De par leurs magnitudes élevées et leur potentiel tsunamigénique, les séismes qui se produisent en contexte de subduction présentent un risque majeur pour les villes côtières souvent densément peuplées. La compréhension de la géométrie et du fonctionnement des zones de failles associées à ces ruptures sismiques a donc fait l'objet de nombreuses recherches sismologiques et géologiques.L’objectif de cette thèse est centré sur la caractérisation des zones de failles paléo-sismiques traversant des formations ophiolitiques subductées puis exhumées en surface des continent et sur leur comparaison avec les zones sismogéniques actuelles. Elle s’appuie sur une approche multi-échelle faisant intervenir les outils de la géologie structurale, de la pétrographie microstructurale, de la minéralogie, de la géochimie ainsi que les données de la géophysique. Le cas de la Corse alpine, de par la présence de nombreuses pseudotachylytes (étant considérées comme des fossiles de séismes) mafiques et ultramafiques constitue un cas d’étude idéal.La rupture sismique dans la nappe du Cima di Gratera est matérialisée par des réseaux de pseudotachylytes parallèles ou à fort pendages situées de part et d’autre de la discontinuité tectonique séparant les unités ultramafiques et mafiques formant la nappe. Le système de faille est caractérisé par une cinématique vers l’ouest associée à la subduction de la plaque océanique liguro-piémontaise sous la plaque adriatique. Les analyses minéralogiques des microlites présentes dans les pseudotachylytes mafiques indiquent une formation des veines en contexte de pression et température du facies eclogite, correspondant à une profondeur comprise entre 60 et 70 km, soit le début de la zone de sismicité dite de profondeur intermédiaire. La géométrie du système de faille a également pu être comparée à des géométries observées via la géophysique au large du nord-est Japon et à des profondeurs similaires.A également été mis en lumière l’impact de la serpentinisation sur le caractère sismique / asismique des discontinuités tectoniques faisant intervenir des formations mafiques et ultramafiques. En effet, la fusion frictionnelle issue des ruptures sismiques et responsable de la formation des veines de pseudotachylytes n’a été observée que dans le cas où était mis en contact la péridotite fraiche ou faiblement serpentinisée et le métagabbro. Les contacts impliquant la serpentinite et le métagabbro n’en présentent jamais et peuvent donc être considérés comme asismiques. Au regard de l’épaisseur des réseaux de pseudotachylytes dans les masses de péridotite et de leur absence dans les serpentinites, les masses de péridotites peuvent donc être assimilées à des aspérités au sein même de la plaque plongeante. / By their high magnitude and their ability to generate tsunami, subduction earthquakes present a major risk for the high population density coastal cities. The understanding of the geometry and the functioning of these seismogenic fault zones was the subject of numerous seismogenic and geologic studies.The objective of this thesis is focus on the characterization of paleo-seismic fault zones cross-cutting subducted ophiolitic formation and exhumed on the continent surface, and their comparison with current seismogenic zones. This study is based on a multi-scale approach and involves structural geology, microstructural petrography, mineralogy, geochemistry and geophysics tools. The Alpine Corsica, by the presence of numerous mafic and ultramafic pseudotachylytes (considered as fossils of past earthquakes) can be considered as an ideal study case.The seismic rupture in the Cima di Gratera Nappe is materialized by pseudotachylyte networks parallel or with a steep dipping to the fault separating the mafic and ultramafic units. The fault system is characterized by a top-to-the-west kinematic associated to the Piemonte-Liguria oceanic plate subduction under the Adriatic plate. The mineralogical analyses of the mafic pseudotachylyte microlites indicate a formation under a pressure and temperature conditions of the eclogite metamorphic facies. These conditions are consistent with a depth between 60 and 70 km which correspond to the upper part of the intermediate-depth seismicity zone. The geometry of the fault system was also compared to some geometry observed by the geophysics in the NE Japan subduction zone and at similar depth.It was also highlighted the role of the serpentinization on the seismic / aseismic character of the fault involving the mafic and ultramafic formations. Indeed, frictional melting resulting from the seismic rupture responsible to the pseudotachylyte veins formation was only observed in the case where the fresh peridotite or weakly serpentinized peridotite is in contact with the metagabbro. By opposition, the deformed zones involving the serpentinite and the metagabbro never show any pseudotachylyte and can be considered as aseismic. Considering the thickness and the polyphaser character of the pseudotachylyte networks and their absence in the serpentinite, the peridotite masses can be considered as asperities within the plate itself.

Study of pseudotachylytes (PT) (frictional melts) can provide information on the physical and chemical conditions at the earthquake source. This study examines the influence of asperityscale fault dynamics on asperity temperature distribution, and therefore, the potential for frictional melting to occur. Frictional melting occurs adiabatically, and is initiated between opposing asperity tips during fault slip. Our model considers 2-D heat conduction in elastic, isotropic, hemispherical asperities, with temperature dependent thermal properties. The only heat source is a point heat flux pulse at the asperity tip. The non-linear problem was solved using the -form of Newton-Kantorovich procedure coupled with the -form of Douglas-Gunn two level finite difference scheme, while the linear problem required only the latter method. Results for quartz and feldspar indicate that peak temperatures can reach melting point values for typical asperity sizes (1-100 mm), provided that contact (frictional) shear stress is sufficiently high. For any asperity size, the temperature distribution peak becomes insignificant by the time it reaches the asperity center. These results imply that much of asperity scale melting is highly localized, which may explain why most PT veins in the field are usually very thin. However, in some cases, successive asperity encounters may generate temperature increases large enough to trigger the massive melting inferred from typical PT exposures. Significant differences were observed between the results of the linear and nonlinear models.

