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Platt, John Daniel. "Dynamics and Materials Physics of Fault Rupture and Glacial Processes." Thesis, Harvard University, 2015. http://nrs.harvard.edu/urn-3:HUL.InstRepos:14226054.
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This thesis focuses on two main topics, the physics governing how faults rapidly weaken during an earthquake and the thermal and mechanical structure of ice stream shear margins. The common theme linking these two projects is the desire to understand how the complicated interactions between stress and temperature control deformation and failure. All of the problems in this thesis are attacked using a combination of analytic and numerical methods, and the interplay between these two approaches provides a powerful way to understand the different physical balances that dominate in different regimes. We also use aspects of materials science to understand how the often complicated rheologies are controlled by underlying physical phenomena such as melting, phase transitions, diffusion, and dislocation motion. With regards to fault mechanics, we begin by showing how co-seismic weakening mechanisms driven by elevated pore fluid pressures lead to micron-scale strain localization during an earthquake. We solve for the localized zone thickness for a range of fault temperatures, test these predictions using numerical simulations, and show how the onset of localization accelerates fault weakening. Next we present the first solutions to account for thermal decomposition reactions during a dynamic rupture, showing that the activation of thermal decomposition may lead to a larger slip duration and total slip. Finally we present a new set of experiments studying flash heating of serpentinite, highlighting the dependence of friction on normal stress and the presence of gouge, and producing the first model to explain the hysteresis commonly observed in flash heating experiments. With regards to ice stream shear margins, we begin by extending the work of Perol and Rice [2011] to study the formation of temperate ice in shear margins, and quantify the total melt that may be generated within the shear margins. We conclude by investigating how the presence of such a channel alters the stress on and strength of the undeforming bed in the shear margin, showing that the transition from a deforming to an undeforming bed across a channel is stable when the water flux in the channel exceeds a critical value.
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Harris, Matthew W. "Numerical realization of the generalized Carrier-Greenspan transform for the shallow water wave equations." Thesis, University of Alaska Fairbanks, 2015. http://pqdtopen.proquest.com/#viewpdf?dispub=1598961.
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<p> Run-up of long waves in sloping U-shaped bays is studied analytically in the framework of the 1-D nonlinear shallow-water theory. By assuming that the wave flow is uniform along the cross-section, the 2-D nonlinear shallow-water equations are reduced to a linear semi-axis variable-coefficient 1-D wave equation via the generalized Carrier-Greenspan transformation (Rybkin et al., 2014). A spectral solution is developed by solving the linear semiaxis variable-coefficient 1-D equation via separation of variables and then applying the inverse Carrier-Greenspan transform. To compute the run-up of a given long wave a numerical method is developed to find the eigenfunction decomposition required for the spectral solution in the linearized system. The run-up of a long wave in a bathymetry characteristic of a narrow canyon is then examined.</p>
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Fortson, Samuel King. "Usability Engineering Applied to an Electromagnetic Modeling Tool." Thesis, Virginia Tech, 2012. http://hdl.handle.net/10919/33665.
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There are very few software packages for model-building and visualization in electromagnetic geophysics, particularly when compared to other geophysical disciplines, such as seismology. The purpose of this thesis is to design, develop, and test a geophysical model-building interface that allows users to parameterize the 2D magnetotellurics problem. Through the evaluation of this interface, feedback was collected from a usability specialist and a group of geophysics graduate students to study the steps users take to work through the 2D forward-modeling problem, and to analyze usability errors encountered while working with the interface to gain a better understanding of how to build a more effective interface. Similar work has been conducted on interface design in other fields, such as medicine and consumer websites.
Usability Engineering is the application of a systematic set of methods to the design and development of software with the goal of making the software more learnable, easy to use, and accessible. Two different Usability Engineering techniques â Heuristic Evaluation and Thinking Aloud Protocol â were involved in the evaluation of the interface designed in this study (FEM2DGUI). Heuristic Evaluation is a usability inspection method that employs a usability specialist to detect errors based on a known set of guidelines and personal experience. Thinking Aloud Protocol is a usability evaluation method where potential end-users are observed as they verbalize their every step as they work through specific scenarios with an interface. These Usability Engineering methods were combined in a effort to understand how the first prototype of FEM2DGUI could be refined to make it more usable and to understand how end-users work through the forward-modeling problem.
The Usability Engineering methods employed in this project uncovered multiple usability errors that were corrected through a refinement of the interface. Discovery of these errors helped with refining the system to become more robust and usable, which is believed to aid users in more efficient model-building. Because geophysical model-building is inherently a difficult task, it is possible that other model-building graphical user interfaces could benefit from the application of Usability Engineering methods, such as those presented in this research.â<br>Master of Science
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Bergman, Björn. "High-Resolution Seismics Methods Applied to Till Covered Hard Rock Environments." Doctoral thesis, Uppsala University, Department of Earth Sciences, 2005. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-4811.
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<p>Reflection seismic and seismic tomography methods can be used to image the upper kilometer of hard bedrock and the loose unconsolidated sediments covering it. Developments of these two methods and their application, as well as identifying issues concerning their usage, are the main focus of the thesis. Data used for this development were acquired at three different sites in Sweden, in Forsmark 140 km north of Stockholm, in the Oskarshamn area in southern Sweden, and in the northern part of the Siljan Ring impact crater area.</p><p>The reflection seismic data were acquired with long source-receiver offsets relative to some of the targeted depths to be imaged. In the initial processing standard steps were applied, but the uppermost part of the sections were not always clear. The longer offsets imply that pre-stack migration is necessary in order to image the uppermost bedrock as clearly as possible. Careful choice of filters and velocity functions improve the pre-stack migrated image, allowing better correlation with near-surface geological information.</p><p>The seismic tomography method has been enhanced to calculate, simultaneously with the velocity inversion, optimal corrections to the picked first break travel times in order to compensate for the delays due to the seismic waves passing through the loose sediments covering the bedrock.</p><p>The reflection seismic processing used in this thesis has produced high-quality images of the upper kilometers, and in one example from the Forsmark site, the image of the uppermost 250 meters of the bedrock has been improved. The three-dimensional orientation of reflections has been determined at the Oskarshamn site. Correlation with borehole data shows that many of these reflections originate from fracture zones. </p><p>The developed seismic tomography method produces high-detail velocity models for the site in the Siljan impact area and for the Forsmark site. In Forsmark, detailed estimates of the bedrock topography were calculated with the use of the developed tomography method.</p>
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Thirunavukkarasu, Senganal. "Impedance Matching for Discrete, Periodic Media and Application to Two-Scale Wave Propagation Models." Thesis, North Carolina State University, 2015. http://pqdtopen.proquest.com/#viewpdf?dispub=3690210.
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Ittharat, Detchai. "3D radio reflection imaging of asteroid interiors." Thesis, Colorado School of Mines, 2014. http://pqdtopen.proquest.com/#viewpdf?dispub=1557520.
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<p> Imaging the interior structure of comets and asteroids in 3D holds the key for understand- ing early Solar System and planetary processes, aids mitigation of collisional hazards, and enables future space investigation. 3D wavefield extrapolation of time-domain finite differ- ences, which is referred to as reverse-time migration (RTM), is a tool to provide high-quality images of the complex 3D-internal structure of the target. Instead of a type of acquisition that separately deploys one orbiting and one landing satellite, I discuss dual orbiter systems, where transmitter and receiver satellites orbit around the asteroid target at different speeds. The dual orbiter acquisition can provide multi-offset data that improve the image quality by illuminating the target from different directions and by attenuating coherent noise caused by wavefield multi-pathing. Shot-record imaging requires dense and evenly distributed receiver coordinates to fully image the interior structure at every source-location. </p><p> I illustrate a 3D imaging method on a complex asteroid model based on the asteroid 433 Eros using realistic data generated from different acquisition designs for the dual orbiter system. In realistic 3D acquisition, the distribution and number of receivers are limited by the acquisition time, revolving speed and direction of both the transmitter and receiver satellites, and the rotation of the asteroid. The migrated image quality depends on different acquisition parameters (i.e., source frequency bandwidth, acquisition time, the spinning rate of the asteroid) and the intrinsic asteroid medium parameters (i.e., the asteroid attenuation factor and an accurate velocity model). </p><p> A critical element in reconstructing the interior of an asteroid is to have different ac- quisition designs, where the transmitter and receivers revolve quasi-continuously in different inclinational and latitudinal directions and offer evenly distributed receiver coordinates in the shot-record domain. Among different acquisition designs, the simplest orbit (where the transmitter satellite is fixed in the longitudinal plane and the receiver plane gradually shifts in the latitudinal direction around the asteroid target) offers the best data coverage and requires the least energy to shift the satellite. To obtain reasonable coverage for successfully imaging the asteroid interior, the selected acquisition takes up to eight months. However, this mission is attainable because the propulsion requirements are small due to the slow (< 10 cm/s) orbital velocities around a kilometer-sized asteroid.</p>
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Johansson, Stefan. "Earthquake Analysis Using a Migration Based Detection Algorithm Applied to Local Earthquake Data." Thesis, Uppsala universitet, Geofysik, 2017. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-325373.
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In this study earthquake data is analyzed using a newly developed Migration Based Detection (MBD) algorithm (Wagner et al. 2017). A software environment suitable for manual analysis of large quantities of earthquakes (events) detected by the MBD algorithm is set up, and the MBD algorithm is applied to 13 days of seismic data from a network of 26 seismic stations in the geologically complex Hengill-area in southwest Iceland. A total of 859 event detections are produced and manually inspected. Out of these, 483 are considered true and/or uncertain, making the assessed number of false detections about 44%. A subset of 53 well defined true events are selected for event relocation using manual picking of first arrival P-waves. The relocation resulted in a mean difference of roughly 0.6 km for each coordinate in the horizontal plane and about 1.4 km in depth. Results of the study provide reference data that may aid further development of the MBD algorithm, as well as provide some insight into the performance of the MBD algorithm. The software environment tailored for analyzing events detected by the MBD algorithm may be used as a foundation for continued analysis of detected events.<br>I denna studie analyserades jordskalvsdata med hjälp av en nyligen utvecklad 'migration based detection'-algoritm (Wagner et al. 2017). En mjukvarumiljö skräddarsydd för manuell analys av stora kvantiteter av jordskalv detekterade av MBD-algoritmen iordningställdes, varpå MBD-algoritmen sedan applicerades på 13 dagar av seismisk data från ett nätverk av 26 seismiska stationer i det geologiskt sett komplexa Hengill-området i sydvästra Island. Totalt detekterades 859 jordskalv som genomgick manuell analys. Av dessa klassificerades 483 stycken som bekräftade eller troliga jordskalv, vilket resulterar i en uppskattad felmarginal om ca. 44 %. En delmängd om 53 väldefinierade jordskalv valdes ut för noggrannare analys av ursprungsplats och tidpunkt genom manuell plockning av P-fasankomst. Omlokaliseringen resulterade i en genomsnittlig differens om ca. 0.6 km i vardera koordinat i horisontalplanet och ca. 1.4 km i höjdled. Resultat från projektet kan användas som referensdata vid vidareutveckling av MBD-algoritmen samt ger viss insyn i prestandan hos MBD-algoritmen. Den iordningställda datormiljön kan användas som bas för vidare analys av jordskalv detekterade av MBD-algoritmen.
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Wheeler, Mark Lee. "A comparative study of art and the convolution method as applied to cross borehole geophysical tomography." Ohio : Ohio University, 1987. http://www.ohiolink.edu/etd/view.cgi?ohiou1183124445.
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Trinh, Phuong-Thu. "3D Multi-parameters Full Waveform Inversion for challenging 3D elastic land targets." Thesis, Université Grenoble Alpes (ComUE), 2018. http://www.theses.fr/2018GREAU033/document.
