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.
Any archaeological site, according to the Brazilian Federal Constitution, is a patrimony of the Union; consequently, when crimes against this cultural patrimony occur, it becomes the responsibility of the Federal Police of Brazil. In 2013, there was a complaint to the Brazilian Federal Public Prosecutor's Office about the depredation of an archaeological site and forced withdrawal of the indigenous people because of the construction of a multimodal port in the city of Guaíra, in the state of Paraná, in southern Brazil. Thus, the Technical–Scientific Sector of the Federal Police Department, in partnership with Brazilian universities, used standard geophysical methods such as ground-penetrating radar (GPR) to investigate and locate buried archaeological targets. This paper discusses the results of 2D and 3D investigations in the Tekoha Jevy indigenous village, located in Guaíra County. In the field, 32 parallel sections of GPR data were acquired using 250 and 700 MHz shielded antennas. The results showed several anomalies, two of which were subjected to field checks using excavations, which revealed several artefacts such as ceramic fragments associated with ancient indigenous occupations on the banks of the Paraná River.
The detection of buried clandestine objects challenges forensic and archeologic search group teams on varying terrains, and variable scales of research. Therefore, the study of controlled buried objects is useful for trainings in geophysical acquisition and processing. In this study, we applied ground survey data for testing the magnetic method at controlled geophysical sites for the location of ordinary objects and firearms. We used data filtering techniques in order to facilitate the location of magnetic targets. Also, we experienced the 3D inversion of analytic signal of the vertically integrated magnetic field (ASVI), for the location of targets in depth. As a result, the study determined the location of four magnetic targets, and a three-dimensional view was constructed from the estimated magnetic susceptibility. We concluded that modeling transformed magnetic data is an affordable technique for application in near-surface investigations. Also, this experiment exemplifies the relevance of magnetic methods for location of excavation sites on the basis of geophysical methods.
Este trabalho demonstra a aplicação dos métodos geofísicos de eletrorresistividade (ER), polarização induzida (IP) e eletromagnético (EM) no aterro sanitário de Guaratuba, litoral do Estado do Paraná. Os objetivos principais da pesquisa foram delimitar a pluma de contaminação em subsuperfície e indicar áreas susceptíveis à contaminação. A área do aterro sanitário é representada por granitos do Proterozóico Inferior e sedimentos recentes do Quaternário. Os dados de ER e IP foram obtidos nas áreas internas e adjacentes aos depósitos atual e futuro, através de caminhamento elétrico 2D, arranjo dipolo-dipolo (AB=MN=20m), além de uma sondagem elétrica vertical (SEV) (AB/2=150m), no centro do depósito atual. O levantamento eletromagnético (EM) foi executado nos mesmos locais das linhas de ER e IP, no modo dipolo vertical, bobinas espaçadas de 20 m e 40 m e intervalo de amostragem de 10 m. Os resultados obtidos principalmente pelos métodos ER e EM permitiram caracterizar os granitos (> 1000 Ohm.m; < 14 mS/m), os sedimentos recentes (entre 800-600 Ohm.m; < 14 mS/m) e áreas possivelmente contaminadas (< 50 Ohm.m; > 20 mS/m). Tais resultados possibilitaram ainda sugerir tratos suspeitos de contaminação (50-70 Ohm.m; 15-20 mS/m) e não contaminados (> 70 Ohm.m; < 15 mS/m), além de estimar em 30 m a espessura do aterro, em correspondência a interpretação da SEV. Os resultados de IP não foram satisfatórios, possivelmente devido à sua sensibilidade a resíduos metálicos no depósito.
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