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Alsaif, Manar. "Upper plate deformation in retreating subduction zones." Thesis, Montpellier, 2019. http://www.theses.fr/2019MONTG026.
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La surface de la Terre est en permanence remodelée par les mouvements des plaques tectoniques, dont le moteur principal est la subduction, i.e. le plongement de plaques océaniques dans le manteau profond. Les fosses océaniques de subduction constituent également des limites de plaques mobiles, et les observations montrent que, sur des échelles de temps géologiques de plusieurs millions d’années, ces fosses reculent (vers la plaque plongeante) ou avancent (vers la plaque chevauchante/supérieure). Historiquement, le retrait de la fosse a été associé à une extension de la plaque supérieure au-dessus du panneau plongeant. Cependant, les zones de subduction sur Terre montrent plusieurs exemples de fosses en recul associées à des contraintes compressives. Cette thèse étudie la déformation (arrière-arc) de la plaque supérieure pour une subduction en retrait. Trois approches ont été utilisées : des modèles numériques explorant les processus physiques mis en jeu à grande échelle, des profils sismiques en mer Égée centrale permettant d’étudier la répartition des failles à l’échelle du bassin, et des observations de terrain pour caractériser l’évolution temporelle de la déformation de la plaque supérieure en mer Égée centrale. Les modèles thermo-mécaniques à grande échelle reproduisent une déformation visqueuse de la plaque supérieure, et permettent d’analyser les relations entre traction du slab, recul du slab, retrait de la fosse et déformation de la plaque supérieure, à des échelles allant de 100 à 1000 km. Ils montrent que des courants dans le manteau asthénosphérique sous les plaques (vers 100-200 km de profondeur) peuvent contrôler à la fois le mouvement relatif de la fosse et la déformation de la plaque supérieure. Cette dernière dépend également des conditions mécaniques aux limites: si la plaque est libre de bouger, sa déformation sera plutôt compressive ; mais une plaque fixe sera en extension. Ce dernier cas est comparable à la région de la mer Égée, une plaque supérieure montrant de l’extension et associée à une zone de subduction étroite en retrait. Les structures extensives associées ont été analysées grâce à l’observation sur le terrain et à l’étude de profils sismiques, révélant des failles normales, obliques et décrochantes synchrones. Cela est interprété comme résultant de la combinaison de contraintes extensives associées au recul de la fosse et de contraintes décrochantes associées à l’extrusion d’un bloc voisin. La rotation et le recul de la fosse réactivent d’anciennes failles normales dans un mode oblique-extensif, et engendrent des nouvelles failles purement normales. Les données suggèrent également un changement récent de l’état de contrainte mécanique dans la plaque, qui pourrait être dû à une déchirure du panneau plongeant côté Ouest. En sus, l’accélération du recul de la fosse et l’intensification de l’extension de la plaque supérieure expliquent probablement le flux de chaleur élevé en mer Égée, ce qui rend l’énergie géothermique potentiellement exploitable dans cette zone. Une évaluation de l’apport de la modélisation tectonique pour prédire le potentiel géothermique est finalement présentée comme perspective de l’application des recherches en géodynamique, s’appuyant sur l’exemple de la plaque supérieure égéenne amincieThe Earth’s surface is constantly reshaped by the tectonic plate motion, which is mainly driven by subduction of plates into the deeper mantle. Subduction trenches are also mobile plate boundaries, and are observed to retreat towards the subducting plate or advance towards the upper plate over geological time. Trench retreat has been historically thought to cause extension in the upper plate above the subducting slab. However, natural subduction systems show several examples of retreating trenches that are associated with upper-plate compression. This thesis explores upper plate (back-arc) deformation in retreating subduction systems. Three techniques are used: large-scale numerical models addressing physical processes; seismic profiles in the Central Aegean addressing basin-scale fault patterns; and field-scale observations clarifying fault kinematics in the Central Aegean. The large-scale thermo-mechanical models deal with viscous deformation of the upper plate, and investigate the relationship between slab pull, slab rollback, trench retreat and upper plate deformation at scales of 100 to 1000 km. They show that asthenosphere flows below the plates (100-200 km depth) can control both trench retreat and upper plate deformation. The type of deformation in the upper plate also depends on the plate’s far-field conditions: if the plate is free to move, deformation tends to be compressive, but a fixed upper plate shows extension. The latter is comparable to the Aegean region, an upper plate exhibiting extension above a narrow, retreating subduction zone. Related extensional structures in the central Aegean have been analysed from seismic and field data, revealing co-existing normal, oblique and strike slip faults. These features reflect a combination of rollback-related extension and extrusion-related strike slip activity. Resulting block rotation and trench retreat re-activate inherited normal faults in oblique-normal slip, while new pure-normal faults are created. We also infer a recent change in stress state possibly related to the slab tear on the western side of the Hellenic slab. Additionally, accelerated trench retreat and upper plate extension are the cause of the Aegean’s high surface heat flow, which makes it potentially suitable for geothermal energy production. As a final perspective on the application of geodynamic research, an assessment of the role of tectonic modelling in predicting geothermal energy potential is presented, using the stretched Aegean upper plate as an example
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Rowland, Andrea Jane. "Numerical modelling of subduction zone magmatism." Thesis, University of Liverpool, 1997. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.266491.
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Daniel, Andrew John. "The geodynamics of spreading centre subduction in southern Chile." Thesis, University of Liverpool, 1996. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.320503.
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Biryol, Cemal Berk. "COMPLEX RUPTURE PROCESSES OF THE SOLOMON ISLANDS SUBDUCTION ZONE EARTHQUAKE AND SUBDUCTION CONTROLLED UPPER MANTLE STRUCTURE BENEATH ANATOLIA." Diss., The University of Arizona, 2009. http://hdl.handle.net/10150/194681.
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This dissertation explores subduction zone-related deformation both on short time scales in the form of subduction zone earthquakes and over larger time and geographical scales in the form of subduction rollback or detachment of the subducting lithosphere. The study presented here is composed of two parts. First, we analyzed the source-rupture processes of the April 1, 2007 Solomon Islands Earthquake (Mw=8.1) using a body-wave inversion technique. Our analysis indicated that the earthquake ruptured approximately 240 km of the southeast Pacific subduction zone in two sub-events.In the second part of this study, we used shear-wave splitting analysis to investigate the effects of the subducting African lithosphere on the upper-mantle flow field beneath the Anatolian Plate in the Eastern Mediterranean region. Our shear-wave splitting results are consistent with relatively uniform southwest-directed flow towards the actively southwestward-retreating Aegean slab. Based on spatial variations in observed delay times we identified varying flow speeds beneath Anatolia and we attribute this variation to the differential retreat rates of the Aegean and the Cyprean trenches.Finally, we used teleseismic P-wave travel-time tomography to image the geometry of the subducting African lithosphere beneath the Anatolia region. Our tomograms show that the subducting African lithosphere is partitioned into at least two segments along the Cyprean and the Aegean trenches. We observed a gap between the two segments through which hot asthenosphere ascends beneath the volcanic fields of western Anatolia. Our results show that the Cyprean slab is steeper than the Aegean slab. We inferred that this steep geometry, in part, controls the flow regime of asthenosphere beneath Anatolia causing variations in flow speeds inferred from shear-wave splitting analysis.
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Kanjorski, Nancy Marie. "Cocos plate structure along the Middle America subduction zone off Oaxaca and Guerrero, Mexico : influence of subducting plate morphology on tectonics and seismicity /." Diss., Connect to a 24 p. preview or request complete full text in PDF format. Access restricted to UC campuses, 2003. http://wwwlib.umi.com/cr/ucsd/fullcit?p3076343.
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Audet, Pascal. "Seismic and mechanical attributes of lithospheric deformation and subduction in western Canada." Thesis, University of British Columbia, 2008. http://hdl.handle.net/2429/2435.
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Convergent continental margins are regions of intense deformation caused by the interaction of oceanic plates with continents. The spatial extent of deformation is broadly commensurate with the specific time scale of the causative phenomenon. For example, subduction-related short-term deformation is limited to <200 km from the margin, whereas long-term plate convergence cause deformation over ∼1000 km landward. Deformation is thus manifested in multiple ways, with attributes depending on the scale of measurement. In this thesis we investigate the use of two geophysical approaches in the study of deformation: 1) The analysis of potential-field anomalies to derive estimates of the elastic thickness (Te) of the lithosphere, and 2) The structural study of past and present subduction systems using seismic observations and modelling. Both approaches involve the development of appropriate methodologies for data analysis and modelling, and their application to the western Canadian landmass. Our findings are summarized as follows: 1) We develop a wavelet-based technique to map variations in Te and its anisotropy; 2) We show how a step-wise transition in Te and its anisotropy from the Cordillera to the Craton is a major factor influencing lithospheric deformation; 3) We implement a waveform modelling tool that includes the effects of structural heterogeneity and anisotropy for teleseismic applications, and use it to model the signature of a fossil subduction zone in a Paleoproterozoic terrane; 4) We use teleseismic recordings to map slab edge morphology in northern Cascadia and show how slab window tectonism and slab stretching led to the creation of the oceanic Explorer plate; 5) We use seismic signals from the subducting oceanic crust to calculate elevated Poisson’s ratio and infer high pore-fluid pressures and a low-permeability plate boundary within the forearc region of northern Cascadia.
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Medema, Guy Frederick. "Juan de Fuca subducting plate geometry and intraslab seismicity /." Thesis, Connect to this title online; UW restricted, 2006. http://hdl.handle.net/1773/6828.
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Seebeck, Hannu Christian. "Normal Faulting, Volcanism And Fluid Flow, Hikurangi Subduction Plate Boundary, New Zealand." Thesis, University of Canterbury. Geological Sciences, 2013. http://hdl.handle.net/10092/8884.
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This thesis investigates normal faulting and its influence on fluid flow over a wide range of spatial and temporal scales using tunnel engineering geological logs, outcrop, surface fault traces, earthquakes, gravity, and volcanic ages. These data have been used to investigate the impact of faults on fluid flow (chapter 2), the geometry and kinematics of the Taupo Rift (chapter 3), the hydration and dehydration of the subducting Pacific plate and its influence on the Taupo Volcanic Zone (chapter 4), the migration of arc volcanism across the North Island over the 16 Myr and the associated changes in slab geometry (chapter 5) and the Pacific-Australia relative plate motion vectors since 38 Ma and their implications for arc volcanism and deformation along the Hikurangi margin (chapter 6). The results for each of these five chapters are presented in
the five paragraphs below.
Tunnels excavated along the margins of the southern Taupo Rift at depths < 500 m provide data on the spatial relationships between faulting and ground water flow. The geometry and hydraulic properties of fault-zones for Mesozoic basement and Miocene strata vary by several orders of magnitude approximating power-law distributions with the dimensions of these zones dependent on many factors including displacement, hostrock type and fault geometries. Despite fault-zones accounting for a small proportion of the total sample length (≤ 15%), localised flow of ground water into the tunnels occurs almost exclusively (≥ 91%) within, and immediately adjacent to, these zones. The spatial distribution and rate of flow from fault-zones are highly variable with typically ≤ 50% of fault-zones in any given orientation flowing. The entire basement dataset shows that 81% of the flow-rate occurs from fault-zones ≥ 10 m wide, with a third of the total flow-rate originating from a single fault-zone (i.e. the golden fracture). The higher flow rates for the largest faults are interpreted to arise because these structures are the most connected to other faults and to the ground surface.
The structural geometry and kinematics of rifting is constrained by earthquake focal mechanisms and by geological slip and fault mapping. Comparison of present day geometry and kinematics of normal faulting in the Taupo Rift (α=76-84°) with intra-arc rifting in the Taranaki Basin and southern Havre Trough show, that for at least the last 4 Myr, the slab and the associated changes in its geometry have exerted a first-order control on the location, geometry, and extension direction of intra-arc rifting in the North Island. Second-order features of rifting in the central North Island include a clockwise ~20° northwards change in the strike of normal faults and trend of the extension direction. In the southern rift normal faults are parallel to, and potentially reactivate, Mesozoic basement fabric (e.g., faults and bedding). By contrast, in the northern rift faults diverge from basement fabric by up to 55° where focal mechanisms
indicate that extension is achieved by oblique to right-lateral strike-slip along basement fabric and dip-slip on rift faults.
