Landslide stability investigation and subsurface deformation mapping by optimizing low-frequency GPR: A mega rainfall susceptible landslide case study (Gilgit Baltistan, Pakistan)

This study uses geophysical techniques to locate subsurface deformations on a ridge that could cause landslide surfaces in a community in Pakistan. After conducting the morphometric analysis, it has been calculated that total slope failure may dislodge a mass of about 14 million cubic meters. Hence, finding the deformational sub-vertical extent was necessary to plan proper mitigation against progressive failure. The study aimed to check the efficiency of unshielded (16–40 MHz) antenna for landslide hazard assessment. We recorded 19 GPR profiles covering the susceptible landslide areas and interpreted them against different subsurface exploration methods, like seismic, electrical, and surface-exposed geology investigation. The investigated slope is an unsorted moraines/fluvioglacial deposits and debris with varying proportions of sand, silt, and clay developing subsidence, sinkholes, and underground piping after irrigation and rainfall. The low-frequency antenna applications marked the effect of subsurface degradation beneath the exposed sinkholes up to 20 m in depth. The subsurface degradation observed in the surface wave analysis technique was also no more than 20–25 m. The interpretation of GPR results allowed us to map the subsidence, piping extent, and sinkhole boundaries by characterizing their internal geometries (deformation style). Therefore, the low-frequency GPR technique helps divide landslide layers accurately and detect the sliding surface with minimum costs and time. This research output can be used as an auxiliary tool for landslide mitigation and will help understand the landslide natures in the Karakoram ranges.