A model tank investigation of the electrical resistivity response over a simulated forensic target

Abstract

The electrical resistivity response of a simulated clandestine buried weapon box-laden ammunition tank was carried out. This was with the aim of determining the adoptability of the resistivity method in search for similar forensic targets. The experiment was carried out in a model tank of dimension 207x160x50 cm3. The model tank was filled with compacted and un-compacted sand and a weapon box-laden ammunition tank was buried within the compacted sand. The ammunition tank was made of stainless steel while the weapon box was metallic. Resistivity measurements were taken on the crest of the tank along five (5) traverses before and after the burial of the ammunition tank. The Electrical Resistivity Imaging (ERI) technique in conjunction with the dipole-dipole array was adopted for the measurements. The data were quantitatively interpreted by inversion and the results were presented as 2-D resistivity structures, maps and stacked profiles. During the pre-burial measurements, resistivity values generally increased with increasing depth and three (3) resistivity classes (101–266, 275–835 and 2113–23,944 Ω-m) resulting from the variation in compaction and/or degree of water saturation were observed. The resistivity classes were present within the depth ranges of 0–8 cm, 8–16 cm and 16–40 cm respectively. A drastically reduced resistivity regime, however characterized the post-burial measurements. The post-burial images of the traverses straddled by the region of burial had their resistivity values decreasing with increasing depth as against the pre-burial pattern. The presence of the stainless steel ammunition tank was attributed to the resulting higher resistivity values introduced within the overburden after its burial. A major low resistivity anomaly coincident on the position of burial of the metallic weapon box indicated its presence. The study demonstrated the potential of the electrical resistivity method in the delineation of similar targets that may have forensic implications.