Landslides assessment using geophysical and passive radon exhalation detection techniques in Murree Hills, northern Pakistan: Implication for environmental hazard assessment

Geophysical investigation of three landslides in Murree Hills was carried out using geophysical techniques (i.e., seismic refraction and electrical resistivity) and geochemical tool (passive radon exhalation detection method). The seismic data was acquired by using reverse shooting scheme employing placement of source after the last active geophone in the spread. The acquired data was analyzed, and layer velocities were estimated by using Hagedoorn's method. The resistivity data was modeled in terms of true resistivity of subsurface material by curve matching technique. The radon emission was determined as alpha track densities for each detector planted in dosimeter in the sub-surface along survey profiles. The results of all the methods employed were interpreted and correlated in the context of local geology, and also considering seasonal and anthropogenic factors. The study guides the importance of local geological structure and lithologies in the formation of thick weathering layer. The weathered layer wet/moistened through rains in the winter and summer seasons or daily use of water due to urbanization of the area, exerts more downslide force thus resulting landslides. This thickness of weathered layer is determined by using seismic refraction and resistivity methods for the three landslides (MIT, Kuldana and Chitta Mor) which is in agreement. Also, the passive radon exhalation detection technique (geochemical investigation) has delineated the stable and unstable areas within the three landslide zones. These geophysical and geochemical investigations are recommended on the major landslides of the area prior to damage control measures.