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

Pringle, Jamie K.; Jervis, John R.

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Authors

John R. Jervis



Abstract

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.

Journal Article Type Article
Acceptance Date Jun 24, 2014
Online Publication Date Jul 1, 2014
Publication Date 2014-09
Publicly Available Date Mar 28, 2024
Journal Journal of Applied Geophysics
Print ISSN 0926-9851
Publisher Elsevier
Peer Reviewed Peer Reviewed
Volume 108
Pages 53 -60
DOI https://doi.org/10.1016/j.jappgeo.2014.06.008
Keywords near-surface geophysics, electrical resistivity, seasonal variation, forensic search, clandestine grave
Publisher URL http://www.journals.elsevier.com/journal-of-applied-geophysics/

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