Electrically inferred subsurface fractures in the crystalline hard rocks of an Experimental Hydrogeological Park, Southern India

An experimental study located at the managed aquifer recharge (MAR) site of EHP has measured a distinct variation in the apparent resistivity for deeper electrical signals that localize the presence of interconnected water-saturated fractures. Profiles close to the MAR tank depict low apparent resistivity values from deep signals across in situ fractures and resistivity amplitude increases away from the tank. We modeled and simulated the presence of water-saturated fractures by a simple three-layered model having embedded shallow heterogeneities in the saprolite layer, vertically interconnected multiple thin conductive horizontal layers in the fissured zone, and an underlain unweathered crystalline granitic basement. An overview of the 3D resistivity model characterizes the subsurface heterogeneities and the presence of possible flow paths for shallow depths <30 m, and it is indicative of possible flows in the interconnected deep fractures for depths >30 m.

Figure: Electrical resistivity slices at 30, 40, and 50 m bgl. The thick black dashed-dotted lines with arrows indicate the possible flow pathways in the fissured layer, represented by low-resistivity anomalies (<250 Ωm). The black thin dashed lines show the 2019 profiles.


Ved Prakash Maurya, Subash Chandra, Sahebrao Sonkamble, Kethavath Lohithkumar, Erugu Nagaiah and Adrien Selles (2021) GEOPHYSICS, VOL. 86, NO. 5 DOI: 10.1190/GEO2020-0327.1