Usage of insar techniques to detect and monitor terrain subsidence due to mining activities

Abstract

Land subsidence is monitored in several ways. Mostly the geodetic technique of geometric levelling is used. Also, the possibility to use the radar interferometry for monitoring has been successfully verified. In the area of Nnorthern Moravia several active mines are located causing in some places a subsidence of more than 1m a year. The existing radar images of this area from the ERS-1, ERS-2 and Envisat satellites, which had been acquired in the period from 1996 to 2008, were processed by 2-pass differential radar interferometry and advanced methods of radar interferometry, and thus subsidence epicentres were indicated and subsidence rates estimated. From the resulting interferograms the evolution and movement of subsidence can be seen, however, when compared to the survey data it is apparent the predicted subsidence rate is heavily underestimated. This is due to the sensitivity of the radar interferometry method to the quality of input data - only a very small number from 128 available images could be properly combined; the reasons are given below. For the advanced methods using the entire time series of shots, not just individual couples, pictures were selected only from a sufficiently short period, during which only a slight movement of subsidence epicentre is assumed over driven mine workings. The attempts to process a longer period of 4 years resulted in the loss of information on the evolution of subsidence in individual points due to their relatively rapid horizontal motion - the subsiding area was detected in this period (1996-2000), but no correct data on the rate of subsidence is available. For the processing the Permanent Scatterers and Small Baseline methods were used, both of them are implemented in the StaMPS program, whose concrete results also exceeded the tested Delft SP Toolbox implementation.