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Sample records for geodynamic model radionuklidnoe

  1. Geodynamics.

    ERIC Educational Resources Information Center

    Flinn, Edward A.

    1983-01-01

    Discusses trends, research activities, and conferences in geodynamics. These include topics on the lithosphere and lower continental crust formation discussed at a U.S. Geodynamics Committee workshop (Austin, Texas 1982) and symposia (each dealing with specific topics) sponsored by the Inter-Union Commission on Dynamics and Evolution of the…

  2. Geodynamics.

    ERIC Educational Resources Information Center

    Flinn, Edward A.

    1983-01-01

    Discusses trends, research activities, and conferences in geodynamics. These include topics on the lithosphere and lower continental crust formation discussed at a U.S. Geodynamics Committee workshop (Austin, Texas 1982) and symposia (each dealing with specific topics) sponsored by the Inter-Union Commission on Dynamics and Evolution of the…

  3. Geodynamics

    NASA Technical Reports Server (NTRS)

    Walter, L. S.

    1984-01-01

    The status of space geodynamics is examined, major scientific questions that need to be addressed are identified, and program activities are recommended for the next decade. Progress made in measuring tectonic plates, polar motion, and coupling of fluid motion of the Earth's core to the mantle is reviewed.

  4. A geodynamic model of Andean mountain building

    NASA Astrophysics Data System (ADS)

    Schellart, Wouter P.

    2017-04-01

    The Andes mountain range in South America is the longest in the world and is unique in that it has formed at a subduction zone and not at a continent-continent collision zone. The mountain range has formed due to overriding plate shortening since the Late Cretaceous, and its origin and the driving mechanism(s) responsible for its formation remain a topic of intense debate. Here I present a buoyancy-driven geodynamic model of South American-style subduction, mantle flow and overriding plate deformation, illustrating how subduction-induced mantle flow drives overriding plate deformation. The model reproduces several first-order characteristics of the Andes, including major crustal thickening (up to double the initial crustal thickness) and hundreds of km of east-west shortening in the Central Andes, as well as a slab geometry that is comparable to that of the Nazca slab below the Central Andes. Ultimately, the geodynamic model shows that subduction-induced mantle flow is responsible for Andean-style mountain building.

  5. Experimental, Numerical and Observational Models in Geodynamics

    NASA Astrophysics Data System (ADS)

    Lithgow-Bertelloni, Carolina

    2015-04-01

    Geodynamics, the study of the forces that drives all Earth's processes is a rich field that deeply connects all aspects of geological and geophysical studies, from surface observations of the sedimentary record to knowledge of deep Earth structure from mineral physics and seismology. In the context of the solid Earth geodynamics primarily focuses on lithosphere and mantle dynamics, while core dynamics is the purview of geomagnetism. I will focus this talk on the former, its historical context and future developments. We have known the equations of motion and mechanics for ~200 years, but only relatively recently can they be solved with enough accuracy and resolution to do geology. We have made great strides since Arthur Holmes conceptual models of mantle flow, thanks to computational and experimental advances. We can know model plate boundaries globally with resolutions in the order of a few kms and image temperature and velocity simultaneously in the laboratory in 3D and non-intrusively. We have also learned a great deal about the physics of the Earth, from composition to rheology. New theories on plate boundary rheology are paving the way for self-consistent generation of plates from mantle flow. New computational methods allow for adaptive meshing, fabric development and history, so we can study deformation and compare directly to geological observations in mountain ranges and continental rifts. We can use ever more sophisticated images of mantle structure from seismic and other geophysical data to probe the relationship between melting, flow and dynamical processes. We can reconstruct landscapes and relief, plate motions and sedimentation and ask how much the mantle has contributed to drainage reversal, sedimentation and climate change. The future of the field is ever brighter.

  6. Modern Geodynamic Model of the Arctic Ocean

    NASA Astrophysics Data System (ADS)

    Petrov, O.; Sobolev, N.; Morozov, A.; Grikurov, G.; Shokalsky, S.; Kashubin, S.; Petrov, E.

    2012-04-01

    In 2011 at VSEGEI (Russia) within the international project "Atlas of Geological Maps of the Circumpolar Arctic", a draft of the structural tectonic map of the Arctic at 1: 5,000,000 scale was prepared. This map is accompanied by a model of deep lithospheric structure of the Russian Arctic, which reflects thickness, types and specific features of crustal structure, and by geodynamic reconstructions. Analysis of the geological and geophysical data enables distinguishing a set of features in the Arctic evolution: - Differences in geological structure and geodynamic evolution of the Western and Eastern Arctic have been spotted no less than since the Early Paleozoic, which was reflected in the formation of caledonides in the West of the Arctic, and ellesmerides in the East. - In the Middle Paleozoic-Mesozoic (Late Devonian-Early Cretaceous), the eastern parts of the Arctic were affected by geodynamic processes taking place in the Paleo-Pacific. The formation of the Canadian basin was a result of the Late Jurassic-Early Cretaceous riftogenesis. A set of features of this basin - such as constrained spreading, considerable depth and topography of the floor, sedimentation specifics - allows us to consider it as a marginal basin of the Paleo-Pacific that moved into an island-arc evolution stage in the Late Jurassic. Collision orogenic activities that widely manifested themselves in the Northern-Eastern part of Asia on the verge of the Early-Late Cretaceous are related to intraplate riftogenic processes in the Central Arctic that were followed by basic magmatism manifestations in Svalbard, Franz Josef Land and New Siberian Islands. Cretaceous stage of the intraplate riftogenesis determined to a great extent the modern-day structure of the Eastern Arctic. - The opening of the Northern Atlantic was accompanied by tectonic compression in the Eastern parts of the Arctic. The formation of the Eurasian basin was preceded by Late Cretaceous-Paleogene period of amplitude

  7. Towards Modelling slow Earthquakes with Geodynamics

    NASA Astrophysics Data System (ADS)

    Regenauer-Lieb, K.; Yuen, D. A.

