Advances in electric resistivity tomography. Theory and case studies

In this work, we aim to investigate the advances in ERT investigation made during the last years for near-surface applications, discussing the role played by the main parameters on data acquisition, forward modeling, and inversion and presenting strategies for removing the ambiguities arising in interpretation of geoelectric models. In Section 2.1, electric theory was briefly introduced considering electrodes both as point sources (commonly used approximation for ERT modeling) and as finite-length objects. The comparison between the two approaches will be discussed as a function of the ratio between electrode shape (length and size) and spacing. Then, we study the role of the mesh coarseness for the accuracy of the forward solver. Data acquisition problems are discussed in Section 2.2, considering common measurement errors and exploring potential and limits of the 3D arrays. The role of inversion parameters within the ERT reconstruction and the strategies for removing ambiguities and for incorporating a priori and a posteriori information are presented in Section 2.3. Finally (Section 3), we illustrate some case studies concerning the application of ERT for archaeological purposes and soil characterization. Synthetic simulations and field data inversion presented hereafter are performed through the VEMI interface, developed by the authors for time-domain and frequency-domain data modeling and inversion of 2D and 3D ERT and IP data.