Long term and seasonal ground deformation monitoring of Larissa Plain (Central Greece) by persistent scattering interferometry

Abstract

The land subsidence which occurs at the Larissa Basin (Thessaly Plain, Central Greece) is due to various causes including aquifer system compaction. Deformation maps of high spatial resolution deduced by the Persistent Scattering Interferometry (PSI) technique (using radar scenes from ERS and ENVISAT satellites) for the period 1992–2006 were produced to study the spatial and temporal ground deformation.A developed GIS database (including geological, tectonic, morphological, hydrological, meteorological and watertable variation from wells in the area) offered the possibility of studying in detail the intense subsidence. The PSI based average deformation image clearly shows that subsidence generally takes place inside the Larissa Plain ranging from 5–250 mm. The largest amplitude rates (−25 mm/yr) are observed around the urban area of Larissa City (especially at Gianouli and Nikea villages), while the Larissa City center appears to be relatively stable with a tendency to subside. The rest of the plain regions seem to subside at moderate rates (about 5–10 mm/yr). The surrounding mountainous area is stable, or has slightly been uplifted with respect to the NE located reference point. It was found that there is a correlation between the seasonal water-table variation (deduced from wells data), the seasonal water demand for irrigation associated with specific types of cultivation (cotton fields), the monthly rainfall, and the observed subsidence rate in the rural regions of the Thessaly Plain.