GPR investigation of karst in a carbonate coastal area for geo-hazard risk assessment

A Ground Penetrating Radar (GPR) survey was conducted to detect karst within the carbonate section at two locations along the coast of Oman. The aim of this study was to assess the effectiveness of the GPR method in identifying the location and size of karst or sinkholes in carbonate rocks that could lead to building collapses in residential areas. Another objective was to evaluate the suitability of alternative construction sites for safe living. To investigate various depths and resolutions, two shielded antennas with central frequencies of 270 MHz and 400 MHz were used. The results revealed several hyperbolic reflections, disrupting the continuity of the GPR signals, which indicated the presence of fracture zones and karst within the limestone. These zones exhibited a significant contrast in dielectric properties between the karst and the surrounding carbonate rocks. The GPR waves were limited to a depth of 2-5 meters in the surveyed areas, likely due to signal attenuation caused by the presence of clays and seawater, which partially or fully saturate the limestone through fractures and karstic cavities. The results not only identified existing subsurface cavities but also highlighted potential geohazards risk assessment, providing valuable information to city planners and civil engineers for taking necessary precautions to avoid undesirable situations.