Tomographic Pseudo-Inversion Of Pole-Pole And Pole-Dipole Resistivity Profiles

Here is presented an approach to carry out a fast construction of pseudosections using resistivity<br>data. The purpose of the procedure is to obtain maps and sections which match as closely<br>as possible the geometry of the structures which are investigated. Even if such a procedure is not<br>a real inversion but only an arrangement of the experimental data, it can nevertheless be used as<br>a useful tool in their interpretation or, at least, as a first step before the inversion, that is in the<br>choice of a preliminary inversion model.<br>In principle the method works like a back-projection in a pixel grid, which is performed by<br>arranging the experimental data in a sort of a sets of convolutions using 2D or 3D filters. The<br>coefficients can be calculated depending on the geometry (type, size, relative position and direction)<br>of the electrode array which is used. Consequently the filters for pole-pole and pole-dipole<br>arrays are presented. Furthermore some aspects of the method are discussed together with some<br>applications, using both synthetic as well as experimental data. The former ones were calculated<br>for a simple model (a buried resistive sphere) while the latter ones concerned some resistivity<br>profiles acquired in Sardinia and in Tuscany, in the course of some archaeological investigations.<br>Key words: pseudosection, resistivity profile, pseudo-depth section, pseudo-inversion, electric<br>tomography, pole-pole andpole-dipole arrays.