SUBSURFACE MODELING FOR IDENTIFYING SLIP SURFACE: USING THE 2D RESISTIVITY METHOD IN PESAWARAN REGENCY
Way Ratai Road in Pesawaran Regency, Lampung Province, is characterized by hilly morphology with steep slopes, rendering the area susceptible to mass movement. To date, no geophysical studies have specifically identified the slip surface zone along this road corridor, making this research essential as a basis for landslide disaster mitigation. This study aims to identify the slip surface with criteria encompassing subsurface layer structure and weak zone depth estimation. Data acquisition was conducted using the dipole-dipole configuration resistivity geoelectrical method with a traverse length of 128 m, employing 33 electrodes at 4 m spacing. Resistivity data inversion modeling was performed using Res2Dinv software. The interpretation results indicate that the subsurface structure of the study area comprises five lithological units, namely clay, gravel, tuff, basite, and quartzite. The slip surface was identified at a depth of 6–21 m, located at the contact zone between the tuff and basalt units, which exhibits significant resistivity contrast. The estimated volume of potential landslide material reaches 34,560 m³. The findings of this research can serve as a reference for structural and non-structural mitigation planning to minimize landslide risk in the Way Ratai Road area.