Hydration and dehydration of the subducting Pacific plate is elucidated by earthquake densities and focal mechanisms within the slab. The hydration of the subducting plate varies spatially and is an important determinant for the location of arc volcanism in the overriding plate. The location and high volcanic productivity of the TVZ can be linked to the subduction water cycle, where hydration and subsequent dehydration of the subducting oceanic lithosphere is primarily accomplished by normal-faulting earthquakes. The anomalously high heat flow and volcanic productivity of the TVZ is spatially associated with high rates of seismicity in the underlying slab mantle at depths of 130-210 km which can be tracked back to high rates of deeply penetrating shallow intraplate seismicity at the trench in proximity to oceanic fluids. Dehydration of the slab mantle correlates with the location and productivity of active North Island volcanic centres, indicating this volcanism is controlled by fluids fluxing from the subducting plate.
The ages and locations of arc volcanoes provide constraints on the migration of volcanism across the North Island over the last 20 Myr. Arc-front volcanoes have migrated southeast by 150 km in the last 8 Ma (185 km since 16 Ma) sub-parallel to the present active arc. Migration of the arc is interpreted to mainly reflect slab steepening and rollback. The strike of the Pacific plate beneath the North Island, imaged by Benioff zone seismicity (50-200 km) and positive mantle velocity anomalies (200-600 km) is parallel to the northeast trend of arc-front volcanism. Arc parallelism since 16 Ma is consistent with the view that the subducting plate beneath the North Island has not
rotated clockwise about vertical axes which is in contrast to overriding plate vertical-axis rotations of ≥ 30º. Acceleration of arc-front migration rates (~4 mm/yr to ~18 mm/yr), eruption of high Mg# andesites, increasing eruption frequency and size, and
uplift of the over-riding plate indicate an increase in the hydration, temperature, and size of the mantle wedge beneath the central North Island from ~7 Ma.
Seafloor spreading data in conjunction with GPlates have been used to generate relative plate motion vectors across the Hikurangi margin since 38 Ma. Tracking the southern and down-dip limits of the seismically imaged Pacific slab beneath the New Zealand indicates arc volcanism in Northland from ~23 Ma and the Taranaki Basin between ~20 and 11 Ma requires Pacific plate subduction from at (or beyond) the northern North Island continental margin from at least 38 Ma to the present. Pacific plate motion in a west dipping subduction model shows a minimum horizontal transport distance of 285 km preceding the initiation of arc volcanism along the Northland-arc normal to the motion vector, a distance more than sufficient for self-sustaining
subduction to occur. Arc-normal convergence rates along the Hikurangi margin doubled from 11 to 23 mm/yr between 20 and 16 Ma, increasing again by approximately a third between 8 and 6 Ma. This latest increase in arc-normal rates coincided with changes in relative plate motions along the entire SW Pacific plate boundary and steepening/rollback of the Pacific plate.
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Schellart, Wouter Pieter. "Subduction rollback, arc formation and back-arc extension." Monash University, School of Geosciences, 2003. http://arrow.monash.edu.au/hdl/1959.1/9485.
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Dehler, Sonya Astrid. "Integrated geophysical modelling of the northern Cascadia subduction zone." Thesis, University of British Columbia, 1991. http://hdl.handle.net/2429/30798.
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The northern Cascadia subduction zone involves convergence of the Explorer Plate and northern part of the Juan de Fuca Plate with the North American Plate along a margin lying west of Vancouver Island, Canada. A wide accretionary complex which underlies the continental slope and shelf has been formed. Two allochthonous terranes, the Crescent Terrane of Eocene oceanic crustal volcanics and the Pacific Rim Terrane of Mesozoic melange sedimentary rocks and volcanics, lie against the Wrangellia Terrane backstop beneath the west coast of Vancouver Island and outcrop on the southern tip of the island. The intrusive Coast Plutonic Complex underlies the westernmost part of the British Columbia mainland east of Vancouver Island and marks the location of the historic and modern volcanic arcs.
An integrated interpretation of geophysical and geological data has been conducted for the northern Cascadia subduction zone. Regionally extensive gravity and magnetic anomaly data have formed the basis of the interpretation, while surface geology, physical properties, and seismic reflection, refraction, heat flow, borehole, magnetotelluric, and seismicity data have provided constraints on structure and composition. Horizontal gradient and vertical derivative maps of the potential field data were calculated to provide additional control on the locations of major faults and lithologic boundaries.
Iterative forward modelling of the gravity and magnetic anomaly data was conducted along three offshore multichannel seismic reflection lines and their onshore extensions. The two-and-a-half-dimensional (2.5-D) models extended from the ocean basin across the accretionary
complex and Vancouver Island to the mainland along lines perpendicular to the major structural trends of the margin and revealed lateral changes in the location of several structural components along the length of the margin. The interpretations were extended
laterally by moving the original models to adjacent parallel positions and perturbing them to satisfy the new anomaly profile data and other constraints. The models thus formed were moved to the next position and the process repeated until a total of eleven models was developed
across the margin. A twelfth line across a gravity anomaly high on southern Vancouver Island was independently modelled to examine the source of this feature.
An average density model for the southern half of the convergent margin was constructed by averaging the models and profiles for seven lines at 10 km spacings. This process removed anomalies due to small source bodies and concentrated on the larger features. Finally, a regional density structural model was developed by linearly interpolating between all eleven cross-margin lines to construct a block model which could then be 'sliced' open to examine the internal structure of the margin at any location.
The final models allow the Pacific Rim and Crescent Terrane positions to be extended along the offshore margin from their mapped locations. The Pacific Rim Terrane appears to be continuous and close to the coastline along the length of Vancouver Island, while the Crescent Terrane either terminates halfway along the margin or is buried at a depth great enough to suppress its magnetic signature. The location of the Westcoast Fault, separating the Pacific Rim and Wrangellia Terranes, has been interpreted to lie west of Barkley Sound at a position 15 km west of its previously interpreted position. Beneath southern Vancouver Island and Juan de Fuca Strait, the Crescent Terrane appears to have been uplifted into an anticlinal structure, bringing high density lower crustal or upper mantle material close to the surface and thereby causing the observed gravity anomaly high.
The western part of the Coast Plutonic Complex has been interpreted as a thin lower density layer extending from its surface contact with Wrangellia to a position 20 to 30 km further east where the unit rapidly thickens and represents the main bulk of the batholith. The complexity of the thermal regime and its effects on density in this region allows for other interpretations.
Finally, a comparison of the models along the length of the margin reveals that the crust of Vancouver Island appears to thin toward the north above the shallower Explorer Plate and the complex low - high density banding used in the southern Vancouver Island models is replaced with a single high density unit on the northernmost line.Science, Faculty of
Earth, Ocean and Atmospheric Sciences, Department of
Graduate
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Mackie, David. "Subduction beneath the Queen Charlotte Islands? : the results of a seismic refraction survey." Thesis, University of British Columbia, 1985. http://hdl.handle.net/2429/24849.
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The Queen Charlotte transform fault zone, which lies immediately east of the Queen Charlotte Islands, marks the boundary between the oceanic Pacific and the continental North American plates. Relative plate motions suggest that oblique underthrusting of the Pacific plate beneath North America may be presently occurring along this transform fault. To investigate this plate boundary and the implications of oblique subduction on crustal structure beneath the region, an onshore-offshore seismic refraction survey was conducted in 1983. The survey was designed to sample the crust beneath the Queen Charlotte Islands and across Hecate Strait to the mainland of British Columbia. Six ocean bottom seismographs and 11 land based stations were deployed along a 200 km line extending from 20 km west of the Queen Charlotte Islands to the mainland. Thirteen 540 kg and twenty 60 kg explosive charges were detonated along a 110 km long east-west line in the ocean to the west of the receivers. The multiple shots recorded on multiple receivers, all along the same line, effectively reverses the profile over some of its length.
The objective of this study is to provide a model of the deep crustal structure beneath the fault zone, the Queen Charlotte Islands, and Hecate Strait. An exemplary subset of the extensive data set was selected to meet this objective. Beneath the deep ocean the Moho dips at about 2° to the east. At the Queen Charlotte terrace, a 25 km wide zone immediately west of the active Queen Charlotte fault, the dip of the Moho increases to about 5°. The crust is about 12 km thick at the terrace and 18 km thick at the eastern edge of the Queen Charlotte Islands, and in excess of 30 km thick at the mainland. The terrace unit itself is divided into two units - an upper unit with low velocity (4.1 km/s) and high gradient (0.3 km/s/km) and a lower unit with a high velocity (6.5 km/s) and a low gradient (0.05 km/s/km). This model, while not definitive, supports the interpretation of oblique shallow underthrusting of the Pacific plate beneath the Queen Charlotte Islands. The upper terrace unit could represent a sedimentary accretionary wedge and the lower terrace unit - the subducting slab. A model in which compression across the Queen Charlotte transform fault zone is taken up by deformation of the Queen Charlotte Islands in the form of crustal shortening and thickening is not compatible with the thin crust beneath the islands and Hecate Strait.Science, Faculty of
Earth, Ocean and Atmospheric Sciences, Department of
Graduate
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Di, Giuseppe Erika. "Dynamics of subduction and implications for plate kinematics : insights from numerical and laboratory models /." Zürich : ETH, 2008. http://e-collection.ethbib.ethz.ch/show?type=diss&nr=17833.
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Murdie, Ruth Elaine. "Seismicity and neotectonics associated with the subduction of an active ocean ridge-transform system in Southern Chile." Thesis, University of Liverpool, 1994. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.385262.
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Sanchez, Lohff Sonia K. "Upper plate response to varying subduction styles in the forearc Cook Inlet basin, south-central Alaska." University of Cincinnati / OhioLINK, 2018. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1530270586819066.
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Mallard, Claire. "Analyse tectonique de la surface des modèles de convection mantellique." Thesis, Lyon, 2017. http://www.theses.fr/2017LYSE1143/document.
