Gravity together with electrical resistivity tomography have proved to be effective tools for imaging subsurface cavities in limestone at shallow depths.
Joint resistivity and gravity interpretation for Karst identification. Results of the electrical-resistivity tomography (ERT) and gravity modeling are shown. The upper part of the figure (a) shows the correlation between the observed residual Bouguer anomaly and the model shown in the middle part (b). The ERT cross-section image is in the lower part of the figure (c).
Aquifer identification using resistivity interpretation