    2006-12-01

    We explore a new, properly scaled, thermal-mechanical geodynamic model{^1} that can generate timescales now very close to those of earthquakes and of the same order as slow earthquakes. In our simulations we encounter two basically different bifurcation phenomena. One in which the shear zone nucleates in the ductile field, and the second which is fully associated with elasto-plastic (brittle, pressure- dependent) displacements. A quartz/feldspar composite slab has all two modes operating simultaneously in three different depth levels. The bottom of the crust is predominantly controlled by the elasto-visco-plastic mode while the top is controlled by the elasto-plastic mode. The exchange of the two modes appears to communicate on a sub-horizontal layer in a flip-flop fashion, which may yield a fractal-like signature in time and collapses into a critical temperature which for crustal rocks is around 500-580 K; in the middle of the brittle-ductile transition-zone. Near the critical temperature, stresses close to the ideal strength can be reached at local, meter-scale. Investigations of the thermal-mechanical properties under such extreme conditions are pivotal for understanding the physics of earthquakes. 1. Regenauer-Lieb, K., Weinberg, R. & Rosenbaum, G. The effect of energy feedbacks on continental strength. Nature 442, 67-70 (2006).

  8. Modeling Geodynamic Mobility of Anisotropic Lithosphere

    NASA Astrophysics Data System (ADS)

    Perry-Houts, J.; Karlstrom, L.

    2016-12-01

    The lithosphere is often idealized as a linear, or plastic layer overlying a Newtonian half-space. This approach has led to many insights into lithospheric foundering that include Rayligh-Taylor drips, slab-style delaminations, and small scale convection in the asthenosphere. More recent work has begun to quantify the effect of anisotropic lithosphere viscosity on these same phenomena. Anisotropic viscosity may come about due to stratigraphic deposition in the upper crust, dike/sill emplacement in the mid crust, or volcanic underplating at the Moho related to arcs or plumes. Anisotropic viscosity is also observed in the mantle, due to preferential orientation of olivine grains during flow. Here we extend the work of Lev & Hager (2008) on modeling anisotropic lithospheric foundering to investigate the effects of anisotropic regions which vary in size, magnitude, and orientation. We have extended Aspect, a modern geodynamic finite element code with a large developer and user base, to model exotic constitutive laws with an arbitrary fourth order tensor in place of the viscosity term. We further implement a material model to represent a transverse isotropic medium, such as is expected in a layered, or fractured lithosphere. We have validated our implementation against previous results, and analytic solutions, reproducing the result that horizontally oriented anisotropy tends to inhibit drips, and produce longer-wavelength instabilities. We expect that increased lateral extent of anisotropic regions will exaggerate this effect, to a limit at which the effect will plateau. Varying lithosphere thickness, and mantle anisotropy anisotropy may produce similar behavior. The implications of this effect are significant to lithospheric foundering beneath arcs and hotspots, possibly influencing the recycling of eclogite, production of silicic magmas, and dynamic topography.

  9. Modeling petrological geodynamics in the Earth's mantle

    NASA Astrophysics Data System (ADS)

    Tirone, M.; Ganguly, J.; Morgan, J. P.

    2009-04-01

    We have developed an approach that combines principles of fluid dynamics and chemical thermodynamics into a fully coupled scheme to model geodynamic and petrological evolution of the Earth's mantle. Transport equations involving pressure, temperature, velocities, and bulk chemical composition are solved for one or more dynamic phases and interfaced with the thermodynamic solutions for equilibrium mineralogical assemblages and compositions. The mineralogical assemblage and composition are computed on a space-time grid, assuming that local thermodynamic equilibrium is effectively achieved. This approach allows us to simultaneously compute geophysical, geochemical, and petrological properties that can be compared with a large mass of observational data to gain insights into a variety of solid Earth problems and melting phenomena. We describe the salient features of our numerical scheme and the underlying mathematical principles and discuss a few selected applications to petrological and geophysical problems. First, it is shown that during the initial stage of passive spreading of plates, the composition of the melt near Earth's surface is in reasonable agreement with the average major element composition of worldwide flood basalts. Only the silica content from our model is slightly higher that in observational data. The amount of melt produced is somewhat lower than the estimated volumes for extrusive and upper crustal intrusive igneous rocks from large igneous provinces suggesting that an active upwelling of a larger mantle region should be considered in the process. Second, we have modeled a plume upwelling under a moving plate incorporating the effects of mineralogy on the density structure and viscous dissipation on the heat transport equation. The results show how these effects promote mantle instability at the base of the lithosphere. Third, we have considered a mantle convection model with viscosity and density directly related to the local equilibrium

  10. Geodynamic evolution of the lithosphere beneath the Eastern Anatolia region: Constraints from geodynamic modeling

    NASA Astrophysics Data System (ADS)

    Memis, Caner; Hakan Gogus, Oguz; Pysklywec, Russell; Keskin, Mehmet; Celal Sengor, A. M.; Topuz, Gultekin

    2016-04-01

    The east Anatolian orogenic plateau is characterized by an average elevation of 2 km, and is delimited by the Bitlis-Zagros collision zone to the south and the Pontide arc to the north. Stratigraphic evidence suggests that the high plateau attained its current elevation since the Serravallian (about 12 million years ago), but probably did not reach its present height until at least the latest Pliocene. While the crustal shortening following the Arabia-Eurasia collision in the south enabled its relatively rapid rise and regional tectonic evolution, the presumed removal of the downgoing slab beneath east Anatolia has potentially played a significant role in this geodynamic configuration. According to the proposed scenario, the northward subducting slab of Neo-Tethys peels away from the overlying crust similar to the lithospheric delamination model. In this work, we performed a series of lithospheric removal models by varying rheological, physical and mechanical properties by using 2D numerical geodynamic experiments, (e.g. plate convergence rate, crustal thickness, mantle lithosphere yield-stress). Our model results show that the average amount of delamination hinge motion is maximum (18 km/my) when the lower crustal rheology is felsic granulite. The slab break-off only occurs at lower convergence rates (≤ 2 cm/yr), and is imposed on the margin of delaminating mantle lithosphere. The surface uplift takes place above the asthenospheric column (or plateau gap) through isostatic and thermal support of asthenospheric upwelling, and varies dependent on the width of the asthenospheric column. However; with higher plate convergence rates (≥3 cm/yr), the asthenospheric column does not widen enough and the continental collision occurs rather than delamination/peeling away. In this case, the average uplift appears in the central section of the crust, and this exceeds a surface elevation of 3 km. All model results are consistent with the observations from the Eastern

  11. Numerical Modeling in Geodynamics: Success, Failure and Perspective

    NASA Astrophysics Data System (ADS)

    Ismail-Zadeh, A.

