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ABSTRACT. This paper presents the results obtained from surface and borehole geophysical investigations carried out at the Shallow Geophysical Test Site of IAG-USP. The main objective was to characterize the sediments and the top of basement. The area is constituted by sandy-clay sediments of São Paulo Basin (São Paulo and Resend Formations) on the granite-gneiss basement with different degrees of weathering. In the area of studies, three boreholes were drilled for geological and geophysical research purposes (pioneer in Brazil). These boreholes were used to verify the stratigraphy, to collect the sample for laboratory measurements, to calibrate the results of surface geophysics and to carry out well logging. The surface methods used were: seismic (reflection and refraction), electric-resistivity (profiling and RESUMO. Este trabalho sintetiza os resultados de investigações geofísicas de superfície e de poço realizadas no Sítio Controlado de Geofísica Rasa do IAG-USP,visando caracterizar os sedimentos e o topo do embasamento. Aáreaé constituída por sedimentos areno-argilosos da Bacia de São Paulo (Formações São Paulo e Resende) sobrepostos ao embasamento granito-gnáissico com diferentes graus de intemperização. Naárea de estudos, também denominada de campo de provas do IAG, foram perfurados três poços para pesquisas geológicas e geofísicas (pioneiros no Brasil), visando verificar a litoestratigrafia, coleta de amostras de calha, calibrar os resultados e realizar as perfilagens geofísicas. Foram utilizados os seguintes métodos: sísmica rasa (reflexão e refração), eletrorresistividade (caminhamento elétrico e sondagem elétrica vertical) e GPR-Ground Penetrating Radar. A integração dos resultados mostrou uma excelente concordância e permitiu elaborar um modelo geológico-geofísico para este ponto da Bacia Sedimentar de São Paulo, bem como testar, em condições controladas de campo, os diversos métodos geofísicos usados rotineiramente em estudos geológicos, geotécnicos e ambientais.

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ABSTRACT. The data interpretation from shallow geophysical survey can be complex because the uncertainty about subsurface targets. To reduce the ambiguity and help in the interpretation of geophysical data, the Shallow Geophysical Test Site of IAG-USP (Sítio Controlado de Geofísica Rasa-SCGR do IAG-USP) was installed inside the campus at USP. Different targets at various depths were installed along seven lines. The targets buried in the Test Site simulate targets found in geotechnical, archaeological, and environmental studies. In this article, the construction methodology of the Test Site and some GPR results along a line characterized by empty metallic tanks are presented. The geophysical characterization in controlled field condition allowed the calibration of geophysical responses due to known targets, such as, metallic tanks. 250 MHz GPR profile showed an excellent agreement with a GPR 2D model determined by finite difference in time domain method. Fk-migration improved the resolution and the spatial position of the metallic tanks. GPR 3D results, such as 3D cube, fence diagrams, and depth slices, were very important to improve the characterization of the targets in subsurface. SCGR-IAG revealed itself as important tool for teaching, research and extension activities in university related to Geophysics, and it will be very important to our community. With the installation of this Test Site, an important step was done in searching the State of Art in Shallow Geophysics in Brazil, were the development of news equipment, modeling and inversion software could be tested and its response calibrated.Keywords: SCGR-IAG, Shallow Geophysical Test Site-IAG, GPR-Ground Penetrating Radar, Modeling GPR 2D, Metallic tanks, Cube 3D, Fence diagrams, Depth slices. RESUMO.A interpretação de dados de investigações geofísicas rasas pode ser complexa devidoàs incertezas a respeito dos alvos em subsuperfície. Para reduzir as ambigüidades e auxiliar a interpretação dos dados geofísicos de superfície foi instalado no campus da USP o Sítio Controlado de Geofísica Rasa do IAG-USP. Diferentes alvos foram instalados em várias profundidades ao longo de 7 linhas. Os alvos instalados no Sítio Controlado simulam alvos encontrados em estudos geotécnicos, ambientais e arqueológicos. Neste artigo são apresentadas as principais etapas envolvidas na construção do Sítio Controlado de Geofísica Rasa do IAG/USP e alguns resultados GPR ao longo de uma linha caracterizada por tambores metálicos vazios. A caracterização geofísica, sob condições controladas de campo, permitiu uma calibração das respostas geofísicas para os tambores metálicos instalados no SCGR-IAG. O perfil GPR de 250 MHz apresentou uma excelente concordância com a modelagem GPR 2D através do método das diferenças finitas no domínio do tempo. A migração-fk melhorou a resolução e o posicionamento espacial dos tambores metálicos. Os resultados GPR 3D na forma de cubo 3D, diagrama de cercas e depth slices, mostraram-se muito importantes para melhorar a caracterização dos alvos em subsupe...

This paper describes some ground-penetrating radar ͑GPR͒ results to characterize steel tanks buried in the subsoil of an urban center. Tanks were installed in the first Brazilian geophysical test site located at the Institute of Astronomy, Geophysics, and Atmospheric Science ͑IAG͒ of the University of São Paulo ͑USP͒. This paper also presents an effective procedure for removal of hyperbolic artifacts associated with GPR reflections between multiple steel tanks. One hundred sixty-five GPR profiles of 200 MHz, 400 MHz, and 500 MHz ͑shielded bistatic antennae͒ were measured. The work was done in two distinct places: on the geophysical test site of the IAG/USP in the city of São Paulo, Brazil, and in an area formerly occupied by a truck cleaning, refueling, and maintenance facility, located in Oscoda, northeastern Michigan, USA. Predictive deconvolution and Kirchhoff migration were first used to improve vertical and lateral resolution. To minimize the hyperbolic artifacts caused by reflections between tanks, high-pass filtering was applied to data. Then, Hilbert transforms emphasize the location of the steel tanks in an energy cross-section form. Further GPR processing, such as vertical and depth slices, were very important to improve visualization and localization of steel tanks and pipes in the subsurface.