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7th International Congress of the Brazilian Geophysical Society
- Conference date: 28 Oct 2001 - 31 Oct 2001
- Location: Salvador, Bahia, Brazil
- Published: 28 October 2001
41 - 60 of 465 results
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Two-Step Inversion Scheme For Complex Magnetotelluric Apparent Resistivity Data
Authors Atahebson B. Santos, Edson E.S. Sampaio and Milton J. PorsaniInterpretation of magnetotelluric data under the assumption of isotropic and one-dimentsional structures is a valuable procedure for exploration and solid earth geophysics investigation.
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Estimativa Das Direções Principais De Tensão In Situ Por Anisotropia De Velocidades
Authors Raquel Velloso, Guilherme Vasquez and Lucia Duarte DillonNeste trabalho estimam-se as direções principais de tensão in situ pelo método denominado VELAN (Velocity Anisotropy), que consiste na medida da velocidade de propagação de ondas ultra-sônicas em diversas direções radiais numa amostra proveniente de um testemunho orientado. Estas medidas permitem determinar as direções de máxima e mínima velocidades
que por sua vez se relacionam com as direções principais de tensões in situ. Realizaram-se ensaios de VELAN com duas amostras que apresentaram resultados bastantes coerentes
entre si. A observação das amplitudes das ondas registradas e a análise de imagens de tomografia computadorizada foram importantes no mapeamento de heterogeneidades, permitindo uma melhor definição das direções de máxima e mínima velocidade. A utilização do método VELAN para a estimativa de direções das tensões in situ mostrou-se bastante vantajosa por se tratar de um método simples, rápido e eficiente.
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Fracture System Analysis Aided By Gpr: Applications On Dimension Stone Quarries Modelling
Authors Adelir José Strieder and Sérgio Alfredo BuffonFracture system analysis is the subject of structural
geology and its methods can be applied in dimension
stone quarries. The dimension stone modelling
through fracture system access can be aided by GPR
(ground penetrating radar) technique in different
ways. The fracture map of a dimension stone massif
demands lateral interpolation of a discontinuous
vector and the extrapolation (projection) of each
fracture set into depth. Controlled GPR scanning
profiles can enable fracture continuation into depth,
even under soil cover, as well as determination of a
large number of fracture features. Modelling
dimension stone deposits requires a well-defined
analysis of disjunctive structures and an adequate
GPR profiling program based on fracture set
characterization. An appropriate GPR data processing
program can be valuable for engineering purposes
(rock massif characterization), placing aside again
structural geology and rock mechanics disciplines.
Key words: dimension stone modelling, structural
analysis, GPR exploration
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Geophysical Tomography In Engineering Geology: An Overview
More LessAn overview of the tomographic interpretation
method in engineering geophysics is presented,
considering the two approaches of the deterministic
tomography inversion, developed for rock elasticity
analysis, and the probabilistic tomography imaging
developed in the potential fields domain. The
theoretical basis of both approaches is shortly
outlined before showing a laboratory and a field
application.
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Magnetômetro Fluxgate, De Circuito Aberto, Para Análise De Ruídos Em Sensores
More LessDescription of the development of a system to
evaluate noises and alignment for fluxgate sensors
of different sizes and geometries is presented. The
first circuit was built for 7 KHz sensors cores
excitation and a second one is being developed for
16.625 KHz sensors core excitation.
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Mapeamento Dos Dutos Na Baía De Guanabara
Com o grande vazamento de óleo ocorrido em
Janeiro de 2000 na Baía de Guanabara, a Petrobrás
foi solicitada em curto prazo, a apresentar perante
aos órgãos governamentais, um mapeamento
detalhado e atualizado de todos os dutos que
compõem sua malha de transporte de derivados entre
a Refinaria Duque de Caxias (REDUC) e os
terminais da Ilha D’Água. Isto implicou em
determinar a posição espacial inicialmente de 9
dutos ao longo de 13 km de trajeto, confirmando
através de inspeção por mergulho, pontos onde o
assentamento não estivesse em posição ideal. Para
tal fim, foram contratadas empresas de
levantamentos geofísicos, geotécnicos e de
mergulho. Os dados geofísicos oriundos dos vários
métodos utilizados perfizeram 2400 km de dados e
para absorver este grande fluxo respondendo
imediatamente aos vários questionamentos surgidos,
foram montadas equipes de processamento e
interpretação que possibilitaram executar
intervenções para detalhamento de interesses
específicos (inspeções submarinas, coletas de
testemunhos, etc.). Como resultado foram
produzidas plantas com a posição espacial de cada
um dos dutos, desde sua partida da refinaria até a
chegada aos terminais marítimos de escoamento
situados na Baia de Guanabara.