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L’imagerie sismique du sous-sol à partir de données terrestres est très difficile à effectuer due à la complexité 3D de la proche surface. Dans cette zone, les ondes sismiques sous forme d’un paquet compact de phases souvent imbriquées sont dominées par des effets élastiques et viscoélastiques, couplés aux effets dus à la surface libre qui génèrent des ondes de surface de grande amplitude et dispersives.L’interaction des ondes sismiques avec une topographie plus ou moins complexe dans un contexte de fortes hétérogénéités de la proche surface induit d’importantes conversions des ondes avec de fortes dispersions d’énergie. Il est donc nécessaire de prendre en compte à la fois une représentation tridimensionnelle précise de la topographie et une physique correcte qui rend compte de la propagation du champ d’onde dans le sous-sol au niveau de précision réclamé par l’imagerie sismique. Dans ce manuscrit, nous présentons une stratégie d’inversion des formes d’onde complètes (FWI en anglais) efficace, autonome et donc flexible, pour la construction de modèles de vitesse à partir de données sismiques terrestres, plus particulièrement dans les environnements dits de chevauchements d’arrière pays(foothills en anglais) aux variations de vitesse importantes.Nous proposons une formulation efficace de cette problématique basée sur une méthode d’éléments spectraux en domaine temporel sur une grille cartésienne déformée, dans laquelle les variations de topographie sont représentées par une description détaillée de sa géométrie via une interpolation d’ordre élevé. La propagation du champ d’onde est caractérisée par une élasticité linéaire anisotrope et par une atténuation isotrope du milieu: cette deuxième approximation semble suffisante pour l’imagerie crustale considérée dans ce travail. L’implémentation numérique du problème direct inclut des produits matricevecteurefficaces pour résoudre des équations élastodynamiques composant un système différentielhyperbolique du second ordre, pour les géométries tridimensionnelles rencontrées dans l’exploration sismique. Les expressions explicites des gradients de la fonction écart entre les données et les prédictions sont fournies et inclut les contributions de la densité, des paramètres élastiques et des coefficients d’atténuation. Ces expressions réclament le champ incident venant de la source au même temps de propagation que le champ adjoint. Pour ce faire, lors du calcul du champ adjoint à partir de l’instant final, le champ incident est recalculé au vol à partir de son état final, de conditions aux bords préalablement sauvegardées et de certains états intermédiaires sans stockage sur disques durs. Le gradient est donc estimé à partir de quantités sauvegardées en mémoire vive. Deux niveaux de parallélisme sont implémentés, l’un sur les sources et l’autre sur la décomposition du domaine pour chaque source, cequi est nécessaire pour aborder des configurations tridimensionnelles réalistes. Le préconditionnement de ce gradient est réalisé par un filtre dit de Bessel, utilisant une implémentation différentielle efficace fondée sur la même discrétisation de l’espace du problème direct et formulée par une approche d’éléments spectraux composant un système linéaire symétrique résolu par une technique itérative de gradient conjugué. De plus, une contrainte non-linéaire sur le rapport des vitesses de compression et de cisaillement est introduite dans le processus d’optimisation sans coût supplémentaire: cette introductions’avére nécessaire pour traiter les données en présence de faibles valeurs de vitesse proche de la surface libre.L’inversion élastique multi-paramètres en contexte de chevauchement est illustrée à travers des exemples de données synthétiques dans un premier temps, ce qui met en évidence les difficultés d’une telle reconstruction…<br>Seismic imaging of onshore targets is very challenging due to the 3D complex near-surface-related effects. In such areas, the seismic wavefield is dominated by elastic and visco-elastic effects such as highly energetic and dispersive surface waves. The interaction of elastic waves with the rough topography and shallow heterogeneities leads to significant converted and scattering energies, implying that both accurate 3D geometry representation and correct physics of the wave propagation are required for a reliable structured imaging. In this manuscript, we present an efficient and flexible full waveform inversion (FWI) strategy for velocity model building in land, specifically in foothill areas.Viscoelastic FWI is a challenging task for current acquisition deployment at the crustal scale. We propose an efficient formulation based on a time-domain spectral element method (SEM) on a flexible Cartesian-based mesh, in which the topography variation is represented by an accurate high-order geometry interpolation. The wave propagation is described by the anisotropic elasticity and isotropic attenuation physics. The numerical implementation of the forward problem includes efficient matrix-vector products for solving second-order elastodynamic equations, even for completely deformed 3D geometries. Complete misfit gradient expressions including attenuation contribution spread into density, elastic parameters and attenuation factors are given in a consistent way. Combined adjoint and forward fields recomputation from final state and previously saved boundary values allows the estimation of gradients with no I/O efforts. Two-levels parallelism is implemented over sources and domain decomposition, which is necessary for 3D realistic configuration. The gradient preconditioning is performed by a so-called Bessel filter using an efficient differential implementation based on the SEM discretization on the forward mesh instead of the costly convolution often-used approach. A non-linear model constraint on the ratio of compressional and shear velocities is introduced into the optimization process at no extra cost.The challenges of the elastic multi-parameter FWI in complex land areas are highlighted through synthetic and real data applications. A 3D synthetic inverse-crime illustration is considered on a subset of the SEAM phase II Foothills model with 4 lines of 20 sources, providing a complete 3D illumination. As the data is dominated by surface waves, it is mainly sensitive to the S-wave velocity. We propose a two-steps data-windowing strategy, focusing on early body waves before considering the entire wavefield, including surface waves. The use of this data hierarchy together with the structurally-based Bessel preconditioning make possible to reconstruct accurately both P- and S-wavespeeds. The designed inversion strategy is combined with a low-to-high frequency hierarchy, successfully applied to the pseudo-2D dip-line survey of the SEAM II Foothill dataset. Under the limited illumination of a 2D acquisition, the model constraint on the ratio of P- and S-wavespeeds plays an important role to mitigate the ill-posedness of the multi-parameter inversion process. By also considering surface waves, we manage to exploit the maximum amount of information in the observed data to get a reliable model parameters estimation, both in the near-surface and in deeper part.The developed FWI frame and workflow are finally applied on a real foothill dataset. The application is challenging due to sparse acquisition design, especially noisy recording and complex underneath structures. Additional prior information such as the logs data is considered to assist the FWI design. The preliminary results, only relying on body waves, are shown to improve the kinematic fit and follow the expected geological interpretation. Model quality control through data-fit analysis and uncertainty studies help to identify artifacts in the inverted models
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Costa, Adeilton Fernandes da. "Emprego do método da eletro-resistividade na caracterização da lixeira de Porto Velho - RO assentada em meio fraturado /." Rio Claro : [s.n.], 2008. http://hdl.handle.net/11449/102890.
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Orientador: Walter Malagutti Filho<br>Banca: Antonio Celso de Oliveira Braga<br>Banca: Jairo Roberto Jimenéz Rueda<br>Banca: Vagner Roberto Elis<br>Banca: Ene Glória da Silveira<br>Resumo: Ensaios geofísicos de eletro-resistividade, através das técnicas da sondagem elétrica vertical e imageamento elétrico (configurações Schlumberger e dipolo-dipolo), foram executados na área da lixeira da cidade de Porto Velho, Estado de Rondônia, com o objetivo de identificar a contaminação do subsolo e das águas subterrâneas. A geologia sobre a qual está assentado o aterro de Porto Velho é constituída por sedimentos pleistoceno (argilo-arenosos com concreções lateríticas) assentados sobre rochas graníticas da Formação Santo Antônio. Os resultados mostraram que a aplicação dessas duas técnicas permite identificar locais de ocorrências dos resíduos, zonas de fraturas, diferentes litotipos do subsolo, fluxo das águas subsuperficiais e avaliar o impacto ambiental causado no meio ambiente.<br>Abstract: Resistivity survey, with vertical electrical sounding and electrical imaging (Schlumberger and dipole-dipole configurations), were done at the waste disposal area, in city of Porto Velho, state of Rondônia, Brazil with the objective to identify the contamination of the subsoil and groundwater. The local geology is constituted by pleistocenic sediments (clay-sandy litology with lateritic concretionary) overlies granitic rocks of Santo Antônio Formation. The results showed that integrating this geophysical techniques can identify places of occurrences of waste, fractures zones, different lithotypes the subsoil, underground flow and evaluate the environmental impact caused by the waste disposal<br>Doutor
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Gandolfo, Otavio Coaracy Brasil. "Um estudo do imageamento geoelétrico na investigação rasa." Universidade de São Paulo, 2007. http://www.teses.usp.br/teses/disponiveis/44/44133/tde-25042008-142218/.
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Este trabalho trata do estudo detalhado e com profundidade das metodologias de aquisição, processamento e interpretação de dados de caminhamentos elétricos, sob o enfoque de investigações voltadas a objetivos rasos. Nas técnicas de aquisição 2D (caminhamentos) foram utilizados os arranjos dipolo-dipolo, pólo-dipolo, pólo-pólo e Wenner, permitindo comparações quanto à eficácia dos mesmos. Foi testada uma genuína aquisição 3D utilizando o arranjo pólo-pólo, avaliando-se suas potencialidades e limitações. O Schlumberger foi o arranjo empregado para a execução de SEVs que auxiliaram na interpretação e quantificação das seções geoelétricas 2D, principalmente no que se refere à distribuição vertical das resistividades. Os modelos geoelétricos 2D foram obtidos com um programa de inversão de dados (RES2DINV) que, em tese, é capaz de corrigir as distorções observadas nas pseudo-seções de resistividade elétrica aparente correspondentes aos diversos arranjos utilizados no trabalho. Estes modelos constituem imagens que apresentam uma melhor correspondência com a realidade geológica em subsuperfície, o que facilita a interpretação dos resultados. Procurou-se explorar o máximo as potencialidades do programa de inversão, visando a obtenção de imagens de boa qualidade. A interpretação geofísica foi sempre efetuada com base em informações diretas disponíveis (furos de sondagem, trincheiras, poços e afloramento). Em uma escala de investigação rasa, a resolução passa a ter uma importância fundamental. Procurou-se demonstrar que, quando são utilizados pequenos espaçamentos entre eletrodos (menores que quatro metros), particularmente no caso do dipolo-dipolo, é possível a execução de mais níveis de investigação em profundidade (superiores a oito) ainda com uma boa qualidade do sinal. Por outro lado, os arranjos dipolo-dipolo e pólo-pólo permitem um número muito maior de níveis de investigação sem a limitação das pequenas aberturas, mas com alguma perda em definição. Como conseqüência, tem-se um significativo aumento na quantidade de dados gerados na seção, o que contribui para o incremento da resolução bi-dimensional. Outro aspecto testado e avaliado foi o da utilização de múltiplos espaçamentos entre eletrodos sobre o mesmo perfil de levantamento. Este interessante procedimento garante, além de resolução nas porções rasas (graças aos espaçamentos pequenos), o alcance de maiores profundidades de investigação (devido aos espaçamentos maiores) em uma mesma seção. A eficácia desta prática foi verificada tanto na construção das pseudo-seções, como nos modelos geoelétricos gerados pela inversão dos dados (modelagem). A metodologia foi testada em três distintas áreas tendo por objetivo o mapeamento de um nível d´água raso, a determinação da profundidade e conformação de topo rochoso e o mapeamento de uma provável pluma de contaminação. Além de uma ampla revisão bibliográfica sobre o assunto, foi também abordado neste trabalho o controverso tema da profundidade de investigação que de fato se verifica com os arranjos de eletrodos comumente empregados em eletrorresistividade. Procurou-se, com esta tese, contribuir para um melhor entendimento acerca do tema \"imageamento geoelétrico\" e alguns tópicos a ele relacionados, quais sejam: arranjo de eletrodos, procedimentos para se conseguir um bom volume de dados na seção, utilização eficiente do programa de inversão que gera os modelos e, finalmente, a interpretação dos resultados sempre balizada por informações diretas disponíveis e por outros métodos ou técnicas geofísicas de apoio.<br>This paper addresses a detailed, in-depth study on data aquisition, processing and interpretation methodologies for 2D electrical profilings, focusing on investigations oriented to shallow targets. Two-dimensional (electrical profilings) acquisition techniques were used on a wide range of arrays - dipole-dipole, pole-dipole, pole-pole and Wenner arrays - for efficiency comparison purposes. A real 3D acquistion was tested with the pole-pole array in order to check its potential use and limitations. Schlumberger was the array used for SEVs, which helped to interpret and quantify 2D geoelectrical sections, especially as to the vertical distribution of resistivity. The 2D geoelectrical models were generated with an inversion computer program (RES2DINV), which basically corrects any distortions found in the apparent resistivity pseudosections corresponding to the arrays included in this study. These models create images that better match the subsurface geological reality, therefore simplifying the interpretation of results. We tried to explore the full potential use of the inversion computer program for good quality images. The geophysical interpretation was always based on the subsurface information available (boreholes, trenches, wells and outcrop). Resolution is critical in a shallow investigation scale. This study tried to show that the use of small spacings between electrodes (less than four meters), particularly in dipole-dipole arrays, allows for more in-depth investigation levels (greater than eight) without compromising signal quality. On the other hand, dipole-dipole and pole-pole arrays allow for a larger number of investigation levels without small spacings limitations, but with a slight loss of definition. Consequently, there is a significant increase in the amount of data generated at the section, enhancing 2D resolution. Another aspect tested and assessed was the use of multiple spacings between electrodes on the same survey profile. In addition to resolution in shallow sections (thanks to small spacings), this interesting procedure allows deeper investigation levels (due to larger spacings) in the same section. The efficacy of this practice was verified both in the development of pseudo-sections and in the geoelectrical models generated by inversion modelling. The methodology was tested in three different areas in order to map a shallow water table, determine the depth and shape of the bedrock, and map a potential contaminant plume. In addition to the broad literature review available, this paper also covered the controversial topic of depth investigation actually present in electrode arrays typically used in electrical resistivity methods. This thesis tried to provide a better understanding of \"geoelectrical resistivity imaging\" and related topics such as: electrode array, procedures required to generate good volumes of data in the section, efficient use of the inversion computer program behind the models and, lastly, interpretation of results, always based on the subsurface information available and on other supporting geophysical methods or techniques.
