Electrical Resistivity Tomography for Mapping Landslide-Prone Zones in Pining Subdistrict, Gayo Lues, Aceh, Indonesia

Abstract

The interaction of topography, weathering, fracturing, lithological variability, and subsurface moisture controls slope instability in humid tropical terrain. This study maps resistivity heterogeneity and evaluates candidate weak zones on a slope showing evidence of movement in Pining Subdistrict, Gayo Lues Regency, using three intersecting electrical resistivity tomography (ERT) profiles. Data were acquired with a SuperSting R8/IP system using a Wenner-Schlumberger array, 55 electrodes at 6 m spacing, and a 324 m profile length. The apparent-resistivity data were inverted in EarthImager 2D using an L2-norm smooth-model scheme with electrode elevations incorporated into the inversion mesh. Inversion terminated after four iterations for Profiles 1 and 2 and five iterations for Profile 3, with final RMS misfits of 11.62%, 11.41%, and 10.42%, respectively. The inverted resistivity models delineate a near-surface high-resistivity domain (>1000 Ohm.m) overlying intermediate- and low-resistivity domains. Broad spatial correspondence is observed between conductive anomalies S1 and S6, S2 and S7, and S3 and S8 on Profiles 1 and 3, whereas conductive anomaly S5 on Profile 2 is spatially associated with S1 and S6 near the profile intersections. Conductive anomalies S1, S5, and S6 have the strongest cross-profile support. Considering the resistivity distribution, geological setting, field evidence of slope movement, and monthly rainfall context, the principal conductive anomalies are interpreted as intensely weathered, locally fractured, and comparatively moist material. The resistivity-gradient boundary at approximately 10-50 m depth marks a geoelectrical transition and is treated as a candidate weak-zone boundary rather than a confirmed slip surface; hydrogeological and geotechnical validation is required.