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Mapa geodynamických jevů v oblasti Slanských vrchů a okolí. / Map of geodynamic phenomena in the Slanské vrchy Mts., and surrounding.Lazoríková, Monika January 2017 (has links)
The aim of the diploma thesis has been evaluation of available geodetic, geomorphological, geological and geophysical data and other possible map data, which are related to the motion and geodynamic properties in this part of Western Carpathians. The purpose has been also to evaluate possible kinematic relations and design appropriate areas for further GNSS monitoring. Especially Slanské vrchy area is located in the zone where there are no supporting GNSS points, despite the area is situated on the main tectonic breaks of eastern Slovakia. The results and all supporting materials have been processed in the GIS program and summarized in the basic geodynamic map of Slanské vrchy and the surroundings.
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Geodynamická mapa Moravy a okolí / Geodynamical Map of Moravian and surrounding.Rajnoha, Milan January 2013 (has links)
Result of this graduation theses is Geodynamic map of Moravia in scale 1:500 000. There were used available data from GPS measurements, seismic, geomorphologic and other data to construct map. Map is worked in GIS software. On the backround of researched data, there are determinated some locations, which are characterized by recent tectonic activity. These are analyzed for more detail.
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La chaîne panafricaine du Nord-Ouest de l'Angola : étude pétrostructurale, géochimique et géochronologique. Implications géodynamiques / The panafrican belt of N-W Angola : petrostructural, geochemical and geochronological constraints. Geodynamical implications.Nsungani, Pedro Claude 30 March 2012 (has links)
Cette thèse est consacrée à l'étude de l'évolution géodynamique de la chaîne panafricaine au NW de l'Angola, sur la marge occidentale du craton du Congo. Ce segment orogénique, conséquence de la convergence des cratons du São Francisco et du Congo à la fin du Néoprotérozoïque et début du Paléozoïque, peut être subdivisé en un domaine externe plissé et peu métamorphique et un domaine interne formé de roches magmatiques et métamorphiques. Les études structurales, pétrologiques, géochimiques et géochronologiques conduisent à distinguer deux unités principales dans le domaine interne : - l'unité supérieure de gneiss et micaschistes (P-Tmax : 8-12 kbar, 650-680°C) dont la déformation D1 est synchrone de la mise en place des nappes vers l'ENE; - l'unité inférieure dans la partie occidentale constituée de gneiss et migmatites (P-Tmax : 7-9 kbar, 700-750°C) affectés par une déformation polyphasée. L'étude géochronologique démontre l'existence de protolithes granitiques datés à ~2 Ga impliqués dans l'orogénèse pan africaine caractérisée par une histoire polyphasée entre 540 Ma pour le pic du métamorphisme syn-D1 et 480 Ma pour les dernières phases de recristallisation et d'exhumation des roches métamorphiques de haut grade. La synthèse des données permet ainsi de reconstruire précisément les deux chemins P-T-D-t de ces deux unités tectono-métamorphiques et de comparer ce segment panafricain à ceux présents de part et d'autre de l'Atlantique Sud. Ce travail témoigne de la complexité des processus géodynamiques de convergence amenant à l'assemblage du Gondwana impliquant à la fois de larges masses cratoniques et des microplaques intercalées entre ces masses. / This thesis is devoted to the study of the geodynamic evolution of the panafrican belt in NW Angola, lying on the western margin of the Congo craton. This orogenic belt, resulting from the late neoproterozoic – early paleozoic convergence of the São Francisco and Congo cratons, can be subdivided into two main domains: 1) an eastern foreland made of folded neoproterozoic sediments and 2) a western hinterland made of magmatic and metamorphic rocks. Our structural, petrological, geochemical and geochronological studies lead to the recognition of two main units within this hinterland : 1) an upper eastern unit made of gneiss and micaschists (P-Tmax : 8-12 kbar, 650-680°C) that preserves D1 deformation structures related to the ENE transport of nappes and 2) a western lower unit made of gneiss and migmatites (P-Tmax : 7-9 kbar, 700-750°C) that were affected by a polyphased deformation. Our geochronological study shows that this belt contains ~2Ga old granites that were involved in a polyphased panafrican evolution between 540 Ma for syn-D1 peak metamorphic conditions and 480 Ma for the last stages of recrystallization and exhumation of high grade rocks. The synthesis of all data leads to a precise reconstruction of P-T-D-t paths in both tectono-metamorphic units and to comparison of this panafrican belt with similar belts distributed on both sides of the Atlantic ocean. This work attests of the complexity of the geodynamic processes resulting in the Gondwana assembly and implying both large cratonic landmasses and intercalated microplates.
