Detection of graves using the micro-resistivity method

Abstract

This paper describes a case history of the application of resistivity methods on the detection of a tomb tentatively associated with Damião de Goes, a prominent Portuguese humanist who lived in the XVI century. The survey carried out inside Varzea Church comprised dipole-dipole, gradient and pole-pole arrays. The results obtained from the 2D inversion of dipole-dipole data and 3D inversion of the gradient array have shown high resistivity anomalies that were assigned to the walls of the tomb. The low resistivity anomalies observed in between were interpreted as due to the presence of water enriched by ions from the decomposition of human bodies. This result is corroborated by the imaging obtained using the 3D probability tomography of the gradient and pole-pole data. Excavation works, carried out in accordance with the results of the geoelectrical investigation, successfully found a 2.7×0.8×1.7 m tomb, where several human bones have been collected. A 3D resistivity model incorporating the main features of the tomb was built after the excavation. The pole-pole model responses calculated from this model reproduce the main features observed in the data.