Author: Kirsty Mckenzie Publisher: ISBN: Category : Languages : en Pages : 0
Book Description
In this dissertation I use observations of upper-plate deformation to constrain the kinematics and dynamics of tectonic processes that occur at subduction zones and within plate boundary transition zones. I combine observations that record deformation over weeks to decades (geodetic observations), tens to hundreds of thousands of years (field observations and geochronology), and millions of years (field observations and plate boundary reconstructions), with earthquake cycle modeling. This research is primarily focused on the Cascadia subduction zone, however the results are applicable across many subduction zones globally. Specific related cases that are highlighted include the Hikurangi margin (New Zealand) and the Nankai trough (SW Japan). The studies in my research range from using observations of slow slip earthquakes to constrain the plate motion direction and forces acting down-dip of the seismogenic zone, to observations of permanent upper-plate deformation to better understand the relationship between shallow mechanical locking on the plate interface and upper-plate deformation. Some key findings I present over several chapters are: (1) a model for the Cascadia subduction zone (and other obliquely-convergence subduction zones) that suggests that loading of the locked region at deep levels is down-dip and thus oblique to the loading direction at shallow levels; (2) a new coupling model for the Cascadia subduction zone that relates the variation in GPS velocities (and permanent deformation) from south to north across the margin to the locations of upper-plate strength (geologic terrane) boundaries; and (3) permanent coastal uplift is not being produced continuously, and instead observations from central Cascadia suggest uplift rates can change significantly over ~20 kyrs.
Author: Timothy H. Dixon Publisher: Columbia University Press ISBN: 9780231138666 Category : Computers Languages : en Pages : 696
Book Description
Subduction zones, one of the three types of plate boundaries, return Earth's surface to its deep interior. Because subduction zones are gently inclined at shallow depths and depress Earth's temperature gradient, they have the largest seismogenic area of any plate boundary. Consequently, subduction zones generate Earth's largest earthquakes and most destructive tsunamis. As tragically demonstrated by the Sumatra earthquake and tsunami of December 2004, these events often impact densely populated coastal areas and cause large numbers of fatalities. While scientists have a general understanding of the seismogenic zone, many critical details remain obscure. This volume attempts to answer such fundamental concerns as why some interplate subduction earthquakes are relatively modest in rupture length (greater than 100 km) while others, such as the great (M greater than 9) 1960 Chile, 1964 Alaska, and 2004 Sumatra events, rupture along 1000 km or more. Contributors also address why certain subduction zones are fully locked, accumulating elastic strain at essentially the full plate convergence rate, while others appear to be only partially coupled or even freely slipping; whether these locking patterns persist through the seismic cycle; and what is the role of sediments and fluids on the incoming plate. Nineteen papers written by experts in a variety of fields review the most current lab, field, and theoretical research on the origins and mechanics of subduction zone earthquakes and suggest further areas of exploration. They consider the composition of incoming plates, laboratory studies concerning sediment evolution during subduction and fault frictional properties, seismic and geodetic studies, and regional scale deformation. The forces behind subduction zone earthquakes are of increasing environmental and societal importance.
Author: Larry J. Ruff Publisher: Birkhäuser ISBN: 3034891407 Category : Science Languages : en Pages : 280
Book Description
Subduction zones consume oceanic lithosphere and are an indispensible part of plate tectonics. Unlike the oceanic lithosphere production system which can be linked as a nearly continuous, albeit sinuous, strand around the earth, subduction zones are a rather dissociated group and are found in several isolated corners of the world. While plate tectonics can predict that subduction zones are required along certain plate boundaries, it does not stipulate how subduction zones initiate and develop. The preservation of newly created oceanic lithosphere and the propensity for spreading centers to fragment continents leaves a wealth of geological informa tion on the initiation and evolution of spreading. On the other hand, the subject of subduction initiation has little observational basis. To find such observations, we need to look at some muddled tectonic regimes. The Macquarie Ridge complex presents a natural laboratory for studies of subduction initiation. 2. Tectonics of the Macquarie Ridge Complex The Macquarie Ridge complex is a complicated physiographic feature that trends approximately north-south between South Island, New Zealand and the Pacific-Antarctica spreading center. This feature consists of a sequence of troughs and ridges, with Macquarie Island as the only exposed expression. The seismically active Macquarie Ridge complex (hereafter: MRC) is crudely continuous with the Tonga-Kermadec-New Zealand seismic activity. The basic physiographic features and seismicity of the MRC are shown in Figure I. The earthquake epicenters generally cluster about the bathymetric expression of the MRC.