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Studium současných geodynamických procesů v oblasti hronovsko-poříčského zlomového pásma / Study of present-day geodynamic processes in the area of Hronov-Poříčí Fault ZoneStejskal, Vladimír January 2011 (has links)
The presented PhD thesis deals with present-day geodynamic processes in the south- western part of Broumov Highland, with a special attention paid to the seismoactive Hronov- Poříčí Fault Zone (HPFZ). Compared to the rest of the Bohemian Massif the studied area exhibits relatively increased level of tectonic activity, which is evidenced by local seismicity and by presence of CO2-rich mineral waters. The present-day activity of geodynamic processes is studied by means of various geomorphological, geotechnical, geophysical and hydrological methods. Following processes and features were studied: activity of slope movements, seismic activity, present-day tectonic movements, relations between landforms and joint and fault tectonics. Based on the previous experience obtained by the author in the seismoactive area of Western Bohemia, groundwater observational network was set up in deep boreholes, in order to detect anomalies related to the tectonic activity of the studied area. The thesis represents a contribution to the deeper understanding of the studied area and also a contribution in respect of possible applications of some new methods that can be used in research of zones with relatively increased tectonic activity inside of stable areas of Central Europe. From geomorphological point of view, the...
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Žemės plutos judesių įvertinimo sudarant geodezinius tinklus tyrimas / Research of the earth crust movement evaluation creating geodetic networksKirklytė, Giedrė 05 June 2012 (has links)
Dabartiniai geodinaminiai procesai žemės paviršiuje pasireiškia vertikaliaisiais ir horiznotaliaisiais žemės plutos judesiais. Dėl vykstančių žemės plutos judesių keičiasi geodezinių ženklų padėtis, o dėl šios priežasties matavimų rezultatai bėgant laikui netenka reikalaujamo tikslumo. Darbo tikslas – ištirti vertikaliųjų žemės plutos judesių įtaką vertikaliesiems geodeziniams tinklams (Lietuvos vertikaliojo geodezinio tinklo pirmojo poligono pavyzdžiu). Tyrimo uždaviniai – atlikti literatūros šaltinių apžvalgą ir išnagrinėti dabartinių žemės plutos judesių vertinimo metodikas, atlikti vertikaliųjų žemės plutos judesių įtakos vertikaliajam geodeziniam tinklui tyrimą ekperimentiniame objekte, apibendrinti tyrimo rezultatus bei pateikti išvadas ir rekomendacijas. Tyrimo metodas – ekpserimentiniai ir analitiniai tyrimai. Iš atliktų tyrimų nustatyta, kad dėl vykstančių geodinaminių procesų apskaičiuotų pataisų reikšmė geodeziniams matavimams yra ne mažesnė už normalinių pataisų reikšmę. Įvertinant žemės plutos judesius, geodezinių ženklų aukščiai eksperimentiniame poligone kinta iki 18 mm, o geodinaminės pataisos yra nuo 3 iki 5 kartų didesnės už leistinas paklaidas. Daroma išvada, kad būtina įvertinti dabartinius žemės plutos judesius. / Recent geodynamic processes in the earth's surface appears by horizontal and vertical movements of the earth's crust. Because of these movements, geodetic marks change their position. Geodetic networks and geodetic measurements lose the required accuracy over the time. It is influenced by vertical movements of the earth's crust. Masters thesis aim - to investigate the vertical movements of the earth's crust affect for the vertical geodetic networks (the first polygon of Lithuanian geodetic vertical network). Masters thesis tasks – to make a literature review, examine the earth's crust movements evaluation methodologies, find out how vertical earth’s crust movement influence geodetic measurements, summarize the results and present conclusions and recommendations. Master thesis method – experimental and analytical investigation. Considering the earth's crust movements, the heights of the experimental character of geodesic polygon varies up to 18 mm, and the geodynamic corrections from 3 to 5 times are higher than the allowable correction. To sum up, the vertical earth’s crust movement impact must be evaluated. Structure: introduction, four chapters, conclusions and suggestions, six appendixes.
