InSAR analysis of Sentinel-1 data for monitoring landslide displacement of the north-easternCopou hillslope, Iaşi city, Romania

This work is aimed at showing the potential use of Synthetic Aperture Radar interferometry (InSAR) for landslide investigation and for the evaluation of the slope displacement over time and identification of unstable areas for the north-eastern Copou hillslope. The available Sentinel1 data have been processed using Advanced Differential Interferometry (A-DInSAR) techniques which includes Permanent Scatterers Interferometry (PSI) and Small BAseline Subset (SBAS). Starting from two or more SAR phase images for the same area with different time acquisition it is possible to measure small deformations of the ground surface by using remote sensing techniques such as InSAR. The detection of ground displacement can be derived if the topographic phase contribution is removed from the generated interferogram. The generation and subtraction of synthetic interferogram allows to create displacement maps, and to overcome its major limitations (temporal and geometric decorrelations, phase unwrapping, the atmospheric component) different algorithms have been developed belonging to two main families: the Permanent (Persistent) Scatterers Interferometry (PSI) and the Small BAseline Subset (SBAS). Even though the techniques are exploiting different strategies, both of them were developed with the same purpose, to identify and measure the ground deformations with sub-centimeter precision. For our study area, the north-eastern part of Iaşi city, over 100 different phase Sentinel-1 images kindly provided by ESA have been processed using both techniques (PSI and SBAS), with the stacking tool of the software Sarscape. The SAR images covers a period of more than 2 years (October 2014 – January 2017) and include both orbits: ascending and descending. Iaşi area is affected by slow moving landslides, which make our testing area to have a good environmental setting for the above mentioned techniques to be applied. According to our results, the Ţicău unstable area has been identified to have in several sectors considerable velocity values, greater than 3 mm/year. These values represent the mean velocity along line of sight (LOS) and illustrate the displacement trend of ground surface over the study period. Keywords— landslide; SAR interferometry; Sentinel-1; PSI; SBAS; Iași; Romania