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Monitoração Sismográfica De Edifícos Adjacentes Aos Túneis Da Av. Luiz Eduardo Magalhães
More LessIn this paper I present the result of studies with respect to vibrations in surrounding building due to blasting carried out to build large tunnels (400m long) in urban areas.
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O Emprego Das Técnicas Sísmica E De Radar Entre Furos (Crosshole) Em Estudo Para Fundação De Obra Subterrânea Na Cidade De São Paulo-Sp
Authors Renato Luiz Prado, Rubens Paschoal Cordeiro and Vicente Luiz GalliAiming for the use of the geophysical crosshole
techniques for studies of the deformability and
resistance of soil mass and its geological
characterization, it was carried out a seismic and radar
crosshole tests in na underground work in São Paulo city, Brazil.
It is discussed the main acquisition procedures of the
both techniques and some empirical relationships
between the elastic and the electromagnetic waves
relating to the mechanic properties and the
sedimentologic characteristics of the soil mass. It is
also presented a tomographic section derived from the radar data.
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O Uso Do Potencial Espontâneo (Sp) Em Caso De Infiltração Em Barragem
Authors José Domingos Faraco Gallas and Walter Malagutti FilhoThis paper presents the application of the self
potential method (SP) for leaking in an earth’s dam.
The tests were carried out in part of the embankment
which was submitted to a partial failure originated by
a leakage. It was employed the gradients technique in
this survey. The results showed the efficiency of the
SP method to detect the anomalous flow from the
reservoir and to indicate the leaking area.
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Utilização Do Gpr No Projeto Executivo Da Barragem De Pindobaçu, Rio Itapicuru-Açu (Ba)
This study shows the results of a geophysical survey
conducted with GPR to support the study of a dam in
Itapicuru-Açu River. The objective of the study was
to identify geologic structures found in the
underground surface (rock mass discontinuity, geologic contacts).
The information available from rotative drillings and
the geologic knowledge of the area enabled a good
correlation between data during result interpretation,
and three different types of lithologies were identified in the area.
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Velocidade De Propagação Sísmica De Ondas Love Em Argila De Pântano
More LessDos ensaios sísmicos realizados in-situ no
terreno pantanoso da futura Fábrica RIO
POLÍMEROS, no Município de Duque de
Caxias/RJ, o qual é caracterizado por uma capa de
argila orgânica saturada, muito mole, de espessura
da ordem de 6 metros, estão focalizados neste
trabalho os resultados das medições da velocidade
de propagação à superfície do terreno, de ondas SH,
ou Love. Os valores obtidos para essas, entre 31 m/s
e 37 m/s, se situam significativamente abaixo dos
indicados na literatura técnica. Como os ensaios
produziram sismogramas confiáveis,
repetitivamente, decidiram os autores divulgar essa
informação para a comunidade geofísica.
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An Interdisciplinary Geophysical Approach To Detect Cavities In A Karst Region
More LessThe aim of this research carried out by Istituto Nazionale di Oceanografia e di Geofisica Sperimentale-OGS Trieste, was to apply several geophysical methodologies such as ERT (Earth
Resistivity Tomography), GPR, and microgravity survey to detect cavities in karst area. A well-known cavity system was chosen as the test site, in order to verify geophysical data with a real situation. The results was really satisfactory, since the methods had a very good power of investigation and they has been complementary which other. The surveying lines location was carried out in collaboration with the “Civico Museo di Storia Naturale” of Trieste.
