Persistent Scatterer Interferometry analysis of multi-temporal Sentinel-1 radar imagery to detect ground subsidence in the city of Tirana, Albania

Persistent Scatterer Interferometry (PSI) analysis of Sentinel-1 C-band radar spaceborne imagery was carried out to detect ground subsidence zones in the city of Tirana, Albania. Fifty-eight Sentinel-1A Interferometric Wide (IW) images of the time period January 2017 – December 2018, with a temporal resolution of 12 days, were used as input to the PSI. The PSI technique can detect millimeter-scale ground motion. The results show a zone of ground subsidence of about 7 mm/year along a segment of the Tirana Outer Ring road, where numerous tall buildings have been constructed in the last twenty years. In the northern part of the Kamza municipality a ground subsidence of about 2-3 mm/year is observed. In the western part of the Kamza municipality, it is also observed a ground subsidence of about 7 mm/year. In general, the areas where ground subsidence was detected from the PSI analysis, are characterized by urban expansion in the last thirty years. The ground subsidence could be a result of the lowering of the water table from the construction works or from over exploitation of groundwater resources. The study represents the first reported analysis of the Sentinel-1 imagery for ground motion detection in the city of Tirana. Further monitoring and detailed studies on the causes of the ground subsidence in this important urban area are necessary.