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Mapa geodynamických jevů v oblasti Nízkých Tater / Map of geodynamic phenomena in Lower Tatra areaJackulíková, Denisa January 2017 (has links)
This investigative thesis provides an overview of the structural and kinematic formation of the Low Tatras in Slovakia. Numerous geological and geomorphological data from previous studies of the researched area were available. These were processed in a graphical user interface ArcMap to produce the Geodynamic map of Low Tatras at a scale of 1:200 000. By illustrating geodetic, geomorphologic, geophysical and other similar data on this map, it was possible to undertake a detailed analysis of the area and allow an assessment of the overall tectonic activity. This revealed two regions with higher than normal stress levels and therefore an associated increase in the risk of future seismic activity.
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Mapeamento geotécnico aplicado ao planejamento do uso e ocupação do solo da cidade de Pelotas/RS : estudo voltado à expansão urbanaXavier, Sinval Cantarelli January 2017 (has links)
O crescimento acelerado das cidades associado à ausência, inadequação ou ineficácia do planejamento urbano, no Brasil, tem acarretado o desequilíbrio dos sistemas ambientais e a imposição de riscos a parcelas significativas da população. Muito embora as numerosas críticas aos modelos de planejamento aplicados no País, o urbanismo continua desempenhando um papel fundamental na organização e desenvolvimento das cidades. A leitura e avaliação das potencialidades e limitações do meio físico urbano são essenciais ao processo de planejamento, organização e controle do uso do solo; sendo assim, a cartografia geotécnica desempenha um papel de relevância no enfrentamento dos problemas inerentes à ação do homem sobre o meio físico. Mas, apesar do considerável desenvolvimento da cartografia geotécnica nacional, ainda são necessários avanços no que se refere à sua aplicação ao ambiente urbano e ao planejamento, bem como uma melhor adequação à realidade econômica e instrumental da maioria dos municípios brasileiros, em especial os de médio e pequeno porte. O presente trabalho pretende contribuir com o desenvolvimento de instrumentos de auxílio ao planejamento do crescimento sustentável da cidade, através da estruturação de um procedimento progressivo de mapeamento geotécnico que incorpora a análise do crescimento da cidade como etapa de seu desenvolvimento. Aplicado ao município de Pelotas/RS, o método tem por base o uso de dados pré-existentes e objetivou a produção de mapas de suscetibilidade e da carta de aptidão à urbanização, aplicáveis ao planejamento territorial urbano Partindo da etapa de inventário e passando pela fase de preparação e geração de dados, o mapeamento foi desenvolvido através da etapa geral e de semi-detalhe do método progressivo, nas quais os atributos do meio físico foram cruzados por meio de análise multivariada e uso de Sistema de Informações Geográficas. O mapeamento dos vazios urbanos e a modelagem e simulação do crescimento da cidade permitiram o direcionamento das etapas finais de mapeamento e a redução das análises geotécnicas às áreas territoriais de urbanização futura, reduzindo esforços e otimizando o processo como um todo. A aplicação do método produziu um grande número de informações, mapas, cartas e caracterizações do meio físico, com larga possibilidade de utilização no planejamento do crescimento futuro da cidade e na implantação de medidas corretivas aos problemas e conflitos decorrentes do processo de urbanização passada. Os resultados alcançados indicam tanto a validade da metodologia para o estudo em particular, quanto seu potencial de utilização, parcial ou total, a outras realidades fisiográficas. Através da contraposição da legislação urbanística, do processo de crescimento da cidade e dos produtos do mapeamento, foi possível concluir que a inexistência da informação geológico-geotécnica foi determinante na ocupação de áreas de muito baixa e baixa aptidão à urbanização na zona urbana do município de Pelotas. Tal constatação reforça, assim, a importância do uso da informação geológicogeotécnica no planejamento e na gestão urbana nacional. / The accelerated growth of towns associated with the absence, inadequacy or low efficiency of urban planning in