InSAR time-series monitoring of ground displacement trends in an industrial area (Oreokastro???Thessaloniki, Greece): detection of natural surface rebound and new tectonic insights

The industrial area of Oreokastro, NW of the city of Thessaloniki, is monitored using radar interferometry to determine the spatial evolution of the underlying ground deformation trends. Previous studies, using SAR data acquired between 1992 and 1999, have revealed subsidence; however, the driving mechanism has not been, so far, solidly explained. Here, SAR satellite data from ERS 1, 2 and ENVISAT missions, acquired between 1992 and 2010, are analysed to enhance our understanding of the ground displacement trends and provide a thorough interpretation of the phenomena. The analysis confirms a subsiding displacement pattern from 1992 to 1999, whereas the recent data indicate that after 2003 the motion direction has changed to uplift. This whole monitoring of subsidence and the subsequent uplift is a rarely documented phenomenon, and in the case of Oreokastro is not reflecting a natural process; on the contrary, the driver is anthropogenic, related to the regional aquifer activity. Our study also highlights the fact that the local faults act as groundwater barriers and captures the existence of a possible previously unknown tectonic structure.