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Aplicação De Ensaios Elétricos E Eletromagnéticos Em Problema De Poluição Ambiental
This work aims at the detection of the contamination
caused by a waste disposal area, through
the electric geophysical methods of resistivity, induced
electromagnetics. Field measurements had been
carried out in Ribeirão Preto, São Paulo, Brazil, in a
deactivated waste disposal area. The obtained data
had been dealt with appropriate softwares that enabled
the distinction of the anomalies which help the
characterization of the environmental pollution problem.
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Caracterização De Paleoambiente Submarino Com Side Scan Sonar, Ecobatímetro E Amostras De Fundo – Bacia De Campos - Rj
Authors Anídio C.T. Corrêa, Luiz A.P. Gamboa and Georgina O. CastañosSide scan sonar images acquired by Petrobrás in
Campos Basin during the year of 1998, presented
large linear features which lay down on the sea floor,
at a water depth of 110m. The features were also
registered in bathymetric profiles and have been
operationally described as beachrocks.
In this study, specially designed softwares for digital
image processing allowed a better view of one of
these occurrences, in the central portion of Campos
Basin, in an area close to the shelf brake.
Based on the studies conducted on the sonographic
images, regarding the submarine environment and the
information provided by samples, which were
collected directly from the sea floor, the features were
assumed to be old sand ridges which laid down along
the shoreline. Afterwards, the ridges were cemented,
in a period of time during which the relative sea level
was stabilized, which is thought to have happened
15.800 years BP. When the sea level re-start to rise
up, the morphologies were drowned, becoming a rigid
substract for the instalation of thick algal banks.
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Characterisation Of Three Different Waste Disposals Using Resistivity And Ip Methods
Authors A. Bratus and D. Nieto YabarThis is the report of an integrated geophysical survey
on a landfill system, composed of three urban solid
waste disposals located in three different old quarries
of sand and gravel.
The landfills have different ages and different isolation
systems. The oldest one (called A) was closed in the
eighties and doesn’t have any isolation, the second one
(called B) was closed in the nineties and has a clay
isolation layer as prescribed by the Italian law of 1982,
the third one (called C) is open and has HDPE isolation.
In all the case studies, the depth of the body waste is
about 20 m and the water table is located at 70 m from
the surface.
To investigate the area, earth resistivity and induced
polarisation tomography have been used.
Two N-S lines of 630 m and one E-W line of 310 m
have been done in different periods of the year in order
to define:
• The most proper measurement array geometry
• The landfills geometry
• The waste resistivity and chargeability features
• Contamination in the surrounding geological strata
due to leachate movement
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Clima De Ondas Na Bacia De Campos: Fundamentos E Análise Dos Dados
More LessEste trabalho tem como principal objetivo o estudo do
clima de ondas na Bacia de Campos. Para realizá-lo foi
utilizada uma bóia oceanográfica do tipo “pitch and
roll”, operada pela Petrobras, no período 91/95, na região
dos campos de Marlim e Barracuda, ambos com mais
de 1000 metros de profundidade. Tal iniciativa foi, até
agora, a mais ampla e detalhada campanha de coleta de
dados de onda feita no Brasil. Os resultados deste estudo
revelaram características desconhecidas do clima de
ondas da região. Mais de 60 parâmetros de onda foram
obtidos, a partir do processamento das medições instrumentais
e da modelagem de algumas grandezas físicas
das ondas. Os resultados possuem aplicação direta em
várias áreas como engenharias oceânica, naval e costeira,
além de meio ambiente e novas pesquisas.
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Climate Changes Of The Recent Past In Southern Parts Of Brazil
Authors Andrei S.B. Cavalcanti and Valiya M. HamzaBore-hole temperature data from 23 localities in
southern Brazil were examined for identifying thermal
signals related to climate changes of the historic
past. Both forward and inverse modeling methods
were employed in the analysis of vertical distribution
of temperatures. The forward modeling approach is
based on the classical method of least square fits to
theoretical curves, with a priori assumption as to the
form of temperature variation. The inverse method
can handle non-linear problems and allows convenient
trade-off between model and data.
