Evaluation of land subsidence from underground coal mining using TimeSAR (SBAS and PSI) in Springfield, Illinois, USA

We used advanced radar interferometry time-series analysis methods, persistent scatterer interferometry and small baseline subset, to delineate areas of ground deformation related to underground coal mining in Springfield, Illinois, USA, and to measure the temporal pattern of deformation. Two satellite radar systems were used: the European Remote Sensing satellites (ERS-1/2) covered a period from June 14, 1992 to August 30, 2000 and the Phased Array type L-band synthetic aperture radar (PALSAR) onboard the Advanced Land Observation Satellite (ALOS) covered from June 18, 2007 to February 11, 2011. Results from ERS-1/2 processing showed several areas in Springfield subsiding. ALOS PALSAR, however, appears to overestimate deformation, probably because of large baselines and the limited number of images. Many of these areas are likely the result of collapse of underground mine workings and are consistent with reported incidents of past mine subsidence. The maximum deformation rate attributed to mine subsidence for the period from 1992 to 2000 was up to about -4.1 mm/year, while for the period from 2007 to 2011 the rate was up to about -35.9 mm/year. In addition, we discovered a railroad right-of-way south of Springfield that had subsided at a rate of about 3 mm/year during the 1992-2000 period. The measurements of both ERS-1/2 and ALOS PALSAR are consistent with on-the-ground survey data taken from November 29, 1989 to April 23, 2008. Our study has revealed several locations of subsidence likely caused by the collapse of abandoned underground mine workings. Also, the unexpected discovery of ground surface displacement of the railroad right-of-way reveals one of the advantages of satellite-based monitoring, namely discovering unknown deformation areas.