Spatiotemporal monitoring of surface motions using DInSAR techniques integrated with geological information: a case study of an iron mine in the Amazon region using TerraSAR-X and RADARSAT-2 data

Abstract

Instabilities are extremely common in the iron open-pit mines located in the Carajas mineral province, the world´s largest iron reserves located in the Brazilian Amazon. Due to deep excavations in rock products of low geomechanical quality, heavy precipitation, and blasting practices, mining operations in the area present surface displacements that potentially lead to slope instabilities with several risks (personnel, equipment, mining infrastructure, etc.). This paper presents the results related to the N5E mine based on DInSAR Time Series (DTS) and Persistent Scatterer Interferometry (PSI) using a temporal series of 33 StripMap TerraSAR-X (SM TSX) images, and geological information provided from a 3D photointerpretation of an SM TSX and Ultra-Fine RADARSAT-2 (UF RST) stereo-pair, calibrated with field data. Measurement point (DTS, PSI) results were compared with in situ geodetic survey information (total station/prism measurements) and showed good agreement indicating that most of the mine can be considered stable during the period of the TSX coverage. The highest accumulated displacements were spatially related to a thematic unit mapped as a landfill. For other sectors of the mine, lower deformation rates were related to photointerpreted lineaments related to the Carajas fault system suggesting that geological structures can play a key role in controlling some surface displacements. The investigation demonstrated that the strategy based on the use of DTS and PSI techniques integrated with geological data provided a synoptic view of the deformation process that affected the mine. The approach was relevant for ground displacements monitoring of the study area with DInSAR results compared with in situ geodetic measurements showing good statistical correlation.