Kinematic segmentation of a DSGSD on the flank of the exhumed Leo Pargil Dome (northwestern Himalaya) using InSAR

Deep-seated landslides in high mountain terrain typically deform slowly over years to decades, making their internal kinematics difficult to characterise from field observations alone. Here we investigate the Leo Pargil landslide on the southwestern flank of the exhumed Leo Pargil gneiss dome in the northwestern Indian Himalaya, a large active deep-seated gravitational slope deformation (DSGSD) in the region. Multi-temporal persistent scatterer interferometric synthetic aperture radar (PS-InSAR) analysis of Sentinel-1 data is combined with geological and structural information to characterise the landslide's present-day kinematics and internal segmentation. Ascending and descending Sentinel-1 data from 2018 to 2023 are combined to decompose InSAR-derived displacement into vertical and horizontal components, allowing spatial variations in displacement magnitude and direction to be resolved across the landslide body. The displacement field is strongly segmented, with faster-moving sections separated by sharp displacement gradients and relatively stable zones, indicating the presence of distinct internal sectors within the landslide. The upper part of the slope shows displacement patterns consistent with a rotational component near the headscarp, whereas the lower part is characterised by predominantly slope-parallel motion. Spatial variations in motion broadly follow mapped structural and lithological boundaries, indicating that inherited structures and slope geometry may influence the present-day deformation pattern. The results show that the Leo Pargil landslide is a segmented deep-seated gravitational slope deformation on the flank of an exhumed gneiss dome, with its present-day kinematics consistent with consistent with inherited structural heterogeneity and ongoing geomorphic processes.