Abstract
The time series of Synthetic Aperture Radar data acquired by four satellite missions (including ERS, Envisat, TerraSAR-X and Sentinel 1) were processed using Persistent Scatterer interferometric synthetic aperture radar (InSAR) techniques. The processed datasets provide a nearly continuous coverage from 1992 to 2017 over the Brussels Region (Belgium) and give evidence of ongoing, slow ground deformations. The results highlight an area of uplift located in the heart of the city, with a cumulative ground displacement of ±4 cm over a 25-year period. The rates of uplift appear to have decreased from 2 to 4 mm/year during the ERS acquisition period (1992–2006) down to 0.5–1 mm/year for the Sentinel 1 data (2014–2017). Uplift of the city centre is attributed to a reduction of groundwater extraction from the deeper (Cenozoic-Paleozoic) aquifers, related to the deindustrialization of the city centre since the 1970s. The groundwater levels attested by piezometers in these aquifers show a clear recharge trend which induced the uplift. Some areas of subsidence in the river valleys such as the Maelbeek can be related to the natural settlement of soft, young alluvial deposits, possibly increased by the load of buildings.
Highlights
Satellite interferometric synthetic aperture radar (InSAR) is a valuable tool for observing the deformation of the earth’s surface
Analysis of the ERS (1992–2006), Envisat (2003–2010) and TerraSAR-X (2011–2014) velocities shows that the city of Brussels is, overall, characterized by a regional uplift, with a diminishing trend through time (Figure 5A–C)
The analysis of 25 years of Persistent Scatterer Interferometry (PSI) measurements in the Brussels region showed that the city centre was affected by an uplift of more than 4 cm along the Senne valley
Summary
Satellite interferometric synthetic aperture radar (InSAR) is a valuable tool for observing the deformation of the earth’s surface. Such techniques use the radar phase information of SAR images acquired at different times over the same area [1,2]. The procedure allows the temporal decorrelation and the geometrical decorrelation to be reduced, which are both problematic for the InSAR technique. Based on these considerations, PSI is efficient in urban areas as the density of reflecting objects and the amplitude of reflection are high
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