Brazil has caused changes of environmental systems and the imposition of risks to significant portions of the population. Despite the numerous criticisms of the planning models applied in the country, urban planning continues to play a fundamental role for the sustainable organization and development of the towns. The analysis and evaluation of the potentialities and limitations of the urban physical environment is essential to the process of planning, organization and control of land use. Therefore, Geotechnical Cartography plays a very important role in facing the problems inherent in the action of man on the physical and natural environment. But, despite the considerable development of the National Geotechnical Cartography, it is still necessary to make progress in its application to the urban environment and planning, as well as a better adaptation to the economic and instrumental reality of the great majority of Brazilian municipalities, especially those of medium and small sizes. The present work intends to contribute with the development of tools to support the planning of towns sustainable growth through the structuring of a progressive geotechnical mapping procedure which incorporates the city growth analysis. Applied to the town of Pelotas / RS, the method uses pre-existing data and had the objective to produce maps of susceptibility and urbanization suitability map applicable to planning Starting from the inventory stage and going through the preparation and generation of data, the mapping was developed through the general and semi-detailled stages of the progressive method. In this case the attributes of the physical medium, represented by of Information Plans on Geographic Information System, were combined through multivariate analysis. The mapping of the urban voids and the modeling and simulation of the city growth allowed the concentration of the final stages of mapping, and the geotechnical analysis, only to the areas of future urbanization, reducing efforts and optimizing the whole process. The results indicate the validity of the method and its capacity to contribute in the regulation of land use in the study area, with potential to use in other situations. By comparing the urban legislation and the spatial growth of the town with the mapping products it was observed that the lack of geotechnical information was determinant in the past occupation of areas of very low and low aptitude for urbanization in Pelotas. This reinforces the importance of utilizing geological-geotechnical information in urban planning and management in Brazil.
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Modeling onshore-offshore based in wide-angle seismic data across the Alagoas-Sergipe passive margins, NE Brazil / Modélisation onshore-offshore basé en données de sismique grand angle à travers des marges passives de Alagoas et Sergipe, NE BrésilPinheiro, João Marcelo 20 December 2017 (has links)
La présente thèse s'insère dans le projet SALSA (Sergipe Alagoas Seismic Acquisition), mené en collaboration entre le Département de Géosciences Marines; I'IFREMER, I'IUEM, la Faculté des sciences de I'Université de Lisbonne (IDL, Portugal), I'Université de Brasilia (Brésil) et la PETROBRAS (Brésil). Des acquisitions conjointes de sismique réflexion (MCS) et de sismique grand-angle (OBS) ont été réalisées sur le N/O L'Atalante (IFREMER) Ie long de 12 profils sur la région du point triple de Camamú, NE, Brazil. Le point triple de Camamú, où le système de rift avorté Recôncavo-Tucano-Jatobá est relié aux systèmes de rift Jequitinhonha-Camamú-Almada et Jacuípe-Sergipe-Alagoas, a joué un rôle essentiel dans l'ouverture de I'océan Atlantique Sud. Parmi eux, cinq ont été prolongés à terre par des stations sismiques terrestres (LSS). Les modèles de vitesse d'onde P ont été construits sur Ia base de I'interprétation conjointe de données sismiques réflexion et grand-angle en utilisant le logiciel RAYINVR. Nous présentons des modèles de vitesse le long de deux profils parallèles situés dans le bassin de Sergipe-Alagoas (SL01 et SL02), s'étendant sur 220 km et 200 km, respectivement du plateau continental au bassin profond de Sergipe au nord de la zone de transfert de Vaza-Barris. L'un d'eux, le profil SL02 se prolonge sur 150 km à travers le continent, dans la partie continentale du bassin de Sergipe -Alagoas. La