3D ESTIMATION OF SLOW GROUND MOTION USING INSAR AND THE SLOPE ASPECT ASSUMPTION, A CASE STUDY: THE PUNCAK PASS LANDSLIDE, INDONESIA

Abstract. The Indonesian Centre of Volcanology and Geological Hazard Mitigation classified the Ciloto district as one of the most landslide prone areas in Indonesia. Some evidence of ground movement and the landslide failures occurred in recent years. Thus, continuous monitoring is necessary for supporting the precautions of an upcoming landslide. This study applies Small Baselines - Slowly Decorrelated Phase Filter (SDPF) for InSAR processing both for the ascending and the descending data. The primary objective is to generate horizontal and vertical components of InSAR results from two different tracks and slope aspect information in order to retrieve a projection to the northward direction. We used the available Sentinel-1 SAR data from 2014 until 2018. Combination of two orbits is approached by the surface and the nearest-neighbor gridding method. The 3D components were examined at the Puncak Pass, Ciloto, an active landslide area. For the case study area, it appeared that soil materials transferred slowly from the top of main body landslide to the accumulated zone near to the buildings owned by a local resort. The cumulative 3D displacements for three years were computed for the depleted zone: it moved −47, 23, −10 mm for dU, dE and dN, respectively. Meanwhile, the accumulated zone was considered having the up-lift motion to maximum 43, −13, 7 mm, respectively.