Mapping water flow pathways in the Fengjiaping landslide using self-potential and electrical resistivity tomography

The Fengjiaping Landslide, located at the transitional zone between the western Qinling Mountains and the southwestern margin of the Loess Plateau in China, is a reactivated loess–mudstone interface landslide. Its complex evolution is influenced by geological, hydrological and climatic factors, as well as human activities. The critical zone regulates precipitation infiltration, which, in turn, controls soil moisture and groundwater dynamics. Although excessive water infiltration is recognized as the primary trigger, the landslide exhibits heterogeneous deformation, with recurrent events not always correlated with rainfall, making its reactivation mechanisms difficult to understand and predict. Potential sliding zones in moisture-induced landslides are typically characterized by high soil moisture and elevated water fluxes, manifesting as low electrical resistivity and enhanced streaming current densities. In this study, we applied an integrated geophysical approach, combining direct-current electrical resistivity tomography (ERT) and self-potential (SP) measurements, to infer subsurface water pathways and identify zones potentially contributing to slope instability. The joint interpretation of SP and ERT data suggests preferential flow channels and groundwater activity beneath scarps and cracks, highlighting their potential role as conduits for infiltration and slope weakening. Despite these insights, uncertainties remain due to limitations in data coverage, boundary effects, and simplified assumptions in the inversion framework. Future work should focus on continuous and time-lapse SP and ERT monitoring, complemented by methods such as induced polarization and borehole investigations, to better constrain subsurface hydrogeological properties and improve the understanding of the processes governing slope instability.