Download or read book Constraining Mantle Heterogeneity and Mantle Flow Using Seismic and Geodynamic Data written by Chang Lu (Ph. D.) and published by . This book was released on 2018 with total page 384 pages. Available in PDF, EPUB and Kindle. Book excerpt: In this dissertation, I have developed new 3-D models of mantle heterogeneity using seismic and geodynamic data to better understand the thermo-chemical composition of the mantle and its dynamics. First, the effect of subducting slabs in global shear wave tomography has been evaluated. By performing a synthetic test, I showed that the existence of subducting slabs could lead to serious earthquake mislocation problems. The mislocation biased travel time residuals, affected the recovery of subducting slabs in tomography, and also introduced significant artifacts into lower mantle structure. The bias was reduced if the tomography inversion used a starting model with 3-D slabs and velocity and source location were simultaneously modeled. I next developed a new tomography model by jointly inverting P and S wave seismic data. In this inversion, a 3-D thermal model of subducting slabs was used as the starting model. The new P and S models featured higher amplitude subducting slabs compared to previous global tomography results. The S to P heterogeneity ratio based on the new tomography model indicates the existence of chemical heterogeneities in the lower mantle although less than some previous studies have found. To better constrain the thermo-chemical structure, and dynamics of Earth’s mantle, I performed joint inversions using seismic and geodynamic data simultaneously. The geodynamic observations include free-air gravity, tectonic plate motions, dynamic surface topography, and excess ellipticity of the core-mantle boundary. These geodynamic observations can be related to density perturbations in the mantle assuming a known mantle viscosity model. Five different viscosity models were tested in the joint inversion. In all of these inversions, a non-thermal origin of density anomalies is required to explain the geodynamic data, though the amount of non-thermal heterogeneities varies between models. Using derived density models and their corresponding viscosity profiles, current mantle convective flow fields were also predicted. Flow fields derived using different viscosity models are similar in general. However, using density models derived from joint inversions compared to scaled seismic velocity models lead to significant differences in predicted mantle flow.

Download or read book Mantle Convection and Surface Expressions written by Hauke Marquardt and published by John Wiley & Sons. This book was released on 2021-07-07 with total page 32 pages. Available in PDF, EPUB and Kindle. Book excerpt: A multidisciplinary perspective on the dynamic processes occurring in Earth's mantle The convective motion of material in Earth's mantle, powered by heat from the deep interior of our planet, drives plate tectonics at the surface, generating earthquakes and volcanic activity. It shapes our familiar surface landscapes, and also stabilizes the oceans and atmosphere on geologic timescales. Mantle Convection and Surface Expressions brings together perspectives from observational geophysics, numerical modelling, geochemistry, and mineral physics to build a holistic picture of the deep Earth. It explores the dynamic processes occurring in the mantle as well as the associated heat and material cycles. Volume highlights include: Perspectives from different scientific disciplines with an emphasis on exploring synergies Current state of the mantle, its physical properties, compositional structure, and dynamic evolution Transport of heat and material through the mantle as constrained by geophysical observations, geochemical data and geodynamic model predictions Surface expressions of mantle dynamics and its control on planetary evolution and habitability The American Geophysical Union promotes discovery in Earth and space science for the benefit of humanity. Its publications disseminate scientific knowledge and provide resources for researchers, students, and professionals.

