Ground deformation of Zakynthos island (Western Greece) observed by PSI and DGPS

Ground deformation studies based on Differential GPS (DGPS) measurements and Permanent Scatterers InSAR (PSI)* analysis using ERS (1992-2000) and ENVISAT (2003-2010) radar data have been conducted on Zakynthos Island (Western Greece) covering the period 1992 to 2012. These results were compared, validated and integrated with geological, geotectonic and seismological data to evaluate possible pre-earthquake deformation process, and the present tectonic regime. The PSI results indicate that a slight subsidence had occurred during the period 1992-2000, while uplift has mainly observed in 2003-2010. DGPS results for 2005-2006 indicated strong opening of the southern part of the island, while in the period 2006-2012 the amplitude of deformation is relatively smaller. The occurrence of the seismic outbreak that took place offshore to the south of Zakynthos during 2005-2006 may have contributed to the different deformational pattern as revealed by the ERS and ENVISAT PSI products, and also elucidate the DGPS results.