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Costa, Adeilton Fernandes da [UNESP]. "Emprego do método da eletro-resistividade na caracterização da lixeira de Porto Velho - RO assentada em meio fraturado." Universidade Estadual Paulista (UNESP), 2008. http://hdl.handle.net/11449/102890.
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Made available in DSpace on 2014-06-11T19:32:18Z (GMT). No. of bitstreams: 0
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costa_af_dr_rcla.pdf: 1751728 bytes, checksum: 47313b86159b0305db3753bcef660368 (MD5)<br>Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)<br>Ensaios geofísicos de eletro-resistividade, através das técnicas da sondagem elétrica vertical e imageamento elétrico (configurações Schlumberger e dipolo-dipolo), foram executados na área da lixeira da cidade de Porto Velho, Estado de Rondônia, com o objetivo de identificar a contaminação do subsolo e das águas subterrâneas. A geologia sobre a qual está assentado o aterro de Porto Velho é constituída por sedimentos pleistoceno (argilo-arenosos com concreções lateríticas) assentados sobre rochas graníticas da Formação Santo Antônio. Os resultados mostraram que a aplicação dessas duas técnicas permite identificar locais de ocorrências dos resíduos, zonas de fraturas, diferentes litotipos do subsolo, fluxo das águas subsuperficiais e avaliar o impacto ambiental causado no meio ambiente.<br>Resistivity survey, with vertical electrical sounding and electrical imaging (Schlumberger and dipole-dipole configurations), were done at the waste disposal area, in city of Porto Velho, state of Rondônia, Brazil with the objective to identify the contamination of the subsoil and groundwater. The local geology is constituted by pleistocenic sediments (clay-sandy litology with lateritic concretionary) overlies granitic rocks of Santo Antônio Formation. The results showed that integrating this geophysical techniques can identify places of occurrences of waste, fractures zones, different lithotypes the subsoil, underground flow and evaluate the environmental impact caused by the waste disposal
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Warneford, Emma S. "The thermal shallow water equations, their quasi-geostrophic limit, and equatorial super-rotation in Jovian atmospheres." Thesis, University of Oxford, 2014. http://ora.ox.ac.uk/objects/uuid:6604fcac-afe6-4abe-8a6f-6a09de4f933f.
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Observations of Jupiter show a super-rotating (prograde) equatorial jet that has persisted for decades. Shallow water simulations run in the Jovian parameter regime reproduce the mixture of robust vortices and alternating zonal jets observed on Jupiter, but the equatorial jet is invariably sub-rotating (retrograde). Recent work has obtained super-rotating equatorial jets by extending the standard shallow water equations to relax the height field towards its mean value. This Newtonian cooling-like term is intended to model radiative cooling to space, but its addition breaks key conservation properties for mass and momentum. In this thesis the radiatively damped thermal shallow water equations are proposed as an alternative model for Jovian atmospheres. They extend standard shallow water theory by permitting horizontal variations of the thermodynamic properties of the fluid. The additional temperature equation allows a Newtonian cooling term to be included while conserving mass and momentum. Simulations reproduce equatorial jets in the correct directions for both Jupiter and Neptune (which sub-rotates). Quasi-geostrophic theory filters out rapidly moving inertia-gravity waves. A local quasi-geostrophic theory of the radiatively damped thermal shallow water equations is derived, and then extended to cover whole planets. Simulations of this global thermal quasi-geostrophic theory show the same transition, from sub- to super-rotating equatorial jets, seen in simulations of the original thermal shallow water model as the radiative time scale is decreased. Thus the mechanism responsible for setting the direction of the equatorial jet must exist within quasi-geostrophic theory. Such a mechanism is developed by calculating the competing effects of Newtonian cooling and Rayleigh friction upon the zonal mean zonal acceleration induced by equatorially trapped Rossby waves. These waves transport no momentum in the absence of dissipation. Dissipation by Newtonian cooling creates an eastward zonal mean zonal acceleration, consistent with the formation of super-rotating equatorial jets in simulations, while the corresponding acceleration is westward for dissipation by Rayleigh friction.
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Habana, Nlingilili Oarabile Kgosietsile. "Gravity Recovery by Kinematic State Vector Perturbation from Satellite-to-Satellite Tracking for GRACE-like Orbits over Long Arcs." The Ohio State University, 2020. http://rave.ohiolink.edu/etdc/view?acc_num=osu1578042687104082.
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Vaucher, Julien. "Processus géophysiques de surface des plaines de lave de la province volcanique de Cerberus, Mars." Phd thesis, Université Paul Sabatier - Toulouse III, 2007. http://tel.archives-ouvertes.fr/tel-00181347.
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Les plaines de laves de Cerberus sur Mars présentent des morphologies volcaniques, fluviatiles et tectoniques. Une étude détaillée de cette région a permis de compiler diverses observations dans une carte géologique dont les morphologies fluviatiles et volcaniques. Les plaines de laves sont datées au plus de 250 millions d'années, et présentent des relations stratigraphiques complexes entre les volcans boucliers et les grosses coulées de lave. Les volumes de laves ont été contraints, à l'aide d'une modélisation originale de bassin, à un maximum de 17.104 km3. La cartographie des plaines de laves à permis de développer deux axes de recherche : (1) L'étude des dépôts volcaniques éoliens. L'étude de la tâche de faible albédo de Cerberus, suggère qu'il s'agit d'une strate de cendres ou de téphras mise à jour par la formation de Grjota' Vallis, distribuée par les vents vers le sud ouest de la zone. Cette tâche est finalement un témoin possible de l'activité explosive de Cerberus. (2) l'étude des dépôts effusifs. L'étude de la rhéologie des coulées de laves met en évidence deux types de viscosités indépendantes des taux d'émission, dont une se situe dans les valeurs de viscosité trouvées sur d'autres édifices martiens (105 Pa.s), et une autre qui présente les plus faibles valeurs de viscosité sur Mars (<103 Pa.s). L'absence d'édifice majeur fait des plaines de Cerberus une province volcanique unique sur Mars, dont l'évolution future reste incertaine.
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Stewart, Andrew L. "The role of the complete Coriolis force in cross-equatorial transport of abyssal ocean currents." Thesis, University of Oxford, 2011. http://ora.ox.ac.uk/objects/uuid:6bf3faff-ec7e-4d11-bdfe-c54ae9d03895.
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In studies of the ocean it has become conventional to retain only the component of the Coriolis force associated with the radial component of the Earth’s rotation vector, the so-called “traditional approximation”. We investigate the role of the “non-traditional” component of the Coriolis force, corresponding to the non-radial component of the rotation vector, in transporting abyssal waters across the equator. We first derive a non-traditional generalisation of the multi-layer shallow water equations, which describe the flow of multiple superposed layers of inviscid, incompressible fluid with constant densities over prescribed topography in a rotating frame. We derive these equations both by averaging the three-dimensional governing equations over each layer, and via Hamilton’s principle. The latter derivation guarantees that conservation laws for mass, momentum, energy and potential vorticity are preserved. Within geophysically realistic parameters, including the complete Coriolis force modifies the domain of hyperbolicity of the multi-layer equations by no more than 5%. By contrast, long linear plane waves exhibit dramatic structural changes due to reconnection of the surface and internal wave modes in the long-wave limit. We use our non-traditional shallow water equations as an idealised model of an abyssal current flowing beneath a less dense upper ocean. We focus on the Antarctic Bottom Water, which crosses the equator in the western Atlantic ocean, where the bathymetry forms an almost-westward channel. Cross-equatorial flow is strongly constrained by potential vorticity conservation, which requires fluid to acquire a large relative vorticity in order to move between hemispheres. Including the complete Coriolis force accounts for the fact that fluid crossing the equator in an eastward/westward channel experiences a smaller change in angular momentum, and therefore acquires less relative vorticity. Our analytical and numerical solutions for shallow water flow over idealised channel topography show that the non-traditional component of the Coriolis force facilitates cross-equatorial flow through an almost-westward channel.
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Luo, Wenyu. "Three-dimensional propagation and scattering around a conical seamount." Thesis, Massachusetts Institute of Technology, 2007. http://hdl.handle.net/1721.1/40296.
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Includes bibliographical references (p. 259-261).<br>This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections.<br>Thesis (Ph. D.)--Joint Program in Applied Ocean Science and Engineering (Massachusetts Institute of Technology, Dept. of Mechanical Engineering; and the Woods Hole Oceanographic Institution), 2007.<br>In this thesis, a numerically effcient three-dimensional propagation and scattering model is developed based on the three-dimensional coupled mode theory for axisymmetric bathymetry. The three-dimensional coupled mode approach applied in this thesis is fundamentally identical to the one applied in earlier models, such as the one presented by Taroudakis [20]. Thus, it is based on a Fourier expansion of the acoustic field around a seamount, with each azimuthal expansion coefficient being represented by a two-way coupled mode formulation. However, earlier formulations were severely limited in terms of frequency, size and geometry of the seamount, the seabed composition, and the distance between the source and the seamount, and are totally inadequate for modeling high-frequency, large-scale seamount problems. By introducing a number of changes in the numerical formulation and using a standard normal mode model (C-SNAP) for determining the fundamental modal solutions and coupling coefficients, orders of magnitude improvement in efficiency and fidelity has been achieved, allowing for realistic propagation and scattering scenarios to be modeled, including effects of seamount roughness and realistic sedimentary structure.<br>(cont.) Also, by the simple superposition principle, the computational requirements are made independent of the distance between the seamount and the source and receivers, and dependent only on the geometry of the seamount and the frequency of the source. First, this thesis investigates the scattering from a cylindrical island, which is the simplest case of a conical seamount problem. Our model, using the superposition method, can solve the cylindrical problem in Athanassoulis and Prospathopoulos's paper [3] with the same accuracy while saving about 4/5 computational effort. Second, this thesis demonstrates the spectral coupled mode approach, which includes a two-way coupled mode model and a superposition representation of the field. Third, this thesis applies the three-dimensional model to investigate some physics issues of three-dimensional seamount scattering. As a result of the investigation, we learn that the Nx2D model is a poor approximation of the true three-dimensional model when the three-dimensional effects are significant, though it is a good approximation of the three-dimensional model otherwise. The convergence of the model in terms of the seamount discretization is also discussed and demonstrated.<br>(cont.) Finally, our three-dimensional spectral coupled mode model is tested by the application of the Kermit Seamount problem with realistic ocean environmental data from the 2004 BASSEX experiment.<br>by Wenyu Luo.<br>Ph.D.