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La théorie de la tectonique des plaques permet de décrire les mouvements de premier ordre qui opèrent à la surface de la Terre. S'il est acquis que la convection dans le manteau terrestre en est le moteur, les liens entre les phénomènes profonds et les caractéristiques tectoniques de la surface restent largement méconnus. Jusqu'à très récemment, les modèles de convection du manteau terrestre ne produisaient pas de tectonique de surface pouvant être comparée à celle de la Terre. Récemment, des modèles globaux de convection qui reproduisent une tectonique de surface comparable à la Terre au premier ordre ont été mis au point. Ces modèles produisent des courants mantelliques ascendants et descendants de grande échelle et des déformations localisées en surface dans les zones de divergence et les zones de convergence. Ils génèrent une expansion des fonds océaniques de manière auto-cohérente proche de celle reconstruite pour les 200 derniers millions d'années de l'histoire de la Terre et une dérive de continents similaire à celle observée grâce au paléomagnétisme. Cette thèse s'inscrit parmi les premières tentatives d'utilisation de modèles de convection sphériques auto-organisés à des fins de compréhension de la tectonique de surface. La tectonique produite dans ce type de modèles de convection sera caractérisée finement à travers l'étude des limites de plaques, de leur agencement et de leurs vitesses de déplacement. L'objectif est de pouvoir comparer qualitativement et quantitativement les résultats des calculs de convection avec les reconstructions des mouvements de la surface terrestre grâce à la tectonique des plaques et aux observations de terrain. Dans cette optique, les limites tectoniques ont été définies à la main dans un premier temps afin de comprendre la physique qui gouverne l'agencement caractéristique des plaques tectoniques terrestres. En effet, celle-ci est composée de sept grandes plaques et plusieurs petites dont la répartition statistique indique deux processus de mise en place distincts. Nous avons déterminé les processus responsables de la mise en place de l'agencement caractéristique des plaques tectoniques en surface en faisant varier la résistance de la lithosphère. Plus la lithosphère est résistante, plus la longueur totale et la courbure des zones de subduction diminue à la surface des modèles. Cela s'accompagne également d'une diminution du nombre de petites plaques. En étudiant la fragmentation au niveau des jonctions triples, nous avons montré que les petites plaques étaient associées aux géométries courbées des fosses océaniques. En revanche, les grandes plaques sont contrôlées par les grandes longueurs d'onde de la convection mantellique. Ces deux processus impliquent deux temps de réorganisation, c'est-à-dire l'apparition et la disparition d'une plaque plongeante dans le manteau terrestre (environ 100 millions d'années) pour les grandes plaques, alors que l'échelle de temps de réorganisation des petites plaques dépend des mouvements des fosses et est ainsi plus rapide d'un ordre de grandeur. Afin d'effectuer des analyses quantitatives rapides, des méthodes d'analyse automatique de la surface et de l'intérieur des modèles ont été développées. La première technique concerne la détection automatique des plaques tectoniques à la surface des modèles (ADOPT). ADOPT est un outil de détection basé sur une technique de segmentation d'images utilisée pour détecter des bassins versants. Les champs à la surface des modèles sont transformés en reliefs, soit directement, soit après un processus de filtrage. Cette détection permet d'obtenir des polygones de plaques comparable aux analyses réalisées à la main. Une autre technique de détection a été mise au point pour étudier les panaches mantelliques [etc...]Plate tectonics theory describes first order surface motions at the surface of the Earth. Although it is agreed upon that convection in the mantle drives the plates, the relationships between deep dynamics and surface tectonics are still largely unknown. Until recently, mantle convection models could not produce surface tectonics that could be compared to that of the Earth. New global models are able to form large-scale ascending and descending mantle currents, as well as narrow regions of localized deformation at the surface where convergence and divergence occur. These models selfconsistently generate an expansion of the oceanic floor similar to that of the last 200 million years on Earth, and continental drift similar to what can be reconstructed with palaeomagnetism. This Ph.D. thesis constitutes one of the first attempts to use self-organised, spherical convection models in order to better understand surface tectonics. Here, the tectonics produced by the models is finely charaterized through the study of plate boundaries, their organisation and their velocities. The goal is to be able to compare qualitatively and quantitatively the results of convection computations with surface motions, as reconstructed using the rules of plate tectonics and field observations. Plate boundaries emerging from the models were first traced and analyzed by hand so as to understand the physics that govern the typical organization of the tectonics plates on Earth. It is characterised by seven large plates and several smaller ones, following a statistical distribution that suggests that two distinct physical processes control the plates’ layout. We have determined the processes responsible for this distribution while varying the strength of the lithosphere (the yield stress). In our models, the stronger the lithosphere, the greater the total subduction length and their curvature, and the fewer the small plates. By studying surface fragmentation with triple junctions, we showed that the formation of small plates is associated with oceanic trench curvature. Large plates, however, are controlled by the long wavelengths of the convection cells. These two processes involve two different reorganisation times, controlled either by the accretion and the subduction of the large plates (about 100 Myrs), or by trench motions for the smaller plates. In order to improve the efficiency of our analysis, we have developed automated methods to study the surface and the interior of the models. The first technique is about detecting the tectonic plates automatically at the surface of the models. It is called ADOPT. It is a tool based on image segmentation technique to detect the watersheds. The surface fields of the convection models are converted into a relief field, either directly or using a distance method. This automatic detection allows to obtain plates polygons similar to the hand analysis. Another technique of detection has been developed to study mantle plumes. These analyzes were used to determine the driving forces behind the plates layout, to quantify the timing of reorganizations and to evaluate the implication of the models rheology on the surface distribution. These new analytical tools and the constant evolution of the quality of mantle convection models allow us to improve our understanding of the link between mantle dynamics and surface tectonics, but also to target necessary improvements in the convection models used
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Hicks, Stephen Paul. "Seismic properties and processes along the subduction plate interface : the Februrary 2010 Mw 8.8 Maule, Chile earthquake." Thesis, University of Liverpool, 2015. http://livrepository.liverpool.ac.uk/2036999/.
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The seismogenic zone of subduction margins has the potential to generate some of the world’s largest earthquakes. A detailed study of the 2010 Mw 8.8 Maule, Chile rupture has enabled interpretation of the controls that govern subduction zone seismic behaviour across the earthquake cycle. In this thesis, we focus on two aspects of the central Chile margin: (1) imaging physical properties in the forearc and along the plate interface; (2) assessing source complexity of megathrust ruptures. We exploit a dataset of seismic body wave onset times from local aftershocks recorded on a temporary network to derive a 3-D seismic velocity model of the Maule rupture area. We image the main domains of the subduction zone and find a high velocity anomaly located along the plate interface, which we initially interpret as a subducted topographic high. We then develop a second, more accurate velocity model that uses an improved arrival time dataset together with observations from ocean-bottom seismometers. This refined model gives a sharper view of both the plate interface close to the trench, and the marine forearc. We show that ancient blocks of dense mantle in the lower forearc may have decelerated slip during the Maule earthquake and contributed to its nucleation. Furthermore, we infer that fluid saturated sediments inhibited significant slip close to the trench. We study source processes of a large aftershock of the Maule sequence, the 2011 Mw 7.1 Araucania earthquake, by inverting local seismic waveforms for a multiple point-source faulting solution. We find this earthquake constituted rupture on the plate interface followed by almost instantaneous slip along a normal fault in the overriding plate: the first observation of its kind. The second rupture of this closely-spaced doublet was hidden from teleseismic faulting solutions, and may have been dynamically triggered by S-waves from the first event. Overall, our work highlights the role played by the upper plate in subduction zone seismogenesis. We suggest that seismic velocities can help to characterise the behaviour of future large megathrust earthquakes. We show that the potential hazard posed by closely-spaced doublets involving the upper plate should be accounted for in real-time tsunami warning systems by using local waveform analysis.
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Bonnet, Guillaume. "Seamount subduction in the Zagros Suture Zone : structural and petrologic characterization and implications for seismogenesis." Electronic Thesis or Diss., Sorbonne université, 2018. https://accesdistant.sorbonne-universite.fr/login?url=https://theses-intra.sorbonne-universite.fr/2018SORUS526.pdf.
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Les monts sous-marins subductés jouent un rôle majeur dans le comportement mécanique et sismogénique des zones de subduction: sont-ils des barrières à la propagation des séismes ou bien des aspérités permettant leur nucléation ? Les rares exemples naturels arrachés de la plaque plongeante le long de l'interface de subduction et préservés de la subduction représentent donc des témoins précieux des processus profonds. Cette thèse de doctorat reporte l'existence d'un mont sous-marin dans la zone de suture du Zagros (l'unité de Siah Kuh). Cette unité de 20x12 km de large et d'un minimum de 1.5 km de hauteur est composée de basaltes en coussins couverts de calcaire récifal et s'est formée au sein d'un arc volcanique au Crétacé supérieur. La présence de minéraux de HP-BT dans l'ensemble de la structure et dans des zones de déformation compressive localisée montrent qu'elle a été subductée jusqu' à environ 30 km. La déformation synchrone de la subduction, liée à l'écaillage interne du mont sous-marin, est assistée par des décollements enracinés dans la serpentinite ou dans des sédiments, ce qui limite possiblement l'essentiel de l'activité sismique, étant donné qu'une unique pseudotachylite a été observée, témoignant d'un séisme de magnitude Mw2-3.Nous discutons des processus océaniques de déstabilisation de pente et de subsidence, et des processus de subduction comme le couplage mécanique, les surpressions de fluide et/ou tectoniques ainsi que la nature des fluides de subduction. Nous finissons en proposant un modèles d'évolution de cette unité en relation avec les autres unités océaniques héritées de la NéotethysEamounts are for the most part subducted with the downgoing oceanic plate. They are expected to critically impact the mechanical and seismogenic behavior of subduction zones, but their exact role is strongly debated (i.e. as to whether they represent barriers to propagation or asperities promoting nucleation). Rare natural examples of metamorphosed seamounts, that got sliced off the slab along the plate interface are therefore precious witnesses to document processes operating at depth.This PhD thesis reports the existence of a former seamount in the Zagros suture zone (the Siah Kuh unit).This 20x12 kilometer-large, minimum 1.5 km-high unit composed of pillow basalts capped by reef limestone was formed in an arc environment during the Late Cretaceous.HP-LT minerals (lawsonite, aragonite veins, blue amphibole) found across the whole structure, particularly in zones of localized compressive deformation, indicate that this seamount was shallowly subducted at 30 km. Syn-subduction deformation is assisted by dŽcollement rooting in serpentinite and/or oceanic sediments and is related to the internal slicing of the seamount. The presence of soft layers may prevent most of the seismic activity, since only one pseudotachylite, recording a Mw2-3 earthquake has been found. The Siah Kuh unit is also a perfect target to investigate oceanic processes such as slope destabilization and subsidence, and subduction processes such as mechanical coupling, fluid/tectonic overpressure and the nature of subduction fluids. We finally build a model for the tectonic evolution of the Siah Kuh unit and its relationship with other ophiolites
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Ning, Zuoli. "Roles of plate locking and block rotation in the tectonics of the Pacific Northwest /." Thesis, Connect to this title online; UW restricted, 2003. http://hdl.handle.net/1773/6833.
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Kamiya, Nana. "Evolution of the Mio-Pleistocene forearc basin induced by the plate subduction in the Boso Peninsula, central Japan." Doctoral thesis, Kyoto University, 2020. http://hdl.handle.net/2433/253260.
Full textAbstract:
京都大学0048
新制・課程博士
博士(工学)
甲第22424号
工博第4685号
新制||工||1731(附属図書館)
京都大学大学院工学研究科都市社会工学専攻
(主査)教授 林 為人, 教授 小池 克明, 准教授 村田 澄彦
学位規則第4条第1項該当
Doctor of Philosophy (Engineering)
Kyoto University
DFAM
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Arkle, Jeanette C. "Orogenesis and landscape evolution above the subduction-transform transition at the southeast Caribbean plate corner, Trinidad and Tobago." University of Cincinnati / OhioLINK, 2019. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1571061691451314.
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Delph, Jonathan, and Jonathan Delph. "Crustal and Upper Mantle Structure of the Anatolian Plate: Imaging the Effects of Subduction Termination and Continental Collision with Seismic Techniques." Diss., The University of Arizona, 2016. http://hdl.handle.net/10150/622908.
Full textAbstract:
The neotectonic evolution of the eastern Mediterranean is intimately tied to interactions between the underthrusting/subducting slab along the southern margin of Anatolia and the overriding plate. The lateral variations in the subduction zone can be viewed as a temporal analogue of the transition between continuous subduction and subduction termination by continent-continent collision. By investigating the lateral variations along this subduction zone in the overriding plate, we can gain insight into the processes that precede continent collision. This dissertation summarizes the results of three studies that focus on different parts of the subduction margin: 1) In the west, where the development of a slab tear represents the transition between continuous and enigmatic subduction, 2) In the east, where continent-continent collision between the Arabian and Eurasian Plate is leading to the development of the third largest orogenic plateau on earth after complete slab detachment, and 3) In central Anatolia, where the subducting slab is thought to be in the processes of breaking up, which is affecting the flow of mantle material leading to volcanism and uplift along the margin. In the first study, we interpret that variations in the composition of material in the downgoing plate (i.e. a change from the subduction of oceanic material to continental material) may have led to the development of a slab tear in the eastern Aegean. This underthrusting, buoyant continental fragment is controlling overriding plate deformation, separating the highly extensional strains of western Anatolia from the much lower extensional strains of central Anatolia. Based on intermediate depth seismicity, it appears that the oceanic portion of the slab is still attached to this underthrusting continental fragment. In the second study, we interpret that the introduction of continental lithosphere into the north-dipping subduction zone at the Arabian-Eurasian margin led to the rollback and eventual detachment of the downgoing oceanic lithosphere attached to the Arabian Plate. After detachment, high rates of exhumation in the overriding plate are recorded due to the removal of the oceanic lithosphere and accompanying rebound of the Arabian continental lithosphere. In the third study, we image a transitional stage between the complete slab breakoff of the second study and the continuous subduction slab of the first study. We interpret that trench-perpendicular volcanism and ~2 km of uplift of flat-lying carbonate rocks along the southern margin of Turkey can be attributed to the rollback and ongoing segmentation of the downgoing slab as attenuated continental material is introduced into the subduction zone. Combining these three studies allows us to understand the terminal processes of a long-lived subduction zone as continental material is introduced.