Made available in DSpace on 2014-06-11T19:32:22Z (GMT). No. of bitstreams: 0 Previous issue date: 2003-12-12Bitstream added on 2014-06-13T19:42:57Z : No. of bitstreams: 1 ribeiro_lfb_dr_rcla.pdf: 2783705 bytes, checksum: e1a426bdf710fbec9239ad48c9b2b00a (MD5) / O embasamento cristalino precambriano no sudeste do Brasil registra uma história tectônica fanerozóica que compreende uma série de reativações tectônicas caracterizadas por soerguimentos, subsidências e reativações de falhas. Para quantificar, datar e associar estas reativações com os eventos tectônicos regionais foram realizadas análises de caráter multidisciplinar, que consistem em reconhecimento de superfície erosivas, bem como delimitação e reconhecimento de depósitos correlativos. Com o intuito de reconhecer e quantificar feições de caráter rúptil, foi realizada análise dinâmica de falhas que inclui paleotensões e reconhecimento da rugosidade de clastos. A interação destas metodologias necessitou de uma associação temporal dos eventos, para isto foi feita datações pelo método Ar/Ar em material de falha e traços de fissão em apatitas próximo a falhas. Os resultados do campo de esforços com a geomorfologia permitiram definir cinco domínios morfoestruturais principais, onde foram registrados antigos eventos tectônicos recorrentes ao longo do Fanerozóico. Estes domínios foram denominados de acordo com o reconhecimento geográfico já proposto para a área, assim temos: A serrania de São Roque, O Planalto de Jundiaí, Mantiqueira Ocidental e Depressão de Cambuí e Planalto de Campos do Jordão. Os episódios tectônicos associados a estes domínios estão relacionados a soerguimentos e nos domínios Serrania de São Roque e Planalto de Jundiaí a geração e deformação de materiais de falha (pseudotaquilitos). Estes soerguimentos preservaram paleosuperfícies erosivas em cotas mais altas, que são indicativas de antigos ciclos de erosão, estas são observadas, principalmente nos domínios Mantiqueira Ocidental e Planalto de Campos do Jordão... / Phanerozoic tectonic histories of basement is registred many reactivations of faults, uplifts and subsidence. To quantify, dater and to associate this reactivations with tectonics events are multidisciplinary analyses, consists relief analysis, paleostress analysis, and structural analysis of faults, fission track and Ar/Ar ages. The results to permit subdivide area in five domains, to registry uplift and reactivation of faults. This faults to origin pseudotachylytes, these rocks . The uplift to basement relation with subsidence of Parana basin showing one complex relation between the basement and the deposition of Parana basin. The evolution of this basin seems to have been strongly influenced by compressive and distensive events associated to the subduction of Panthalassan plate under the southwestern, Gondwana margin, reflected as important unconformities in the stratigraphic framework of the Parana basin the elucidation of the uplift and denudation histories of the basement shield is crucial to the understanding of these tectonics effects.

Orientador: Peter Christian Hackspacher / Banca: Julio César Hadler Neto / Banca: Cláudio Coelho de Lima / Banca: Iandara Alves Mendes / Banca: Norberto Morales / Resumo: O embasamento cristalino precambriano no sudeste do Brasil registra uma história tectônica fanerozóica que compreende uma série de reativações tectônicas caracterizadas por soerguimentos, subsidências e reativações de falhas. Para quantificar, datar e associar estas reativações com os eventos tectônicos regionais foram realizadas análises de caráter multidisciplinar, que consistem em reconhecimento de superfície erosivas, bem como delimitação e reconhecimento de depósitos correlativos. Com o intuito de reconhecer e quantificar feições de caráter rúptil, foi realizada análise dinâmica de falhas que inclui paleotensões e reconhecimento da rugosidade de clastos. A interação destas metodologias necessitou de uma associação temporal dos eventos, para isto foi feita datações pelo método Ar/Ar em material de falha e traços de fissão em apatitas próximo a falhas. Os resultados do campo de esforços com a geomorfologia permitiram definir cinco domínios morfoestruturais principais, onde foram registrados antigos eventos tectônicos recorrentes ao longo do Fanerozóico. Estes domínios foram denominados de acordo com o reconhecimento geográfico já proposto para a área, assim temos: A serrania de São Roque, O Planalto de Jundiaí, Mantiqueira Ocidental e Depressão de Cambuí e Planalto de Campos do Jordão. Os episódios tectônicos associados a estes domínios estão relacionados a soerguimentos e nos domínios Serrania de São Roque e Planalto de Jundiaí a geração e deformação de materiais de falha (pseudotaquilitos). Estes soerguimentos preservaram paleosuperfícies erosivas em cotas mais altas, que são indicativas de antigos ciclos de erosão, estas são observadas, principalmente nos domínios Mantiqueira Ocidental e Planalto de Campos do Jordão... (Resumo completo, clicar acesso eletrônico abaixo) / Abstract: Phanerozoic tectonic histories of basement is registred many reactivations of faults, uplifts and subsidence. To quantify, dater and to associate this reactivations with tectonics events are multidisciplinary analyses, consists relief analysis, paleostress analysis, and structural analysis of faults, fission track and Ar/Ar ages. The results to permit subdivide area in five domains, to registry uplift and reactivation of faults. This faults to origin pseudotachylytes, these rocks . The uplift to basement relation with subsidence of Parana basin showing one complex relation between the basement and the deposition of Parana basin. The evolution of this basin seems to have been strongly influenced by compressive and distensive events associated to the subduction of Panthalassan plate under the southwestern, Gondwana margin, reflected as important unconformities in the stratigraphic framework of the Parana basin the elucidation of the uplift and denudation histories of the basement shield is crucial to the understanding of these tectonics effects. / Doutor