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Sivelle, Vianney. "Couplage d'approches conceptuelles, systémiques et distribuées pour l'interprétation de traçages artificiels en domaine karstique : implications pour la détermination de la strucure interne des aquifères karstiques." Thesis, Toulouse 3, 2019. http://www.theses.fr/2019TOU30180.
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L'objectif principal de ces travaux de thèse consiste à améliorer la compréhension de la structure interne des aquifères karstiques en s'appuyant sur l'interprétation de traçages artificiels. Pour répondre à cet objectif, cette thèse s'appuie sur les bassins versants karstiques du Baget et d'Aliou (Ariège, France) ainsi que d'autres hydrosystèmes karstiques (les systèmes de Norville, du Val de Loire et de Foubanne) inclus dans le Service National d'Observation des Karsts (SNO Karst, INSU-CNRS) et sur la base de données BD traçage du BRGM incluant notamment le système karstique de l'Ouysse. L'approche globale retenue pour ces travaux de thèse consiste à coupler les résultats de différentes approches. [1] La modélisation conceptuelle à réservoirs avec l'outil dédié KarstMod permet de partitionner les écoulements à l'échelle du bassin versant et d'appréhender la dynamique des échanges entre la matrice et les conduits, à court et long terme. On estime que la contribution annuelle de la matrice au débit à l'exutoire est d'environ 3% et qu'elle peut augmenter jusqu'à 25% en période de faible précipitation. [2] Une approche systémique de type "fonction de transfert" a été développée et appliquée à divers hydrosystèmes (dont les systèmes de Norville, de l'Ouysse, du Val de Loire et de Foubanne). Cette approche consiste à étudier la dynamique du transport de masse en soluté en interprétant des données de traçages artificiels et permet de partitionner les écoulements en estimant les temps de résidence des différentes composantes qui contribuent en transfert de solutés entre les points d'injection et de restitution. [3] Une approche distribuée intégrant un couplage de données géophysiques et de simulations pseudo-génétique permet de simuler des réseaux de drainage. Les écoulements et le transport de masse en soluté associé sont ensuite simulés et confrontés à des données de terrain. Cela constitue une approche originale pour déduire la structuration des écoulements souterrains à partir des données de traçages artificiels<br>The main objective of these thesis is to improve the understanding of the internal structure of karstic aquifers by relying on the interpretation of artificial tracer tests. To meet these objectives, this thesis is based on the karst watersheds of Baget and Aliou (Ariège, France) as well as other karst hydrosystems (the Norville, Val de Loire and Foubanne systems) included in the National Karts Observation Service (SNO Karst, INSU-CNRS) and the tracing database of the BRGM including the Ouysse karst system. The overall approach adopted for this thesis is to couple the results of different approaches. [1] Conceptual reservoirs modeling with the dedicated KarstMod model allows the partitioning of flows at the scale of the watershed and to understand the dynamics of the exchanges between the matrix and the conduits, in the short and long term. It is estimated that the annual contribution of the matrix to the total outflow is about 3% and can increase up to 25% during periods of low precipitation. [2] A systemic approach of the "transfer function" type has been developed and applied to various hydrosystems (the Norville, Ouysse, Val de Loire and Foubanne systems). This approach consists of studying the dynamics of solute mass transport by interpreting artificial tracer tests data and partitioning the flows by estimating the residence times of the different components that contribute to solute transfer between the injection and recovery points. [3] A distributed approach integrating a coupling of geophysical data and pseudo-genetic simulations makes it possible to simulate drainage networks. The associated solute flows and mass transport are then simulated and compared with field data. This is an approach to deduce the structuring of underground flows from the data of artificial tracer tests
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Touchard, Frédéric. "Caractérisation hydrogéologique d'un aquifère en socle fracturé : Site de Ploemeur (Morbihan)." Phd thesis, Université Rennes 1, 1998. http://tel.archives-ouvertes.fr/tel-00675884.
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En Bretagne, l'alimentation en eau potable est assurée à 20% par les ressources en eaux souterraines contenues, principalement dans le socle fracturé. Du fait de la géométrie du réseau de fractures et des propriétés hydrauliques des roches, la productivité des aquifères bretons est généralement faible (400 à 1000 m3/j). A Ploemeur(Morbihan), un important gisement d'eau souterraine est exploité pour l'alimentation en eau potable, depuis juin 1991, à un débit moyen de 3000 m3/j. Les caractéristiques principales de cet aquifère sont 1) des arrivées d'eaux importantes, localisées au niveau de filons de pegmatites fracturées, et 2) une eau brute de bonne qualité ([N03]<1 Omg/I). Dans les milieux fracturés, les circulations de fluide et le transport de matière sont fortement dépendantes de la géométrie du réseau de fracture. C'est pourquoi, une meilleure compréhension du fonctionnement hydrogéologique est fondamentale quant à la gestion et la protection des ressources en eaux souterraines. Nous avons entrepris une caractérisation hydrogéologique afin de définir la structure du sous-sol e~ d'identifier les principaux processus à l'origine de la productivité de cet aquifère et de la qualité de l'eau. Cette étude pluridisciplinaire est basée sur des observations de terrain et sur l'utilisation de méthodes géophysiques, hydrauliques et hydrochimiques. La zone fracturée se trouve au contact entre des micaschistes et du granite et possède une géométrie subhorizontale favorisant sa recharge donc sa productivité. Ce modèle contraste avec ce qui est traditionnellement proposé pour les milieux fracturés en Bretagne. L'imagerie géophysique donne grossièrement la géométrie mais ne permet pas une détection fine des filons de pegmatites fracturés. Des essais de pompage ont permis de caractériser les propriétés hydrauliques. Ce type d'aquifère ne répond pas aux modèles standards développés en hydrogéologie; à la 1 fois, par son hétérogénéité intrinsèque et par la dimension de la zone d'écoulement. Par conséquent, le modèle mOy9n qui semble approprié est un aquifère fractal de dimension 1,4. Enfin l'analyse des chroniques chimiques, notamment des nitrates, a mis en évidence les processus 1) de mélange d'une eau récente (infiltrée après 1950 et polluée par les nitrates) avec une eau ancienne et 2) de dénitrification naturelle par oxydation de la pyrite. Une modélisation de ces chroniques sur la base d'une dénitrification bactérienne a permis de quantifier la cinétique de cette réaction d'oxydo-réduction et la dynamique du mélange qui évolue pendant le - ~ - pompage, par la mise en écoulement de drains préférentiels, entre la surface et la zone fracturée profonde.
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Becker, Kyle M. "Geoacoustic inversion in laterally varying shallow-water experiments using high-resolution wavenumber estimation." Thesis, Massachusetts Institute of Technology, 2001. http://hdl.handle.net/1721.1/29056.
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Thesis (Ph. D. in Applied Ocean Sciences)--Joint Program in Applied Ocean Physics and Engineering (Massachusetts Institute of Technology, Dept. of Ocean Engineering; and the Woods Hole Oceanographic Institution), February 2002.<br>Includes bibliographical references (leaves 161-170).<br>Sound propagation in shallow water is highly dependent on the interaction of the sound field with the bottom. In order to fully understand this problem, it is necessary to obtain reliable estimates of bottom geoacoustic properties that can be used in acoustic propagation codes. In this thesis, perturbative inversion methods and exact inverse methods are discussed as a means for inferring geoacoustic properties of the bottom. For each of these methods, the input data to the inversion is the horizontal wavenumber spectrum of a point-source acoustic field. The main thrust of the thesis work concerns extracting horizontal wavenumber content for fully three-dimensionally varying waveguide environments. In this context, a high-resolution autoregressive (AR) spectral estimator was applied to determine wavenumber content for short aperture data. As part of this work, the AR estimator was examined for its ability to detect discrete wavenumbers in the presence of noise and also to resolve closely spaced wavenumbers for short aperture data. As part of a geoacoustic inversion workshop, the estimator was applied to extract horizontal wavenumber content for synthetic pressure field data with range-varying geoacoustic properties in the sediment. The resulting wavenumber content was used as input data to a perturbative inverse algorithm to determine the sound speed profile in the sediment. It was shown using the high-resolution wavenumber estimator that both the shape and location of the range-variability in the sediment could be determined.<br>(cont.) The estimator was also applied to determine wavenumbers for synthetic data where the water column sound speed contained temporal variations due to the presence of internal waves. It was shown that reliable estimates of horizontal wavenumbers could be obtained that are consistent with the boundary conditions of the waveguide. The Modal Mapping Experiment (MOMAX), an experimental method for measuring the full spatial variability of a propagating sound field and its corresponding modal content in two-dimensions, is also discussed. The AR estimator is applied to extract modal content from the real data and interpreted with respect to source/receiver motion and geometry. For a moving source, it is shown that the wavenumber content is Doppler shifted. A method is then described that allows the direct measure of modal group velocities from Doppler shifted wavenumber spectra. Finally, numerical studies are presented addressing the practical issues associated with using MOMAX type data in the exact inversion method of Gelfand-Levitan.<br>by Kyle M. Becker.<br>Ph.D.
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Degenhardt, John Jerome. "A model for the development of a lobate alpine rock glacier in southwest Colorado, USA implications for water on Mars /." Texas A&M University, 2002. http://hdl.handle.net/1969/320.
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Hincapie, Jaime Omar. "Shallow geophysical techniques applied to archaeology, economic geology, and groundwater resources." To access this resource online via ProQuest Dissertations and Theses @ UTEP, 2008. http://0-proquest.umi.com.lib.utep.edu/login?COPT=REJTPTU0YmImSU5UPTAmVkVSPTI=&clientId=2515.
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Flores, Zamora Juan Carlos. "Integration of Geophysical Interpretation Methods Applied in the Perdido Fold Belt." Thesis, Norges teknisk-naturvitenskapelige universitet, Institutt for petroleumsteknologi og anvendt geofysikk, 2013. http://urn.kb.se/resolve?urn=urn:nbn:no:ntnu:diva-23129.
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Today, with discoveries of the fields Great White, Baha, Trident and Tobago in U.S portion and the recent drilling of wells Trion-1 and Supremus-1 in Mexican waters, have established the Perdido fold belt in the Gulf of Mexico as a significant potential petroleum province in its initial stages of evaluation. This area according with studies realized so far, shows an important potential of reservoirs associated with extra-light crude oil, however to explore, delimitate, characterize and produce these resources is necessary the implementation of the most modern technology of interpretation, drilling and development. In this work, I considered one of the new wells discovered in the Mexican portion into the Perdido Fold Belt system, where the main target of this project is establish and delimitate the probable and possible extension of hydrocarbons associated with such well. To develop this, first was carried out the seismic interpretation of area of study, and thus establish all the geological setting associated to the reservoir. Although most of Perdido Fold Belt structures usually are anticlines of great magnitude, experiences obtained in U.S wells has showed that hydrocarbon distribution is most related with the presence of stratigraphic traps associated with submarine fans and channels systems that often shows a response of amplitude below of seismic resolution, making their definition and interpretation more complex. So this type of traps in the Mexican portion also was evident during the interpretation of this project, which was characterized by two types of traps: one structural characterized by a set of high amplitude anomalies limited by normal fault blocks and other stratigraphic interpreted as a system of submarine channels with medium to high amplitude produced as a result of depositional system of Northern and Northwest Gulf of Mexico. Hence, an AVO analysis has been proposed as part of this project allowing calibrate the amplitude anomalies identified in the reservoirs and understand their relationship with the type of fluids associated to the reservoir and lithological changes, being possible to derive two types of hydrocarbons in each reservoir; one associated to gas and other to oil. Once obtained the AVO analysis results, the LMR and EI seismic inversion were performed, where the main goal of this was to complement the AVO analysis and therefore, reduce the uncertainties associated to the amplitude anomalies identified and their relationship with the reservoir conditions. With this analysis was possible to establish and define not only the reservoir rock distribution, but also the areas associated with higher hydrocarbon saturation and water saturation characterized by low and high values of Lamnda-rho and Elastic Impedance respectively. In addition of establish the seismic properties response associates to each stratigraphic unit interpreted in this area. Thereby, reducing the geological risk and delimiting and identifying new potential areas to contain hydrocarbons.