modélisation de la marge passive du bassin de Sergipe Alagoas contraint précisément les géométries crustales et la segmentation. Les différences entre les profils éclairent I'influence de I'héritage tectonique résultant de Ia zone de transfert de Vaza-Barris. Ces informations intégrées permettent de nouvelles conjectures autour de I'histoire géodynamique de la région. / The present thesis is inserted in the SALSA project (Seryipe Alagoas Seismic Acquisition), which was conducted by a collaboration between the Department of Marine Geosciences : IFREMER, the Laboratory of Oceanic Domain IUEM, the Faculdade de Ciências da Universidade de Lisboa (IDL, Portugal), the Universidade de Brasilia (Brazil) and PETROBRAS (Brazil).Seismic shot, Multi-Channel Seismic acquisition (MCS) and Ocean Bottom Seismometers (OBS) deployments were performed by the R/V L'Atalante (IFREMER) along 1-2 profiles.Among them, five were extended onshore by Land Seismic Stations (LSS). P-wave velocity models were constructed based on the joint interpretation of multichannel and wide-angle seismic data using the RAYINVR software.We present models derived from wide-angle refraction and coincident reflection data along two parallel profiles located on the Sergipe-Alagoas basin (SL01 and SL02), extending approximately 220 km and 200 km from the continental shelf to the distal Sergipe basin north to the Vaza-Barris Transfer zone, and one of them, the SL02 prolongates for 150 km through the continent, on Sergipe -Alagoas continental basin and its basement, the Sergipana FoId Belt.The foward modelling of the passive margin in the Sergipe Alagoas basin precisely constrains crustal geometries and segmentation. The crustal geometry puts in question the origin of the Sergipana Fold Belt, when compared with the geometries of the adjacent geological domains, the Sao Francisco Craton and the Borborema Province.The differences between the profiles illuminate the influence of the tectonic inheritance resulted by the Vaza-Barris Transfer Zone. These integrated information allowed some new conjectures around the geodynamic history of the region.
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Origin and evolution of two distinct Cretaceous oceanic plateaus accreted in Western Ecuador (South America) : Petrological, geochemical and isotopic evidenceMamberti, Marc 04 April 2001 (has links) (PDF)
La géologie de l'Equateur se distingue de celle du reste des Cordillères andines par la présence de terrains océaniques qui s'accrètent successivement à la marge depuis la fin du Crétacé jusqu'au Paléocène. Ces terrains exotiques sont constitués de fragments de deux plateaux océaniques du Crétacé inférieur (123 Ma) et supérieur (90 Ma) et de plusieurs arcs insulaires (100 à 40 Ma). Dans la Cordillère occidentale, le plateau crétacé inférieur et les terrains océaniques du crétacé supérieur (plateau et arcs insulaires) s'accrètent respectivement à 85-80 Ma et 70-65 Ma. Le plateau océanique daté à 123 Ma est constitué: (i) de cumulats basiques et ultrabasiques (série de San Juan) et (ii) de basaltes en coussins et de dolérites massives recoupés par des petites intrusions de gabbro sub-doléritique. Les cumulats forment une série continue depuis des dunites et wehrlites jusqu'à des gabbros à clinopyroxène. Basaltes, dolérites et gabbros présentent tous les caractères de basalte de plateau océanique (OPB; MgO = 7%; spectres de terres rares plats, pas d'anomalie négative en Nb et Ta). Les compositions isotopiques (Nd et Pb) des cumulats et de l'ensemble basalte-dolérite sont identiques et démontrent que toutes ces roches dérivent d' une source mantellique enrichie. Les picrites et les basaltes enrichis ou non en MgO, associés à des dolérites et des gabbros, représentent des témoins accrétés du plateau océanique crétacé supérieur caraïbe. Les picrites (MgO -20 %) sont appauvries en terres rares légères, peu radiogéniques en Pb et caractérisées par des eNd élevés (+8 à +10). Les basaltes riches en MgO (9-10%) sont enrichis en terres rares légères. La géochimie en éléments traces des basaltes pauvres en MgO est identique à celle d'OPB. Par contre, les rapports isotopiques du Pb des basaltes, riches en MgO ou non, sont très élevés indiquant que toutes ces laves dérivent d'une source enrichie de type HIMU, caractère commun à tous les basaltes du plateau caraïbe .