    2005-12-01

    A real success in numerical modeling of dynamics of the Earth can be achieved only by multidisciplinary research teams of experts in geodynamics, applied and pure mathematics, and computer science. The success in numerical modeling is based on the following basic, but simple, rules. (i) People need simplicity most, but they understand intricacies best (B. Pasternak, writer). Start from a simple numerical model, which describes basic physical laws by a set of mathematical equations, and move then to a complex model. Never start from a complex model, because you cannot understand the contribution of each term of the equations to the modeled geophysical phenomenon. (ii) Study the numerical methods behind your computer code. Otherwise it becomes difficult to distinguish true and erroneous solutions to the geodynamic problem, especially when your problem is complex enough. (iii) Test your model versus analytical and asymptotic solutions, simple 2D and 3D model examples. Develop benchmark analysis of different numerical codes and compare numerical results with laboratory experiments. Remember that the numerical tool you employ is not perfect, and there are small bugs in every computer code. Therefore the testing is the most important part of your numerical modeling. (iv) Prove (if possible) or learn relevant statements concerning the existence, uniqueness and stability of the solution to the mathematical and discrete problems. Otherwise you can solve an improperly-posed problem, and the results of the modeling will be far from the true solution of your model problem. (v) Try to analyze numerical models of a geological phenomenon using as less as possible tuning model variables. Already two tuning variables give enough possibilities to constrain your model well enough with respect to observations. The data fitting sometimes is quite attractive and can take you far from a principal aim of your numerical modeling: to understand geophysical phenomena. (vi) If the number of

  12. Constraining the rheology of mantle and slabs from geodynamic modeling

    NASA Astrophysics Data System (ADS)

    Liu, L.; Stegman, D. R.

    2012-12-01

    The rheologic profiles of the ambient mantle and the viscous strength of oceanic plates after subduction are critical parameters governing the convection pattern of the solid Earth. Recent advancements in laboratory experiment provide useful constraints on rock rheology. However, both the extrapolation of lab-derived values to Earth-like dimensions on geological time scales and the imperfect knowledge of mantle compositions raise cautions on extending laboratory results into numerical modeling of mantle convection. Geodynamic inversions, on the other hand, provide an alternative measure on mantle rheology, although the resulting viscosity profiles differ significantly when different observational constraints are involved. We present a result from simulating the history of the Cenozoic Farallon subduction and from comparison with recent high-resolution seismic tomography of western US. The radial viscosity profile of the mantle, fundamental to our understanding of mantle dynamics, has only been constrained in relative or depth-averaged terms by models of the dynamic geoid, post-glacial rebound, or inversions of plate motions. Here we employ an alternative method to constrain this important property by comparing the locations and geometries of several individual slab segments across a range of depths in geodynamic models with seismic tomographic models. This method is critically dependent on matching sinking trajectories of slabs through absolute viscosity profiles. The exact match to the shape, angle, and depth of fast seismic anomalies critically depends on the integrated time-history of each segment's sinking trajectory and deformation which is controlled by absolute values of viscosity for several essential components in the system, including the slab, mantle wedge, plate boundaries, and radial profile of the upper mantle. Our study also provides a tight constraint on the viscous strength the subducting slabs, by matching the resulting slab curvature and position

  13. Efficient stencil assembly in global geodynamic models

    NASA Astrophysics Data System (ADS)

    Bauer, Simon; Mohr, Marcus; Rüde, Ulrich; Wittmann, Markus

    2016-04-01

    In mantle circulation models the simulation domain is a thick spherical shell representing the earth's mantle. Typically, finite elements are the method of choice to account for the spherical geometry. The wide range of length scales involved in earth dynamics is a major challenge. Capturing localized features such as faulted plate boundaries requires local resolutions in the order of

  14. Chinese Lithosphere Rheology and Geodynamic Modeling

    NASA Astrophysics Data System (ADS)

    Shi, Y.; Zhang, H.; Cao, J.; Zhang, C.; Sun, L.

    2009-04-01

    Rock rheology is of critical importance to affect lithosphere deformation. Laboratory experiments show that viscosity of rocks strongly depends on temperature. Therefore, reliable estimation of geotherm is the first step for understanding lithospheric rheology. Deduction of geotherm from surface heat flow and thermal conductivity has been applied widely. However, error in temperature estimated this way increases with depth. In our study, we use seismic tomographic data to estimate mantle temperature ranges 50 to 200 km depth, and get a better constraint of temperature at depth. We use new petrology data to construct the crustal structure and viscosity model of China. To test the validity of extrapolation of flow law of rock from laboratory sample size and higher strain rate to large field scale and much lower strain rate, we use post seismic GPS deformation observation to invert lower crust viscosity for comparison. We then apply the viscosity model to simulate a number of tectonic problems in China, such as GPS velocity clockwise rotation around the eastern syntax of the Himalaya and uplift of the Tibetan plateau, decoupling of stress indicated by compression in the upper crust and extensional normal fault earthquake in the upper mantle in Taiwan southwest coast, and different stress accumulation rate in the upper and lower crust in Longmenshan area, Sichuan Province to estimate the reccurence time of large earthquakes.

  15. Recent advances in data assimilation in computational geodynamic models

    NASA Astrophysics Data System (ADS)

    Ismail-Zadeh, Alik

    2010-05-01

    To restore dynamics of mantle structures in the geological past, data assimilation can be used to constrain the initial conditions for the mantle temperature and velocity from their present observations and estimations. The initial conditions so obtained can then be used to run forward models of mantle dynamics to restore the evolution of mantle structures. If heat diffusion is neglected, the present mantle temperature and flow can be assimilated using the backward advection (BAD) into the past. Two- and three-dimensional numerical approaches to the solution of the inverse problem of the Rayleigh-Taylor instability were developed for a dynamic restoration of diapiric structures to their earlier stages (e.g., Ismail-Zadeh et al., 1998, 2001, 2004; Kaus and Podladchikov, 2001). The mantle flow was modelled backwards in time from present-day mantle density heterogeneities inferred from seismic observations (e.g., Steinberger and O'Connell, 1998; Conrad and Gurnis, 2003). The variational (VAR) (or also called adjoint) data assimilation has been pioneered by meteorologists and widely used in oceanography and in hydrological studies. The use of VAR data assimilation in models of geodynamics has been put forward by Bunge et al. (2003) and Ismail-Zadeh et al. (2003). The VAR data assimilation algorithm was employed to restore numerically models of mantle plumes (Ismail-Zadeh et al., 2004, 2006; Hier-Majumder et al., 2005; Liu and Gurnis, 2008; Liu et al., 2008). The use of the quasi-reversibility (QRV) technique (more robust computationally) implies the introduction into the backward heat equation of the additional term involving the product of a small regularization parameter and a higher order temperature derivative (the resulting regularized heat equation is based on the Riemann law of heat conduction). The data assimilation in this case is based on a search of the best fit between the forecast model state and the observations by minimizing the regularization parameter

