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1st EEGS Meeting
- Conference date: 25 Sep 1995 - 29 Sep 1995
- Location: Torino, Italy
- ISBN: 978-94-6282-129-3
- Published: 25 September 1995
41 - 60 of 142 results
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Processing of Very High Resolution 3D Marine Seismic Data
Authors T. Missiaen, B. Marsset, M. Noble and W. VersteegVery High Resolution marine 3D seismics offers wide use both in the field of engineering geophysics as well as for geological and environmental site investigations. Considering the frequency content of the data, specific 3D processing techniques have to be applied in order to obtain a correct image of the subsurface. Due to the average wavelength of the "seismic signal and the width of its associated Fresnel zone, CMP-like processing can still lead to a destructive stack of misplaced events. The latter will also be the case if precise time delay corrections are not applied. A first step in the development of such 3D processing techniques was done using a very high resolution 3D data volume previously acquired on the river Schelde in Antwerpen.
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High Resolution, Microseismic Profiling in the Coastal Zone
By A. StefanonThe latest techniques and instrumentation allow to perform successful reflection seismic surveys both at sea and in inland waters, even at very shallow water depth and using small crafts. Such talk is not easily achieved, but the obtainable results are definitely rewarding and pay welf botte for the indispensable effort and for the money involved.
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Geophysical Remote Sensing of Sea Floor Sediment Properties
Authors A. M. Davis and M. D. RichardsonIn the marine environment, geophysical methods have for many years been used to investigate subsurface structure and to map the distribution of sediments at the seabed surface, the latter using a purely qualitative approach.
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Sea Floor Sensing of Sediment Shear Wave Properties
More LessKnowledge of sediment geoacoustic properties is of fundamental importance to marine environmental end engineering applications. For instance, geoacoustic approaches are currently being applied to predictions of marine slope stability, evaluation of the consolidation behaviour and strength of marine foundations, studies of mine burial, assessment of contaminant distribution, and prediction of high frequency acoustic bottom scattering. Within the engineering community the geophysical parameter currently receiving most attention is the seismic shear wave velocity, this being recognised as a definitive soil property indicative of the structural stiffness of the material. Out of this has arisen a requirement for new methods for in-situ evaluation.
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Preliminary Results of Seismic and GPR Surveys on the Hells Gate lce Shelf (Victoria Land -Antarctica)
Authors A. Lozej, I. Tabacco, F. Merlanti and M. PavanIn the course of the ItaliAntartide Expedition of the summer 1993-1995, geophysical surveys, seismic and GPR, were undertaken on the Hells Gate Ice Shelf with the objective of defining the structural and physical characteristics of the ice body. The Hells Gate Ice Shelf (HGIS) is one of the minor glacial structures in the North Victoria Land area, the geomorphology and glaciology of which are described by Baroni & Orombelli (1987) and Baroni (1990), among others.
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Radar and Seismic Survey on Temperate Glaciers in Northern Italy, Adamello and Stelvio Glacier
Authors I. Tabacco, P. Pettinicchio and L. VeroneseRadar survey on temperate glaciers is more difficult on respect of the other one on polar, Gold glaciers, because the presence of a scattered layers that usually prevent the transmission of e.m. waves. Bogodorosky (1985) consider that the scattered layer is due to in fraglacial discontinuity and to physical caratheristics of the ice body.
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Investigation of Fine Structures of Buried River Beds
Authors B. Neducza and M. PattantyusThe objective of investigations for buried river beds and alluvial fans might primarily be water or raw material prospecting but it might be of archaeological importance, too. Ancient settlements can frequently be found close to a water supply, e.g. a river, thus, delineation of river beds could help in finding ancient or historical settlements. Analyzis of aerial photographs and topographic maps of proper scale is the best means for this purpose.
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High-Resolution Seismic Mapping of Glacial and Proglacial Sediments in the Swiss Molasse Basin
Authors F. Buker, A. Pugin, H. Horstmeyer and A. GreenQuarternary sediments in the Swiss Molasse Basin contain more than two-thirds of the country's aquifers and large amounts of industrial minerals. Glacial sediments are highly inhomogenous, such that their lithology and hydraulic conductivity may change significantly over short distances. As groundwater flow is influenced strongly by hydraulic conductivity, evaluations of the safety of waste disposal sites and predictions about hazardous contaminant flow require reliable information about the three-dimensional distribution of the near-surface sediments that are highly permeable.
