Joint Analysis of InSAR, ERT, and in-Situ Geological Survey in Landslide Prone Area: A Case in Laeya Village, North Buton Regency, Indonesia

Landslide investigation in Laeya Village of North Buton Regency, Indonesia, is necessary since this area is frequently experiencing landslides. In this study, we applied a joint analysis of interferometric synthetic aperture radar (InSAR), electrical resistivity tomography (ERT), and in-situ geology observation. The objectives of this multidisciplinary study are: a) to estimate ground deformation through the InSAR method, b) estimation of subsurface characteristics based on the electrical resistivity of rocks, as well as estimation of the shape of the slip plane and the type of landslide that resulted; and c) to identify the surface geology conditions of the site from an in-situ geology survey. The InSAR data of the Sentinel-1A acquired from 2015 to 2017 were processed using the Sentinel toolbox. The resistivity data collected utilizing the electrodes array of the Wenner-Schlumberger configuration were processed employing the RES2DINV. The in-situ geology survey involving the observation of elevation, slope, and soil and rock type was also carried out in the landslide area. The InSAR method may estimate the deformation of slope material of the investigated sites with a magnitude ranging from -53 mm to +55 mm. The negative mark of the magnitude means that the ground deformation is ground subsidence and the positive means ground uplift. The ERT method has successfully estimated the existence of the saturated zones, the clay layer that acts as a slip plane, and the slip surface type. There are at least two types of slip planes estimated, namely the planar and uneven curvature slip planes that generate the translational and the complex landslides, respectively. In-situ observations of geological conditions support the results obtained from the InSAR and ERT methods.