70 / 2021-09-15 20:39:53

Twenty years of mining induced subsidence in the USCB in Poland identified using InSAR

InSAR, mining subsidence, USCB, subsidence troughs, radar interferometry

The paper presents the results of terrain subsidence monitoring in the mining area of the Upper Silesian Coal Basin in Poland using Differential Interferometry Synthetic Aperture Radar (DInSAR) (Massonnet D., Feigl K.L., 1998) and Persistent Scatterer Interferometry (PSInSAR) (Ferreti A., et al., 2001). This remote sensing monitoring techniques allow the identification of vertical mining induced terrain displacements with centimeter accuracy (Przyłucka M., et al., 2015). The study area accounts for almost three million inhabitants where mining subsidence has produced severe damage to urban structures and infrastructures in recent years. Mining activity started in the 19th century and operates till now, producing around 60 million tons of coal each year (Kowalski A., 2020). Geodetic measurements documented a 7 m vertical displacement in an urban area as a result of a 63-year period of mining exploitation, whereas, calculated theoretical total subsidence outside built-up areas could be as much as 30 m (Klabis L., Kowalski A., 2014).



The aim of the analyzes was to combine eight different datasets, processed in two techniques, coming from different sensors and covering different periods. As a result, a map of areas that have been exposed to subsidence within 148 hard coal deposits (3,045 square kilometers) was obtained. The map covers period of twenty years of intensive mining works, i.e. 1992-2012. A total of 80 interfergrams (18 from the archival ERS and ENVISAR C-band scenes, 25 from the processing of ALOS L-band scenes and 37 from the X-band scenes of TerraSAR-X satellite) were used in the study. The interferograms allowed not only to determine subsidence troughs formed in the period from 1992 to 2012, but also to observed subsidence development over time in several dozen days long increments. The work also included 5 sets of PSInSAR processing, also covering different time and spatial range. 3 sets come from ERS satellite (period 1992-2000), one from Envisat satellite (2003-2010) and one from TerraSAR-X satellite (2011-2012). The PSInSAR point datasets were used to determine zones of residual subsidence.



Thanks to InSAR datasets, an area of 521 square kilometers under the influence of mining activities was determined. Within the subsiding zones an area of 312.5 square kilometers of rapid increase in subsidence  was identified on the interferograms. The data was validated in two mining areas using monthly mining production data and the levelling networks run by the mines on the surface. The study of combined different InSAR datasets provided large-area and long-term information on the impact of mining activities in Upper Silesia Coal Basin. No other monitoring technique makes it possible to perform such extensive analyzes, especially if there is a need for archival research. The work shows the great advantage of remote monitoring methods, which is the possibility of showing the environmental impact in a large area and the possibility of studying displacements that occurred in the past.