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Drew, Jeffrey John. "A re-evaluation of the seismic structure across the active subduction zone of Western Canada." Thesis, University of British Columbia, 1987. http://hdl.handle.net/2429/26248.
Full textAbstract:
The 1980 Vancouver Island Seismic Project (VISP) was conducted to investigate lithospheric structure associated with the underthrusting oceanic Juan de Fuca plate and the overriding continental America plate. The principal components of the survey were: (l) an onshore-offshore refraction line, which was approximately perpendicular to the continental margin (line 1), and (2) a refraction line which ran along the length of Vancouver Island approximately parallel with the continental margin (line IV). Lines I and IV were originally interpreted by Spence el a.1. (1985) and McMechan and Spence (1983), respectively. However since the original interpretations of these lines, deep multichannel seismic reflection data have been obtained on southern Vancouver Island as part of the 1984 LITHOPROBE project and off the west coast of the island during a marine survey in 1985.
This study was undertaken to resolve differences between the subsurface structures proposed in the original interpretations of lines I and IV and those suggested by the more recently acquired deep reflection data. The vertical two-way traveltimes to prominent
reflectors, observed in the onshore-offshore deep reflection data, were used as a constraint in constructing velocity models which are consistent with both the reflection and refraction data. The traveltimes and amplitudes observed in the VISP refraction data were modeled using a two-dimensional raytracing and asymptotic ray theory synthetic
seismogram routine.
The principal difference between the model originally interpreted for line I and the revised model involves the introduction of a twice repeated sequence of a low velocity zone (≈ 6.4 km/s) above a thicker high velocity zone (≈ 7.1 km/s) for the underplated region directly above the subducting Juan de Fuca plate in place of the single high velocity block underlain by a thick low velocity zone. The revised model for line IV is significantly different from the originally interpreted model. The two low-high velocity zones of line 1 are continued along the length of the island at depths between 10 and 35 km. Below this, the structure of the subducted plate is included to maintain consistency with the revised model developed for line 1.
Additional features of the revised onshore-offshore model corresponding to line 1 include
an oceanic lithosphere that dips approximately 3° beneath the continental slope, then 14° to 16° beneath the continental shelf and Vancouver Island, and an average velocity for the upper oceanic mantle of 8.22 km/s. Two separate two-dimensional models were needed to explain the data collected along line IV as a result of considerable
azimuthal coverage due to a 30° change in profile direction. The revised models developed for line IV are consistent with the revised model developed for line 1. The velocity in the upper 10 km ranges from 5.5 km/s to approximately 6.7 km/s. Below 10 km the velocity structure is consistent with that interpreted for line 1 and shows some variations along strike of the subduction zone.
Several possible interpretations can be made for the origin of the sequence of layers directly above the subducting plate beneath Vancouver Island. The two favored interpretations
are: (1) a. three stage tectonic process consisting of: stage 1 — offscraping of sediment from the top of the subducting plate forms the uppermost low velocity layer in the sequence; stage 2 — an imbricated package of mafic rocks derived by continuous accretion from the top of the subducting oceanic crust forms the first high velocity layer; and stage 3 — stages 1 and 2 repeat themselves with stage 2 currently occurring; or (2) remnant, pieces of oceanic lithosphere left stranded above the current subducting
plate during two previous episodes of subduction in which the subduction thrust jumped further westward isolating the remnant. The revised model along line IV indicates
that this process of subduction underplating could have been a pervasive feature of this convergent margin.Science, Faculty of
Physics and Astronomy, Department of
Graduate
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Nugroho, Hendro. "GPS Velocity Field In The Transition From Subduction To Collision Of The Eastern Sunda And Banda Arcs, Indonesia." Diss., CLICK HERE for online access, 2005. http://contentdm.lib.byu.edu/ETD/image/etd885.pdf.
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Ng, Max Kin-Fat. "Assessment of tsunami hazards on the British Columbia coast due to a local megathrust subduction earthquake." Thesis, University of British Columbia, 1990. http://hdl.handle.net/2429/29633.
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Strong evidence suggests that the Cascadia subduction zone, off the west coast of Canada and the United States, is strongly seismically-coupled and that a possible
megathrust earthquake might occur in that area in the near future. A study of tsunami hazards along the Canadian west coast associated with such a hypothetical earthquake is presented in this report. Numerical simulations of tsunami generation and propagation have been carried out using three models based on shallow water wave theory.
Three cases of ground motion representing the ruptures of different crustal segments
in the area have been examined. Computed results provide information on tsunami arrival times and a general view of the wave height distribution. The outer coast of Vancouver Island was found to be the most strongly affected area. At the head of Alberni Inlet, wave amplitudes reached up to three times the source magnitude.
Inside the Strait of Georgia, the wave heights are significant enough to receive closer attention, especially in low-lying areas.Science, Faculty of
Physics and Astronomy, Department of
Graduate
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Luo, Yan. "Spatial and temporal variations of earthquake frequency-magnitude distribution at the subduction zone near the Nicoya Peninsula, Costa Rica." Thesis, Georgia Institute of Technology, 2011. http://hdl.handle.net/1853/45963.
Full textAbstract:
The Nicoya Peninsula of Costa Rica is unusually close to the Middle America Trench (MAT), such that interface locking along the megathrust is observable under land. Here, rapid convergence between the downgoing Cocos and the over-riding Caribbean plates at ~85mm/yr allows for observable high strain rates, frequent large earthquakes and ongoing micro-seismicity. By taking advantage of this ideal location, a network of 20 on-land broadband seismometers was established in cooperation between UC Santa Cruz, Georgia Tech, and OVSICORI, with most stations operating since 2008.
To evaluate what seismicity tells us about the ongoing state of coupling along the interface, we must consistently evaluate the location and magnitude of ongoing micro- seismicity. Because of large levels of anthropogenic, biologic, and coastal noise, automatic detection of earthquakes remains problematic in this region. Thus, we resorted to detailed manual investigation of earthquake phases. So far, we have detected nearly 7,000 earthquakes below or near Nicoya between February and August 2009. From these events we evaluate the fine-scale frequency-magnitude distribution (FMD) along the subduction megathrust. The results from this b-value mapping‟ are compared with an earlier study of the seismicity 9 years prior. In addition, we evaluate them relative to the latest geodetically derived locking. Preliminary comparisons of spatial and temporal variations of the b-values will be reported here.
Because ongoing manual detection of earthquakes is extremely laborious and some events might be easily neglected, we are implementing a match-filter detection algorithm to search for new events from the continuous seismic data. This new approach has been previously successful in identifying aftershocks of the 2004 Parkfield earthquake. To do so, we use the waveforms of 858 analyst-detected events as templates to search for similarly repeating events during the same periods that have been manually detected. Preliminary results on the effectiveness of this technique are reported.
The overall goal of this research is to evaluate the evolution of stress along the megathrust that may indicate the location and magnitude of potentially large future earthquakes. To do so, I make the comparison between the FMD and the interface locking. Only positive correlations are observed in the Nicoya region. The result is different from the one derived from the seismic data set that was recorded 9 years before our data. Therefore, to substantiate the causes for the different relationships between the b-value and the coupling degree, we need additional data with more reliable magnitudes.
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Cameron, Milo Louis. "Rifting and subduction in the papuan peninsula, papua new guinea| The significance of the trobriand tough, the nubara strike-slip fault, and the woodlark rift to the present configuration of papua new guinea." Thesis, The University of Alabama, 2014. http://pqdtopen.proquest.com/#viewpdf?dispub=3620068.
Full textAbstract:
The calculated extension (~111 km) across the Woodlark rift is incompatible with the > 130 km needed to exhume the Metamorphic Core Complexes on shallow angle faults (< 30°) using N-S extension in the Woodlark Basin. High resolution bathymetry, seismicity, and seismic reflection data indicate that the Nubara Fault continues west of the Trobriand Trough, intersects the Woodlark spreading center, and forms the northern boundary of the Woodlark plate and the southern boundary of the Trobriand plate. The newly defined Trobriand plate, to the north of this boundary, has moved SW-NE along the right lateral Nubara Fault, creating SW-NE extension in the region bounded by the MCC's of the D'Entrecasteaux Islands and Moresby Seamount. Gravity and bathymetry data extracted along four transect lines were used to model the gravity and flexure across the Nubara Fault boundary. Differences exist in the elastic thickness between the northern and southern parts of the lines at the Metamorphic Core Complexes of Goodenough Island (Te_south = 5.7 x 103 m; Te_north = 6.1 x 103 m) and Fergusson Island (Te_south = 1.2 x 103 m; Te_north = 5.5 x 103 m). Differences in the elastic strength of the lithosphere also exist at Moresby Seamount (Te_south = 4.2 x 103 m; Te_north = 4.7 x 103 m) and Egum Atoll (Te_south =7.5 x 103 m; Te_north = 1.3 x 104 m). The differences between the northern and southern parts of each transect line imply an east-west boundary that is interpreted to be the Nubara Fault. The opening of the Woodlark Basin resulted in the rotation of the Papuan Peninsula and the Woodlark Rise, strike slip motion between the Solomon Sea and the Woodlark Basin at the Nubara Fault, and the formation of the PAC-SOL-WLK; SOL-WLK-TRB triple junctions. The intersection of the Woodlark Spreading Center with the Nubara Fault added the AUS-WLK-TRB triple junction and established the Nubara Fault as the northern boundary of the Woodlark plate.
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Herman, Scott William. "A paleomagnetic investigation of vertical-axis rotations in coastal Sonora, Mexico| Evidence for distributed transtensional deformation during the Proto-Gulf shift from a subduction-dominated to transform-dominated plate boundary in the Gulf of California." Thesis, University of California, Santa Barbara, 2013. http://pqdtopen.proquest.com/#viewpdf?dispub=1536547.
Full textAbstract:
The history of late Miocene (Proto-Gulf) deformation on the Sonoran margin of the Gulf of California is key to understanding how Baja California was captured by the Pacific plate and how strain was partitioned during the Proto-Gulf period (12.5-6 Ma). The Sierra el Aguaje and Sierra Tinajas del Carmen are located in southwestern coastal Sonora, Mexico, and represent the eastern rifted margin of the central Gulf of California. The ranges are composed of volcanic units and their corresponding volcaniclastic units which are the result of persistent magmatic activity between 20 and 8.8 Ma, including three packages of basalt and andesite that make excellent paleomagnetic recorders. Based on cross cutting relations and geochronologic data for pre-, syn-, and post-tectonic volcanic units, most of the faulting and tilting in the Sierra El Aguaje is bracketed between 11.9 and 9.0 Ma, thus falling entirely within Proto-Gulf time.
A paleomagnetic investigation into possible vertical axis rotations in the Sierra el Aguaje has uncovered evidence of clockwise rotations between ~13º and ~105º with possible translations. These results are consistent with existing field relations, which suggest the presence of large (>45°) vertical axis rotations in this region. This evidence includes: a) abrupt changes in the strike of tilted strata in different parts of the range, including large domains characterized by E-W strikes b) ubiquitous NE-SW striking faults with left lateral-normal oblique slip, that terminate against major NW-trending right lateral faults, and c) obliquity between the general strike of tilted strata and the strike of faults. These rotations occurred after 12 Ma and largely prior to 9 Ma, thus falling into the Proto-Gulf period. Such large-scale rotations lend credence to the theory that the area inboard of Baja California was experiencing transtension during the Proto-Gulf period, rather than the pure extension that would be the result of strain partitioning between Sonora and the Tosco-Abreojos fault offshore Baja California.
