controlling burning coal seams the timely and reliable detection and mapping of the affected regions is critical. This has proven to be extremely difficult in the remote regions of northern China, where many of the fires have been caused by uncontrolled, small-scale mining operations. Both the volume change of the burning coal and thermal effects in the adjacent rock mass are expected to cause measurable surface displacements and collapses of the earth's surface have often been reported. Unfortunately, reliable data on surface deformation accompanying the fires have not been acquired. However, theory and individual reports suggest that subsidence mapping using differential InSAR may be a suitable tool to detect burning regions and map the spatial extent of the affected areas. Though topography, temporal decorrelation, and poor data coverage complicate the analysis we have identified several localized areas of subsidence in the region. Here we discuss the promise and limitations of using InSAR for coal-fire detection in northern China.