A study of the affect of seasonal climatic factors on the electrical resistivity response of three experimental graves

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Jervis, JR ; Pringle, JK (2014)

Electrical resistivity surveys have proven useful for locating clandestine graves in a number of forensic searches. However, some aspects of grave detection with resistivity surveys remain imperfectly understood. One such aspect is the effect of seasonal changes in climate on the resistivity response of graves. In this study, resistivity survey data collected over three years over three simulated graves were analysed in order to assess how the graves' resistivity anomalies varied seasonally and when they could most easily be detected. Thresholds were used to identify anomalies, and the ‘residual volume’ of grave-related anomalies was calculated as the area bounded by the relevant thresholds multiplied by the anomaly’s average value above the threshold. The residual volume of a resistivity anomaly associated with a buried pig cadaver showed evidence of repeating annual patterns and was moderately correlated with the soil moisture budget. This anomaly was easiest to detect between January and April each year, after prolonged periods of high net gain in soil moisture. The resistivity response of a wrapped cadaver was more complex, although it also showed evidence of seasonal variation during the third year after burial. We suggest that the observed variation in the graves' resistivity anomalies was caused by seasonal change in survey data noise levels, which was in turn influenced by the soil moisture budget. It is possible that similar variations occur elsewhere for sites with seasonal climate variations and this could affect successful detection of other subsurface features. Further research to investigate how different climates and soil types affect seasonal variation in grave-related resistivity anomalies would be useful.
  • References (6)

    Aaltonen, J., Olofsson, B., 2002. Direct current (DC) resistivity measurements in long-term groundwater monitoring programs. Environ. Geol. 41, 662-671.

    DOI:10.1007/s00254-001-0447-1 Al Chalabi, M.M., Rees, A.I., 1962. An experiment on the effect of rainfall on electrical resistivity anomalies in the near surface. Bonn. Jahrb. 162, 266-271.

    Binley, A., Winship, P., West, L.J., Pokar, M., Middleton, R., 2002. Seasonal variation of moisture content in unsaturated sandstone inferred from borehole radar and resistivity profiles. J. Hydrol. 267, 160-172. DOI:10.1016/S0022-1694(02)00147-6 Buck, S.C., 2003. Searching for graves using geophysical technology: field tests with ground penetrating radar, magnetometry and electrical resistivity. J. Forensic Sci. 48, 1-7.

    DOI:10.1520/JFS2002165 Cheetham, P., 2005. Forensic geophysical survey, in: Hunter, J., Cox, M. (Eds.), Forensic Archaeology: Advances in Theory and Practice. Routledge, Oxon, pp. 62-95.

    ISBN:0415273129 Clark, A.J., 1996. Seeing Beneath the Soil: Prospecting Methods in Archaeology, first rev.

    ed. Batsford Ltd., London. ISBN:0415214408 Jervis, J.R., Pringle, J.K., Cassella, J.P., Tuckwell, G., 2009a. Using soil and groundwater data to understand resistivity surveys over a simulated clandestine grave, in: Ritz, K., Dawson, L., Miller, D. (Eds.), Criminal and Environmental Soil Forensics. Springer Scollar, I., Tabbagh, A., Hesse, A., Herzog, I., 1990. Archaeological Prospecting and

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