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Rzeznik, Andrew Joseph. "Applied math in geophysical fluids : partially trapped wave problems and mining plumes." Thesis, Massachusetts Institute of Technology, 2018. http://hdl.handle.net/1721.1/120657.
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Thesis: Ph. D., Massachusetts Institute of Technology, Department of Mathematics, 2018.<br>Cataloged from PDF version of thesis.<br>Includes bibliographical references (pages 129-132).<br>The first portion of this work focuses on leaky modes in the atmospheric sciences. Leaky modes (related to quasi-modes, scattering resonances, and the singularity expansion method) are discrete, oscillatory and decaying modes that arise in conservative systems where waves are partially trapped. By replacing the infinite domain with a finite domain and appropriate boundary conditions it is possible in many cases to construct a complete basis for the solution in terms of these modes. Formulating such effective boundary conditions requires a notion of the direction of propagation of the waves. For this purpose we introduce a generalization of the concept of group speed for exponentially decaying but conservative waves. This is found via an extended modulation argument and a generalization of Whitham's Average Lagrangian theory. The theory also shows that a close relationship exists between the branch cuts of the dispersion relation and the propagation direction, and is used to create spectral decompositions for simple problems in internal gravity waves. The last chapter considers deep-sea nodule mining operations, which potentially involve plans for discharge plumes to be released into the water column by surface operation vessels. We consider the effects of non-uniform, realistic stratifications with vertical shear on forced compressible plumes. The plume model is developed to account for the influence of thermal conduction through the discharge pipe and an initial adjustment phase. We investigate the substantial role of compressibility, for which a dimensionless number is introduced to determine its importance compared to that of the background stratification. Our results show that (i) small-scale stratification features can have a significant impact, (ii) in a static ambient there exists a discharge flow rate that minimizes the plume vertical extent, (iii) the ambient velocity profile plays an important role in determining the final plume scale and dilution factor, and (iv) for a typical plume the dilution factor is expected to be several hundred to a thousand.<br>by Andrew Joseph Rzeznik.<br>Ph. D.
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Fortin, Jerome. "Compaction homogène et compaction localisée des roches poreuses.Etude expérimentale et théorique." Phd thesis, Université Pierre et Marie Curie - Paris VI, 2005. http://tel.archives-ouvertes.fr/tel-00180388.
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Pour de nombreux problèmes de sismo-tectonique et d'ingénierie de réservoir, la capacité à prévoir l'ampleur de la déformation inélastique et les ruptures repose sur une compréhension de la phénoménologie et de la micromécanique de la dilatance et de la compaction dans les roches. Pour les roches poreuses, la compaction inélastique peut être diffuse ou localisée dans la roche. La compaction d'une roche sous une pression isotrope est le résultat de la destruction du réseau poreux. Pour quantifier l'évolution de l'endommagement pendant la compaction, nous utilisons un modèle de milieu effectif. Nous montrons ainsi comment le broyage des grains transforme la roche en un milieu granulaire, où, même à sec, le rapport Vp/Vs croit, ce qui n'avait jamais été observé. Lorsque la roche est soumise à champ de contrainte déviatorique, la compaction inélastique est<br />localisée. Sous certaines pressions moyennes effectives, la déformation inélastique se développe sous forme de bandes de compaction. Pour comprendre la formation des bandes de compaction, nous avons enregistré, puis re-localisé les émissions acoustiques au cours de plusieurs expériences.
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Amitrano, David. "Complexité et Dynamique de l'endommagement et de la rupture,Mécanique, sismicité et invariance d'échelle des objets géologiques." Habilitation à diriger des recherches, Institut National Polytechnique de Lorraine - INPL, 2005. http://tel.archives-ouvertes.fr/tel-00173641.
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Ce rapport rassemble des travaux portant sur l'endommagement et la rupture de roches à des échelles allant de celle de l'échantillon de laboratoire à la celle de la croûte terrestre en passant par celle des massifs rocheux (falaises et mines souterraines). On y associe l'analyse de données acquises au laboratoire et in situ , leur modélisation statistique et conceptuelle et la simulation numérique. Cette approche permet d'appréhender la complexité du comportement des roches selon différents aspects. L'accent est d'abord mis sur les propriétés statistiques et les invariances d'échelles des structures d'endommagement et des événements sismiques observés pendant le processus de déformation et de rupture. Un modèle numérique, basé sur une approche mésoscopique de l'endommagement, est présenté pour la simulation des processus de rupture à court et long terme. Il permet de reproduire de nombreuses observations expérimentales en leur donnant un cadre mécanique et en permettant ainsi de préciser leurs conditions d'apparition. Cette approche permet de considérer le processus de déformation et de rupture des roches comme un système complexe dont les propriétés macroscopiques émergent de l'interaction entre éléments de plus petite échelle ayant des propriétés simples. Le rôle des fluides dans ce processus est abordé par l'observation de la sismicité induite dans un massif rocheux fracturé et la simulation numérique du couplage roche fluides. Enfin un projet de recherche est développé sur le thème de l'endommagement à long terme et du couplage hydromécanique.
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Skrede, Ole-Johan. "Explicit, A Priori Constrained Model Parameterization for Inverse Problems, Applied on Geophysical CSEM Data." Thesis, Norges teknisk-naturvitenskapelige universitet, Institutt for matematiske fag, 2014. http://urn.kb.se/resolve?urn=urn:nbn:no:ntnu:diva-27343.
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This thesis introduce a new parameterization of the model space in global inversion problems. The parameterization provides an explicit representation of the model space with a basis constrained on a priori information about the problem at hand. It is able to represent complex model structures with few parameters, and thereby enhancing the speed of the inversion, as the number of iterations needed to converge is heavily scaled with the number of parameters in stochastic, global inversion methods. A standard Simulated Annealing optimization routine is implemented, and further extended to be able to optimize for a dynamically varying number of variables. The method is applied on inversion of marine CSEM data, and inverts both synthetic and real data sets and is able to recover resistivity profiles that demonstrate good resemblance with provided well bore log data. The trans-dimensional, self-parameterizing Simulated Annealing algorithm which is introduced in this thesis proves to be superior to the regular algorithm with fixed parameter dimensions.
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Machado, Cruz Alberto. "Integrated geological and geophysical studies applied to understanding the evolution of the Offshore Amazon Basin." Electronic Thesis or Diss., Sorbonne université, 2018. http://www.theses.fr/2018SORUS466.
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Le Bassin de l'Embouchure de l'Amazone (en portugais Bacia da Foz do Amazonas) est situé dans l'extrême nord de la Marge Équatoriale Brésilienne. Ce bassin a attiré l'attention de la communauté scientifique pendant plusieurs décennies en raison de ses processus sédimentaires à grande échelle liés à l'afflux colossal de sédiments fourni par l’Amazone. Cependant, la plupart des investigations menées sur ce bassin étaient limités à sur la partie supérieure de la succession Quaternaire de le Cône d'Amazone et certains travaux pionniers visant des strates plus profondes ne disposaient pas d'un contrôle chronostratigraphique fiable. Afin de mieux comprendre l'évolution temporelle et spatiale de la succession stratigraphique post-rift du Bassin de l'Embouchure de l'Amazone, des études multidisciplinaires soutenues par des interprétations de données sismiques, diagraphiques, chronostratigraphiques et de modèles de anomalies gravitaires et magnétiques ont été réalisées au cours de cette thèse<br>The Offshore Amazon Basin (known in Portuguese as Bacia da Foz do Amazon) is located in the far north of the Brazilian Equatorial Margin. This basin has attracted the attention of the scientific community for several decades due to its large-scale sedimentary processes related to the colossal sediment influx provided by the Amazon River. However, most of the investigations carried on the Offshore Amazon Basin were restricted to the uppermost Quaternary succession of the Amazon Deep-sea Fan and some pioneer works aiming deeper strata lacked a reliable chronostratigraphic control. In order to better understand the temporal and spatial evolution of the post-rift stratigraphic succession of the Offshore Amazon Basin, multidisciplinary studies supported by interpretations of seismic, well log, chronostratigraphic data and geophysical potential field models were carried out during this PhD thesis
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Garvey, Ryan J. "A study of unstable rock failures using finite difference and discrete element methods." Thesis, Colorado School of Mines, 2013. http://pqdtopen.proquest.com/#viewpdf?dispub=3557944.
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<p> Case histories in mining have long described pillars or faces of rock failing violently with an accompanying rapid ejection of debris and broken material into the working areas of the mine. These unstable failures have resulted in large losses of life and collapses of entire mine panels. Modern mining operations take significant steps to reduce the likelihood of unstable failure, however eliminating their occurrence is difficult in practice. Researchers over several decades have supplemented studies of unstable failures through the application of various numerical methods. The direction of the current research is to extend these methods and to develop improved numerical tools with which to study unstable failures in underground mining layouts. </p><p> An extensive study is first conducted on the expression of unstable failure in discrete element and finite difference methods. Simulated uniaxial compressive strength tests are run on brittle rock specimens. Stable or unstable loading conditions are applied onto the brittle specimens by a pair of elastic platens with ranging stiffnesses. Determinations of instability are established through stress and strain histories taken for the specimen and the system. </p><p> Additional numerical tools are then developed for the finite difference method to analyze unstable failure in larger mine models. Instability identifiers are established for assessing the locations and relative magnitudes of unstable failure through measures of rapid dynamic motion. An energy balance is developed which calculates the excess energy released as a result of unstable equilibria in rock systems. These tools are validated through uniaxial and triaxial compressive strength tests and are extended to models of coal pillars and a simplified mining layout. </p><p> The results of the finite difference simulations reveal that the instability identifiers and excess energy calculations provide a generalized methodology for assessing unstable failures within potentially complex mine models. These combined numerical tools may be applied in future studies to design primary and secondary supports in bump-prone conditions, evaluate retreat mining cut sequences, asses pillar de-stressing techniques, or perform backanalyses on unstable failures in select mining layouts.</p>
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Kelbert, Anna. "Geophysical inverse theory applied to reconstruction of large-scale heterogeneities in electrical conductivity of earth's mantle." Thesis, Cardiff University, 2006. http://orca.cf.ac.uk/54090/.
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This thesis addresses the non-linear ill-posed inverse problems of reconstructing the three-dimensional distribution of electrical conductivity in Earth's mantle. This problem has never previously been fully attacked. The major objective of this thesis is to develop a methodology allowing to resolve any large-scale three-dimensional inhomogeneities in Earth's mantle based on a regularised inversion of electromagnetic field data. We generalise the global three-dimensional forward problem of electromagnetic induction in the frequency domain for arbitrary sources, and solve it in a linear algebraic formulation. We develop the data sensitivities analysis based on the generalised forward problem, and derive the analytic and numerical expressions for the Jacobian and the derivative of the regularised least squares penalty functional. This allows us to set up a non-linear conjugate gradient inverse solution. In doing so, we parameterize the model space by layered spherical harmonics. This inverse solution is tested on a series of checkerboard experiments; on this basis, we discuss spatial resolution of our analysis at different depths in the mantel. This methodology is then applied to the most current low-frequency global observatory data set, and models are obtained satisfying the data statistically well. We discuss the features of these models and the implications of our experiments. We also plot and compare the corresponding magnetic fields and responses at the Earth's surface, and provide suggestions for future directions of research.
