GPR and ERT detection and characterization of a mass burial, Spanish Civil War, Northern Spain

From Its Core to the Niche: Insights from GPR Applications

Thanks to its non-destructive, high-resolution imaging possibilities and its sensitivity to both conductive and dielectric subsurface structures, Ground-Penetrating Radar (GPR) has become a widely recognized near-surface geophysical tool, routinely adopted in a wide variety of disciplines. Since its first development almost 100 years ago, the domain in which the methodology has been successfully deployed has significantly expanded from ice sounding and environmental studies to precision agriculture and infrastructure monitoring. While such expansion has been clearly supported by the evolution of technology and electronics, the operating principles have always secured GPR a predominant position among alternative inspection approaches. The aim of this contribution is to provide a large-scale survey of the current areas where GPR has emerged as a valuable prospection methodology, highlighting the reasons for such prominence and, at the same time, to suggest where and how it could be enhanced even more.

A novel approach to 3D modelling ground-penetrating radar (GPR) data - A case study of a cemetery and applications for criminal investigation

Ground-penetrating radar (GPR) is an established geophysical technique used extensively for the accurate reconstruction of the shallow (<10 m) subsurface. Reconstructions have largely been completed and presented as 2D vertical and horizontal planes, leaving limited visualization of subsurface 3D shapes and their spatial relationships. With technological advancements, particularly the availability and integration of various software platforms, 3D modelling of GPR data is now emerging as the new standard. However, despite these developments, there remains an inadequate examination and testing of these techniques, particularly in determining if their application is beneficial and warranted. In this study we conducted a GPR grid survey on a churchyard cemetery to generate and evaluate 2D and 3D-modelled reconstructions of the cemetery burial sites. Data collection and processing was completed using a Sensors and Software Incorporated pulseEKKO™ Pro SmartCart GPR system and EKKO_Project™ software, respectively. The modelling component was achieved using Schlumberger's Petrel™ E & P software platform, which is tailored to the petroleum industry. The subsurface patterns present in the 2D and 3D models closely matched the cemetery plot plan, validating our data collection, processing, and modelling methods. Both models were adequate for 2D horizontal visualization of reflection patterns at any specific depth. The 3D model was used to identify the presence of a companion burial plot (stacked caskets) and possible leachate plumes below and encircling burial sites, both of which were not evident in the 2D model, highlighting the benefits of 3D modelling when discerning subsurface objects. We expect our findings to be of value to similar GPR studies, with particular significance to geoforensic studies and criminal investigations.

Using Ground Penetrating Radar and Resistivity Methods to Locate Unmarked Graves: A Review

The location of unmarked graves in forensic and archaeological investigations is legally and culturally important. In a forensic context, locating covert burials of missing persons can provide closure to the family, as well as facilitating the successful prosecution of the individual(s) responsible. Archaeologically, burials provide an important source of information about health, diet, physical anthropology, and culture. Despite the importance of these features, the location of unmarked graves with conventional archaeological and forensic techniques, such as excavation, is difficult and expensive. As a result, geophysical techniques have been widely applied to the location of unmarked graves as they are non-invasive, cost and time effective, and avoid the unnecessary disturbance of human remains. This article brings together the literature on ground penetrating radar (GPR), and two resistivity methods, electrical resistivity tomography (ERT) and fixed probe resistivity (FPR), on their ability to locate burials and reviews their use in forensic and archaeological investigations. This paper aims to provide law enforcement personnel, archaeologists, geophysicists, and interested academics with an overview of how these techniques work, how they have been previously applied to grave detection, and the strengths and weakness of these methods.

Identifying Changes in Sediment Texture along an Ephemeral Gravel-Bed Stream Using Electrical Resistivity Tomography 2D and 3D

Differences in deposit geometry and texture with depth along ephemeral gravel-bed streams strongly reflect fluctuations in bedload which are due to environmental changes at the basin scale and to morphological channel adjustments. This study combines electrical resistivity tomography (ERT) with datasets from borehole logs to analyse the internal geometry of channel cross-sections in a gravel-bed ephemeral stream (southeast Spain). The survey was performed through longitudinal and transverse profiles in the upper channel stretch, of 14 to 30 m in length and 3 to 6 m in depth, approximately. ERT values were correlated with data on sediment texture as grain size distribution, effective grain sizes, sorting, and particle shape (Zingg’s classification). The alluvial channel-fills showed the superposition of four layers with uneven thickness and arrangement: (1) the softer rocky substrate (<1000 Ω.m); (2) a thicker intermediate layer (1000 to 2000 Ω.m); and (3) an upper set composed of coarse gravel and supported matrix, ranging above 2000 Ω.m, and a narrow subsurface layer, which is the most resistive (>5000 Ω.m), corresponding to the most recent armoured deposits (gravel and pebbles). The ERT results coupled with borehole data allowed for determining the horizontal and vertical behaviour of the materials in a 3D model, facilitating the layer identification.

Anatomy of Infraorbital Foramen: Influence of Sex, Side, and Cranium Size

Several researchers have analyzed the collocation of infraorbital foramen, but no study has so far considered the possible influence of cranial size.Three measurements (distances from anterior nasal spine, inferior orbital rim, angle at the intersection between the line from anterior nasal spine and the transversal plane parallel to the Frankfurt plane) were taken on 100 skulls belonging to a contemporary skeletal collection. In addition, maximum cranial length, maximum cranial breadth, cranial height, and bizygomatic breadth were measured, together with 2 indices (horizontal cephalic index and Giardina Y-index). Differences according to sex and side were assessed through 2-way analysis of variance test (P <0.05). Measurements showing statistically significant differences according to sex were further assessed through 1-way analysis of covariance test including cranial measurements and indices as covariates (P <0.05).Statistically significant differences according to sex and side were found respectively for the distance from anterior nasal spine and the angle at infraorbital foramen (P <0.05). One-way analysis of covariance test verified that the sexual dimorphism of infraorbital foramen- anterior nasal spine distance was independent from the general measurements of cranium.The present study first proved that sexually dimorphic parameters useful for the localization of infraorbital foramen do not depend upon the cranium size.