Analysis of 2D and 3D GPR responses in the Federal University of Paraná Forensic Geophysics Controlled Site – a Case Study

Abstract

ABSTRACT. In 2016, the Laboratory for Research in Applied Geophysics (LPGA), at the Federal University of Paraná, in partnership with the Federal Police of the State of Paraná and the University of Brasília built a Forensic Geophysics Controlled Site (FGCS-UFPR) to calibration of the applied geophysical method and strengthen forensic sciences in the State of Paraná. In the FGCS, several objects that simulate forensic, archaeological and paleontological targets were installed at extremely shallow depths. The materials were covered with clayey soil, typical of the region, and in some pits, fine sandy sediments were deposited. This study aims to verify the 2D and 3D responses of the ground penetrating radar (GPR) method applied to targets installed in the FGCS, in a post-precipitation period. In the acquisition of GPR data, a 700 MHz shielded antenna was used, with parallel 2D profiles and spaced 0.1 meters. The results indicated that the high clay content present in the soil, below 0.5 meters deep, caused a high attenuation of the electromagnetic signal and defined patterns of reflectors associated with the targets, excavations and the investigated environment. Thus, only targets with high electrical impedance were visualized in 2D and 3D GPR images.Keywords: ground penetrating radar, clay soil, targets, forensic sciences, archaeogeophysics. Análise dos resultados 2D e 3D de GPR no Sitio Controlado de Geofísica Forense da UFPRRESUMO. Em 2016, o Laboratório de Pesquisas em Geofísica Aplicada (LPGA), da Universidade Federal do Paraná, em parceria com a Polícia Federal do Paraná e a Universidade de Brasília, instalou um Sítio Controlado de Geofísica Forense (SCGF-UFPR) para a calibração do método geofísico aplicado e o fortalecimento das ciências forenses no Estado do Paraná. No SCGF foram instalados, em profundidades extremamente rasas, diversos objetos que simulam alvos forenses, arqueológicos e paleontológicos. Os materiais foram recobertos com solos argilosos, típicos da região, e em algumas cavas foram depositados sedimentos arenosos finos. Este estudo objetiva a verificação das respostas 2D e 3D do método radar de penetração no solo (GPR) aplicada aos alvos instalados no SCG, em um período pós-precipitação pluviométrica. Nas aquisições de dados de GPR foi aplicada a antena blindada de 700 MHz, com perfis 2D paralelos e equiespaçados em 0,1 metro. Os resultados indicaram que o alto teor de argila presente no solo, abaixo de 0,5 metro de profundidade, causou uma elevada atenuação do sinal eletromagnético e definiu-se padrões de refletores associados aos alvos, as escavações e ao meio investigado. Assim, apenas os alvos com alta impedância elétrica foram visualizados nas imagens GPR 2D e 3D.Palavras-chave: ground penetrating radar, solo argiloso, artefatos, ciência forense, arqueogeofísica.

Geophysical surveying for the detection of ferrous-based objects: possibilities for depth estimative combining analytic signal and vertical integral of the anomalous magnetic field

“…Such technique has been explored in Brazil on several studies (e.g., Porsani, 2002;Buck, 2003;Rodrigues, 2004;Rodrigues and Porsani, 2006;Borges, 2007;De Paula et al, 2007;Luiz et al, 2007;Blum and Russo, 2012;Alves et al, 2013;Buso et al, 2016;Cavalcanti et al, 2018). In the same way, the Laboratory for Research in Applied Geophysics (LPGA) performed researches on forensic studies, initially focused on Ground Penetrating Radar techniques (Bongiolo et al, 2019;Canata et al, 2019Canata et al, , 2020Canata, 2020). In this work, we bring results of the terrestrial magnetic acquisition for these test sites, in order to exemplify the possibilities of magnetics in the search of ordinary objects and buried firearms.…”

“…The geological background of the geophysical research site is composed by clayey sediments of the Guabirotuba Formation over migmatites and gneiss from the Atuba Complex (Bigarella et al, 1961) as shown in Figure 3. Due to the clayey soil, sand was placed around some artifacts, in order to better understand the impact of those sedimentary backgrounds for the GPR research (Canata, 2020;Canata et al, 2020). However, for magnetic studies, the geophysical signal is unaffected by such soil changes.…”

Ground Penetrating Radar applied to asphaltic pavements – a study in a controlled site

“…Test sites are important to understand forthcoming results in any geophysical survey, both geotechnical (Grandjean et al, 2000;Paniagua et al, 2004;Porsani et al, 2006;Borges, 2007;Orfanos & Apostolopoulos, 2012;Santos et al, 2019), and archeological (Porsani et al, 2006;Borges, 2007, Aragão et al, 2010, and forensic studies (Brasil, 2013;Cavalcanti, 2017;Canata et al, 2020). The previously known characteristics of buried targets, such as physical properties, geometry, and depth, collaborate in future interpretations of geophysical responses in different materials (Borges, 2007).…”