  16. Coupling a geodynamic seismic cycling model to rupture dynamic simulations

    NASA Astrophysics Data System (ADS)

    Gabriel, Alice; van Dinther, Ylona

    2014-05-01

    The relevance and results of dynamic rupture scenarios are implicitly linked to the geometry and pre-existing stress and strength state on a fault. The absolute stresses stored along faults during interseismic periods, are largely unquantifiable. They are, however, pivotal in defining coseismic rupture styles, near-field ground motion, and macroscopic source properties (Gabriel et al., 2012). Obtaining these in a physically consistent manner requires seismic cycling models, which directly couple long-term deformation processes (over 1000 year periods), the self-consistent development of faults, and the resulting dynamic ruptures. One promising approach to study seismic cycling enables both the generation of spontaneous fault geometries and the development of thermo-mechanically consistent fault stresses. This seismo-thermo-mechanical model has been developed using a methodology similar to that employed to study long-term lithospheric deformation (van Dinther et al., 2013a,b, using I2ELVIS of Gerya and Yuen, 2007). We will innovatively include the absolute stress and strength values along physically consistent evolving non-finite fault zones (regions of strain accumulation) from the geodynamic model into dynamic rupture simulations as an initial condition. The dynamic rupture simulations will be performed using SeisSol, an arbitrary high-order derivative Discontinuous Galerkin (ADER-DG) scheme (Pelties et al., 2012). The dynamic rupture models are able to incorporate the large degree of fault geometry complexity arising in naturally evolving geodynamic models. We focus on subduction zone settings with and without a splay fault. Due to the novelty of the coupling, we first focus on methodological challenges, e.g. the synchronization of both methods regarding the nucleation of events, the localization of fault planes, and the incorporation of similar frictional constitutive relations. We then study the importance of physically consistent fault stress, strength, and

  17. Geodynamical Analysis of Plate Reconstructions based on Subduction History Models

    NASA Astrophysics Data System (ADS)

    Quevedo, L. E.; Butterworth, N. P.; Matthews, K. J.; Morra, G.; Müller, R. D.

    2011-12-01

    We present a novel method to produce global subduction history models from plate reconstructions and use their predicted geodynamic behaviour as a quality metric for the physical consistency of absolute motions. We show that modelled slabs constructed by advecting material into the mantle according to absolute and relative plate motions given by a particular reconstruction are better correlated with the present day slab dips observed in mantle tomography than instantaneous kinematic quantities like present convergence rate. A complete simulation incorporating lithospheric thickness derived from oceanic age and a rheological model of the lithosphere was run using the Boundary Element Method-based software BEMEarth to infer the global pattern of mantle flow. The predicted plate motion orientations in the form of Euler pole location for the present day and mid-Cretaceous (125 Ma) were compared with the kinematic model for a set of rheologies and mantle structures, and found to be a robust and efficient indicator of the physical consistency of kinematic reconstructions based on their effect on the balance of plate driving forces. As an application example, during the Early Cretaceous, the predicted motion of the Farallon plate was found to be more consistent with the regional geology of the Western North American Cordillera system than the instantaneous motion suggested by a reconstruction at 125 Ma based on sparse hotspot track data on the Pacific Plate. This suggests that a methodology based on forward geodynamic modellling could be used to predict absolute plate motions in reconstructions for times that are ill-constrained by observations constraining absolute plate motions.

  18. Coupling geodynamic with thermodynamic modelling for reconstructions of magmatic systems

    NASA Astrophysics Data System (ADS)

    Rummel, Lisa; Kaus, Boris J. P.; White, Richard

    2016-04-01

    Coupling geodynamic with petrological models is fundamental for understanding magmatic systems from the melting source in the mantle to the point of magma crystallisation in the upper crust. Most geodynamic codes use very simplified petrological models consisting of a single, fixed, chemistry. Here, we develop a method to better track the petrological evolution of the source rock and corresponding volcanic and plutonic rocks by combining a geodynamic code with a thermodynamic model for magma generation and evolution. For the geodynamic modelling a finite element code (MVEP2) solves the conservation of mass, momentum and energy equations. The thermodynamic modelling of phase equilibria in magmatic systems is performed with pMELTS for mantle-like bulk compositions. The thermodynamic dependent properties calculated by pMELTS are density, melt fraction and the composition of the liquid and solid phase in the chemical system: SiO2-TiO2-Al2O3-Fe2O3-Cr2O3-FeO-MgO-CaO-Na2O-K2O-P2O5-H2O. In order to take into account the chemical depletion of the source rock with increasing melt extraction events, calculation of phase diagrams is performed in two steps: 1) With an initial rock composition density, melt fraction as well as liquid and solid composition are computed over the full upper mantle P-T range. 2) Once the residual rock composition (equivalent to the solid composition after melt extraction) is significantly different from the initial rock composition and the melt fraction is lower than a critical value, the residual composition is used for next calculations with pMELTS. The implementation of several melt extraction events take the change in chemistry into account until the solidus is shifted to such high temperatures that the rock cannot be molten anymore under upper mantle conditions. An advantage of this approach is that we can track the change of melt chemistry with time, which can be compared with natural constraints. In the thermo-mechanical code the

  19. On the Coupling of Geodynamic and Resistivity Models: A Progress Report and the Way Forward

    NASA Astrophysics Data System (ADS)

    Heise, Wiebke; Ellis, Susan

    2016-01-01

    Magnetotelluric (MT) studies represent the structure of crust and mantle in terms of conductivity anomalies, while geodynamic modelling predicts the deformation and evolution of crust and mantle subject to plate tectonic processes. Here, we review the first attempts to link MT models with geodynamic models. An integration of MT with geodynamic modelling requires the use of relationships between conductivity and rheological parameters such as viscosity and melt fraction, which are provided by laboratory measurements of rock properties. Owing to present limitations in our understanding of these relationships, and in interpreting the trade-off between scale and magnitude of conductivity anomalies from MT inversions, most studies linking MT and geodynamic models are qualitative rather than providing hard constraints. Some recent examples attempt a more quantitative comparison, such as a study from the Himalayan continental collision zone, where rheological parameters have been calculated from a resistivity model and compared to predictions from geodynamic modelling. We conclude by demonstrating the potential in combining MT results and geodynamic modelling with examples that directly use MT results as constraints within geodynamic models of ore bodies and studies of an active volcano-tectonic rift.

