3D geoelectric tomography and archaeological applications¹

Following a previous paper in which the principles of a 3D ground‐surface tomographic processing of self‐potential data were established, we extend the method to active source geoelectric surveying. The main purpose of the new tomographic approach is to obtain a physical image reconstruction of the induced electric charges distributed over buried resistivity discontinuities. The information is produced in a probabilistic sense, as the mathematical formulation underlying the method treats only the intrinsic physical nature of the generated electric field underground and the method of its ground‐surface detection, independently of the geometry of the unknown structures. In practice, a 3D tomography is realized by cross‐correlating a set of distributed electric‐field ground‐surface data with a scanning function, representing a unit positive point charge located anywhere in the lower half‐space. The resolution of the method is tested on the synthetic response of a 3D structural simulation of an archaeological target, consisting of an infinitely resistive prismatic body immersed in a half‐space, including surface inhomogeneities and layering. Finally, the field response of a 3D structure consisting of a hypogeal dromos ‐chamber tomb inside the Sabine Necropolis at Colle del Forno, close to Rome, is presented and discussed.