Abstract

Singular value decomposition (SVD) based geophysical inversion method is developed and successfully applied to the modeling of resistivity profiles from the hard rock area of Konkan, coastal Maharashtra. 58-number of vertical electrical sounding (VES) collected over Kudal-Vengurla- Malvan and its surrounding area is modeled using the new methods. The results are interpreted in light of the geological setting to know the aquifer infected with the saline water in the study area. Prior to applying the method on actual resistivity data, the efficiency of the method was tested on simulating the synthetic signals generated possible combination of resistivity and layer thickness for a large number of hypothetical setting. The inversion results based on the new algorithm suggest a very high resistivity structure in the north-eastern part of the area, which could be caused due to the presence of laterites. In the south- eastern part of the study area, a very high resistivity zone is observed, which is also caused possibly due to the presence of laterites. The NE-SW trending major lineaments and its criss-crosses are indentified from the apparent and true resistivity surface map. In the south-western part, a very high conductive zone is observed near the coast indicating extensive influence of saltwater water intrusion. Our results also show that the effect of intrusion of saline water diminishes from the southern western part to the north eastern part of the region. Two dimensional modeling of four resistivity profiles data from the study region shows that the flow of saline water from the coastal side partly controlled by the lineaments and conduits. The method is robust for modeling resistivity data in hard rock terrain and the results obtained here are useful for interpreting the fractures, major joints and lineaments, and also for constraining the geophysical models used for the study of the drainage pattern in the hard rock area.