Download or read book Mantle Convection and Surface Expressions written by Hauke Marquardt and published by John Wiley & Sons. This book was released on 2021-06-10 with total page 32 pages. Available in PDF, EPUB and Kindle. Book excerpt: A multidisciplinary perspective on the dynamic processes occurring in Earth's mantle The convective motion of material in Earth's mantle, powered by heat from the deep interior of our planet, drives plate tectonics at the surface, generating earthquakes and volcanic activity. It shapes our familiar surface landscapes, and also stabilizes the oceans and atmosphere on geologic timescales. Mantle Convection and Surface Expressions brings together perspectives from observational geophysics, numerical modelling, geochemistry, and mineral physics to build a holistic picture of the deep Earth. It explores the dynamic processes occurring in the mantle as well as the associated heat and material cycles. Volume highlights include: Perspectives from different scientific disciplines with an emphasis on exploring synergies Current state of the mantle, its physical properties, compositional structure, and dynamic evolution Transport of heat and material through the mantle as constrained by geophysical observations, geochemical data and geodynamic model predictions Surface expressions of mantle dynamics and its control on planetary evolution and habitability The American Geophysical Union promotes discovery in Earth and space science for the benefit of humanity. Its publications disseminate scientific knowledge and provide resources for researchers, students, and professionals. Find out more about this book from this Q&A with the Author.

Download or read book The Earth s Heterogeneous Mantle written by Amir Khan and published by Springer. This book was released on 2015-04-28 with total page 538 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book highlights and discusses recent developments that have contributed to an improved understanding of observed mantle heterogeneities and their relation to the thermo-chemical state of Earth's mantle, which ultimately holds the key to unlocking the secrets of the evolution of our planet. This series of topical reviews and original contributions address 4 themes. Theme 1 covers topics in geophysics, including global and regional seismic tomography, electrical conductivity and seismic imaging of mantle discontinuities and heterogeneities in the upper mantle, transition zone and lower mantle. Theme 2 addresses geochemical views of the mantle including lithospheric evolution from analysis of mantle xenoliths, composition of the deep Earth and the effect of water on subduction-zone processes. Theme 3 discusses geodynamical perspectives on the global thermo-chemical structure of the deep mantle. Theme 4 covers application of mineral physics data and phase equilibrium computations to infer the regional-scale thermo-chemical structure of the mantle.

Download or read book Using Geodynamic Models to Constrain the Timing and Depth of Seismic Anisotropy Development Under the Western United States written by Thomas Robert Chaparro and published by . This book was released on 2017 with total page 47 pages. Available in PDF, EPUB and Kindle. Book excerpt: Mantle flow aligns highly anisotropic olivine crystals in the mantle, and thus anisotropy observed through seismic shear save (SKS) splitting observations is often directly associated to active mantle flow. The Western United States has a circular pattern of SKS splits, and numerous studies have attempted to predict the cause of this phenomena. To predict the current pattern of SKS splits, we use a geodynamic numerical model to simulate anisotropy development in the mantle using both time integrated mantle velocities and instantaneous mantle velocities. In summary, we model that anisotropy patterns that more generally match the observed SKS signal around Nevada are the direct result of complex 3D toroidal flow from the segmenting of the Farallon slab. We found that a strong circular pattern of anisotropy can be predicted for depths between 200-400 km using mantle flow velocities integrated from 10 Ma to present. Our geodynamic models also suggest that geophysical studies should incorporate the full time-dependent history of mantle flow when studying SKS splits, as models that use present day velocities do not provide good agreement to current SKS splitting observations. Thus, SKS measurements represent the full history of olivine deformation due to changes in mantle flow regimes and not necessarily what is currently happening in today's relatively static mantle flow field.

Download or read book Treatise on Geophysics written by and published by Elsevier. This book was released on 2015-04-17 with total page 5604 pages. Available in PDF, EPUB and Kindle. Book excerpt: Treatise on Geophysics, Second Edition, is a comprehensive and in-depth study of the physics of the Earth beyond what any geophysics text has provided previously. Thoroughly revised and updated, it provides fundamental and state-of-the-art discussion of all aspects of geophysics. A highlight of the second edition is a new volume on Near Surface Geophysics that discusses the role of geophysics in the exploitation and conservation of natural resources and the assessment of degradation of natural systems by pollution. Additional features include new material in the Planets and Moon, Mantle Dynamics, Core Dynamics, Crustal and Lithosphere Dynamics, Evolution of the Earth, and Geodesy volumes. New material is also presented on the uses of Earth gravity measurements. This title is essential for professionals, researchers, professors, and advanced undergraduate and graduate students in the fields of Geophysics and Earth system science. Comprehensive and detailed coverage of all aspects of geophysics Fundamental and state-of-the-art discussions of all research topics Integration of topics into a coherent whole