  20. Introduction to the special issue celebrating 200 years of geodynamic modelling

    NASA Astrophysics Data System (ADS)

    Strak, Vincent; Schellart, Wouter P.

    2016-10-01

    Since the first published laboratory models from Sir James Hall in 1815, analogue and numerical geodynamic modelling have become widely used as they provide qualitative and quantitative insights into a broad range of geological processes. To celebrate the 200th anniversary of geodynamic modelling, this special issue gathers review works and recent studies on analogue and numerical modelling of tectonic and geodynamic processes, as an opportunity to present some of the milestones and recent breakthroughs in this field, to discuss potential issues and to highlight possible future developments.

  1. The continental collision zone, South Island, New Zealand: Comparison of geodynamical models and observations

    SciTech Connect

    Beaumont, C.; Hamilton, J.; Fullsack, P.; Kamp, P.J.J.

    1996-02-10

    In this report geodynamical models are used to test the applicability of the mantle subduction model to the compressional character and evaluation of the South Island continental convergence zone of New Zealand.

  2. Consistent implementation of phase changes into geodynamic models

    NASA Astrophysics Data System (ADS)

    Hetényi, György; Connolly, James A. D.; Godard, Vincent; Cattin, Rodolphe

    2010-05-01

    Numerical modelling of geodynamic processes occurring on geologic timescales is a rapidly evolving field of research. Despite this rapid growth, one of the initial simplifying assumptions of early numerical models is still overlooked, as the continuity equation regarding mass is mostly left out of consideration. In fluid dynamics this is known as the Boussinesq approximation. In visco-elastic models of the lithosphere this manifests in using phase equilibria calculations to modify the density of rocks without considering any volumetric effect. We explore the consequences of this simplification by developing an approach that allows us to obtain rigorously correct solutions for continuity. In technical terms, we use the finite element thermo-mechanical modelling tool Cast3M. This tool was previously developed for geodynamic applications, and handles elastic and visco-elastic rheology, erosion laws, as well as remeshing. We further develop the numerical code to incorporate the volumetric changes due to mineralogic phase transformations through modification of the regional stress-field. Exact density values are derived from petrogenetic grid calculated by software Perple_X. Our application focuses on mountain range evolution. We study the evolution of its deformation at surface as well as at depth, with and without different modelling conditions to evaluate their respective importance: elastic vs. visco-elastic behaviour; erosion; horizontal convergence; hydration level of the mafic lower crust; and consistent application of phase changes. We focus on the metamorphic reactions occurring in the lower crust, as this is where the largest density and hence volumetric effects are expected to occur in the lithosphere. The results after 4 Myr simulation time show that, when enforcing continuity, metamorphic reactions play an important role on the deformation of the orogen: the effects on the evolution of topography are of the same order of magnitude as effects resulting from

  3. Simulation of 3D Global Wave Propagation Through Geodynamic Models

    NASA Astrophysics Data System (ADS)

    Schuberth, B.; Piazzoni, A.; Bunge, H.; Igel, H.; Steinle-Neumann, G.

    2005-12-01

    This project aims at a better understanding of the forward problem of global 3D wave propagation. We use the spectral element program "SPECFEM3D" (Komatitsch and Tromp, 2002a,b) with varying input models of seismic velocities derived from mantle convection simulations (Bunge et al., 2002). The purpose of this approach is to obtain seismic velocity models independently from seismological studies. In this way one can test the effects of varying parameters of the mantle convection models on the seismic wave field. In order to obtain the seismic velocities from the temperature field of the geodynamical simulations we follow a mineral physics approach. Assuming a certain mantle composition (e.g. pyrolite with CMASF composition) we compute the stable phases for each depth (i.e. pressure) and temperature by system Gibbs free energy minimization. Elastic moduli and density are calculated from the equations of state of the stable mineral phases. For this we use a mineral physics database derived from calorimetric experiments (enthalphy and entropy of formation, heat capacity) and EOS parameters.

  4. Implementation of Newton-Rapshon iterations for parallel staggered-grid geodynamic models

    NASA Astrophysics Data System (ADS)

    Popov, A. A.; Kaus, B. J. P.

    2012-04-01

    Staggered-grid finite differences discretization has a good potential for solving highly heterogeneous geodynamic models on parallel computers (e.g. Tackey, 2008; Gerya &Yuen, 2007). They are inherently stable, computationally inexpensive and relatively easy to implement. However, currently used staggered-grid geodynamic codes employ almost exclusively the sub-optimal Picard linearization scheme to deal with nonlinearities. It was shown that Newton-Rapshon linearization can lead to substantial improvements of the solution quality in geodynamic problems, simultaneously with reduction of computer time (e.g. Popov & Sobolev, 2008). This work is aimed at implementation of the Newton-Rapshon linearization in the parallel geodynamic code LaMEM together with staggered-grid discretization and viso-(elasto)-plastic rock rheologies. We present the expressions for the approximate Jacobian matrix, and give detailed comparisons with the currently employed Picard linearization scheme, in terms of solution quality and number of iterations.

  5. Fundamentals studies in geodynamics

    NASA Technical Reports Server (NTRS)

    Anderson, D. L.

    1980-01-01

    Research in geodynamics, seismology, and planetary quakes is presented. Terradynamics and plate tectonics are described using dynamic models. The early evolution of the Earth's mantle is also discussed.

  6. Kinematic model for Tenerife Island (Canary Islands, Spain): Geodynamic interpretation in the Nubian plate context

    NASA Astrophysics Data System (ADS)

    Berrocoso, M.; Carmona, J.; Fernández-Ros, A.; Pérez-Peña, A.; Ortiz, R.; García, A.

