Ground Deformation Monitoring in the Greater Cairo Metropolitan Region (Egypt) by SAR Interferometry,

Subsidence, earthquakes, landslides represent trigger of many ground motion events biasing also building stability. The related deformation is often caused by human activities such as water and oil pumping, slopes undercut by roads, mining etc. This problem affects largely the built-up Greater Cairo metropolitan area, which, as any part of the world, is subjected to natural hazards represented by ground subsidence that is evident from accidents involving many establishments in different parts of the city. The present study concerns the application of SAR interferometric techniques for detecting ground deformation in the Greater Cairo Metropolitan Region since 2002. For this analysis a set of C-band ENVISAT ASAR Single Look Complex (SLC) VV-polarization scenes of a descending mode, spanning the 2003 to 2009 period, were used. The applied methodologies were Interferometric Stacking and Persistent Scatterers Interferometry (PSI). The first technique provides a preliminary estimation of the deformation pattern, detecting relatively stable areas which could be used as a reference in the successive point target analysis. The second one was based on the IPTA (Interferometric Point Target Analysis) processing scheme; temporal and spatial features of interferometric signatures collected from point targets were exploited to accurately map average ground deformation rates and deformation histories. Stacking and PS techniques gave almost identical results. In general, interpretation of the data shows that deformation patterns can be recognized mostly in the suburban areas of Cairo, except for some isolated spots in the main urban center. In particular, the Mokkatam area, where the presence of two spot zones point out medium subsidence rate, must be mentioned; in this area many catastrophic landslides occurred, the main cause being the presence of probable active faults.