Geoelectrical modelling of a landslide surface through an unstructured mesh

Mass movements in wavy topographic zones pose a constant danger to infrastructure, water management, plantation formation, and human life. A commonly used method in near-surface geophysical surveys is Electrical Resistivity Tomography (ERT) to define various strata levels and calculate the likely slip surface of landslides. We use a developed algorithm named ResIPy to be able to incorporate surface topography using triangular cells in finite element forward and inversion processes. Initially, a synthetic landslide case demonstrates that employing the triangular mesh results in more accurate identification of the geological formations than the rectangular mesh, which requires more CPU time. Then, field data from a prone landslide at approximately 20 km NW of the Tehran province, in Iran, was investigated using eight geoelectrical profiles spaced 20 m along the sliding surface accompanying one borehole. The sliding surface corresponds to a deep zone with low resistivity due to the presence of shale, and the sliding material is composed of gravelly soil, silt, and tuff. According to the field observations, the crown portion is vulnerable to sliding because there are transverse cracks in the uphill slope.