Download or read book Seismology and Structure of the Earth written by Barbara Romanowicz and published by Elsevier. This book was released on 2010-04-20 with total page 873 pages. Available in PDF, EPUB and Kindle. Book excerpt: Treatise on Geophysics: Seismology and Structure of the Earth, Volume 1, provides a comprehensive review of the state of knowledge on the Earths structure and earthquakes. It addresses various aspects of structural seismology and its applications to other fields of Earth sciences. The book is organized into four parts. The first part principally covers theoretical developments and seismic data analysis techniques from the end of the nineteenth century until the present, with the main emphasis on the development of instrumentation and its deployment. The second part reviews the status of knowledge on the structure of the Earths shallow layers, starting with a global review of the Earth's crustal structure. The third part focuses on the Earth's deep structure, divided into its main units: the upper mantle, the transition zone and upper-mantle discontinuities, the D region at the base of the mantle, and the Earth's core. The fourth part comprises two chapters which discuss constraints on Earth structure from fields other than seismology: mineral physics and geodynamics. Self-contained volume starts with an overview of the subject then explores each topic with in depth detail Extensive reference lists and cross references with other volumes to facilitate further research Full-color figures and tables support the text and aid in understanding Content suited for both the expert and non-expert

Download or read book The Core Mantle Boundary Region written by Michael Gurnis and published by American Geophysical Union. This book was released on 1998-02-04 with total page 352 pages. Available in PDF, EPUB and Kindle. Book excerpt: The two giant heat engines responsible for plate tectonics and the geodynamo dynamically interact at the core-mantle boundary of the Earth's interior. A multidisciplinary approach is required to determine the composition, structure, and dynamics of the interface. This volume describes original and fundamental research in seismology, geodynamics, mineral physics, and geomagnetism.

Download or read book Plate Deformation from Cradle to Grave written by Andy Nowacki and published by Springer Science & Business Media. This book was released on 2012-12-14 with total page 177 pages. Available in PDF, EPUB and Kindle. Book excerpt: The Earth's rocky mantle convects to lose heat, which comes from the liquid iron core below. The mantle's interfaces - the core-mantle boundary, and the lithosphere - may hold the key to understanding mantle motion because of the seismic anisotropy present in these parts of the Earth. In this thesis, Andy Nowacki presents a precise but comprehensive review of the current state of the art in studying flow with anisotropy, mineral physics and geodynamics. New measurements of shear wave anisotropy in the lowermost mantle and at mid-ocean ridges are used to constrain mechanisms of creep and melt extraction in the mantle. A model of global flow is used to predict anisotropy in the deep Earth, and novel methods to forward model shear wave splitting are described. Future studies of mantle flow must incorporate the understanding gained in this thesis. The thesis contains a substantive introduction to the structure of the Earth, seismic anisotropy in general and in the core-mantle boundary region, and mid-ocean ridge processes. It also describes novel methods for forward modelling and interpreting shear wave splitting data. Three chapters present timely research into dynamics at divergent plate boundaries and at the core-mantle boundary.