    2010-12-01

    Establishment of a geodetic network in Tenerife is the starting point for the use of GPS and other precise geodetic techniques in the support of the study of kinematics and their relation with island volcanic activity. This paper is focused on the characterization of volcanotectonic activity of Tenerife, to determine the geodynamic framework for volcanic surveillance. TEGETEIDE network, set up in 2005 and re-observed each year, is composed of seven GNSS-GPS stations scattered throughout the island. A horizontal deformation model is presented in order to explain the observed island displacement pattern in the geodynamic context of the Nubian plate. According to the models obtained, the most important geologic structures, such as the volcanic rifts and the caldera, determine the current deformation pattern of Tenerife. The geodynamics of the most stable areas of the island behave similarly to that observed from the permanent GNSS-GPS reference stations located in La Palma and Gran Canaria Islands. Anomalous geodynamic behaviour has been detected in two zones of Tenerife, which configure an NW-SE axis crossing the central sector of the island, related with the volcanotectonic activity of the island and its surroundings.

  7. New Melting Parameterization for Geodynamic Modelling: Preliminary Results Applied to Plume Setting

    NASA Astrophysics Data System (ADS)

    Manjón-Cabeza Córdoba, Antonio; Ballmer, Maxim D.

    2017-04-01

    Melting poses a challenge in geodynamic numerical modelling: thermodynamic models are computationally expensive and they present serious restrictions as far as P-T conditions are concerned; on the other hand, simple parameterizations usually cannot address major element contents of melts, and thus physical properties. Here, we present a new polynomic parameterization based on pMELTS [Ghiorso et. al., 2002] to be used in geodynamic models. In addition, we show a first application to a geodynamic model. Our parameterization is adapted for continuous melt fractionation under decompression. The input parameters are initial pressure of melting, pressure, critical porosity, water content and temperature. The parameterization can be further calibrated for different rock compositions. It yields as the amount of melt retained in the rock, total degree of melting plus major element compositions in the form of wt% of oxides, such as: SiO2, MgO, FeO, CaO, Al2O3 and Na2O. The parameterization has the same limitations as the thermodynamic model on which it is based (MELTS), and somewhat bigger errors due to statistical fitting. In turn, it involves advantages in terms of computational speed, and ease of implementation. Most importantly, extrapolation of the model along this parameterization can provide statistically meaningful results. To demonstrate this, we benchmark these results with high pressure melting experiments. Finally, we show first applications of our parameterization as it is coupled to simple thermomechanical plume models. In these models, different melt compositions are obtained when changing potential temperature, plume buoyancy flux, and plume temperature. Although the parameterization errors are probably too high for petrological ends (where MELTS and pMELTS should be used instead), it presents an efficient and suitable option for geodynamic models.

  8. Pushing the Frontier of Data-Oriented Geodynamic Modeling: from Qualitative to Quantitative to Predictive

    NASA Astrophysics Data System (ADS)

    Liu, L.; Hu, J.; Zhou, Q.

    2016-12-01

    The rapid accumulation of geophysical and geological data sets poses an increasing demand for the development of geodynamic models to better understand the evolution of the solid Earth. Consequently, the earlier qualitative physical models are no long satisfying. Recent efforts are focusing on more quantitative simulations and more efficient numerical algorithms. Among these, a particular line of research is on the implementation of data-oriented geodynamic modeling, with the purpose of building an observationally consistent and physically correct geodynamic framework. Such models could often catalyze new insights into the functioning mechanisms of the various aspects of plate tectonics, and their predictive nature could also guide future research in a deterministic fashion. Over the years, we have been working on constructing large-scale geodynamic models with both sequential and variational data assimilation techniques. These models act as a bridge between different observational records, and the superposition of the constraining power from different data sets help reveal unknown processes and mechanisms of the dynamics of the mantle and lithosphere. We simulate the post-Cretaceous subduction history in South America using a forward (sequential) approach. The model is constrained using past subduction history, seafloor age evolution, tectonic architecture of continents, and the present day geophysical observations. Our results quantify the various driving forces shaping the present South American flat slabs, which we found are all internally torn. The 3-D geometry of these torn slabs further explains the abnormal seismicity pattern and enigmatic volcanic history. An inverse (variational) model simulating the late Cenozoic western U.S. mantle dynamics with similar constraints reveals a different mechanism for the formation of Yellowstone-related volcanism from traditional understanding. Furthermore, important insights on the mantle density and viscosity structures

  9. Combined micro and macro geodynamic modelling of mantle flow: methods, potentialities and limits.

    NASA Astrophysics Data System (ADS)

    Faccenda, M.

    2015-12-01

    Over the last few years, geodynamic simulations aiming at reconstructing the Earth's internal dynamics have increasingly attempted to link processes occurring at the micro (i.e., strain-induced lattice preferred orientation (LPO) of crystal aggregates) and macro scale (2D/3D mantle convection). As a major outcome, such a combined approach results in the prediction of the modelled region's elastic properties that, in turn, can be used to perform seismological synthetic experiments. By comparison with observables, the geodynamic simulations can then be considered as a good numerical analogue of specific tectonic settings, constraining their deep structure and recent tectonic evolution. In this contribution, I will discuss the recent methodologies, potentialities and current limits of combined micro- and macro-flow simulations, with particular attention to convergent margins whose dynamics and deep structure is still the object of extensive studies.

  10. Geodynamics for Everyone: Robust Finite-Difference Heat Transfer Models using MS Excel 2007 Spreadsheets

    NASA Astrophysics Data System (ADS)

    Grose, C. J.

    2008-05-01

    Numerical geodynamics models of heat transfer are typically thought of as specialized topics of research requiring knowledge of specialized modelling software, linux platforms, and state-of-the-art finite-element codes. I have implemented analytical and numerical finite-difference techniques with Microsoft Excel 2007 spreadsheets to solve for complex solid-earth heat transfer problems for use by students, teachers, and practicing scientists without specialty in geodynamics modelling techniques and applications. While implementation of equations for use in Excel spreadsheets is occasionally cumbersome, once case boundary structure and node equations are developed, spreadsheet manipulation becomes routine. Model experimentation by modifying parameter values, geometry, and grid resolution makes Excel a useful tool whether in the classroom at the undergraduate or graduate level or for more engaging student projects. Furthermore, the ability to incorporate complex geometries and heat-transfer characteristics makes it ideal for first and occasionally higher order geodynamics simulations to better understand and constrain the results of professional field research in a setting that does not require the constraints of state-of-the-art modelling codes. The straightforward expression and manipulation of model equations in excel can also serve as a medium to better understand the confusing notations of advanced mathematical problems. To illustrate the power and robustness of computation and visualization in spreadsheet models I focus primarily on one-dimensional analytical and two-dimensional numerical solutions to two case problems: (i) the cooling of oceanic lithosphere and (ii) temperatures within subducting slabs. Excel source documents will be made available.

