Application of resistivity and GPR techniques for the characterization of the coastal litho-stratigraphy and aquifer vulnerability due to seawater intrusion

The objective of this study is to identify geological properties and structural settings, allowing salt-water intrusion to the aquifers in oceanic originated rock formations of the South Andaman Island. To evaluate the impact of seawater in groundwater aquifer, several geophysical surveys using ground penetrating radar (GPR) and resistivity sounding were performed through the most significant sites, located near coastal areas, tidal channels and agriculture land. High-resolution GPR images were obtained and combined with resistivity sounding, which allows to identify the mixing/transition zone of fresh and saline groundwater and also successfully delineated the structural geometry and litho-stratigraphic details of aquifers. We show that the sedimentary formations are highly susceptible to seawater intrusion than the mantle originated ophiolites. Further, potential impacts from seawater intrusion are higher along the west coast than the east coast because of macro-pore tendency of soils allows seawater filtration.