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Khazaradze, Giorgi. "Tectonic deformation in western Washington State from global positioning system measurements /." Thesis, Connect to this title online; UW restricted, 1999. http://hdl.handle.net/1773/6841.
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Fasola, Shannon Lee. "New perspective on the transition from flat to steeper subduction in Oaxaca, Mexico, based on seismicity, nonvolcanic tremor, and slow slip." Miami University / OhioLINK, 2016. http://rave.ohiolink.edu/etdc/view?acc_num=miami1461778598.
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Buscher, Jamie Todd. "Long-term exhumation of landscapes along the Pacific-North American plate boundary as inferred from apatite (U-Th)/He and ArcGIS analyses." Diss., Virginia Tech, 2007. http://hdl.handle.net/10919/27760.
Full textAbstract:
The Pacific-North American plate boundary is typified by transpression and convergence, yet the relationship between interplate deformation and long-term crustal shortening is not fully understood. The continuous belt of rugged topography that extends along the entire plate boundary is generally associated with oblique tectonic plate motion, strong interplate coupling, and terrane accretion, but relating plate boundary orogenesis to variations in plate geometry and behavior requires detailed case studies. The northern San Gabriel Mountains along the San Andreas fault and the Chugach-Kenai Mountains above the Aleutian subduction zone are located along highly tectonically active sections of the Pacific-North American plate boundary and have not been studied from the context of long-term landscape development. To determine whether mountain building along these sections of the plate boundary reflects recent, rapid exhumation as observed in bordering mountain belts, low-temperature thermochronometry and topographic analyses were applied to each area. In the northern San Gabriel Mountains, apatite (U-Th)/He ages are >10 Ma along narrow crystalline ridges topped by low-slope erosional surfaces located within ~5 km of the San Andreas fault zone. In the Chugach-Kenai Mountains, the youngest apatite (U-Th)/He ages (~5 Ma) are an order of magnitude older than those from the Yakutat collision zone to the east, despite the presence of a continuous swath of glaciated, rugged topography between the two areas. Exhumation rates inferred from these ages are <1 mm/yr, suggesting that there has been minimal recent denudation in the northern San Gabriel and Chugach-Kenai Mountains. The lack of evidence for recent mountain building in both of these case studies implies that interplate deformation is heterogeneous and that other factors (secondary structures, climate) besides plate kinematics and topographic character must be considered for understanding landscape development.Ph. D.
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Deshayes, Perrine. "Tomographie en vitesse et en atténuation de la zone de subduction au Chili central - ouest de l'Argentine (29°S-34°S) à partir de données sismologiques locales: apport à l'étude de la composition minéralogique." Phd thesis, Université de Nice Sophia-Antipolis, 2008. http://tel.archives-ouvertes.fr/tel-00360063.
Full textAbstract:
Dans la région du Chili-central-ouest de l'Argentine (29°S-34°S), la plaque océanique Nazca subductesous la plaque continentale sud-Américaine. Cette région est une zone de transition entre une
subduction plate et une subduction pentue. Au nord de 33°S, où le slab devient plat vers 100 km de
profondeur, la ride de Juan Fernandez subducte le long de la plaque océanique Nazca. Alors que dans
cette région, le volcanisme quaternaire s'arrête vers 5-7 Ma, au sud de 33°S, où la plaque océanique
plonge avec un angle de 30°,la majorité des édifices volcaniques sont actifs. A partir de l'enregistrement
de séismes locaux au travers de deux campagnes sismologiques, nous avons réalisé une tomographie des
écarts des temps d'arrivée et du paramètre d'atténuation t* = t/Q, afin de déterminer des modèles
tridimensionnels d'une part de vitesse et d'autre part d'atténuation des ondes P et S. La plaque subduite,
plus froide que le manteau dans lequel elle plonge, est un milieu où les ondes P et S se propagent
rapidement et sont faiblement atténuées. L'un des blocs tectoniques constituant la croûte continental
(bloc Cuyania) se caractérise par des vitesses rapides des ondes sismiques et une forte atténuation de
l'onde S. Sous les édifices volcaniques actifs, la vitesse de ses ondes est plus faible due probablement à la
présence de fusion partielle. Les modèles de vitesse des ondes P et S, combinés à un modèle thermique
bidimensionnel à 31.5°S déterminé dans cette étude, ont permis d'obtenir un modèle minéralogique de
la lithosphère continentale et de la croûte océanique de la plaque Nazca. Cette croûte est composée
de Blueschists jusqu'à 80 km de profondeur et d'Eclogite plus profond. De la serpentine est observée
dans le coin mantellique considéré comme "froid". Le manteau continental est constitué par un mélange
d'Harzburgites et de Lherzolites plus ou moins hydratées. Un faciès éclogite est observé à la base de
la croûte continentale. Les modèles d'atténuation ont une résolution spatiale trop faible pour pouvoir
améliorer les modèles thermiques et par conséquent les modèles minéralogiques de la zone de subduction
plate.
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Pedley, Katherine Louise. "Modelling Submarine Landscape Evolution in Response to Subduction Processes, Northern Hikurangi Margin, New Zealand." Thesis, University of Canterbury. Geological Sciences, 2010. http://hdl.handle.net/10092/4648.
Full textAbstract:
The steep forearc slope along the northern sector of the obliquely convergent Hikurangi subduction zone is characteristic of non-accretionary and tectonically eroding continental margins, with reduced sediment supply in the trench relative to further south, and the presence of seamount relief on the Hikurangi Plateau. These seamounts influence the subduction process and the structurally-driven geomorphic development of the over-riding margin of the Australian Plate frontal wedge.
The Poverty Indentation represents an unusual, especially challenging and therefore exciting location to investigate the tectonic and eustatic effects on this sedimentary system because of: (i) the geometry and obliquity of the subducting seamounts; (ii) the influence of multiple repeated seamount impacts; (iii) the effects of structurally-driven over-steeping and associated widespread occurrence of gravitational collapse and mass movements; and (iv) the development of a large canyon system down the axis of the indentation. High quality bathymetric and backscatter images of the Poverty Indentation submarine re-entrant across the northern part of the Hikurangi margin were obtained by scientists from the National Institute of Water and Atmospheric Research (NIWA) (Lewis, 2001) using a SIMRAD EM300 multibeam swath-mapping system, hull-mounted on NIWA’s research vessel Tangaroa. The entire accretionary slope of the re-entrant was mapped, at depths ranging from 100 to 3500 metres. The level of seafloor morphologic resolution is comparable with some of the most detailed Digital Elevation Maps (DEM) onshore. The detailed digital swath images are complemented by the availability of excellent high-quality processed multi-channel seismic reflection data, single channel high-resolution 3.5 kHz seismic reflection data, as well as core samples. Combined, these data support this study of the complex interactions of tectonic deformation with slope sedimentary processes and slope submarine geomorphic evolution at a convergent margin.
The origin of the Poverty Indentation, on the inboard trench-slope at the transition from the northern to central sectors of the Hikurangi margin, is attributed to multiple seamount impacts over the last c. 2 Myr period. This has been accompanied by canyon incision, thrust fault propagation into the trench fill, and numerous large-scale gravitational collapse structures with multiple debris flow and avalanche deposits ranging in down-slope length from a few hundred metres to more than 40 km. The indentation is directly offshore of the Waipaoa River which is currently estimated to have a high sediment yield into the marine system. The indentation is recognised as the “Sink” for sediments derived from the Waipaoa River catchment, one of two target river systems chosen for the US National Science Foundation (NSF)-funded MARGINS “Source-to-Sink” initiative. The Poverty Canyon stretches 70 km from the continental shelf edge directly offshore from the Waipaoa to the trench floor, incising into the axis of the indentation. The sediment delivered to the margin from the Waipaoa catchment and elsewhere during sea-level high-stands, including the Holocene, has remained largely trapped in a large depocentre on the Poverty shelf, while during low-stand cycles, sediment bypassed the shelf to develop a prograding clinoform sequence out onto the upper slope. The formation of the indentation and the development of the upper branches of the Poverty Canyon system have led to the progressive removal of a substantial part of this prograding wedge by mass movements and gully incision. Sediment has also accumulated in the head of the Poverty Canyon and episodic mass flows contribute significantly to continued modification of the indentation by driving canyon incision and triggering instability in the adjacent slopes.
Prograding clinoforms lying seaward of active faults beneath the shelf, and overlying a buried inactive thrust system beneath the upper slope, reveal a history of deformation accompanied by the creation of accommodation space. There is some more recent activity on shelf faults (i.e. Lachlan Fault) and at the transition into the lower margin, but reduced (~2 %) or no evidence of recent deformation for the majority of the upper to mid-slope. This is in contrast to current activity (approximately 24 to 47% shortening) across the lower slope and frontal wedge regions of the indentation. The middle to lower Poverty Canyon represents a structural transition zone within the indentation coincident with the indentation axis. The lower to mid-slope south of the canyon conforms more closely to a classic accretionary slope deformation style with a series of east-facing thrust-propagated asymmetric anticlines separated by early-stage slope basins. North of the canyon system, sediment starvation and seamount impact has resulted in frontal tectonic erosion associated with the development of an over-steepened lower to mid-slope margin, fault reactivation and structural inversion and over-printing.
Evidence points to at least three main seamount subduction events within the Poverty Indentation, each with different margin responses:
i) older substantial seamount impact that drove the first-order perturbation in the margin, since approximately ~1-2 Ma
ii) subducted seamount(s) now beneath Pantin and Paritu Ridge complexes, initially impacting on the margin approximately ~0.5 Ma, and
iii) incipient seamount subduction of the Puke Seamount at the current deformation front.
The overall geometry and geomorphology of the wider indentation appears to conform to the geometry accompanying the structure observed in sandbox models after the seamount has passed completely through the deformation front. The main morphological features correlating with sandbox models include: i) the axial re-entrant down which the Poverty Canyon now incises; ii) the re-establishment of an accretionary wedge to the south of the indentation axis, accompanied by out-stepping, deformation front propagation into the trench fill sequence, particularly towards the mouth of the canyon; iii) the linear north margin of the indentation with respect to the more arcuate shape of the southern accretionary wedge; and, iv) the set of faults cutting obliquely across the deformation front near the mouth of the canyon. Many of the observed structural and geomorphic features of the Poverty Indentation also correlate well both with other sediment-rich convergent margins where seamount subduction is prevalent particularly the Nankai and Sumatra margins, and the sediment-starved Costa Rican margin. While submarine canyon systems are certainly present on other convergent margins undergoing seamount subduction there appears to be no other documented shelf to trench extending canyon system developing in the axis of such a re-entrant, as is dominating the Poverty Indentation.
Ongoing modification of the Indentation appears to be driven by: i) continued smaller seamount impacts at the deformation front, and currently subducting beneath the mid-lower slope, ii) low and high sea-level stands accompanied by variations on sediment flux from the continental shelf, iii) over-steepening of the deformation front and mass movement, particularly from the shelf edge and upper slope.
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Lallemand, Serge. "La fosse du japon : contexte geodynamique et effets de la subduction d'asperites sur la tectogenese de la marge (programme kaiko)." Orléans, 1987. http://www.theses.fr/1987ORLE2039.
Full textAbstract:
On presente dans un premier temps, la chronologie et les modalites d'ouverture de la mer du japon et de ses differents bassins. Ils se sont ouverts en pull-apart le long de deux zones de cisaillement ou resultent du blocage du mouvement le long de la faille est-coreenne ou encore d'extension arriere-arc liee a la subduction pacifique. Ceci constitue le contexte geodynamique de la marge pacifique au niveau de la fosse du japon. On observe ensduite la subduction des asperites de la croute oceanique telles que horsts, grabens de la plaque plongeante, anciennes failles reactivees on volcans sous-marins. Le modele du prisme de coulomb semble s'appliquer parfaitement au passage d'un volcan sous une marge
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Legendre, Lucie. "Cinématique des déformations fragiles dans la partie Nord de l'arc des Petites Antilles." Thesis, Antilles, 2018. http://www.theses.fr/2018ANTI0276/document.