  11. Subduction zones dynamics and structure from coupled geodynamic and seismological modelling

    NASA Astrophysics Data System (ADS)

    Faccenda, Manuele

    2017-04-01

    The present-day structure of subduction settings is mainly determined by means of seismological methods. The interpretation of seismological data (e.g., isotropic and anisotropic velocity anomalies) is however non-unique, as different processes occurring simultaneously at subduction zones can be invoked to explain the observations. A further complication arises when regional tomographic seismic models ignore seismic anisotropy, in which case apparent seismic anomalies due to non-uniform sampling of anisotropic areas will appear. In order to decrease the uncertainties related to the interpretation of seismological observations, geodynamic modelling can be exploited to reproduce the micro and macro scale dynamics and structure of subduction settings, yielding a valuable first-order approximation of the rock isotropic and anisotropic elastic properties. The model output can be subsequently tested against observations by performing seismological synthetics (e.g., SKS splitting, travel-time tomography, receiver functions, azimuthal and radial anisotropy). When the misfit between the modelled and measured seismic parameters is low, the geodynamic model likely provides a good approximation of the recent dynamics and present-day structure of the subduction setting. Such a model can then be used to give a more robust and thermomechanically-based interpretation of the observables and/or further improve the seismological model by providing a-priori information for subsequent inversions. The methodology is still in its infancy, but we envisage that future developments could substantially improve seismological models and, overall, our understanding of complex subduction settings.

  12. Geodynamic Modeling of the Subduction Zone around the Japanese Islands

    NASA Astrophysics Data System (ADS)

    Honda, S.

    2017-06-01

    In this review, which focuses on our research, we describe the development of the thermomechanical modeling of subduction zones, paying special attention to those around the Japanese Islands. Without a sufficient amount of data and observations, models tended to be conceptual and general. However, the increasing power of computational tools has resulted in simple analytical and numerical models becoming more realistic, by incorporating the mantle flow around the subducting slab. The accumulation of observations and data has made it possible to construct regional models to understand the detail of the subduction processes. Recent advancements in the study of the seismic tomography and geology around the Japanese Islands has enabled new aspects of modeling the mantle processes. A good correlation between the seismic velocity anomalies and the finger-like distribution of volcanoes in northeast Japan has been recognized and small-scale convection (SSC) in the mantle wedge has been proposed to explain such a feature. The spatial and temporal evolution of the distribution of past volcanoes may reflect the characteristics of the flow in the mantle wedge, and points to the possibility of the flip-flopping of the finger-like pattern of the volcano distribution and the migration of volcanic activity from the back-arc side to the trench side. These observations are found to be qualitatively consistent with the results of the SSC model. We have also investigated the expected seismic anisotropy in the presence of SSC. The fast direction of the P-wave anisotropy generally shows the trench-normal direction with a reduced magnitude compared to the case without SSC. An analysis of full 3D seismic anisotropy is necessary to confirm the existence and nature of SSC. The 3D mantle flow around the subduction zone of plate-size scale has been modeled. It was found that the trench-parallel flow in the sub-slab mantle around the northern edge of the Pacific plate at the junction between

  13. Lower Mantle melting model and it's geodynamical applications

    NASA Astrophysics Data System (ADS)

    Fomin, I.; Tackley, P. J.

    2014-12-01

    Model of solid-liquid equilibrium laws and substances properties in lower mantle conditions is important to understand the early stages of evolution of terrestrial planets, such as core formation and magma ocean crystallization. This model is also necessary to prove theories on some modern seismic features of the Earth (e.g. ultra-low velocity zones) and petrological observations (e.g. lower mantle mineral assemblage inclusions in diamonds). Numerous experimental and numerical studies of the lower mantle phases provide sufficient amount of data to build up a thermodynamic model, which can be used in geophysical fluid dynamics research. Experimental studies are the direct source of soliduses values, but other thermodynamic parameters stay unclear. Molecular Dynamics modeling provides data on thermodynamic properties of solids and liquids (density, heat capacity, latent heat of melting etc.). But absence of minor components (iron, alkali etc.) and some numerical issues (e.g. [Belonoshko, 2001]) make it to overestimate melting temperatures significantly (up to 20-30%). Our approach is to develop a model based on MD data by [de Koker et al., 2013] with evaluation of all important parameters according to classical thermodynamic equations. But melting temperatures (especially at eutectic points) are corrected along Clausius-Clapeyron slopes to agree with modern experimental data ([Andrault et al., 2011], [Andrault et al., 2014], [Fiquet et al., 2010], [Hirose et al., 1999], [Mosenfelder et al., 2007], [Nomura et al., 2014],[Ozawa et al., 2011], [Zerr et al., 1998]). Notable effect on melt and solid densities has iron partitioning, so KD value reported by [Andrault et al., 2012] was used. Proposed model was implemented into StagYY software (e.g. [Tackley, 2008]). It is a finite-volume discretization code for advection of solid and liquid in a planetary scale. CMB temperature was set to be 4000-4400 K. Calculations predict appearing and disappearing batches containing up

  14. Geodynamics Project

    ERIC Educational Resources Information Center

    Drake, Charles L.

    1977-01-01

    Describes activities of Geodynamics Project of the Federal Council on Science and Technology, such as the application of multichannel seismic-reflection techniques to study the nature of the deep crust and upper mantle. (MLH)

  15. Geodynamics Project

    ERIC Educational Resources Information Center

    Drake, Charles L.

    1977-01-01

    Describes activities of Geodynamics Project of the Federal Council on Science and Technology, such as the application of multichannel seismic-reflection techniques to study the nature of the deep crust and upper mantle. (MLH)

  16. Probing sub-slab anisotropy beneath Central America and Tonga from geodynamic models

    NASA Astrophysics Data System (ADS)

    Lynner, C.; Long, M. D.

