Combining Sentinel-1 Ascending and Descending Data to Aspect Information in Term of the 3D Slope Creep Behavior

Slow downward movements of slope due to long term influence of gravity and physical environment are becoming a slope creep and intentionally towards the high risk ground movement area. We identify the creeping slopes in Ciloto, the prone landslide area in Indonesia using the advanced InSAR technique. Slowly Decorrelated Phase Filter is chosen as the processing multi-temporal method because the number of scatter candidates are greater than single master persistent scatter (PS) technique considering to rural and agriculture tested areas. A partial tropospheric propagation delay has been reduced as well in term of the phase-based power law correction on each interferogram. The InSAR displacement results are describing a very slow motion which might be no surface geomorphic evidence at the site but result in tilt of poles, slump and crack of structures and roads, or abnormal curvature of trees. We use two independent InSAR observations and aspect information determined by digital elevation model (DEM) assuming that the motion's direction is going to the downward slope. The least square inversion model takes into account for each selected merging ascending and descending scatters to derive 3D vectors; vertical, east-west and north-south components. The firstly two of them are defined based on SAR geometry line of sight looking both from ascending and descending. Since the north-south vector is the most insensitive of slant-range deformation, we assume the horizontal motion owning a projected relationship to slope direction. The result is then simulated to the vertical surface model and horizontal vector displacement on two active zones, Puncak Pass and Puncak Highway Landslides. Considering to two successive Puncak Pass Landslides occurred in February and March 2018, we construct the pre-event history from 2014 to 2017 and locate the zone of depletion and accumulation with the slope creep displacement of 1-2 cm/year. The vertical moves faster than the horizontal at the head scarp while it shows otherwise on the foot body.