Geoelectrical Resistivity for Delineating Slip Surfaces in Landslide Areas: A Case Research from Selopamioro, Bantul, Indonesia

Abstract

Landslides are a common natural disaster in Indonesia, particularly in areas with steep slopes and high rainfall intensity. They can cause significant damage to property, loss of life, and disrupt the daily lives of affected communities. Bantul Regency is especially susceptible to landslides due to its geological structure and the tectonic activity resulting from the convergence of three major tectonic plates in the region. This research aimed to identify subsurface lithology and slip surface in the landslide-prone area of Selopamioro Village, Imogiri District, Bantul Regency, using the Wenner configuration resistivity geophysical method. Four measurement lines were conducted, each with a length of 225–240 meters and an electrode spacing of 15 meters. Data processing was performed using the Res2Dinv application to produce a two-dimensional resistivity model and RockWorks 17 for three-dimensional visualization. The modeling results revealed resistivity values ranging from 0.11 to 779 Ω·m, which were classified as sandy clay (0.11–44 Ω·m) and breccia (>44 Ω·m). The low resistivity zone indicated the presence of a wet sandy clay layer. The slip surface is estimated to be located at a depth of 20–30 meters below the surface, marked by a resistivity contrast boundary between the sandy clay layer and the fractured breccia. Local geological conditions, including volcanic breccia, rock fractures, and high rainfall infiltration, exacerbate the potential for slope instability.