Author: Gabriele Morra Publisher: John Wiley & Sons ISBN: 1118888995 Category : Science Languages : en Pages : 208
Book Description
Subduction dynamics has been actively studied through seismology, mineral physics, and laboratory and numerical experiments. Understanding the dynamics of the subducting slab is critical to a better understanding of the primary societally relevant natural hazards emerging from our planetary interior, the megathrust earthquakes and consequent tsunamis. Subduction Dynamics is the result of a meeting that was held between August 19 and 22, 2012 on Jeju island, South Korea, where about fifty researchers from East Asia, North America and Europe met. Chapters treat diverse topics ranging from the response of the ionosphere to earthquake and tsunamis, to the origin of mid-continental volcanism thousands kilometers distant from the subduction zone, from the mysterious deep earthquakes triggered in the interior of the descending slabs, to the detailed pattern of accretionary wedges in convergent zones, from the induced mantle flow in the deep mantle, to the nature of the paradigms of earthquake occurrence, showing that all of them ultimately are due to the subduction process. Volume highlights include: Multidisciplinary research involving geology, mineral physics, geophysics and geodynamics Extremely large-scale numerical models with sliate-of-the art high performance computing facilities Overview of exceptional three-dimensional dynamic representation of the evolution of the Earth interiors and of the earthquake and subsequent tsunami dynamics Global risk assessment strategies in predicting natural disasters This volume is a valuable contribution in earth and environmental sciences that will assist with understanding the mechanisms behind plate tectonics and predicting and mitigating future natural hazards like earthquakes, volcanoes and tsunamis.
Author: Amy E. Draut Publisher: Geological Society of America ISBN: 0813724368 Category : Science Languages : en Pages : 446
Book Description
"Inspired by a GSA Penrose Conference held in 2005 (cosponsored by the International Association of Sedimentologists and the British Sedimentological Research Group), the 17 papers in this volume explore sedimentary environments in arc collision zones and their utility in recording the evolution of modern and ancient convergent margins. The first set of papers in the collection focuses on formation and evolution of the sedimentary record in arc settings and arc collision zones, concentrating on modern intra-oceanic examples. Papers include studies of flexural modeling and factors that affect development of siliciclastic and carbonate deposits around modern arcs. The second half of the volume presents new applications of arc sedimentary records. These relate primarily to constraining tectonic events in the evolution of arc systems, but also concern the links among tectonic uplift, collision, and geomorphic and climatic feedback mechanisms in arc collision zones."--Publisher's website.
Author: Publisher: ISBN: Category : Languages : en Pages : 0
Book Description
On earth, two types of convergent plate boundaries exist, namely subduction zones and collision zones. Subduction zones are the main driver of plate tectonics through sinking of negatively buoyant oceanic lithospheric slabs in the mantle and the subduction-induced large-scale mantle flow. Collision zones form when two positively buoyant continental plates meet and collide, following a phase of subduction. Both subduction zones and collision zones cause frequent and tremendous geological activities, which cause overriding plate deformation and form large-scale topography. However, the processes of subduction and collision and the mechanisms driving the associated overriding plate deformation and topography still remain unclear. Since subduction and collision operate at large spatial and temporal scales, a useful and effective way to investigate the processes of subduction and collision is by using analog or numerical modeling. Therefore, in this PhD project, I implement four-dimensional subduction and collision experiments to investigate different subduction/collision styles and mechanisms for deforming the overriding plate and forming topography during subduction/collision. This project comprises two equally weighted parts: (1) The first part investigates the two end-member styles of subduction, namely slab rollback and slab rollover, and their effect on overriding plate deformation and topography, because little research has been conducted on the rollover subduction style, and it remains unclear how and why these different subduction styles emerge. Therefore, Chapters 2 and 3 focus on subduction styles and how the two contrasting subduction styles affect mantle flow, overriding plate deformation and topography in subduction zones. This part of the thesis demonstrates how plate length can control the subduction style, and how the subduction style affects the overriding plate differently.