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Dans la partie Nord de la zone de subduction des Petites Antilles, la convergence est fortement oblique alors qu’au Sud elle est frontale. Cette étude vise à comprendre les conséquences de l’entrée en subduction du plateau des Bahamas fortement flottant par l’étude de l'évolution du champ de contrainte dans le NE de la plaque Caraïbes, depuis l’Eocène. Ce travail montre que sur les îles les plus anciennes, l’arc volcanique s'initie à l’Eocène. La migration de l’arc vers sa position actuelle se produit durant la période Miocène inférieur – Miocène supérieur. La période Oligo-Miocène est charnière : le champ de contrainte évolue d'une extension pure parallèle à la fosse de subduction, à une extension radiale. Après une restauration de la déformation régionale, j'attribue ce changement d’état de contrainte, à l’initiation du partitionnement de la déformation dans le NE de la plaque Caraïbe qui accommode la courbure de la fosse faisant suite à l’entrée en subduction du banc des Bahamas. Dans l’archipel Guadeloupéen, les analyses structurales à terre et en mer montrent des régimes en extension pure perpendiculaire à la fosse. Les orientations des failles similaires depuis l’Eocène confirment un fort héritage structural. À l’actuel, dans le coin NE des Petites Antilles, le régime tectonique est décrochant avec une direction d’extension principale orientée NO-SE soit parallèle à la fosse. Dans l’archipel Guadeloupéen le régime tectonique est purement extensif orienté NE-SO perpendiculairement à la fosse. Cette rotation est interprétée comme résultant de l’augmentation vers le Nord de l’obliquité de la convergence du fait de la courbure de la zone de subductionTo the north of the Lesser Antilles subduction zone, from North to South, the obliquity of the subduction is decreasing. This study is focus on the consequences of the entrance of Bahamas bank buoyant plateau into the subduction by studying stress field evolution in the NE of the Caribbean plate since Eocene. This work show that the volcanic arc activity on Anguilla bank islands begin at the Eocene. The volcanic arc migration toward his actual localisation occurs during early Miocene – late Miocene period. The Oligo-Miocene period is transitional as a switch in the stress field from pure parallel-to-the-trench to radial extension occurs. A restoration of the regional deformation shows that this switch is related to strain partitioning initiation in the upper Caribbean Plate in response to trench bending that followed the entrance of the Bahamas Bank in the subduction zone. In the Guadeloupean archipelago, kinematic analyses onshore and offshore show a pure extension with a perpendicular-to-the-trench σ3. The similar faults orientations since Eocene confirm that inherited structures control strain localisation. At present day, in NE corner of the Lesser Antilles, the NW-SE main extensional direction of strike-slip stress regime is trench-parallel. In the Guadeloupean archipelago, the pure extensive stress regime is trench-perpendicular (NE-SW). These different orientations of the stress field are interpreted to be the result of increasing trench bending to the North responsible for a northern increase of subduction obliquity
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Tan, Zhou. "P-T-deformation-time evolution of the Akeyasi HP/UHP complex (SW-Tianshan, China) and implications for subduction dynamics." Thesis, Sorbonne université, 2018. http://www.theses.fr/2018SORUS185/document.
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Cette étude vise à caractériser des fragments clés d’une interface de subduction fossile affleurant dans la Ceinture Métamorphique du Sud-Tianshan (Chine). Nous étudions les processus de subduction au travers de la profondeur critique de ~80 km, au-delà de laquelle la géophysique et les modèles prévoient un changement du couplage mécanique, et les roches océaniques ne sont normalement pas exhumées. Ce travail s’intéresse au Complexe Métamorphique Akeyazi (AMC), un épais empilement de roches métavolcanoclastiques enveloppant des écailles éclogitiques, exposé sur ~30 km dans la vallée de Kebuerte, et préservant de nombreuses reliques de coésites. L’étude structurale révèle que l’AMC est un dôme métamorphique consistant de plusieurs nappes cohérentes d’ampleur kilométrique avec des histoire P-T-t-d distinctes. 4 unités sur 6, i.e. UH (2.75 GPa/480-560°C), EB (2.1/505), MU (1.45/485) et GT (>0.7-1.0/470-520) ont été subduites à des profondeurs de ~85, 65, 45 et 30 km respectivement. La déformation rétrograde des unités, liée à leur exhumation, est caractérisée par des bandes de cisaillement top vers le Nord au faciès schiste bleu. Le pic d’enfouissement de ces unités a eu lieu à 320±1, 332±2, 359±2 et 280-310 Ma pour les unités UH, EB, MU et schiste vert, indiquant plusieurs courts épisodes de détachement de matériel de la plaque plongeante. L’évolution tectono-métamorphique de ~12 à 5-7°C/km au cours du temps peut refléter le refroidissement progressif de la subduction. La juxtaposition et l’exhumation à 1-3 mm/an de ces 4 unités à des profondeurs crustales a eu lieu autour de 290-300 MaThis study attempts to characterize key fossil fragments of material equilibrated along subduction plate boundary, now exposed in Chinese SW-Tianshan Metamorphic Belt (STMB). We herein elucidate some subduction zone processes across a critical depth range of ~80km, beyond which geophysicist and modeler infer a change in mechanical coupling and oceanic rocks are usually not recovered. It focuses on an unusually thick pile of HP/UHP metavolcanoclastics, wrapping eclogite slices and preserving pervasive coesite relics, along a ~30km-long transect across the Akeyazi metamorphic complex (AMC) in the Kebuerte valley. Structural studies reveal the current geometry of the AMC is a metamorphic dome with evidence of internal nappe stacking and should be subdivided into several coherent, km-scale tectonic units with distinct P-T-time-deformation histories. At least 4 of 6 sub-units identified here, i.e., the UH (2.75 GPa/480-560°C), EB (2.1/505), MU (1.45/485) and GT units (>0.7-1.0/470-520) were subducted and buried to depths of ~85, 65, 45 and 30 km respectively. Deformation following EC/BS-EC peak burial is marked by pervasive BS facies exhumation-related shear senses with a top to North component. Radiometric constraints yield peak burial ages of 320±1, 332±2, 359±2 and 280-310 Ma, respectively, for the UH, EB, MU and GS facies units, indicating several short-lived detachment episodes of material from the downgoing plate. The tectono-metamorphic evolution from ~12 to 5-7°C/km with time may reflect progressive cooling of the subduction system. Juxtaposition & exhumation of those 4 units to mid-crustal depth, at rates on the order of 1-3 mm/yr, was accomplished around 290-300Ma
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Marot, Marianne. "Zones de subduction horizontale versus normale : une comparaison basée sur la tomographie sismique en 3-D et de la modélisation pétrologique de la lithosphère continentale du Chili Central et d’Ouest de l’Argentine (29°S-35°S)." Thesis, Nice, 2013. http://www.theses.fr/2013NICE4046/document.
Full textAbstract:
Sous le Chili central et l’ouest de l'Argentine (29°-35°S), la plaque océanique Nazca, en subduction sous la plaque continentale Amérique du Sud, change radicalement de géométrie : inclinée à 30°, puis horizontale, engendrée par la subduction de la chaine de volcans de Juan Fernandez. Le but de mon étude est d'évaluer, la variation de nature et de propriétés physiques de la lithosphère chevauchante entre ces deux régions afin de mieux comprendre (1) sa structure profonde et (2) les liens entre les déformations observées en surface et en profondeur. Pour répondre à cette thématique, j’utilise une approche originale couplant la sismologie, la thermométrie, et la pétrologie. Je montre ainsi des images 3-D de tomographie sismique les plus complètes de cette région par rapport aux études précédentes, qui intègrent (1) de nombreuses données sismiques provenant de plusieurs catalogues, (2) un réseau de stations sismiques plus dense permettant de mieux imager la zone de subduction. J’apporte la preuve que la plaque en subduction se déshydrate dans deux régions distinctes : (1) le coin mantellique, et (2) le long de la ride subduite avant que celle-ci ne replonge plus profondément dans le manteau. La croûte continentale au-dessus du flat slab possède des propriétés sismiques très hétérogènes en relation avec des structures de déformation profondes et des domaines géologiques spécifiques. La croûte chevauchante d’avant-arc, au-dessus du flat slab, est décrite par des propriétés sismiques inhabituelles, liées à la géométrie particulière du slab en profondeur, et/ou liées aux effets du séisme de 1997 de Punitaqui (Mw 7.1). Mes résultats, confirmant les études antérieures, montrent que : - le bloc Cuyania situé plus à l’est, dans la zone d’arrière-arc est plus mafique et contient une croûte inférieure éclogitisée ; quant à, la croûte continentale inférieure sous l’arc Andin, est épaisse et non-éclogitisée, décrivant surement le bloc felsique de ChileniaBeneath central Chile and western Argentina, the oceanic Nazca slab drastically changes geometry from horizontal to dipping at an angle of 30°, and correlates with the subduction of the Juan Fernandez seamount ridge. The aim of our study is to assess, using a thermo-petrological-seismological approach, the differences of the overriding lithosphere between these two regions, in order to better understand the deep structure of the continental lithosphere above the flat slab, and the links between the deformations at the surface and at depth. We show the most complete regional 3-D seismic tomography images of this region, whereby, in comparison to previous studies, we use (1) a much larger seismic dataset compiled from several short-term seismic catalogs, (2) a much denser seismic station network which enables us to resolve better the subduction zone. We show significant seismic differences between the flat and normal subduction zones. As expected, the flat slab region is impacted by colder temperatures, and therefore by faster seismic velocities and more intense seismic activity, compared to the normal slab region. We show evidence that the flat slab dehydrates within the mantle wedge, but also along the subducting ridge prior to re-subducting. The forearc crust above the flat slab is described by unusual seismic properties, correlated to the slab geometry at depth, and/or, to the aftershock effects of the 1997 Mw 7.1 Punitaqui earthquake which occurred two years before the recording of our events. The continental crust above the flat slab has very heterogeneous seismic properties which correlate with important deformation structures and geological terranes at the surface. We confirm previous studies that have shown that the thick lower crust of the present day Andean arc is non-eclogitized and maybe representing the felsic Chilenia terrane, whereas to the east, the Cuyania terrane in the backarc is more mafic and contains an eclogitized lower crust
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Villanueva, Robles Fernando. "The role of the Investigator Fracture Zone in the Sumatra subduction zone process using high-resolution bathymetry, seismic data, and numerical geodynamic models." Thesis, Sorbonne Paris Cité, 2019. http://www.theses.fr/2019USPCC074.
