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3rd EEGS Meeting
- Conference date: 09 Aug 1997 - 11 Aug 1997
- Location: Aarhus, Denmark
- ISBN: 978-94-6282-128-6
- Published: 09 August 1997
81 - 100 of 124 results
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Landslide assessment with seismic techniques. A case study
Authors R. G. Francese, A. Grespan and V. IlicetoA high resolution P-wave seismic reflection and refraction survey was caried out in the foothill area of the Verona Province - Northern Italy. The objectives of the survey were to investigate structure and stratigraphy of near-surface Tertiary and Quaternary deposits and to develop a working procedure for Iandslide assessment using both refraction and reflection techniques.
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VibroScan - A powerful tool for environmental vibration protection investigations
More LessIt is well known that railway transport is very advantageous with regard to environmental protection. Reduction of air pollution is a typicai example. But railways have their characteristic environmental problems as well. According to an opinion poll in Vienna from 1991 noise imrnissions (41 %) and vibrations (19 %) are considered to be the most important ones by the urban population.
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Frequence domain electromagnetic source polarization investigation in case of a 2-D seafloor trench
Authors G. Petho, P. Kaikkonen and L. L. VanyanIn the course of seafloor EM survey the topographical changes of the seafloor can have influence on the EM components. These topographical inhomogeneities are 3-D ones. However, they are frequently elongated in one direction and can be treated as 2-D inhornogeneties. The aim of this model study is to present a numerical method for frequency domain marine controlled-source electromagnetic measurements using horizontal electric dipole sources on the seafloor and illustrate how the EM responses are affected by a 2-D trench. The horizontal electric dipole source is parallel and perpendicular to the struetural strike and the EM field components are computed along an in-line horizontal seafloor profile perpendicular to the axis of the trench at two frequencies.
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Fast transient electromagnetics: Real device modeling and information analysis
Authors A. B. Cheryauka and S. V. MartakovThe use of methods of alternating electromagnetic field for studying of the nearborehole space in dielectric logging and subsurface layers in shallow depth soundings deals with account of joint influence of conductivity and displacement currents.
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Removing topography influence in VLM-EM data by linear filtering
Authors N. A. Edsen and B. H. JacobsenWhen surveying upon a level homogenous halfspace or over borizontally layered lithologies no anomalies are seen in the conventional VLF-EM method. But in situations where the topography represents a surface with varying relief even upon a homogenous halfspace the terrain itself will generate VLF-EM anomalies which can be misinterpreted as originating from subsurface conductors.
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Main principles of the NPEMFE method employment for decision of different problems of mining geomechanics at mines of Donbass
Authors I. V. Kuznetsov and M. K. OsykinThe Donbass region is characteried by enough complex mining-geomechanic conditions of an underground coal mining, beds of which are subjected to tectonical, plicative dislocations with a break in continuity, complicating a picture of stresses distribution around working. Besides, the long coal nuning during many decades on horizons from 300-400 m to 1 km and more causes the problem of old abandoned underground working revealing, under which cauldrons dangerous for engineering constructions, are formed.
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Site investigation using EKS groundwater flow pathway images
Authors R. H. Clarke and J. W. A. MillarWe report the development and use of equipment which images groundwater distribution and the water flow pathways in aquifers. Aquifer permeability profiles and maps are obtained from electrokinetic signals using algorithms based upon theoretical and laboratory studies (Chandler, 1971, Nourbehecht 1963).
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Improvement in TDEM interpretations by joint inversion of different data sets
Authors S. Krivochieva and M. ChouteauThe TDEM methods are widely used in hydrogeological and environemental problems. Large depth of investigation, expeditive measurements and excellent sounding capabilities in 1D environment are their main advantages. Usually central loop sounding measurements are collected and 1D interpretation is performed at each site.
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Automatic 1D inversion of electrical well logs using the L1-norm and fixed layer-boundaries
By M. HalkjærFor electrical well logs, it is well known that the measured apparent resistivity differs from the true foririation resistivity in a region around boundaries between formations with different electrical resistivity. The apparent resistivity varies with electrode configuration and with resistivity contrast. In this paper, it is shown that inversion of the electrical log leads to a substantial increased resolution of the lithologic sequence. The inversion is performed with a simple one dimensional (1-D) L1-norm inversion routine which can accommodate for a very high number of layers wîth fixed layer boundaries.