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McElroy, William John. "Development of geophysical mapping and data processing methods applied to base metal ore deposits in Ireland." Thesis, Queen's University Belfast, 1994. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.296823.
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Sarafian, Emily Kathryn. "Geophysical and petrological constraints on ocean plate dynamics." Thesis, Massachusetts Institute of Technology, 2017. http://hdl.handle.net/1721.1/111716.
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Thesis: Ph. D., Joint Program in Oceanography/Applied Ocean Science and Engineering (Massachusetts Institute of Technology, Department of Earth, Atmospheric, and Planetary Sciences; and the Woods Hole Oceanographic Institution), 2017.<br>Cataloged from PDF version of thesis.<br>Includes bibliographical references.<br>This thesis investigates the formation and subsequent motion of oceanic lithospheric plates through geophysical and petrological methods. Ocean crust and lithosphere forms at mid-ocean ridges as the underlying asthenosphere rises, melts, and flows away from the ridge axis. In Chapters 2 and 3, I present the results from partial melting experiments of mantle peridotite that were conducted in order to examine the mantle melting point, or solidus, beneath a mid-ocean ridge. Chapter 2 determines the peridotite solidus at a single pressure of 1.5 GPa and concludes that the oceanic mantle potential temperature must be -60 °C hotter than current estimates. Chapter 3 goes further to provide a more accurate parameterization of the anhydrous mantle solidus from experiments over a range of pressures. This chapter concludes that the range of potential temperatures of the mantle beneath mid-ocean ridges and plumes is smaller than currently estimated. Once formed, the oceanic plate moves atop the underlying asthenosphere away from the ridge axis. Chapter 4 uses seafloor magnetotelluric data to investigate the mechanism responsible for plate motion at the lithosphere-asthenosphere boundary. The resulting two dimensional conductivity model shows a simple layered structure. By applying petrological constraints, I conclude that the upper asthenosphere does not contain substantial melt, which suggests that either a thermal or hydration mechanism supports plate motion. Oceanic plate motion has dramatically changed the surface of the Earth over time, and evidence for ancient plate motion is obvious from detailed studies of the longer lived continental lithosphere. In Chapter 5, I investigate past plate motion by inverting magnetotelluric data collected over eastern Zambia. The conductivity model probes the Zambian lithosphere and reveals an ancient subduction zone previously suspected from surface studies. This chapter elucidates the complex lithospheric structure of eastern Zambia and the geometry of the tectonic elements in the region, which collided as a result of past oceanic plate motion. Combined, the chapters of this thesis provide critical constraints on ocean plate dynamics.<br>by Emily Kathryn Sarafian.<br>Ph. D.
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Zarroug, Moundheur. "Asymptotic methods applied to some oceanography-related problems." Doctoral thesis, Stockholm : Department of Meteorology, Stockholm University, 2010. http://urn.kb.se/resolve?urn=urn:nbn:se:su:diva-37763.
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Diss. (sammanfattning) Stockholm : Stockholms universitet, 2010.<br>At the time of the doctoral defense, the following papers were unpublished and had a status as follows: Paper 3: Manuscript. Paper 4: Manuscript.
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Angeli, Matthieu. "Etude multiéchelle de la dégradation des roches par la cristallisation de sels dans les réseaux poreux." Phd thesis, Université de Cergy Pontoise, 2007. http://tel.archives-ouvertes.fr/tel-00239456.
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La cristallisation de sels solubles dans les réseaux poreux est une source majeure de détérioration pour les pierres naturelles. L'objectif de cette thèse est de préciser ce mécanisme de détérioration par le sel dans le cas du sulfate de sodium. Le point de départ de cette étude est de suivre l'évolution d'échantillons de neuf roches sédimentaires d'origines différentes (deux calcaires biodétritiques, un calcaire détritique, un calcaire lacustre, trois grès riches en quartz et deux grès argileux lités) au cours des tests de dégradation accélérée. Tout d'abord, le mécanisme de cristallisation du sulfate de sodium est étudié grâce à un suivi thermique des échantillons. Différentes séquences de cristallisation sont proposées pour expliquer la détérioration au cours des cycles. Ensuite une nouvelle manière de quantifier l'altération à long terme par le sel est proposée, tenant compte des propriétés hydromécaniques des roches. L'importance des microstructures sur l'altération (connectivité et tortuosité du réseau poreux, fractures intra- grains) est aussi déterminée par une étude par porosimétrie au mercure. Enfin, l'influence des conditions environnementales sur l'altération est aussi évaluée : l'évaporation et la température influencent tous les deux à la fois la localisation mais aussi l'amplitude des dégâts causés par le sel.
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Wagner, Gregory LeClaire. "On the coupled evolution of oceanic internal waves and quasi-geostrophic flow." Thesis, University of California, San Diego, 2016. http://pqdtopen.proquest.com/#viewpdf?dispub=10128416.
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<p> Oceanic motion outside thin boundary layers is primarily a mixture of quasi-geostrophic flow and internal waves with either near-inertial frequencies or the frequency of the semidiurnal lunar tide. This dissertation seeks a deeper understanding of waves and flow through reduced models that isolate their nonlinear and coupled evolution from the Boussinesq equations. Three physical-space models are developed: an equation that describes quasi-geostrophic evolution in an arbitrary and prescribed field of hydrostatic internal waves; a three-component model that couples quasi-geostrophic flow to both near-inertial waves and the near-inertial second harmonic; and a model for the slow evolution of hydrostatic internal tides in quasi-geostrophic flow of near-arbitrary scale. This slow internal tide equation opens the path to a coupled model for the energetic interaction of quasi-geostrophic flow and oceanic internal tides. </p><p> Four results emerge. First, the wave-averaged quasi-geostrophic equation reveals that finite-amplitude waves give rise to a mean flow that advects quasi-geostrophic potential vorticity. Second is the definition of a new material invariant: Available Potential Vorticity, or APV. APV isolates the part of Ertel potential vorticity available for balanced-flow evolution in Eulerian frames and proves necessary in the separating waves and quasi-geostrophic flow. The third result, hashed out for near-inertial waves and quasi-geostrophic flow, is that wave-flow interaction leads to energy exchange even under conditions of weak nonlinearity. For storm-forced oceanic near-inertial waves the interaction often energizes waves at the expense of flow. We call this extraction of balanced quasi-geostrophic energy 'stimulated generation' since it requires externally-forced rather than spontaneously-generated waves. The fourth result is that quasi-geostrophic flow can encourage or 'catalyze' a nonlinear interaction between a near-inertial wave field and its second harmonic that transfers energy to the small near-inertial vertical scales of wave breaking and mixing. </p>
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Valois, Rémi. "Caractérisation structurale de morphologies karstiques superficielles et suivi temporel de l'infiltration à l'aide des méthodes électriques et sismiques." Phd thesis, Université Pierre et Marie Curie - Paris VI, 2011. http://tel.archives-ouvertes.fr/tel-00659289.
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Tous les sites étudiés lors de cette thèse, qui se situent tous dans des régions tabulaires ou monoclinales, ont permis d'observer et d'analyser d'un point de vue géophysique une diversité de morphologies associées aux karsts de plateaux et aux karsts sous couverture : tertres émissifs et dolines de suffusion dans l'Est de la France, dolines de dissolution et dolines masquées dans les Causses du Quercy, épikarst et altération sur le Causse du Larzac. Les tomographies de résistivité électrique et de sismique réfraction ont en effet été très utiles pour caractériser la géométrie de ces objets. L'apport de la sismique réfraction 3D s'est révélée considérable pour l'imagerie de la fracturation et de l'altération dans l'épikarst. Un suivi temporel électrique et sismique a également été mis en place sur un aquifère karstique en Corrèze et sur deux secteurs épikarstiques sur le Causse du Larzac. Si le suivi par tomographie de résistivité ne s'est pas avéré très efficace, le suivi par tomographie de sismique réfraction montre un potentiel conséquent pour identifier les zones de stockage et les zones d'infiltration, particulièrement dans l'épikarst. Des résultats nouveaux ont été obtenus dans : (1) la compréhension des morphologies karstiques par l'analyse de leur structure, (2) la structure et le fonctionnement de l'épikarst, (3) l'efficacité des méthodes électriques et sismiques pour l'imagerie structurale et le suivi temporel en milieu karstique.
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Morin, Eymeric. "Évolution morpho-sédimentaire de la vallée de la Choisille (sud-ouest du Bassin parisien, France) depuis le Weichsélien. Spécificité de l'impact climatique et anthropique en Europe du Nord-Ouest." Phd thesis, Université François Rabelais - Tours, 2011. http://tel.archives-ouvertes.fr/tel-00627074.
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La variabilité spatio-temporelle de l'évolution morpho-sédimentaire du fond de la vallée de la Choisille (bassin versant : 288 km²), affluent de la Loire moyenne dans le sud-ouest du Bassin parisien (37), a été étudiée par 78 forages (8 transects), prospection géophysique, analyses sédimentologiques et datations 14C et OSL. Huit phases d'évolution du système fluviatile depuis le début Weichsélien ont été définies et corrélées avec les données palynologiques et archéologiques locales, afin de comprendre l'impact des facteurs forçants : climat ou/et anthropisation. Du Weichsélien jusqu'au début du Subatlantique, l'activité d'incision ou de sédimentation de la Choisille a évolué sous contrôle climatique strict. Depuis l'Allerød, cette évolution a été différente de celles observées sur d'autres rivières en Europe du Nord-Ouest, indiquant des spécificités climatiques et géologiques régionales. Dès l'Âge du Bronze, la rivière a évolué sous contrôle climatique et anthropique ; l'impact anthropique sur la sédimentation fut prépondérant, mais très variable dans le temps et l'espace au sein du bassin selon les potentialités agricoles des secteurs considérés.
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Smigelski, Jeffrey Ralph. "Water Level Dynamics of the North American Great Lakes:Nonlinear Scaling and Fractional Bode Analysis of a Self-Affine Time Series." Wright State University / OhioLINK, 2013. http://rave.ohiolink.edu/etdc/view?acc_num=wright1379087351.
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Taboga, Alessia. "The development of integrated high-resolution geophysical, photogrammetric and GPS surveying applied to landslides in the South Wales coalfield." Thesis, Cardiff University, 2011. http://orca.cf.ac.uk/54058/.
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The aim of this research is to develop an integrated and cost-effective site investigation approach for slow moving landslides or potentially unstable slopes found within the South Wales Coalfield, an area of complex geology and hydrogeology. The research was based on the use and assessment of a wide range of surface geophysical techniques, supported by GPS and Digital Photogrammetry surveying, and the joint interpretation of the results which such techniques provide. The South Wales Coalfield has one of the highest concentrations of urban landslides in the UK due to its layered Carboniferous geology. Quaternary / Holocene geomorphology, coal mining history and relatively high rainfall. Mynydd yr Eglwys landslide (Ystrad, Rhondda Cynon Taff) was selected as the field study site because it can be considered representative of the active landslides found within the area. In autumn 1998, following an exceptional heavy rainfall period, a new compound deep- seated failure developed in a previously mined hillslope. This deep-seated failure then caused the reactivation of ancient periglacial debris slides downslope creating a serious risk to the modern housing estate located close to the toe. Electromagnetic (GEM-2), self potential, electrical resistivity tomography, seismic refraction tomography, MASW and induced polarization geophysical data were all acquired on the landslide. This combination of techniques provided information on lithology, faulting, degree of rock fracturing/weathering, thickness of displaced material, spatial distribution of areas with high water/clay content and the direction of groundwater flow. The repetition of a few ERT and SP profiles showed the applicability of geophysical monitoring in detecting changes in groundwater content and defining preferential groundwater pathways within the hillslope. Digital Photogrammetry from Helium balloon can provide a 3D landslide topographic model with 10cm-level accuracy. Topcon HiPer Pro GPS+ instrument can be used in RTK mode to monitor movement with 12mm and 15mm horizontal and vertical precision respectively.