Full textAbstract:
La plupart des grands séismes se produit sur les frontières de plaques tectoniques en subduction mais la segmentation sismique au long des zones de subduction reste encore mal comprise. Pour mieux comprendre cette segmentation sismique, j’ai traité, analysé et interprété des données de bathymétrie multifaisceaux et de sismique réflexion de haute résolution. Ces données ont été acquises durant la campagne géophysique MegaTera. Celle-ci a levé la région où la Zone de Fracture Investigator (IFZ en anglais), constituée de longues rides sous-marines, rentre dans la zone de subduction de Sumatra central. Les résultats de l’interprétation montrent que la subduction de ce groupe de quatre rides a un impact considérable sur la morphologie du prisme d’accrétion, notamment des failles normales et décrochantes, ainsi que des chevauchements, conduisant sous l’effet de l’érosion au développement de systèmes de canaux et de bassins complexes. Le relief des rides IFZ a soulevé les sédiments de l’avant-arc, produisant aussi de la subsidence à la suite de la subduction des rides. Les parties frontales des rides en subduction ont favorisé le maintien des chevauchements sur de longues durées, alors que le décollement passe horizontalement par les sédiments situés au-dessus des deux rides voisines. J’ai également réalisé des modèles 3D géodynamiques numériques afin d’étudier les effets de la subduction oblique de rides sur l’évolution de la contrainte persistante et les types de déformation permanente de l’avant-arc. Finalement, J’ai analysé et comparé les résultats des modèles numériques avec l’interprétation du plancher océanique et les structures situées sous la surface du fond marin. Les résultats intégrés indiquent que les rides IFZ en subduction ont généré une déformation du prisme d’accrétion et un comportement de la contrainte qui sont hétérogènes au long du prisme. Par conséquent, la subduction des rides IFZ pourrait favoriser l’hétérogénéité du couplage interplaque, agissant comme une frontière de segmentation sismique et représentant donc un candidat plausible pour arrêter la propagation du grand tremblement de terre de 2005 Nias-Simeulue, Mw 8.7Major earthquakes occur mainly on subduction plate boundaries, but what causes the along strike earthquake segmentation remains poorly understood. To understand earthquake segmentation, I have processed, analysed and interpreted high-resolution seismic reflection and multibeam bathymetry data acquired during the MegaTera experiment of 2015. The MegaTera survey covered an area where the Investigator Fracture Zone (IFZ), a linear group of long ridges, impinges the trench along the central Sumatra subduction zone. The interpretation results show the subduction of these four groups of ridges has a considerable impact on the accretionary wedge morphology, including strike-slip and normal faulting, along with thrusts, leading to the development of complex channel systems and basins, and hence erosion. The relief of IFZ ridges has uplifted the forearc sediments, creating subsidence in the wake of subducting ridges. Frontal parts of the subducting ridges have created long-lived thrusts, whereas the décollement horizontally passes through the sedimentary sequences on the top of two neighbouring ridges. Additionally, I have performed 3-D numerical geodynamic models to study the effects of oblique subduction of ridges on the persistent stress evolution and the permanent forearc deformation patterns. Finally, I have analysed and compared the numerical experiments to the interpretation of the seafloor and subsurface features. The overall results indicate the subducting IFZ create heterogeneous wedge deformation and stress behaviour along the accretionary prism. Hence, the subduction of the IFZ might promote a heterogeneous inter-plate coupling, acting as a segment boundary and being a proper candidate for having stopped the south-eastward propagation of the 2005 Mw 8.7 Nias-Simeulue earthquake
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Pichot, Thibaud. "Les rides de Barracuda et de Tiburon, à l'Est de la subduction des Petites Antilles : origine, évolution et conséquences géodynamiques." Phd thesis, Université de Bretagne occidentale - Brest, 2012. http://tel.archives-ouvertes.fr/tel-00846889.
Full textAbstract:
Les rides de Barracuda et de Tiburon sont deux reliefs sous-marins situés dans la partie ouest de l'océan Atlantique, là où la lithosphère océanique des plaques Amérique du Nord (NAM) et Amérique du Sud (SAM) est entraînée par subduction sous la plaque Caraïbe, formant l'arc volcanique des Petites Antilles et le prisme d'accrétion de Barbade. Le processus et la période de soulèvement conduisant au relief actuel de ces rides (qui semblent être un marqueur important dans l'histoire géodynamique de la région) sont sujets à débat depuis des décennies.L'interprétation de nouvelles données de sismique réflexion et de bathymétrie multifaisceaux acquises à travers les rides de Barracuda et de Tiburon (campagne Antiplac, 2007 ) a permis de dater les périodes de soulèvements des rides et réaliser des reconstructions paléogéographiques incluant les flux sédimentaires majeurs, depuis le Crétacé jusqu' à l'Actuel.L'analyse structurale révèle des phases de réactivations tardives d'anciennes zones de fractures dans un contexte transpressif, conduisant aux surrections des rides de Tiburon et de Barracuda.Les processus géologiques possibles impliqués dans la formation des rides de Barracuda et de Tiburon coïncident avec les modèles cinématiques récents décrivant les mouvements relatifs entre les plaques NAM et SAM, le long de la limite de plaque diffuse.Ces résultats permettent de mieux définir la limite de plaque entre NAM et SAM. Elle est nécessairement hétérogène exploitant les zones de faiblesses dans la lithosphère que sont les zones de fracture. Au sein de cette limite de plaque la lithosphère serait donc fragmentée.
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Gao, Haiying. "The seismic structures of the U.S. Pacific Northwest and the scaling and recurrence patterns of slow slip events." Thesis, University of Oregon, 2011. http://hdl.handle.net/1794/11230.
Full textAbstract:
xv, 136 p. : ill. (some col.)The Pacific Northwest of the United States has been tectonically and magmatically active with the accretion of the Farallon oceanic terrane "Siletzia" ∼50 Ma. The accretion of Siletzia terminated the flat-slab subduction of the Farallon slab and initiated the Cascadia subduction zone. In this dissertation, I focus on both the large-scale tectonic structures preserved seismically in the crust and upper mantle, and the small-scale, short-term aseismic processes on the plate interface. I measure the shear-wave splitting trends around eastern Oregon with a dataset of ∼200 seismometers from 2006-2008 to analyze the upper-mantle anisotropy. The delay times between splitted shear-waves range from 0.8 s to 2.7 s. In the High Lava Plains, the fast polarization direction is approximately E-W with average delay time ∼1.8 s. I infer that there must be significant active flow in a roughly E-W direction in the asthenosphere beneath this area. The splitting pattern is more variable and complicated in NE Oregon, where the crust and mantle lithosphere may be a significant contribution. In terms of the imaged seismic velocity structures, I infer that the Eocene sedimentary basins in south-central Washington lie above a magmatically underplated crust of extended Siletzia lithosphere. Siletzia thrusts under the pre-accretion forearc, and its southeast termination is especially strong and sharp southeast of the Klamath-Blue Mountains gravity lineament. Magmatic intrusion has increased upper crustal velocity as in the less active Washington Cascades, but the higher temperatures beneath the magmatically active Oregon Cascades have a dominating effect. To better understand the physical mechanism of slow slip events on the plate interface, I explore the scaling relationships of various source parameters collected mainly from subduction zones worldwide and also other tectonic environments. The source parameter scaling relationships of slow slip events highlight the similarities and differences between slow slip phenomena and earthquakes. These relationships hold implications for the degree of heterogeneity and fault healing characteristics. The recurrence statistics of northern Cascadia events behave weakly time predictable and moderately anti-slip predictable, which may indicate healing between events. This dissertation includes co-authored materials both previously published and submitted for publication.
Committee in charge: Eugene Humphreys, Chairperson; David Schmidt, Member; Ray Weldon, Member; James Isenberg, Outside Member
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Rosenbaum, Gideon. "Tectonic reconstruction of the Alpine orogen in the western Mediterranean region." Monash University, School of Geosciences, 2003. http://arrow.monash.edu.au/hdl/1959.1/9481.
Full text
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Marot, Marianne. "Zones de subduction horizontale versus normale : une comparaison basée sur la tomographie sismique en 3-D et de la modélisation pétrologique de la lithosphère continentale du Chili Central et d'Ouest de l'Argentine (29°S-35°S)." Phd thesis, Université Nice Sophia Antipolis, 2013. http://tel.archives-ouvertes.fr/tel-00917761.
Full textAbstract:
Sous le Chili central et l'ouest de l'Argentine (29°-35°S), la plaque océanique Nazca, en subduction sous la plaque continentale Amérique du Sud, change radicalement de géométrie : inclinée à 30°, puis horizontale, engendrée par la subduction de la chaine de volcans de Juan Fernandez. Le but de mon étude est d'évaluer, la variation de nature et de propriétés physiques de la lithosphère chevauchante entre ces deux régions afin de mieux comprendre (1) sa structure profonde et (2) les liens entre les déformations observées en surface et en profondeur. Pour répondre à cette thématique, j'utilise une approche originale couplant la sismologie, la thermométrie, et la pétrologie. Je montre ainsi des images 3-D de tomographie sismique les plus complètes de cette région par rapport aux études précédentes, qui intègrent (1) de nombreuses données sismiques provenant de plusieurs catalogues, (2) un réseau de stations sismiques plus dense permettant de mieux imager la zone de subduction. J'apporte la preuve que la plaque en subduction se déshydrate dans deux régions distinctes : (1) le coin mantellique, et (2) le long de la ride subduite avant que celle-ci ne replonge plus profondément dans le manteau. La croûte continentale au-dessus du flat slab possède des propriétés sismiques très hétérogènes en relation avec des structures de déformation profondes et des domaines géologiques spécifiques. La croûte chevauchante d'avant-arc, au-dessus du flat slab, est décrite par des propriétés sismiques inhabituelles, liées à la géométrie particulière du slab en profondeur, et/ou liées aux effets du séisme de 1997 de Punitaqui (Mw 7.1). Mes résultats, confirmant les études antérieures, montrent que : - le bloc Cuyania situé plus à l'est, dans la zone d'arrière-arc est plus mafique et contient une croûte inférieure éclogitisée ; quant à, la croûte continentale inférieure sous l'arc Andin, est épaisse et non-éclogitisée, décrivant surement le bloc felsique de Chilenia.
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Handayani, Lina. "Seismic tomography constraints on reconstructing the Philippine Sea Plate and its margin." Texas A&M University, 2004. http://hdl.handle.net/1969.1/1497.
Full textAbstract:
The Philippine Sea Plate has been surrounded by subduction zones throughout Cenozoic time due to the convergence of the Eurasian, Pacific and Indian-Australian plates. Existing Philippine Sea Plate reconstructions have been made based primarily on magnetic lineations produced by seafloor spreading, rock magnetism and geology of the Philippine Sea Plate. This dissertation employs seismic tomography model to constraint the reconstruction of the Philippine Sea Plate. Recent seismic tomography studies show the distribution of high velocity anomalies in the mantle of the Western Pacific, and that they represent subducted slabs. Using these recent tomography data, distribution maps of subducted slabs in the mantle beneath and surrounding the Philippine Sea Plate have been constructed which show that the mantle anomalies can be related to the various subduction zones bounding the Philippine Sea Plate.
The high velocity mantle anomalies are clearly coincident with Wadati-Benioff zones in the upper mantle. The lower mantle anomalies, although distributed in the transition zone (500-1000 km) as stagnant slabs in some cases, can clearly be mapped as continuations of upper mantle subduction zones. Reconstructing the subduction of the slabs now in the mantle best fits Philippine Sea Plate reconstructions that involve the minimal or simplest rotations. Northward movement of the Philippine Sea Plate, WNW subduction of the Pacific Plate since Eocene time (~50 Ma), and northward subduction of the Indian/Australian Plate along Indonesia best explain the subducted slab mantle anomalies. The origin of the eastern plate boundary was a transform zone that evolved into a subduction zone a few million years before the Pacific Plate changed its movement. In addition, the initiation of this subduction zone might possibly be one of the triggers of the Pacific Plate motion changes.
The 90 degree rotation of the Philippine Sea Plate including southward plate subduction at its northern boundary proposed in the reconstruction by Hall (2002) is not supported by seismic tomography evidence for slab distribution in the mantle beneath the Philippine Sea region. A hypothesis of minimal rotation of the Philippine Sea Plate, supported by the seismic tomography, guides the reconstruction model presented.
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Rossi, Tristan. "Contribution à l'étude géologique de la frontière Sud-Est de la plaque Caraïbes : La Serrania Del Interior Oriental (Venezuela) sur le transect Cariaco-Maturin : Synthèses paléogéographique et géodynamique." Brest, 1985. http://www.theses.fr/1985BRES0001.
