Constraining electric resistivity tomography by direct push electric conductivity logs and vibracores: An exemplary study of the Fiume Morto silted riverbed (Ostia Antica, western Italy)

The inversion of geoelectric data is non-unique. Therefore, electric resistivity tomography (ERT) usually results in different subsurface models that fit observed apparent resistivity values equally well. To reduce the uncertainty, constraints on both geometry and resistivity of subsurface structure can be incorporated into the ERT inversion. In our study, we test different ways of constraining ERT by a) applying improved starting models, b) applying structural constraints and c) applying both structural and resistivity constraints. A priori information is needed for these approaches, which is acquired from Direct Push Electrical Conductivity (DP-EC) logs and vibracores in our study. We found that adapting high vertical resolution of DP-EC logs to coarser ERT resolution requires blocking of the logs. These blocked logs can be used for constraining the ERT inversion with resistivity and structural constraints along so-called regions around the log locations, which was found to be the best approach. In this...