Dynamics of a giant slow landslide complex along the coast of the Aral Sea, Central Asia*

Abstract

We report here a slow-moving landslide complex of the lateral spreading type revealed by Sentinel-1 interferometric timeseries analysis. Located along the western coast of the Aral Sea, with a >150-km length and 3-km width, a giant active landslide complex, slides with a constant velocity of up to 60 mm/year. Systematic subsidence up to 5 mm/year is also observed along narrow strips of terraces that appear to result from rotations of fault-bounded blocks. The landslide deformation velocity does not correlate with the annual variations of the water level in the southwestern lake of the Aral Sea during the observation period of 2014-2022, indicating a long-term forcing of this landslide that is rather interpreted to be caused by the long-term sea-level drop. The lateral spreading involves the competent limestone beds lying horizontally on plastic clay- and evaporite-rich layers. We propose a conceptual model for the kinematic of landslides that appear to be controlled by the attitude of bedding, lithological sequence, hydrogeology, and low angle faults.