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Guyoton, Fabrice. "Sismicité et structure lithosphérique des Alpes occidentales." Phd thesis, Grenoble 1, 1991. http://tel.archives-ouvertes.fr/tel-00544553.
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Le mémoire de thèse comporte deux études relatives aux Alpes occidentales: 1) une étude de la sismicité(relocalisation des séismes locaux à l'aide d'un modèle 3D); 2) une étude de la structure lithosphérique à l'aide de résidus télésismiques, Ces deux études sont les premiers résultats significatifs utilisant les données du nouveau réseau SISMALP. La première partie traite essentiellement des problèmes de localisation des séismes alpins. Compte tenu de la complexité structurale des Alpes, un modèle de vitesse 3D a été élaboré afin d'obtenir des relocalisations précises des foyers sismiques. Le modèle crustal, partitionné en blocs de taille variable, est déduit d'une compilation des données et des résultats géophysiques. La méthode est appliquée à la relocalisation de deux crises sismiques : l'une en Ubaye, l'autre en mer Ligure. Une troisième application à l'échelle des Alpes occidentales et concernant quatre années de sismicité, met en évidence des essaims sismiques très bien contraints et montre une nouvelle image de la sismicité. La seconde partie présente une analyse des anomalies des temps de propagation des ondes P télésismiques. Une étude des variations azimutales des résidus relatifs permet de confirmer l'existence d'un plongement Iithosphérique situé en bordure ouest de la plaine du Pô. Un autre résultat important est la mise en évidence d'un accident Iithosphérique majeur orienté N140 séparant une microplaque de Provence d'une microplaque du Briançonnais. L'application d'une méthode de tracé de rais dans un milieu 2,5D montre : l'existence d'une paléo-subduction de la microplaque du Briançonnais sous le promontoire Adriatique atteignant 220 km de profondeur; l'existence d'une asthénosphère très lente sous la plaque Europe et l'existence d'une probable anisotropie de vitesse à grande échelle. De nouvelles implications géodynamiques pour les Alpes occidentales sont discutées.
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Graciolli, Vinicius Medeiros. "A novel classification method applied to well log data calibrated by ontology based core descriptions." reponame:Biblioteca Digital de Teses e Dissertações da UFRGS, 2018. http://hdl.handle.net/10183/174993.
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Um método para a detecção automática de tipos litológicos e contato entre camadas foi desenvolvido através de uma combinação de análise estatística de um conjunto de perfis geofísicos de poços convencionais, calibrado por descrições sistemáticas de testemunhos. O objetivo deste projeto é permitir a integração de dados de rocha em modelos de reservatório. Os testemunhos são descritos com o suporte de um sistema de nomenclatura baseado em ontologias que formaliza extensamente uma grande gama de atributos de rocha. As descrições são armazenadas em um banco de dados relacional junto com dados de perfis de poço convencionais de cada poço analisado. Esta estrutura permite definir protótipos de valores de perfil combinados para cada litologia reconhecida através do cálculo de média e dos valores de variância e covariância dos valores medidos por cada ferramenta de perfilagem para cada litologia descrita nos testemunhos. O algoritmo estatístico é capaz de aprender com cada novo testemunho e valor de log adicionado ao banco de dados, refinando progressivamente a identificação litológica. A detecção de contatos litológicos é realizada através da suavização de cada um dos perfis através da aplicação de duas médias móveis de diferentes tamanhos em cada um dos perfis. Os resultados de cada par de perfis suavizados são comparados, e as posições onde as linhas se cruzam definem profundidades onde ocorrem mudanças bruscas no valor do perfil, indicando uma potencial mudança de litologia. Os resultados da aplicação desse método em cada um dos perfis são então unificados em uma única avaliação de limites litológicos Os valores de média e variância-covariância derivados da correlação entre testemunhos e perfis são então utilizados na construção de uma distribuição gaussiana n-dimensional para cada uma das litologias reconhecidas. Neste ponto, probabilidades a priori também são calculadas para cada litologia. Estas distribuições são comparadas contra cada um dos intervalos litológicos previamente detectados por meio de uma função densidade de probabilidade, avaliando o quão perto o intervalo está de cada litologia e permitindo a atribuição de um tipo litológico para cada intervalo. O método desenvolvido foi testado em um grupo de poços da bacia de Sergipe- Alagoas, e a precisão da predição atingida durante os testes mostra-se superior a algoritmos clássicos de reconhecimento de padrões como redes neurais e classificadores KNN. O método desenvolvido foi então combinado com estes métodos clássicos em um sistema multi-agentes. Os resultados mostram um potencial significante para aplicação operacional efetiva na construção de modelos geológicos para a exploração e desenvolvimento de áreas com grande volume de dados de perfil e intervalos testemunhados.<br>A method for the automatic detection of lithological types and layer contacts was developed through the combined statistical analysis of a suite of conventional wireline logs, calibrated by the systematic description of cores. The intent of this project is to allow the integration of rock data into reservoir models. The cores are described with support of an ontology-based nomenclature system that extensively formalizes a large set of attributes of the rocks, including lithology, texture, primary and diagenetic composition and depositional, diagenetic and deformational structures. The descriptions are stored in a relational database along with the records of conventional wireline logs (gamma ray, resistivity, density, neutrons, sonic) of each analyzed well. This structure allows defining prototypes of combined log values for each lithology recognized, by calculating the mean and the variance-covariance values measured by each log tool for each of the lithologies described in the cores. The statistical algorithm is able to learn with each addition of described and logged core interval, in order to progressively refine the automatic lithological identification. The detection of lithological contacts is performed through the smoothing of each of the logs by the application of two moving means with different window sizes. The results of each pair of smoothed logs are compared, and the places where the lines cross define the locations where there are abrupt shifts in the values of each log, therefore potentially indicating a change of lithology. The results from applying this method to each log are then unified in a single assessment of lithological boundaries The mean and variance-covariance data derived from the core samples is then used to build an n-dimensional gaussian distribution for each of the lithologies recognized. At this point, Bayesian priors are also calculated for each lithology. These distributions are checked against each of the previously detected lithological intervals by means of a probability density function, evaluating how close the interval is to each lithology prototype and allowing the assignment of a lithological type to each interval. The developed method was tested in a set of wells in the Sergipe-Alagoas basin and the prediction accuracy achieved during testing is superior to classic pattern recognition methods such as neural networks and KNN classifiers. The method was then combined with neural networks and KNN classifiers into a multi-agent system. The results show significant potential for effective operational application to the construction of geological models for the exploration and development of areas with large volume of conventional wireline log data and representative cored intervals.
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Masuda, Ryuichi. "A comparative study of the algebraic reconstruction technique and the constrained conjugate gradient method as applied to cross borehole geophysical tomography." Ohio : Ohio University, 1989. http://www.ohiolink.edu/etd/view.cgi?ohiou1182444036.
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Faroqy, Anna. "Investigating the changes in the geophysical and geotechnical properties of fine-grained soils when exposed to changes in vertically applied loads." Thesis, University of Birmingham, 2018. http://etheses.bham.ac.uk//id/eprint/8811/.
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Fine-grained soils, containing clay minerals, are known to experience potentially considerable changes in geotechnical properties when exposed to external loads. These could lead to loss of mechanical performance or catastrophic failure. Therefore, this research focuses on simple geophysical sensing techniques which could contribute to a warning system based on correlations between geotechnical and geophysical parameters. Fine-grained soils of differing plasticity were exposed to changes in vertical loading in bespoke experimental chambers. The geophysical properties investigated were apparent permittivity (AP) and bulk electric conductivity (BEC) in a kHz frequency range, measured with time domain reflectometry (TDR) and bulk electrical conductivity (EC) in a Hz frequency range, measured with electrical resistivity (ER). For what is believed to be the first time, TDR measurements were carried out continuously and in both the vertical and horizontal direction during the volumetric change of the soil, induced by changes in the loading conditions. In parallel, EC was measured, utilising the bespoke test chambers and custom-built acquisition system. Based on the results, it is envisaged that monitoring the relative change in AP and BEC over time, in conjunction with spatially distributed ER arrays, could provide temporal indication of the soil response to load under near-saturated conditions.
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Delacou, Bastien. "Tectonique et géodynamique actuelle de l'arc alpin - Approche sismotectonique et modélisation numérique." Phd thesis, Université de Nice Sophia-Antipolis, 2004. http://tel.archives-ouvertes.fr/tel-00008598.
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Le régime tectonique actuel de la chaîne des Alpes centrales/occidentales est analysé grâce à une compilation de 389 mécanismes au foyer. Cette synthèse met en évidence l'importance des phénomènes extensifs, caractérisant l'ensemble de la 'haute' chaîne. Les directions d'extension sont orientées perpendiculairement à l'orogène, tandis qu'en domaine externe, les directions de compression sont orientées en éventail perpendiculaire à l'arc alpin, dans un contexte globalement décrochant (dérivant localement vers l'extension ou la compression).<br />Un modèle de ré-équilibrage gravitaire est avancé et testé par modélisation numérique en éléments finis, d'une part en 2.5D, d'autre part en 2D (coupe ECORS). Ces études de modélisation montrent l'importance des phénomènes d'étalement gravitaire dans la chaîne, aboutissant à un régime de déformation/contraintes proche de celui observé par les outils sismotectoniques et permet de proposer un régime tectonique actuel post-collisionnel au niveau des Alpes centrales/occidentales.<br />Des études de quantifications de la déformation montrent des taux de déformation faibles, de l'ordre de 1 à 3 mm/a pour les calculs sur base GPS et de 0.1 à 0.4 mm/a pour les calculs sur une base sismologique (la différence entre les deux quantifications posant la question des déformations asismiques dans la chaîne). Les taux de rotation montrent des rotations faibles, de 2 à 2.5 degrés/Ma, probablement associé à la rotation antihoraire de la plaque Apulienne qui entraînerait la rotation antihoraire du coeur de l'arc, tandis que des rotations horaires observées en domaine externe résulteraient de la rotation de blocs situés le long des grands décrochements dextres de la bordure occidentale de l'orogène.
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Gac, Sébastien. "Modélisation numérique 3D des caractéristiques physiques des segments de dorsale lente." Phd thesis, Université de Bretagne occidentale - Brest, 2002. http://tel.archives-ouvertes.fr/tel-00008837.
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J'ai développé des modèles numériques 3D de l structure thermiques et des caractéristiques géophysiques résultants des segments de dorsale lente pour vérifier si la présence d'une zone chaude sous les centres de segment rend compte des observations géophysiques axiales et hors-axe et pour déterminer les caractéristiques d'une telle zone chaude. Les observations sur la dorsale Médio-Atlantique montrent des variations le long de l'axe des caractéristiques géophysiques des centres de segment vers leurs extrémités. Les observations hors-axe montrent l'existence de formes rhomboédriques suggérant qu'un segment s'allonge puis se raccourcit au cours du temps sur une période de 3 à 9 Ma. Dans mon modèle, la structure thermique est contrôlée par la géométrie et les dimensions d'une zone chaude permanente impose sous le centre du segment, dans laquelle est simulée la remontée adiabatique de matériel mantellique. Les processus physiques à l'origine d'une telle zone chaude ne sont pas considérés. A partir de la structure thermique, les paramètres géophysiques (anomalies gravimétriques, anomalies magnétiques, profondeur maximale des microséismes et variation axiale de l'épaisseur crustale) sont simulées et comparées à ceux observés pour identifier les dimensions et géométrie particulières de la zone chaude qui reproduisent les observations géophysiques. Les structures thermiques de différents types de segment, caractérisés par des longueurs différentes, sont déterminées de cette façon. Les modèles montrent que, les autres paramètres restant constants, l'allongement de la zone chaude est suffisant pour rendre compte de la variation des caractéristiques des différents types de segment. Cette simple évolution de la zone chaude suggère que les différents types de segment représentent différentes phases dans l'évolution d'un type unique de segment. Pour tester si une telle évolution peut rendre compte des observations hors-axe j'ai modélisé cette évolution de la zone chaude et les structure et évolution thermiques résultantes. Une telle évolution rend compte des observations hors-axe si la zone chaude s'allonge progressivement pendant 3 Ma puis se raccourcit pendant 3 Ma.