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Une etude de terrain detaillee sur le transect cariaco-maturin a permis de dresser des cartes de repartition de facies mettant en evidence deux organisations successives et completement differentes : - du neocomien (. ) - barremien a la base du miocene inferieur, le dispositif paleogeographique est celui d'une marge passive (caracterisee par un tres vaste domaine de plate-forme) ouverte vers l'ocean au nord et au nord-est (ocean tethysien puis atlantique). La sedimentation enregistre differentes variations eustatiques et mouvements verticaux epirogeniques mais pas de transformation majeure. - du miocene inferieur a l'actuel, la tectonisation de la bordure septentrionale de ce domaine aboutit a la formation d'un bassin interieur ouvert sur l'ocean atlantique vers l'est et le nord-est. Il sera progressivement comble et repousse vers l'est. L'analyse tectonique detaillee du transect a partir de donnees de surface de sub-surface, a permis de definir le style structural (importance des chevauchements), de preciser la nature et l'histoire des grands accidents tels les failles de caripe, de san francisco, de pirital et de rio grande, et de mettre en evidence l'importance des phenomenes de tectonique gravitaire (collapse-structures).
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Maunder, Benjamin Louis. "The role of the dynamics of the subducting plate in generating arc magmatism." Thesis, Durham University, 2017. http://etheses.dur.ac.uk/12333/.
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The thermal state of subducting plates is thought to be of great importance in the generation of the arc magmatism above them. The temperature of slabs affects dehydration, the primary driver of arc magmatism, but may also determine whether the slab itself undergoes partial melting. The focus of this study has therefore been slab temperature: how sensitive it is to the dynamic properties of the slab, and exactly what effect it has on arc magmatism today and back in Earth’s early history. Through the use of numerical models, we improve on existing proxies for slab temperature. Our models demonstrate that the temperature of different parts of the slab depend variably on slab age, trench normal convergence rate, slab dip and the decoupling depth of the subducting and over-riding plates. In addition to forward modelling, we worked backwards from real-world data. To this end we developed a tool to search for statistically significant correlations between the same slab parameters, as well as over-riding crustal thickness, and the trace element characteristics of arc lavas in global databases. We also investigate a recently proposed dynamic process which may have an effect on arc processes: the formation of plumes of slab derived material (relamination). We find that the relamination of mafic oceanic crust is more likely under Archean conditions, potentially explaining systematic differences between the chemistry of Archean rocks and more modern continental crust and arc rock. We also undertook a preliminary investigation on the feasibility and effect that episodically driven subduction could have on the thermal profile of subducting slabs. We demonstrate here that through forward numerical modelling and analysis of the chemistry of arc lavas, we can gain valuable insight into the thermal state and complex dynamics of the slab in the critical sub-arc region.
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Magni, Valentina <1984>. "Numerical models of trench migration for lateral heterogeneous subducting plates." Doctoral thesis, Alma Mater Studiorum - Università di Bologna, 2012. http://amsdottorato.unibo.it/4280/.
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The aim of this Thesis is to investigate the effect of heterogeneities within the subducting plate on the dynamics of subduction. In particular, I study the motion of the trench for oceanic and continental subduction, first, separately, and, then, together in the same system to understand how they interact. The understanding of these features is fundamental to reconstruct the evolution of complex subduction zones, such as the Central Mediterranean.
For this purpose, I developed 2D and 3D numerical models of oceanic and continental subduction where the rheological, geometrical and compositional properties of the plates are varied. In these models, the trench and the overriding plate move self-consistently as a function of the dynamics of the system.
The effect of continental subduction on trench migration is largely investigated. Results from a parametric study showed that despite different rheological properties of the plates, all models with a uniform continental crust share the same kinematic behaviour: the trench starts to advance once the continent arrives at the subduction zone. Hence, the advancing mode in continental collision scenarios is at least partly driven by an intrinsic feature of the system. Moreover, the presence of a weak lower crust within the continental plate can lead to the occurrence of delamination. Indeed, by changing the viscosity of the lower crust, both delamination and slab detachment can occur. Delamination is favoured by a low viscosity value of the lower crust, because this makes the mechanical decoupling easier between crust and lithospheric mantle. These features are observed both in 2D and 3D models, but the numerical results of the 3D models also showed that the rheology of the continental crust has a very strong effect on the dynamics of the whole system, since it influences not only the continental part of plate but also the oceanic sides.
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Norabuena, Edmundo O. "Velocity Structure of the Subducting Nazca Plate beneath central Peru as inferred from Travel Time Anomalies." Thesis, Virginia Tech, 1993. http://hdl.handle.net/10919/36657.
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Arrival times from intermediate-depth (110-150 km) earthquakes within the region of flat subduction beneath central Peru provide constraints on the geometry and velocity structure of the subducting Nazca plate. Hypocenters for these events, which are beneath the sub-andean and eastern Peruvian basins, were determined using a best-fitting onedimensional velocity-depth model with a 15-station digitally-recording network deployed in the epicentral region. For that model, P-wave travel times to coastal stations, about 6° trenchward, exhibit negative residuals of up to 4 seconds and have considerably more complexity than arrivals at the network stations.
The residuals at coastal stations are conjectured to result from travel paths with long segments in the colder, higher velocity subducting plate. Travel time anomalies were modeled by 3-D raytracing. Computed ray paths show that travel times to coastal stations for the eastern Peru events can be satisfactorilymodeled if velocities relative to the surrounding mantle are 6% lower within the uppermost slab (a 6 km thick layer composed of basaltic oceanic crust) and 8% higher within the cold peridotitic layer (which must be at least 44 km thick). Raytracing runs for this plate model show that "shadow zones" can occur if the source-slab-receiver geometry results in seismic rays passing through regions in which the slab undergoes significant changes in slope. Such geometries exist for seismic waves propagating to some coastal stations from sources located beneath the eastern Peruvian basin. Observed first-arrival times for such cases do in fact have less negative residuals than those for geometries which allow for \direct\ paths. Modeling such arrivals as trapped mode propagation through the high-velocity part of the plate produces arrival times consistent with those observed.Master of Science
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Ohkura, Takahiro. "Layered structure of the subducting oceanic plates; implications for the intraplate seismic zones." 京都大学 (Kyoto University), 1998. http://hdl.handle.net/2433/157163.
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本文データは平成22年度国立国会図書館の学位論文(博士)のデジタル化実施により作成された画像ファイルを基にpdf変換したものであるKyoto University (京都大学)
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新制・論文博士
博士(理学)
乙第9782号
論理博第1328号
新制||理||1060(附属図書館)
UT51-98-G381
(主査)教授 安藤 雅孝, 教授 尾池 和夫, 助教授 中西 一郎
学位規則第4条第2項該当
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Miller, Matthew Robert. "The seismic structure beneath the Aysén Region of Chile : constraints on the subduction of young (< 6 Ma) oceanic plates." Thesis, University of Cambridge, 2010. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.608999.
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Contreras-Reyes, Eduardo [Verfasser]. "Evolution of the seismic structure of the incoming, subducting oceanic Nazca Plate off South Central Chile / Eduardo Contreras-Reyes." Kiel : Universitätsbibliothek Kiel, 2008. http://d-nb.info/1019669535/34.
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Margirier, Audrey. "Tectonique et processus d’exhumation des Cordillères Blanche et Noire en contexte de subduction horizontale (Nord Pérou)." Thesis, Université Grenoble Alpes (ComUE), 2015. http://www.theses.fr/2015GREAU023/document.
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Ma thèse se focalise sur l'étude des mécanismes qui ont conduit au soulèvement et à la construction du relief dans les Andes du Nord du Pérou. Dans cette région, la Cordillère Blanche forme les plus hauts sommets péruviens (> 6000 m) et constitue une anomalie à l'échelle des Andes. La morphologie de cette région des Andes est marquée par un pluton de forme atypique, allongé et à l'affleurement sur plus de 150 km. Ce pluton est bordé par une faille normale de plus de 200 km de long. La présence de cette faille normale majeure en contexte de subduction plane reste surprenante car ces zones de subduction planes semblent induire une augmentation du raccourcissement dans la plaque chevauchante. Mon travail a eu pour objectifs de caractériser les variations de l'état de contraintes régional, l'âge du soulèvement et de discuter les processus géodynamiques qui ont contribué à la formation du relief. Dans ce cadre, j'ai utilisé une approche pluridisciplinaire impliquant sur plusieurs échelles spatio-temporelles et comprenant à la fois de nouvelles données de terrain, leur analyse et leur modélisation.Mes données de microtectonique indiquent qu'il est possible de générer de l'extension au dessus d'une subduction plane à l'échelle régionale. Ces données sont en contradiction avec l'augmentation du raccourcissement classiquement attendue dans la plaque chevauchante. Mes nouvelles données de thermochronologie basse température et leur modélisation montrent une augmentation de l'exhumation induite par le soulèvement de la Cordillère Occidentale à 15 Ma. En les confrontant aux modèles précédents, je propose un soulèvement régional lié à l'aplatissement de la subduction et à la topographie dynamique associée.J'ai également étudié l'impact de l'arc Miocène sur le soulèvement à une échelle plus locale. Pour cela, j'ai compilé tous les âges de refroidissement du pluton disponibles dans la littérature. En parallèle, j'ai obtenu les premières données de profondeur de mise en place du batholite de la Cordillère Blanche. Cela m'a permis de proposer une structure du batholite en sills empilés puis basculés vers l'est. De plus, la modélisation des variations spatio-temporelle des taux d'érosion à partir des données de thermochronologie basse température indique une augmentation importante des taux d'érosion dans la Cordillère Blanche à partir de 2 Ma. L'arc Miocène ne semble donc pas contribuer significativement au soulèvement malgré sa probable contribution à l'épaississement de la lithosphère. En revanche, l'érosion glaciaire récente semble contribuer fortement à l'exhumation de la Cordillère Blanche et au basculement du batholite.Dans la dernière partie de ma thèse, pour quantifier l'importance de l'érosion dans la création du relief et le soulèvement, j'ai modélisé l'évolution du paysage de la région (FastScape). Mes modélisations numériques démontrent le rôle majeur de l'érosion et du rebond flexural associé dans la création du relief et les taux de soulèvement. Pour finir, basée sur les données de la littérature et celles apportées par mon travail de thèse, je propose un nouveau modèle pour expliquer la faille normale de la Cordillère Blanche dans son contexte régional. Ce modèle implique une faille normale d'extrado et l'érosion importante du mur de la failleMy thesis focuses on the mechanisms that controlled the uplift and construction of the relief in the northern Peruvian Andes. In this area, the Cordillera Blanca forms the highest peaks in Peru (> 6000 m), which is a topographic anomaly across the Andes. The morphology of the Cordillera Blanca is marked by an elongated pluton, which outcrops over 150 km. In addition, this pluton is bordered by the largest normal fault from South America. The presence of this major normal fault in a flat-slab context remains surprising because flat slabs usually induce an increase of the shortening in the overriding plate. The aim of my work is to characterize the variations of the regional stress field, the age of the uplift and discuss the geodynamic processes that contributed to relief building. To address these issues, I used a multidisciplinary approach involving new field data, their analysis and modeling.My microtectonic dataset reveals regional extension above the Peruvian flat-slab. This data contradicts the expected increase of shortening in the overriding plate. Modeling my new thermochronologic data shows an increase in the exhumation rates induced by the uplift of the Cordillera Occidental since 15 Ma. I propose that the regional uplift relates to the flattening of the subduction and associated dynamic topography.To address the impact of the Miocene arc on the uplift at a more local scale, I compiled the cooling ages of the pluton available in the literature. In parallel, I obtained the first amphibole thermo-barometry data that constrains emplacement depth of the Cordillera Blanca batholith. Following these data, I propose that the batholith is structured in eastward-tilted sills. In addition, modeling of the space and time variations of erosion rates based on the inversion of thermochronologic data indicates that erosion rates significantly increased in the Cordillera Blanca since 2 Ma. The Miocene arc seems to insignificantly contribute to the local uplift despite its contribution to the thickening of the lithosphere. Thus, I suggest that the recent glacial erosion contributes to the exhumation of the Cordillera Blanca and subsequent tilting of the batholith.Then, I modeled the landscape evolution for the Cordillera Blanca region to quantify the contribution of erosion in the relief building and the uplift. My numerical models (FastScape) evidence the importance of erosion and associated flexural rebound in fostering relief building and the uplift rates.Finally, based on all available data, I propose a new regional model to explain the Cordillera Blanca normal fault. This model implies an extrado normal fault and erosion of the footwall