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Lithologic inversion of tomographic data
Authors T. Fechner and P. DietrichSubsurface heterogeneity, i.e. the spatial variability of porous rock properties such as porosity or hydraulic conductivity, plays an important role in the spreading of a solute in the subsurface. A few highly-conductive zones may dominate the overall flow regime. Due to drilling costs the number of boreholes drilled to investigate an area is limited leading to uncertainties in determining the hydraulic properties and in resolving structures relevant for subsurface solute movement. A detailed subsurface characterization is however of vital importance for clean up technologies: for instance the efficiency and effectiveness of a "funnel & gate"-systems is dependent on its optimal positioning. It is shown, that high-resolution measurements such as seisinic and electric tomography can be used to identify hydraulic subsurface structures. For the problem of inversion of hydraulic properties and related subsurface structures a new formalism based on multivariate statistics is proposed.
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The location of infinite electrodes in pole-pole electrical surveys and the resulting error for 2D electrical imaging. A practical point of view
Authors H. Robain, Y. Albouy, M. Dabas, M. Descloitres, C. Camerlynck, P. Menchler and A. TabbaghThe improvement of multi-electrode arrays for resistivity measurements has led to an important development of electrical imaging for subsurface surveys. These arrays produce wide apparent resistivity pseudosections, presenting a large set of close data. It allows precise direct or inverse interpretation of 2D ground resistivity at shallow depth.
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Automated gravity terrain corrections using satellite stereo-pairs
Authors R. Davies, M. O‘Neill and R. McDonaldBy using SPOT stereo-pairs it is possible to automate the extraction of conjugate pairs of (matched) image co-ordinates. Propagation of these data through an appropriate sensor model, constrained by at least three ground control points, produces irregularly distributed height estimates which provide the basis of two elevation models. The first is a DEM of orthogonal grid points which is generated by Kriging.
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Filters for fast 2D and 3D pseudo-inversion of the resistivity profiles
Authors P. Cosentino, D. Luzio and R. MartoranaThe aim of the methodological approach here presented is to construct fast pseudosections starting from resistivity data: the pseudo-sections should match as closely as possible the geometry of the investigated structures.
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ELTOMO 97 - a software package for inversion and interpretation of resistivity data
Authors E. Danckwardt, F. Jacobs, S. Kuhn and G. PetzoldA device independent software package was developed for data conversion to an independent data format from any field devices, inversion with selection from some realized algorithms and a comfortable 2D- and 3D interpretation.
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Explorations on the Earth's relativistic gravity field
By W. ShenAccording to Newtonian theory, space and time are absolute, and consequently, once a length measure standard and a time measure standard are chosen, they keep invariant. According to relativity however, the length and time measure standards may vary with different positions and different reference systems. This implies that the observed values at points A and B are not absolute. Hence, we must establish a "common measure standard system", into which all observed values must be transformed.
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IP and resistivity survey at the INEL Cold Test Pit
By W. FrangosInduced polarization ([P) is a technique for detection of diffiise occurrences of metallic material. The Idaho National Laboratory (tNEL) CoId Test Pit (CTP) has been carefiilly constructed to simulate stored hazardous waste occurrences. IP and resistivity surveys of the CTP show a very strong IP response and a modest resistivity response associated with the simulated waste. Several false positive resistivity anomalies are noted.
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A radiomagnetotelluric survey at the Idaho National Engineering Laboratory Cold Test Pit
Authors B. Tezkan, S. Dautel and L. PellerinMany gravel pits have been filled in the last 50 years with household refuse, building debris and industrial waste. They were filled up in an uncontrolled manner with poor or no documentation. Nowadays most of these waste sites are covered by thin gravel and soil layer and are recultivated. however, they bear a huge risk to the environment due to the possible pollution of the aquifers. Therefore the detection of the dimensions of a waste site and especially the determination of different regions inside a waste site are very important for environmental protection studies.
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A test site for geophysical methods
Authors J. -L. Chazelas, D. Leparoux and A. Hollier-LarousseThis conimunication presents a new facility designed to help the development of geophysical rnethods in urban environment, particularly for trenchless technology applications. It is a test site whose dimensions and consistensy have been thought to provide as perfectly known and noiseless conditions as possible for expenments. The different aspects of this site and the care taken to its construction are indicated in order to invite searchers to use It. Some rough results illustrate the quality of measurement conditions and wide range of possibiities.
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Integrated near-surface geophysics applied to clay prospection
Authors H. Matias, J. Carvalho, L. Torres and R. GonçalvesThe area of study is of great importance for day industry. Nevertheless, known day reservoirs have become in the last years close to exhaustion. Also a dear delimitation of day exploration areas, is essential from a land planning perspective, and is one of the major goals of the work of IGM in the area. In fact the area is being studied in a broader programme involving geological reconnaissance, geophysical surveys - mainly EM-34, selective mechanical drilling, day sampling and technological tests on the materials.
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