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Geophysical Investigation on Geometry and Internal Structure of the Lago Sackung, Calabria
Authors F. Ferrucci, M. Sorriso-Valvo and C. TansiQuantitative studies of deep-seated gravitational dope deformations, that often represent the longlasting preparatory phase of catastrophic landslides, though seldom carried out are undoubtedly relevant to hazard assessment and to the correct planning of environmental frameworking.
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Transient Electromagnetic Soundings at the Taquari-Vassouras Potash Mine (Brazil)
Authors M. Chouteau, S. Krivochieva and R. FrankTaquari-Vassouras is an underground potash mine exploiting silvinite ore at a depth of approximately 500 metres. The mining method used is room-and-pillars. Of main concern to the mine operation is the presence of an aquifer zone 50 to 100 metres above the potash zone. The danger of water inflow through fractures could result in safety hazards and large remediation costs for the company Vale do Rio Doce. Fractures may result from the collapse of the salt sequence.
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Seismic First Breaks lnterpreted as the Diving Waves
Authors J. D. Laski, F. Kohlbeck and J. SkowyraTime distance curves of seismic first breaks may be looked upon as consecutive straight lines (velocity of refractor and overburden constant) or more realistic as consecutive lines slightly curved (velocity of refractor and/or overburden increasing with depth). In the last case raypaths are curved and the first breaks correspond to diving waves penetrating the refractors.
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To Imaging of Q-1 Model in an Attenuation Tomography on the Creeping Waves
Authors V. N. Troyan and A. P. KrauklisPropagating along concave boundaries P and S waves (creeping waves) can be used in seismics and acoustics to locate a fracture zone, corrosian induced pits, topographic irregularities, etc. For example in last time a lot of circumferential acoustical devices for well logging were constructed which use the creeping wanes for the solution of such problems.
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Body Wave Dispersion in Formations Crossed by Boreholes: Consequences on Velocity Calculation
Authors D. Jeantet and A. RousseauOne of the most important parameters provided by well-logging is the body wave velocity of formations crossed by a borehole. The body wave velocity calculation is based on the difference between the propagation times of the waves which propagated in those formations and which have been recorded by two or more receivers.
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Assessing Systematic Errors in Seismic Crosshole Data
By H. MaurerSmall scale structures with velocity anomalies of a few percent are often the targets of the seismic travel time tomography between boreholes or tunnels. To successfully invert for these velocity structures, accurate knowledge of the source and receiver coordinates and of the shot times is required.
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Viscoelastic Finite-Difference Modeling of Shallow Seismic Data: Formation of Near-Surface Waveguides
Authors J. O. A. Robertsson, A. Pugin, K. Holliger and A. GreenWaveguides are formed in grossly layered media bounded by strong physical property contrasts. In ocean acoustics, the formation of shallow water waveguides is known to have a significant impact on wave propagation (Brekhovskikh and Lysanov, 1991). We suggest that similar waveguides may exist near the solid earth's surface and investigate the effects of such waveguides on high-resolution shallow seismic data.
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The Bedrock in Refraction Seismics as an Inhomogeneous Medium with Vetocity Gradient
Authors S. Hrach, J. Skopec and J. VilhelmSeismic methods have recently been used more and more frequently for studying shallow parts of subsurface media. Their application is increasing in the prospecting for some raw material deposits, in engineering geology and in hydrogeological investigations as well. They have been applied to determine the overburden thickness and the degree of subsurface fracturing of individual rock blocks as well as to study the extent and quality of quarry-stone deposits etc.
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High Resolution Seismic Revised
More LessDuring the last ten years seismic methods have lost much of its interest among all geophysical methods. Shallow investigations related to environmental problems are often made more efficiently using non seismic methods.
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Application of Statistical Pattern Recognition Techniques to Geophysical Data
Authors I. Rosati and E. CardarelliEach geophysical survey is accomplished via a detailed program of sampling. In other words, by choosing the right amount of data to be collected with respect to the type of analysis to be carried out, to the type of anomalies that have to be surveyed, and to the relative costs.
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High Resolution Shallow Seismic Reflection Study for Hydrological Site Characterisation near Acerra (Naples): Preliminary Results
Authors P. P. Bruno, E. Carrara, A. Rapolla and N. RobertiIn the past the Campani an Plane was famous for its fertility and abundance of water. Unfortunately the disorderly industrial, and urban development of the last forty years, especially in the proximity of the city of Naples, has resulted in a strong negative impact on the geological medium in terms of pollution and depauperation of the land and its alluvial hydrological resources. On the other hand the increased population pressure (one of the highest of Italy) has also increased the demand for clean fresh water both for human and agricultural utilisation and consequently new water resources (i.e. alluvial acquifers) must be located.
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