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