Delineation of weathered/fracture zones for aquifer potential using an integrated geophysical approach: A case study from South China

An integrated geophysical approach involving 2D modeling of electrical resistivity tomography (ERT) and magnetic methods has been employed at a highly heterogeneous site in Guangdong, South China, with a view at mapping the subsurface structures and delineating the weathered/fracture zones for groundwater potential. This study was carried out by ERT and magnetic surveys along the same profiles. One ERT survey was performed by the ABEM LUND Imaging System along four profiles each with a total of 81 electrodes, electrode spacing of 5 m and a spread length of 400 m. Another magnetic survey was conducted by two Geometrics G-856 proton precession magnetometers of 0.1 nT sensitivity along four profiles each with 79 magnetic measurements, a station interval of 5 m and a spread length of 390 m. The 2D modeling results of ERT and magnetic methods delineated several discontinuities (weathered/fracture zones) and three distinct layers i.e., top soil cover, weathered layer (weathered tuff) and unweathered layer (fresh bedrock). The integration of ERT and magnetic models shows good correlation with available upfront borehole information. The results suggest that groundwater is best accessible within the weathered/fracture zones in the study area. This integrated geophysical approach can be affectively used in weathered environment for groundwater exploration.