A study on recent ground deformation near Patras, Greece

Abstract

In recent years urbanized areas have been expanding more and more into hillside areas, which increases the risk for landslides to destroy or gravely damage human settlements, industrial establishments and important infrastructure. Greece and in particular the northwestern tip of the Peloponnese Peninsula are often affected by landslides. A well-known and documented landslide south-east of Patras is located in that area and was chosen as the main focus for this study. The landslide collapsed and thus submerged the main road connecting the small village Moira and Patras on January 20, 2016. Immediately afterwards the geometry and geology of the affected area have been determined using GNSS Measurements, UAV Campaigns and DInSAR techniques. However, the velocity of the post-collapse movement has not been investigated. In order to make this determination two time series of SAR images acquired by the two Sentinel-1 satellites from an ascending and descending orbit were evaluated using the advanced InSAR technique of persistent scatterer interferometry. The result is a map of the mean velocities the identified persistent scatterers were experiencing in the time period from January 2017 to June 2019. The persistent scatterer density in the rural areas of the region was sufficient enough to identify the landslide within the results. Roughly 80 persistent scatterer with a velocity of more than ± 8 mm/a in the line of sight of the sensor were identified within the outlines of the landslide (approximately 750 m2), indicating that the landslide is experiencing post-collapse movement.