Download or read book Geodynamics of Lithosphere Earth s Mantle written by Jaroslava Plomerova and published by Birkhäuser. This book was released on 2012-12-06 with total page 496 pages. Available in PDF, EPUB and Kindle. Book excerpt: Plate tectonics has significantly broadened our view of the dynamics of continental evolution, involving both the processes currently active at the surface and those extending deep into the interior of the Earth. Seismic anisotropy provides some of the most diagnostic evidence for mapping past and present deformation of the entire crustmantle system. This volume contains papers presented originally at an international workshop at the Chateau of Trest in the Czech Republic in 1996. This workshop brought together geophysicists and geologists who work in the field of observational and theoretical seismology, mineral and rock physics, gravity studies and geodynamic modelling. Topics include large-scale anisotropy of the Earth's mantle, mantle heterogeneity vs. anisotropy 3-D velocity and density structures and inferences on mantle dynamics, mineral and rock physics studies, and mathematical aspects of complex wave propagation.

Download or read book Heterogeneity and Flow in the Deep Earth written by Sanne Cottaar and published by . This book was released on 2013 with total page 322 pages. Available in PDF, EPUB and Kindle. Book excerpt: Over the past half century, study of deep regions in the Earth has revealed them to be complex and dynamic. Much of our knowledge comes from seismological data, and ultimately these observations need to be linked to results from geodynamics and mineral physics in order to make inferences about compositional heterogeneities and flow. One example of a strongly-heterogeneous region is the lower thermal boundary layer of the mantle, i.e. the layer of several hundred kilometers thickness above the core-mantle boundary, commonly referred to as D''. This region appears to be characterized by two large provinces of distinctive slow shear velocities, 4000-5000 km across, one beneath the Pacific and one beneath Africa. Surrounding these regions, seismic velocities are faster, and often interpreted as corresponding to a graveyard of slabs. A recently discovered phase transition from perovskite to postperovskite may also occur in this depth range and has been associated with an intermittently observed seismic discontinuity at the top of D'' This study adds to the seismological evidence for complexities both in isotropic seismic velocities as well as in anisotropic velocities and how those can be linked to flow of material. We map a distinctive small "pile" of slow shear velocity beneath Russia through direct waveform evidence. This "pile" is less than 1000 km across, and thus much smaller than the Pacific and African provinces. Its height is several hundreds of kilometers and its velocity reduction suggests it is composed of the same material as the large provinces of slow shear velocity. Beneath Hawaii, at the northern edge of the Pacific province, we find an extended thin zone of ultra-low velocities. This is the first time the three-dimensional extent of such a zone is constrained with some accuracy. The constraints on its morphology come from the presence of strong postcursors to shear waves diffracted along the core-mantle boundary, delayed by 30 to 50 seconds with respect to the main diffracted arrival. The zone is almost 1000 km across and roughly 25 km high. Its shear velocity is reduced by ~20% with respect to the global average, which is possible through strong iron enrichment or the presence of partial melt. Given its location, one can speculate that this zone may represent an anchor to a whole-mantle plume reaching the surface of the Earth beneath the Hawaiian hotspot and may also represent the source of geochemical anomalies in Hawaiian basalts. Around the southern margin of the African low shear velocity province, we map strong variations in anisotropic velocity structure. These could be interpreted as evidence for strong flow outside the region of slow velocity, and insignificant flow within. To understand observations of seismic anisotropy in terms of flow in a more general context, we adopt a multi-disciplinary approach. We forward model anisotropic texture development through geodynamical models, reflecting mineral-physical constraints on the deformational behavior and elastic constants of possible compositions. In both two and three-dimensional models, we find that perovskite and post-perovskite result in distinctive anisotropic patterns. Deformation on different crystallographic lattice planes within post-perovskite also results in different signatures. In general, the presence of post-perovskite appears to best explain seismic observations of anisotropy in the deep mantle. One other region of strong heterogeneous and anisotropic velocity variations is the inner core. In the last chapter, we model thermal histories to assess the possibility of episodes of convection over the course of the inner core growth. Our numerical model predicts strains due to convective flow that could cause texturing and seismic anisotropy. An early termination of this convection can explain the stronger anisotropy seen in the innermost inner core (the most central 500 km).