Author: Serge Lallemand Publisher: Springer Science & Business Media ISBN: 3540879749 Category : Science Languages : en Pages : 278
Book Description
Subduction is a major process that plays a first-order role in the dynamics of the Earth. The sinking of cold lithosphere into the mantle is thought by many authors to be the most important source of energy for plates driving forces. It also deeply modifies the thermal and chemical structure of the mantle, producing arc volcanism and is responsible for the release of most of the seismic energy on Earth. There has been considerable achievements done during the past decades regarding the complex interactions between the various processes acting in subduction zones. This volume contains a collection of contributions that were presented in June 2007 in Montpellier (France) during a conference that gave a state of the art panorama and discussed the perspectives about "Subduction Zone Geodynamics". The papers included in this special volume offer a unique multidisciplinary picture of the recent research on subduction zones geodynamics. They are organized into five main topics: Subduction zone geodynamics, Seismic tomography and anisotropy, Great subduction zone earthquakes, Seismogenic zone characterization, Continental and ridge subduction processes. Each of the 13 papers collected in the present volume is primarily concerned with one of these topics. However, it is important to highlight that papers always treat more than one topic so that all are related lighting on different aspects of the complex and fascinating subduction zones geodynamics.
Author: Zhihao Chen Publisher: ISBN: Category : Languages : en Pages : 286
Book Description
Subduction zones are thought to be the main driver of plate tectonics and mantle convection. Since the development of the theory of plate tectonics, subduction zones have been investigated and discussed, but in many ways they are still an enigma. Geodynamic modelling (analogue or numerical) can be an effective tool to gain insight into the temporal evolution of subduction zones as it provides quantitative and conceptual insights into the interactions between the plates, the slab and the mantle. Moreover, modelling results can then be compared to their natural prototypes providing crucial insight into regional processes.In my PhD project I use four-dimensional laboratory-based (analogue) geodynamic models to investigate the kinematics and dynamics of subduction, with a particular emphasis on the deformation in the overriding plate. I then compare and constrain my results with natural observations from subduction zones. My thesis has been divided into two parts. The first part focuses on the patterns of overriding plate deformation during progressive subduction when some parameters of the overriding plate are varied. In the first work (Chapter 4), the strength of the overriding plate (i.e., viscosity ratio between the overriding plate and the sub-lithospheric upper mantle, and the overriding plate thickness) is varied to quantify the energy dissipation of overriding plate deformation. The results show that only a small portion of the slab negative buoyancy force and its potential energy are used to deform the overriding plate, and the force required to deform the overriding plate is comparable in magnitude with the ridge push force. Furthermore, the results also show that the bending dissipation at the subduction zone hinge remains relatively low (during steady state subduction), irrespectively of including/excluding an overriding plate in the models. In the second work (Chapter 5), far-field boundary conditions of the overriding plate and subducting plate are varied. The results indicate that such a variation has an influence on the slab geometry and subduction kinematics. The models imply that in natural (narrow) subduction zones, assuming a homogeneous overriding plate, the formation of a backarc basin (e.g., Tyrrhenian Sea, Aegean Sea, Scotia Sea) is generally expected to occur at a comparable location with respect to the trench, irrespective of the boundary condition. In addition, my models indicate that the style of forearc deformation (shortening or extension) is affected by the mobility of the overriding plate through controlling the force normal to the subduction zone interface (trench suction). Finally, the results of the model with both plates fixed at their