Simulation numérique de la propagation d'ondes sismiques dans les milieux stratifiés à deux ou trois dimensions PDF Download
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Author: Laurence Martineau-Nicoletis
Publisher:
ISBN:
Category : Seismic waves
Languages : fr
Pages : 288
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Author: Laurence Martineau-Nicoletis
Publisher:
ISBN:
Category : Seismic waves
Languages : fr
Pages : 288
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Book Description
Author: Laurence Martineau-Nicoletis
Publisher:
ISBN:
Category : Seismic waves
Languages : fr
Pages :
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Author: William Edward Fitzgibbon
Publisher: SIAM
ISBN: 9780898712056
Category : Mathematics
Languages : en
Pages : 306
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Author: Laurence Martineau Nicoletis
Publisher:
ISBN:
Category :
Languages : fr
Pages : 288
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Author: Martin Eugene Dougherty
Publisher:
ISBN:
Category : Marine geophysics
Languages : en
Pages : 572
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Seismic studies of the oceanic crust, both experimental and theoretical, often assume a flat seafloor and laterally homogeneous crust. This is done regardless of the appearance in seismic data of obvious effects due to scattering from lateral heterogeneities both on and in the seafloor. Detailed fine scale surveys of mid-ocean ridges, where the upper oceanic crust is exposed, have revealed the presence of lateral heterogeneities in the form of complicated topography, extrusive volcanic structure, and abundant fracturing and faulting. These heterogeneities have a significant affect on the propagation of seismo/acoustic energy through the crust, especially in the immediate vicinity of the seafloor. This thesis deals with the problem of scattering of seismo/acoustic energy from a number of forms of lateral heterogeneity in the upper oceanic crust. A common theme throughout this work is that the size of the heterogeneity on or in the seafloor is of the same order of magnitude as the seismo/acoustic wavelength. This is the realm of scattering theory where the wave-like characteristics of seismic energy have a particularly large influence on the outcome of interaction with structure in the media. The work presented here involves the application of the finite difference modeling technique to problems concerning laterally heterogeneous elastic media. This method is a full wave solution to the elastic wave equation and as such includes all wave interactions with the media. The finite difference formulation is used to study four distinct phenomena; scattering from discrete deterministic seafloor features; wave propagation through continuous randomly heterogeneous upper oceanic crust; scattering from more complicated topographic profiles and the limitations of the method for the rough seafloor problem; and the problem of plane acoustic wave scattering from an infinite elastic cylinder. The principal finding of this work is that lateral heterogeneities in the upper oceanic crust can have a dramatic affect on seismo/acoustic wave propagation. Scattering from rough seafloors and/or volume heterogeneities is often quite similar and causes the occurrence of signal generated 'noise' (coda), decorrelation of primary arrivals, and anomalies in arrival travel time and amplitude. Topographic and volume scatterers acting as secondary sources of seismic energy can cause a resonant coupling of body wave energy into interface (Stoneley) waves at the seafloor. This is possibly one mechanism by which natural seismic and storm generated acoustic energy can be coupled into seafloor noise. The applicability of the use of the finite difference method for non-planar water-solid interfaces is also discussed. Models were calculated which approximate sinusoidal seafloors and plane acoustic wave scattering from an infinite elastic cylinder. The discretization of a rectangular difference grid must be extremely fine to accurately accommodate a smoothly varying water-solid interface which does not align with the grid. Regardless of the discretization concerns, the rough seafloor models presented here demonstrate the arrivals expected from larger scale sinusoidal topography as well as the importance of considering quite small (
Author: Keiiti Aki
Publisher: Birkhauser
ISBN:
Category : Nature
Languages : en
Pages : 462
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Author: Richard Limeburner
Publisher:
ISBN:
Category : Ocean-atmosphere interaction
Languages : en
Pages : 648
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CTD observations were made off the northern California coast during R/V Wecoma cruise W8905 May 5-14, 1989 as part of the Shelf Mixed Layer Experiment (SMILE). The surveys consisted of two sampling plans - a large-scale grid of four cross-shelf transects extending to both sides of Point Arena and Point Reyes, and a small-scale grid of six cross-shelf transects located near the central SMILE mooring site. All of the cross-shelf transects extended beyond the shelf break and the maximum sampling depth at each station was near-bottom or 1500 m. The average along-shelf separation between cross-shelf transects was about 15 km for the small-scale surveys and 50 km for the large-scale grid. The primary objectives of the hydrographic measurement program were to observe and characterize the temperature, salinity, density, and light transmission fields and their temporal and spatial variability in the surface boundary layer along the continental shelf and slope near the SMILE moored array, and to acquire estimates of the cross- and along-shelf scales over which the mixed-layer depth varies. This report presents a summary in graphic and tabular form of the hydrographic observations made during cruise W8905 on the R/V Wecoma.
Author:
Publisher:
ISBN:
Category : Petroleum
Languages : en
Pages : 756
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Author: Elise Delavaud
Publisher:
ISBN:
Category :
Languages : fr
Pages :
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Ce travail de thèse est consacré au développement d'un outil numérique capable de modéliser la propagation 3D d'ondes sismiques dans les milieux géologiques complexes caractérisés par des effets de site. La méthode des éléments spectraux (SEM) est particulièrement adaptée à la problématique de la réponse sismique dans de tels milieux: estimation précise des ondes de surface, capacité à prendre en compte des géométries compliquées (topographie des surfaces libres, interfaces) et possibilité d'ajuster la résolution des longueurs d'ondes sismiques dans des conditions de milieux hétérogènes par des maillages non-structurés. Des extensions numériques de la SEM liées à la réponse de bassin ont été développées: Perfectly Matched Layers filtrantes et introduction efficace d'un champ incident. La principale limitation actuelle des SEM reste cependant liée au manque de flexibilité des maillages hexaédriques malgré l'utilisation de ces maillages non-structurés dont la génération constitue une tâche complexe. Ce travail de thèse souligne ainsi les difficultés associées à la prise en compte de telles structures et décrit le processus complet qu'implique la modélisation de la réponse sismique dans des milieux géologiques complexes, de l'élaboration du modèle physique et numérique à l'analyse des résultats.Je présente des simulations 3D de la réponse sismique dans la région de Caracas (Venezuela), incluant la géométrie 3D du bassin et la chaîne de montagnes Ávila qui borde la ville. L'importance des effets liés à ces deux types de structures est évaluée, par différents scénarios d'excitation par une onde plane. Ces effets géométriques 3D révèlent des phénomènes complexes d'amplification associés à la réflexion et à la focalisation d'ondes se propageant dans toutes les directions, ainsi qu'à la génération d'ondes de surface au niveau des bords et des zones de rétrécissement du remplissage sédimentaire. Une comparaison avec des simulations 2D montre l'intérêt d'une modélisation 3D, de nettes différences en terme de temps de résidence et de niveau d'énergie et d'amplification ayant été constatées
Author:
Publisher:
ISBN:
Category : Petroleum
Languages : en
Pages : 606
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