Detecção de cavidades EM arenitos utilizando gravimetria, eletrorresistividade e GPR

Abstract

This paper shows the results of geophysical research in areas of sand exploration near the city of Descalvado, SP, Brazil. The main objective of this research is to detect cavities inside sandstones belonging to the Piramboia and Botucatu Formations in the Parana sedimentary basin. These cavities were indirectly caused by human activity, i.e., the lowering of the water table for the purpose of sand extraction. The geophysical techniques employed were: gravity, resistivity (dipole-dipole electrical profiling) and ground penetrating radar (GPR). In the first stage of the work gravity and resistivity surveys were used to indicate where exists voids due to the collapse of the roof of a cavity. The results obtained with these two techniques were coherent because the gravity showed a "mass absence" in the area of influence of the cavity and the dipole-dipole electrical profiling detected an increase of electric resistivity in this same area. In the second stage, the GPR survey detected the same cavities by means of the hyperbolic features that appear in the radargrams.