Processing Radargrams to Obtain Resistivity Sections

Abstract

Ground penetrating radar (GPR) is routinely used to locate the isolated elements that produce reflection hyperbolas in radargrams. However, we propose a method in this study for locating the various interfaces appearing in a medium by studying the signal attenuation to obtain resistivity sections. GPR signal decay has a strong relationship with the electromagnetic properties of the medium, particularly the electrical resistivity and permittivity. To assign values of resistivity to different layers, a relationship between the attenuation coefficient and the above parameters must be used. Moreover, there are geometric effects that affect the energy loss and, therefore, the signal amplitude, that are jointly considered for the elimination of such effects before calculating the attenuation coefficient. An envelope function of the traces previously corrected for geometric effects was created to detect interfaces in the medium and generate a local decay curve and radargram zonation. Two relationships are necessary for obtaining the resistivity values from signal decay: first, a relationship between the resistivity and relative permittivity of the medium; and second, a relationship between the attenuation coefficient and resistivity. A resistivity section obtained from the GPR data is shown with an electrical tomography section at the same location.