Landslide dynamics and coupling revealed by L-band InSAR in central Georgia

Abstract

Abstract. The republic of Georgia is a mountainous and tectonically active area that is vulnerable to landslides. Because landslides are one of the most devastating natural hazards, their detection and monitoring is of great importance. In this study we report on a previously unknown landslide in central Georgia at the site of the village of Itskisi near the town of Sachkhere. We used a set of ALOS PALSAR data to generate displacement maps using Interferometric Synthetic Aperture Radar (InSAR). We detected a sliding zone of dimensions 2 km north-south by 0.6 km east-west that threatens four villages. We estimated surface displacement of up to ~ 30 cm yr−1 over the sliding body in the satellite line-of-sight (LOS) direction, with the greatest displacement occurring after a local tectonic earthquake. We mapped the morphology of the landslide mass by aerial photography and field surveying. We found a complex set of interacting processes, including surface fracturing, shear and normal faults at both the headwall and the sides of the landslide, local landslide velocity changes, earthquake-induced velocity peaks, and loss in toe support due to mining activity. Important implications that are applicable elsewhere can be drawn from this study of coupled processes. We used inverse dislocation modelling to find a possible dislocation plane resembling the landslide basal decollement, and we used that plane to calculate the volume of the landslide. The results suggest a decollement at ~ 120 m depth dipping at ~ 10° sub-parallel to the surface, which is indicative of a translational-type landslide.