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Three-dimensional thermo-mechanical modeling of deformation at plate boundaries : case study San Andreas Fault SystemPopov, Anton January 2008 (has links)
It has always been enigmatic which processes control the accretion of the North American terranes towards the Pacific plate and the landward migration of the San Andreas plate boundary. One of the theories suggests that the Pacific plate first cools and captures the uprising mantle in the slab window, and then it causes the accretion of the continental crustal blocks. The alternative theory attributes the accretion to the capture of Farallon plate fragments (microplates) stalled in the ceased Farallon-North America subduction zone. Quantitative judgement between these two end-member concepts requires a 3D thermomechanical numerical modeling. However, the software tool required for such modeling is not available at present in the geodynamic modeling community.
The major aim of the presented work is comprised basically of two interconnected tasks. The first task is the development and testing of the research Finite Element code with sufficiently advanced facilities to perform the three-dimensional geological time scale simulations of lithospheric deformation. The second task consists in the application of the developed tool to the Neogene deformations of the crust and the mantle along the San Andreas Fault System in Central and northern California.
The geological time scale modeling of lithospheric deformation poses numerous conceptual and implementation challenges for the software tools. Among them is the necessity to handle the brittle-ductile transition within the single computational domain, adequately represent the rock rheology in a broad range of temperatures and stresses, and resolve the extreme deformations of the free surface and internal boundaries. In the framework of this thesis the new Finite Element code (SLIM3D) has been successfully developed and tested. This code includes a coupled thermo-mechanical treatment of deformation processes and allows for an elasto-visco-plastic rheology with diffusion, dislocation and Peierls creep mechanisms and Mohr-Coulomb plasticity. The code incorporates an Arbitrary Lagrangian Eulerian formulation with free surface and Winkler boundary conditions.
The modeling technique developed is used to study the aspects influencing the Neogene lithospheric deformation in central and northern California. The model setup is focused on the interaction between three major tectonic elements in the region: the North America plate, the Pacific plate and the Gorda plate, which join together near the Mendocino Triple Junction. Among the modeled effects is the influence of asthenosphere upwelling in the opening slab window on the overlying North American plate. The models also incorporate the captured microplate remnants in the fossil Farallon subduction zone, simplified subducting Gorda slab, and prominent crustal heterogeneity such as the Salinian block.
The results show that heating of the mantle roots beneath the older fault zones and the transpression related to fault stepping, altogether, render cooling in the slab window alone incapable to explain eastward migration of the plate boundary. From the viewpoint of the thermomechanical modeling, the results confirm the geological concept, which assumes that a series of microplate capture events has been the primary reason of the inland migration of the San Andreas plate boundary over the recent 20 Ma. The remnants of the Farallon slab, stalled in the fossil subduction zone, create much stronger heterogeneity in the mantle than the cooling of the uprising asthenosphere, providing the more efficient and direct way for transferring the North American terranes to Pacific plate.
The models demonstrate that a high effective friction coefficient on major faults fails to predict the distinct zones of strain localization in the brittle crust. The magnitude of friction coefficient inferred from the modeling is about 0.075, which is far less than typical values 0.6 – 0.8 obtained by variety of borehole stress measurements and laboratory data. Therefore, the model results presented in this thesis provide additional independent constrain which supports the “weak-fault” hypothesis in the long-term ongoing debate over the strength of major faults in the SAFS. / Seit jeher rätselhaft sind die Prozesse, die die Akkretion der Nordamerikanischen Terranen in Richtung der Pazifischen Platte sowie die Wanderung der Plattengrenze der San-Andreas-Verwerfung in Richtung Festland bestimmen. Eine Theorie besagt, dass sich die Pazifische Platte erst abkühlt und den aufsteigenden Mantel im „Slab Window“ fängt und somit die Akkretion der kontinentalen Krustenblöcke bewirkt. Die andere Theorie geht von einer Akkretion durch das Fangen von Teilen der Farallon-Platte (Mikroplatten) aus, die in der inaktiven nordamerikanischen Farallon-Subduktionszone fest stecken. Die quantitative Beurteilung dieser beiden gegensätzlichen Konzepte erfordert eine thermomechanische numerische 3-D-Modellierung. Das dafür benötigte Software Tool steht jedoch der geodynamischen Modellierung derzeit noch nicht zur Verfügung.