trailing edges are applied to the Calabria subduction zone. This model explains the latest Middle Miocene to present backarc and forearc extension at the Calabria subduction zone as a direct consequence of subduction of the narrow Calabrian slab and the immobility of both the subducting African plate and overriding Eurasian plate.The second part of this thesis focuses on the role of subduction-induced mantle flow in driving deformation of the overriding plate, including (horizontal) trench-normal backarc deformation (Chapter 6) and topography of the overriding plate (Chapter 7). In Chapter 6, a stereoscopic Particle Image Velocimetry (sPIV) technique was used to map simultaneously the horizontal overriding plate deformation and the 3D subduction-induced mantle flow underneath and around the overriding plate. The results show that the strain field of the overriding plate is characterized by localization of an area of maximum extension within its interior (at 300-500 km from the trench). The position of this maximum extension corresponds to that of the maximum trench-normal horizontal velocity gradient measured in the mantle at a scaled depth of 15-25 km below the base of the overriding plate. The results robustly support the hypothesis that in narrow subduction zones backarc extension in the overriding plate is mainly a consequence of the trench-normal horizontal gradients of basal drag force at the base of overriding plate. Such gradients result from a differential in the mantle flow velocity field induced by slab rollback. In Chapter 7, I also used the sPIV technique to investigate the vertical displacement of the overriding plate in a self-consistent subduction model with free boundary conditions. It is suggested that the trench suction force normal to the subduction zone interface, in combination with the shear force at the interface, has an overall influence on the topography of the overriding plate, through bending the overriding plate downward at the trench. Furthermore, the overriding plate is characterized by a transient topographic subsidence located in the forearc, at ~2-5 cm (scaling to 100-250 km) from the trench, with a magnitude of 0.65-1.35 mm (scaling to 3.25-6.75 km). These transient features are most pronounced during the early, transient, free slab sinking phase and predominantly results from the variation of the vertical component of the trench suction along the subduction zone interface, which is induced by the gradual slab steepening during this early phase. The downward mantle flow in the nose of the mantle wedge plays a minor role in the forearc subsidence.
Author: Joao C. Duarte Publisher: John Wiley & Sons ISBN: 1119053978 Category : Science Languages : en Pages : 379
Book Description
The beginning of the new millennium has been particularly devastating in terms of natural disasters associated with tectonic plate boundaries, such as earthquakes in Sumatra, Chile, Japan, Tahiti, and Nepal; the Indian Ocean and the Pacific Ocean tsunamis; and volcanoes in Indonesia, Chile, Iceland that have produced large quantities of ash causing major disruption to aviation. In total, half a million people were killed by such natural disasters. These recurring events have increased our awareness of the destructive power of natural hazards and the major risks associated with them. While we have come a long way in the search for understanding such natural phenomena, and although our knowledge of Earth dynamics and plate tectonics has improved enormously, there are still fundamental uncertainties in our understanding of natural hazards. Increased understanding is crucial to improve our capacity for hazard prediction and mitigation. Volume highlights include: Main concepts associated with tectonic plate boundaries Novel studies on boundary-related natural hazards Fundamental concepts that improve hazard prediction and mitigation Plate Boundaries and Natural Hazards will be a valuable resource for scientists and students in the fields of geophysics, geochemistry, plate tectonics, natural hazards, and climate science. Read an interview with the editors to find out more: https://eos.org/editors-vox/plate-boundaries-and-natural-hazards
Author: Kirsty Mckenzie
Author: Timothy H. Dixon
Author: Larry J. Ruff
Author: Gabriele Morra
Author: Amy E. Draut
Author: 
Author: Serge Lallemand
Author: Zhihao Chen
Author: Joao C. Duarte
Author: Larry J. Ruff