Download or read book Constraints on Mantle Convection from Seismic Tomography and Flow Modeling written by Hrafnkell Kárason and published by . This book was released on 2002 with total page 228 pages. Available in PDF, EPUB and Kindle. Book excerpt: In this thesis I combine high resolution seismic tomography and realistic flow modeling to constrain mantle convection. The bulk of the data used in the tomographic imaging are millions of P, pP and pwP travel time residuals, read from high frequency seismic records. The distribution of earthquakes and stations results in uneven data coverage and to improve the model I use core phases (PKP, Pdiff) for the deep mantle and surface reflected phases (PP) for the shallow mantle. Since narrow rays are not adequate for low frequency measurements, I construct broad 3-D sensitivity kernels to relate some of the added data to earth's structure. Furthermore, the parameterization of the tomographic model is adapted to data density and the model shows, among other details, the varying style of subduction in the shallow mantle and complex flow patterns around the transition zone between the upper and lower mantle. I develop a novel and efficient method of modeling buoyancy driven mantle flow in spherical geometry. Here, the linear Stokes equation is solved using a Green's function approach and 3-D surfaces, representing the boundaries of dense material, such as subducting slabs, are tracked through time.

Download or read book Mantle Circulation Models written by Peter Webb and published by . This book was released on 2012 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Mantle circulation models are a modified class of mantle convection simulations assimilating recent plate motions as the surface velocity boundary condition. In this thesis, I present a suite of mantle circulation models assimilating the past 300 million years of tectonic history. By comparing model predictions of present day mantle temperature anomalies to mantle structure imaged by seismic tomography one can better understand the physical properties of Earth's mantle. Given a mantle model with realistic physical properties, plate reconstructions can also be tested. Mantle viscosity is the most significant property affecting mantle circulation models. For subducted slabs to sink to depths predicted by tomography studies a lower mantle viscosity increase of around thirty times is required. For models with a factor of ten increase slabs do not remain at mid-mantle depths for long enough, while a factor of one hundred increase causes slab sinking rates too slow to match imaged tomographic anomalies. An endothermic phase changes could potentially layer mantle convection into two independent layers. In models assimilating plate motions, no model containing an endothermic phase change reaches a fully layered state, even with unrealistically large, negative Clapeyron slopes. The onset of plate tectonics could potentially break down a two-layered mantle into a partially layered state, similar to the present day mantle. Predictions of mantle heterogeneity from high-resolution, global mantle circulation models match well with complex mantle structure imaged by seismic tomography in the Tethys region. These models indicate that a more complicated history of subduction during the closure of the Neotethys Ocean is required to match the imaged mantle structure. Subduction is required in two locations, one at the Eurasian margin and a second behind a back-arc ocean opening in the Neotethys Ocean. Simultaneous subduction at both plate boundaries appears not to be necessary. Global mantle circulation models estimate long-wavelength dynamic topography with amplitudes of up to five kilometres. The largest amplitude signal of dynamic topography is at plate boundaries, suggesting that near surface density variations in the mantle contribute significantly to the dynamic topography signal. The five-kilometre amplitude of topography is larger than predicted elsewhere and is explained by the inclusion of near surface density variations, commonly ignored by other global calculations of dynamic topography. If dynamic topography is defined as 'any topography arising from flow within Earth's mantle' then near surface density variations are significant to the dynamic signal. Predictions of dynamic topography from mantle circulation models reveal a dichotomy between continental and oceanic regions. Oceanic crust is a part of the mantle convection system and so predicted topography for ocean regions matches well with the expected depth versus age curve for oceanic crust. Continental regions are significantly subsided relative to oceans in the dynamic signal, suggesting that isostatic effects mask continental dynamic topography. When predictions of dynamic topography are corrected for isostatic effects and crustal thickness, an accurate estimate of Earth's observed topography is generated. This work contributes to an on going debate on the nature of dynamic topography on global and regional scales.