Das Hauptziel der vorliegenden Arbeit umfasst im Wesentlichen zwei miteinander verbundene Aufgaben. Die erste besteht in der Entwicklung und Erprobung des Finite-Element-Codes, dessen Eigenschaften den hohen Anforderungen an die Ausführung der dreidimensionalen Simulationen lithosphärischer Deformation auf geologischer Zeitskala gerecht werden müssen. Die zweite Aufgabe ist die Anwendung des entwickelten Tools auf die neogenen Deformationen der Kruste und des Mantels entlang der San-Andreas-Verwerfung in Zentral- und Nordkalifornien.
Die Modellierung auf geologischer Zeitskala lithosphärischer Deformation bringt für die Software Tools in Bezug auf Konzept und Durchführung zahlreiche Herausforderungen mit sich. Unter anderem gilt es, den Brittle-Ductile-Übergang in einem einzigen Modell sowie die Gesteinsrheologie in einer breiten Spanne unterschiedlicher Temperaturen und Spannungen adäquat darzustellen und die extremen Deformationen der freien Oberfläche und internen Grenzen aufzulösen. Im Rahmen der vorliegenden Arbeit erfolgte die erfolgreiche Entwicklung und Erprobung des neuen Finite-Element-Codes (SLIM3D). Dieser Code beinhaltet eine gekoppelte thermomechanische Behandlung von Deformationsprozessen und ermöglicht eine elasto-visko-plastische Rheologie mit Diffusion, Dislokation, Peierls Kriechmechanismen und Mohr-Coulomb-Plastizität. Der Code verbindet eine Arbitrary Lagrangian-Eulerian kinematische Formulierung mit freien Oberflächen- und Winkler-Randbedingungen.
Das entwickelte Modellierungsverfahren wird für die Untersuchung der Aspekte verwendet, die die neogene lithosphärische Deformation in Zentral- und Nordkalifornien beeinflussen. Die Modellanordnung konzentriert sich auf die Interaktion zwischen drei großen tektonischen Elementen in dieser Region: die Nordamerikanische Platte, die Pazifische Platte sowie die Gorda-Platte, die sich in der Mendocino-Triple-Junction treffen. Unter anderem verdeutlicht die Modellierung den Einfluss des Aufsteigens der Asthenosphäre in das sich öffnende „slab window“ der übergelagerten Nordamerikanischen Platte. Die Modelle beziehen auch die angelagerten Überreste der Mikroplatten in der fossilen Farallon-Subduktionszone, die vereinfachte subduzierende Gorda-Platte sowie markante Heterogenitäten der Kruste, wie beispielsweise den „Salinian Block“, mit ein.
Die Ergebnisse zeigen, dass die Erwärmung der Mantellithosphäre unter den älteren Störungszonen sowie die Transpression eine Abkühlung im „Slab Window“ als alleinige Begründung für die Ostwärtsbewegung der Plattengrenze nicht zulassen. Aus Sicht der thermomechanischen Modellierung bestätigen die Ergebnisse das geologische Konzept, welches durch das mehrmalige Fangen von Mikroplatten den Hauptgrund für die Wanderung der Plattengrenze der San-Andreas-Verwerfung in Richtung Festland über die letzten 20 Millionen Jahre sieht. Die Überreste der Farallon-Platte, die in der fossilen Subduktionszone gefangen sind, verursachen im Mantel eine wesentlich stärkere Heterogenität als die Abkühlung der Asthenosphäre und stellen somit den effizienteren und direkteren Weg für die Anlagerung der nordamerikanischen Gebiete an die Pazifische Platte dar.
Die Modelle demonstrieren, dass ein hoher effektiver Reibungskoeffizient an großen Störungen nicht in der Lage ist, die eindeutigen Zonen der Dehnungslokalisierung in der spröden Kruste vorherzusagen. Die Größe des Reibungskoeffizienten, die sich aus der Modellierung ableitet, beträgt etwa 0,075 und ist damit wesentlich kleiner als die durch unterschiedliche Bohrlochmessungen und Labordaten ermittelten Spannungswerte zwischen 0,6 und 0,8. Daher liefern die in dieser Arbeit präsentierten Ergebnisse der Modelle in der seit langem geführten Debatte über die Stärke von großen Störungen in der San-Andreas-Verwerfung eine zusätzliche unabhängige Begründung der „Weak-Fault“-Hypothese.
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