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Horning, Gregory (Gregory William). "Geophysical and geochemical constraints on the evolution of oceanic lithosphere from formation to subduction." Thesis, Massachusetts Institute of Technology, 2017. http://hdl.handle.net/1721.1/108908.
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Thesis: Ph. D., Joint Program in Oceanography/Applied Ocean Science and Engineering (Massachusetts Institute of Technology, Department of Earth, Atmospheric, and Planetary Sciences; and the Woods Hole Oceanographic Institution), 2017.<br>Cataloged from PDF version of thesis.<br>Includes bibliographical references (pages 104-115).<br>This thesis investigates the evolution of the oceanic lithosphere in a broad sense from formation to subduction, in a focused case at the ridge, and in a focused case proximal to subduction. In general, alteration of the oceanic lithosphere begins at the ridge through focused and diffuse hydrothermal flow, continues off axis through low temperature circulation, and may occur approaching subduction zones as bending related faulting provides fluid pathways. In Chapter 2 1 use a dataset of thousands of microearthquakes recorded at the Rainbow massif on the Mid-Atlantic Ridge to characterize the processes which are responsible for the long-term, high-temperature, hydrothermal discharge found hosted in this oceanic core complex. I find that the detachment fault responsible for the uplift of the massif is inactive and that the axial valleys show no evidence for faulting or active magma intrusion. I conclude that the continuous, low-magnitude seismicity located in diffuse pattern in a region with seismic velocities indicating ultramafic host rock suggests that serpentinization may play a role in microearthquake generation but the seismic network was not capable of providing robust focal mechanism solutions to constrain the source characteristics. In Chapter 3 I find that the Juan de Fuca plate, which represents the young/hot end-member of oceanic plates, is lightly hydrated at upper crustal levels except in regions affected by propagator wakes where hydration of lower crust and upper mantle is evident. I conclude that at the subduction zone the plate is nearly dry at upper mantle levels with the majority of water contained in the crust. Finally, in Chapter 4 I examine samples of cretaceous age serpentinite sampled just before subduction at the Puerto Rico Trench. I show that these upper mantle rocks were completely serpentinized under static conditions at the Mid-Atlantic Ridge. Further, they subsequently underwent 100 Ma of seafloor weathering wherein the alteration products of serpentinization themselves continue to be altered. I conclude that complete hydration of the upper mantle is not the end point in the evolution of oceanic lithosphere as it spreads from the axis to subduction.<br>by Gregory Horning.<br>Ph. D.
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Wisely, Beth, and Beth Wisely. "Geophysical and Hydrogeologic Investigations of Two Primary Alluvial Aquifers Embedded in the Southern San Andreas Fault System: San Bernardino and Upper Coachella Valley." Thesis, University of Oregon, 2012. http://hdl.handle.net/1794/12427.
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This study of alluvial aquifer basins in southern California is centered on observations of differential surface displacement and the search for the mechanisms of deformation. The San Bernardino basin and the Upper Coachella Valley aquifers are bound by range fronts and fault segments of the southern San Andreas fault system. I have worked to quantify long-term compaction in these groundwater dependent population centers with a unique synthesis of data and methodologies using Interferometric Synthetic Aperture Radar (InSAR) and groundwater data. My dissertation contributes to the understanding of alluvial aquifer heterogeneity and partitioning. I model hydrogeologic and tectonic interpretations of deformation where decades of overdraft conditions and ongoing aquifer development contribute to extreme rapid subsidence.
I develop the Hydrogeologic InSAR Integration (HII) method for the characterization of surface deformation in aquifer basins. The method allows for the separation of superimposed hydraulic and/or tectonic processes in operation. This formalization of InSAR and groundwater level integration provides opportunities for application in other aquifer basins where overdraft conditions may be causing permanent loss of aquifer storage capacity through compaction.
Sixteen years of SAR data for the Upper Coachella Valley exhibit rapid vertical surface displacement (#8804; 48mm/a) in sharply bound areas of the western basin margin. Using well driller logs, I categorize a generalized facies analysis of the western basin margin, describing heterogeneity of the aquifer. This allowed for assessment of the relationships between observed surface deformation and sub-surface material properties.
Providing the setting and context for the hydrogeologic evolution of California's primary aquifers, the mature San Andreas transform fault is studied extensively by a broad range of geoscientists. I present a compilation of observations of creep, line integrals across the Pacific-North America Plate Boundary, and strain tensor volumes for comparison to the Working Group 2007 (UCERF 2) seismicity-based deformation model. I find that the moment accumulation across the plate boundary is consistent with the deformation model, suggesting fault displacement observations within the plate boundary zone accurately capture the strain across the plate boundary.
This dissertation includes co-authored materials previously published, and also includes unpublished work currently under revisions for submission to a technical journal.
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Guichet, Xavier. "Etude expérimentale des propriétés électriques des roches; potentiels d'électrofiltration, suivi des mouvements de fluides en zones hydrothermales." Phd thesis, Université Paris-Diderot - Paris VII, 2002. http://tel.archives-ouvertes.fr/tel-00148804.
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Dans ce mémoire sont présentés des résultats expérimentaux des phénomènes d'électrofiltration pour des conditions physico-chimiques représentatives de systèmes naturels, ainsi qu'une comparaison des mesures de laboratoire avec des mesures de polarisation spontanée (PS) effectuées sur le terrain. Les résultats expérimentaux montrent que : a) la circulation d'un fluide en condictions diphasiques n'augmente pas le coefficient d'électrofiltration [Guichet et al., J.G.R., 2003] comme cela a été longtemps suspecté, b) la présence de minéraux néoformés (calcite et hydroxydes d'aluminium) peut masquer les propriétés électriques de la roche sur laquelle ils précipitent. Ainsi une inversion du signe du coefficient de couplage électrocinétique est observée avec les deux minéralogies secondaires étudiées [Guichet and Zuddas, G.R.L., 2003], rendant inexacte l'interprétation qualitative habituelle des mesures PS. <br />Des mesures de coefficients de couplage PS mesurés sur le terrain, et des analyses géochimiques de fluides ont été regroupées, et comparées à l'ensemble des données de laboratoire. L'ordre de grandeur des mesures de terrain coïncide avec l'ordre de grandeur de mesures de laboratoire, lorsque les mesures PS sont faites à proximité de sources. Sinon plusieurs hypothèses, reflétant souvent des modèles géologiques très différents, peuvent être avancées pour imputer l'origine du signal PS à des circulations de fluides ayant été échantillonnées régionalement. Finalement un suivi géochimique des fluides est indispensable pour interpréter correctement les données d'électrofiltration.<br />Enfin nous avons suivi l'électrofiltration lors de précipitation de calcite, dans la gamme de pH 4 à 12 et montré que l'électrofiltration change de signe sous certaines conditions, et interprété ces mesures par une modélisation de la triple-couche électrique [Guichet et al., G. J. I., 2006].
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Socquet, Anne. "Accommodation du mouvement relatif entre l'Inde et la Sonde depuis la faille de Sagaing (Birmanie) jusqu'à la Syntaxe Est Himalayenne." Phd thesis, Université Paris Sud - Paris XI, 2003. http://tel.archives-ouvertes.fr/tel-00006110.
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Dans cette thèse, sont présentées la façon dont est accommodé le mouvement relatif entre les blocs Inde et Sonde à l'actuel ainsi que l'évolution de la déformation de la Zone de Cisaillement Est Indienne depuis le cénozoïque.<br />J'ai utilisé une approche pluridisciplinaire, basée sur la combinaison de la géodésie spatiale et de la géologie structurale, pour répondre à ces questions. Le GPS (Global Positioning System) permet de quantifier les déplacements relatifs des plaques ainsi que les mouvements intra-continentaux instantanés. La cartographie de failles à partir d'images satellitaires et les données structurales de terrain permettent d'identifier les structures tectoniques sur lesquelles ces déplacements ont été accommodés au cours du temps, ainsi que le type de déformation qui leur est associé.<br />J'ai pu contraindre le pôle de rotation entre les plaques Inde et Sonde. Leur mouvement relatif à la frontière n'est pas accommodé sur une seule faille isolée, mais sur plusieurs structures discrètes affectant une bande large d'environ 500 km, correspondant géographiquement à la Birmanie. La faille de Sagaing, intersismiquement bloquée, n'accommode que 18 mm/an en décrochement dextre. La partie restante de la déformation est sans doute prise dans le prisme indo-birman, aussi bien en décrochement qu'en chevauchement.<br />Au nord, le système partitionné birman se connecte à la Syntaxe Est Himalayenne. La transition entre ces deux systèmes est assurée, au Yunnan Occidental (Chine), par la rotation de microblocs le long de failles sénestres NE-SW, depuis le pliocène.<br />Auparavant, entre l'éocène et le miocène, la zone de cisaillement Shan Scarp - Gaoligong Shan constituait la limite majeure dextre entre l'Inde et l'Indochine tandis que les massifs de l'Ailao / Diangcan Shan et de la Chong Shan étaient cisaillés en sénestre, autorisant un déplacement du bloc Indochinois vers le SE.
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Chambon, Guillaume. "Caractérisation expérimentale du frottement effectif des zones de faille." Phd thesis, Université Paris Sud - Paris XI, 2003. http://tel.archives-ouvertes.fr/tel-00006613.
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Nous présentons une série de résultats expérimentaux visant à modéliser le comportement mécanique d'une zone de faille. Nous avons utilisé un appareil de cisaillement simple annulaire permettant d'appliquer des cisaillements plurimétriques à des échantillons épais de gouge granulaire (sable de quartz). Nos résultats mettent en évidence un nouveau processus spectaculaire d'adoucissement en glissement: le coefficient de frottement effectif de la gouge décroît de 70% sur des distances caractéristiques décimétriques. La diminution progressive du frottement avec le glissement est bien représentée par une loi puissance sans échelle caractéristique de longueur. On constate que ce nouveau processus d'adoucissement permet de rendre compte quantitativement des distances d'adoucissement apparentes et des énergies de fracture mises en jeu durant les grands séismes. Nous proposons de l'inclure dans une extension des lois de frottement classiques de type RSF (``rate- and state-dependent friction''). Outre ces résultats macroscopiques, nous avons aussi pu mesurer, par corrélations d'images, les déformations microscopiques à l'intérieur des échantillons. Dès le début du glissement, la déformation se localise dans une bande de cisaillement broyée d'épaisseur constante. Cette bande est séparée du reste du matériau par une fine zone de transition indurée. On remarque que le processus d'adoucissement macroscopique est systématiquement associé à un effet de relaxation lente des incréments de déformation hors de la bande de cisaillement. Nous interprétons ces deux processus concomitants comme résultant d'un découplage progressif entre la bande de cisaillement et le reste de l'échantillon. L'épaisseur mécanique effective de la gouge est donc significativement plus grande que l'épaisseur de la bande de cisaillement. Nous proposons d'extrapoler nos résultats aux zones de faille naturelles, dont la structure présente souvent de fortes analogies avec celle de nos échantillons cisaillés.