Download or read book Heterogeneity in the Crust and Upper Mantle written by John A. Goff and published by Springer. This book was released on 2012-10-21 with total page 349 pages. Available in PDF, EPUB and Kindle. Book excerpt: Most of our knowledge about the physical structure and the chemical composition of the Earth's deep interior is inferred from seismic data. The interpretation of seismic waves generally follows the assumption that the Earth's physical structure is grossly layered and that fluctuations of the physical parameters within individual layers are smooth in structure and small in magnitude. While this view greatly facilitates the analytic and interpretative procedure, it is clearly at odds with evidence from outcrops and boreholes, which indicates that compositional, structural and petrophysical heterogeneity in the Earth prevails over a wide range of scales. This book is the first to unify three different views of crustal and upper mantle heterogeneity. It brings together the geological view, which is derived from the analysis of crustal exposures and deep boreholes; the stochastic view, which attempts to find order and structure in these seemingly chaotic data; and the seismological view, which considers the end product of the complex interaction of seismic energy with the heterogeneous structure at depth. John Goff and Klaus Holliger have compiled chapters that explore and quantify the relationship between geological and petrophysical heterogeneity and its seismic response, and use seismic data to probe the fabric of the Earth's interior. Geologists, geostaticians, and geophysicists alike will benefit from the integrative perspective presented in Heterogeneity in the Crust and Upper Mantle: Nature, Scaling, and Seismic Properties, making this text an unparalleled reference for professionals and students in Earth science fields.

Download or read book Geodynamics of Lithosphere and Earth s Mantle written by Jaroslava Plomerova and published by Springer Science & Business Media. This book was released on 1998-04 with total page 520 pages. Available in PDF, EPUB and Kindle. Book excerpt: Reprint from Pure and Applied Geophysics (PAGEOPH), Volume 151 (1998), No. 2/3/4

Download or read book Post Perovskite written by Kei Hirose and published by John Wiley & Sons. This book was released on 2013-04-30 with total page 478 pages. Available in PDF, EPUB and Kindle. Book excerpt: Published by the American Geophysical Union as part of the Geophysical Monograph Series, Volume 174. Discovery of the perovskite to post-perovskite phase transition in MgSiO3, expected to occur for deep mantle conditions, was first announced in April 2004. This immediately stimulated numerous studies in experimental and theoretical mineral physics, seismology, and geodynamics evaluating the implications of a major lower mantle phase change. A resulting revolution in our understanding of the D′′ region in the lowermost mantle is well underway. This monograph presents the multidisciplinary advances to date ensuing from interpreting deep mantle seismological structures and dynamical processes in the context of the experimentally and theoretically determined properties of the post-perovskite phase change; the last silicate phase change likely to occur with increasing pressure in lowermost mantle rocks.

Download or read book The Early Earth written by James Badro and published by John Wiley & Sons. This book was released on 2015-10-05 with total page 193 pages. Available in PDF, EPUB and Kindle. Book excerpt: The Early Earth: Accretion and Differentiation provides a multidisciplinary overview of the state of the art in understanding the formation and primordial evolution of the Earth. The fundamental structure of the Earth as we know it today was inherited from the initial conditions 4.56 billion years ago as a consequence of planetesimal accretion, large impacts among planetary objects, and planetary-scale differentiation. The evolution of the Earth from a molten ball of metal and magma to the tectonically active, dynamic, habitable planet that we know today is unique among the terrestrial planets, and understanding the earliest processes that led to Earth’s current state is the essence of this volume. Important results have emerged from a wide range of disciplines including cosmochemistry, geochemistry, experimental petrology, experimental and theoretical mineral physics and geodynamics. The topics in this volume include: Condensation of primitive objects in the solar nebula, planetary building blocks Early and late accretion and planetary dynamic modeling Primordial differentiation, core formation, Magma Ocean evolution and crystallization This volume will be a valuable resource for graduate students, academics, and researchers in the fields of geophysics, geochemistry, cosmochemistry, and planetary science.