The data set examined so far reveal the following
information about recent climate changes in southern Brazil:
- the form of temperature variation is indicative of a
warming trend in all of the 23 localities;
- the magnitudes of temperature variations are in the
range of 1 to 40C while the time elapsed vary from
20 to 200 years;
- the climate change seem to be more pronounced in
coastal areas compared to that in inland and semiarid
zones;
- there is a progressive increase in the age of climatic
perturbation, as one moves from the coastal area
towards the interior of the continent;
- changes in vegetation cover have marked effects on
surface temperatures in southern parts of Brazil;
- the changes found in semi-arid zones, being unaffected
by changes in vegetation cover, appears to be
indicative of global climate changes.
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Cronologia De Sedimentação Recente Na Baía De Todos Os Santos Usando Pb210 E Cs137
Authors Roberto Max de Argollo and Antônio Expedito G. de AzevedoThree sediment cores from Todos os Santos Bay were
analysed for 210Pb, 137Cs and 226Ra. The core BTS-7,
collected alongside a channel, had predominance of
fine sand followed by mud; the cores BTS-8 and BTS-
9, coming from a low energy area, had predominance
of mud. The recent mass and linear sedimentation rates
determined in these cores were, respectively, for the
BTS-7, 3.8 kg m–2 a–1 and 4.5 mm a–1; for the BTS-8
7.6 kg m–2 a–1 and 9.5 mm a–1 and for the BTS-9 8.6 kg
m–2 a–1 and 9.9 mm a–1. For the core BTS-9 was noted
an increase in the sedimentation rate from 2.9 mm a–1
in the lower part to 9.9 mm a–1 in the upper 33 cm,
probably due to changes induced by the deforestation
of the margin of the Bay on that place. The activity
levels of 137Cs do not exceed 5 Bq kg-1, which
correspond to 20 % of those found in sediments of
nothern hemisphere. In the core BTS-9, 137Cs had its
activity peak (4.90 Bq kg-1) in the depth of 32.5 cm,
corresponding to the year of 1965 and was detected up
to 40.5 cm, year of 1958. , suggesting that 137Cs did not
migrate to the lower layers after its deposition.
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Delimitação Da Pluma De Contaminação Dos Resíduos Sólidos Do Lixão Do Aurá (Ananindeua/Pa) Por Imageamento Elétrico
Na área de abrangência do lixão do Aurá foi realizado
imageamento elétrico ao longo de nove perfis, usando
arranjo Wenner. Os resultados obtidos com essa
metodologia confirmam trabalhos realizados
anteriormente na área, indicando que a água
subterrânea está sendo atingida pelo deslocamento da
pluma de contaminação provocada pelo chorume
produzido pela degradação dos resíduos sólidos da área.
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Environmental Gamma Radiation Dose In Municipalities, Eastern São Paulo State, Brazil
Authors Rodrigo O. Bastos and Elisabete M. PascholatiAerial gamma spectrometric data were reprocessed
aiming to estimate outdoor gamma radiation dose for
an area of about 11500 Km2 in eastern of São Paulo
state, Brazil, which covers fifty municipalities.
To evaluate the reliability of these
reprocessed data, a residual analysis was carried out
for grids constructed by different methods of
interpolation, and results for the Itu Intrusive Suite
obtained from the aerial data were compared with
published values estimated from terrestrial survey.
This comparison shows up attenuation regarding
probably to soil moisture and vegetal recovery of at least 20%.
A map of average radiation dose per
municipality is presented. The averages varied from
665 μSv. year -1 in Engenheiro Coelho to 1276 μSv.
year -1, in Votorantim. Median values were estimated
for Campinas, Itu and Paulínia (924 μSv. year -1,
900 μSv. year -1 e 847 μSv. year–1 , respectively). The
population-weighted average dose for the area was 888 μSv. year -1.
The municipalities situated over sediments
of Paraná Basin presented lowers averages. The
higher ones were estimated in municipalities where
part of the area covers granite intrusive suites.
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