    2015-12-01

    A number of conceptual models have been proposed to explain trench parallel shear wave splitting observations beneath subducting slabs. Recently, Lynner and Long (2014) tested several of these conceptual models against a quasi-global source-side shear wave splitting dataset and found that a model in which sub-slab dynamics varies with the age of the down-going plate best matches the observations. A major limitation of that study, however, was the employment of very simplified geodynamics; especially in cases that invoke 3-dimensional return flow, where highly complex flow patterns are expected near and around slab edges. Here, we examine sub-slab shear wave splitting patterns from geodynamic models aimed at mimicking real world subduction beneath Central American and Tonga; which exhibit entrained and 3D return flow patterns, respectively. Using a variety of olivine LPO and other anisotropic fabrics, we compare shear wave splitting from these models against actual source-side measurements in order to better understand sub-slab deformation.

  17. Slab detachment modelling: geodynamic regimes, topographic response, and rheological mechanisms

    NASA Astrophysics Data System (ADS)

    Duretz, Thibault; Gerya, Taras

    2010-05-01

    A set of numerical experiments were carried out to study the effect of slab breakoff on a subduction-collision system. The numerical code I2VIS (Gerya & Yuen, 2003) used for this purpose allows activation of plasticity, viscous creep and Peierls creep. A two-dimensional systematic study was performed by varying the oceanic slab age and initial plate convergence rate. In this parameter space, four different end-members were observed where breakoff depth can range from 40 to 400 km. Different combinations of rheological mechanisms lead to different breakoff modes. Activation of Peierls mechanism generally allows slabs to break faster and shallower. Each breakoff end-member has its own topographic signal evolution and always display a sharp breakoff signal. Averaged post-breakoff uplift rates ranges between 0,8 km/My for shallow detachment and 0,2 km/My for deep detachment in foreland and hinterland basins. Initiation of continental crust subduction was observed when using an oceanic lithosphere older than 30 My. Different exhumation processes such as slab retreat and eduction were observed. Large post-breakoff rebound associated with plate de- coupling occurs if the subducted oceanic slab is old enough. REFERENCES Gerya, T. V. & Yuen, D. A. 2003: Charaterictics-based marker method with conservative finite-difference schemes for modeling geological flows with strongly variable transport properties. Physics of the Earth an Planetary Interiors 140 (4), 293-318.

  18. Asymmetric Subductions in an Asymmetric Earth: Geodynamics and Numerical Modeling

    NASA Astrophysics Data System (ADS)

    Dal Zilio, L.; Ficini, E.; Doglioni, C.; Gerya, T.

    2016-12-01

    The driving mechanism of plate tectonics is still controversial. Moreover, mantle kinematics is still poorly constrained due to the limited information available on its composition, thermal state, and physical parameters. The net rotation of the lithosphere, or so-called W-ward drift, however, indicates a decoupling of the plates relative to the underlying asthenosphere at about 100-200 km depth in the Low-Velocity Zone and a relative "E-ward" mantle counterflow. This mantle flow can account for a number of tectonic asymmetries on subduction dynamics such as steep versus shallow slab dip, diverging versus converging subduction hinge, low versus high topography of mountain belts, etc. This asymmetry is generally interpreted to reflect the age-dependent negative buoyancy of the subducting lithosphere. However, slab dip is insensitive to the age of the lithosphere. Here we investigate the role of mantle flow in controlling subduction dynamics using a high-resolution rheologically consistent two-dimensional numerical modeling. Results show the evolution of a subducting oceanic plate beneath a continent: when the subducting plate is dipping in opposite direction with respect to the mantle flow, the slab is sub-vertically deflected by the mantle flow, thus leading the coeval development of a back-arc basin. In contrast, agreement between mantle flow and dipping of the subducting slab relieves shallow dipping subduction zone, which in turn controls the development of a pronounced topography. Moreover, this study confirms that the age of the subducting oceanic lithosphere (i.e. its negative buoyancy) has a second order effect on the dip angle of the slab and, more generally, on subduction dynamics. Our numerical experiments show strong similarities to the observed evolution of subduction zone worldwide and demonstrate that the possibility of a horizontal mantle flow is universally valid.

  19. Probabilistic seismic hazard study based on active fault and finite element geodynamic models

    NASA Astrophysics Data System (ADS)

    Kastelic, Vanja; Carafa, Michele M. C.; Visini, Francesco

    2016-04-01

    We present a probabilistic seismic hazard analysis (PSHA) that is exclusively based on active faults and geodynamic finite element input models whereas seismic catalogues were used only in a posterior comparison. We applied the developed model in the External Dinarides, a slow deforming thrust-and-fold belt at the contact between Adria and Eurasia.. is the Our method consists of establishing s two earthquake rupture forecast models: (i) a geological active fault input (GEO) model and, (ii) a finite element (FEM) model. The GEO model is based on active fault database that provides information on fault location and its geometric and kinematic parameters together with estimations on its slip rate. By default in this model all deformation is set to be released along the active faults. The FEM model is based on a numerical geodynamic model developed for the region of study. In this model the deformation is, besides along the active faults, released also in the volumetric continuum elements. From both models we calculated their corresponding activity rates, its earthquake rates and their final expected peak ground accelerations. We investigated both the source model and the earthquake model uncertainties by varying the main active fault and earthquake rate calculation parameters through constructing corresponding branches of the seismic hazard logic tree. Hazard maps and UHS curves have been produced for horizontal ground motion on bedrock conditions VS 30 ≥ 800 m/s), thereby not considering local site amplification effects. The hazard was computed over a 0.2° spaced grid considering 648 branches of the logic tree and the mean value of 10% probability of exceedance in 50 years hazard level, while the 5th and 95th percentiles were also computed to investigate the model limits. We conducted a sensitivity analysis to control which of the input parameters influence the final hazard results in which measure. The results of such comparison evidence the deformation model and

  20. Postcollisional lithospheric evolution of the Southeast Carpathians: Comparison of geodynamical models and observations

    NASA Astrophysics Data System (ADS)

    Göǧüş, Oǧuz H.; Pysklywec, Russell N.; Faccenna, Claudio

    2016-05-01

    Seismic evidence and thermal and topographic transients have led to the interpretation of lithospheric removal beneath the Southeast Carpathians region. A series of numerical geodynamic experiments in the context of the tectonic evolution of the region are conducted to test the surface-crustal response to lithosphere delamination and slab break-off. The results show that a delamination-type removal ("plate-like" migrating instability) causes a characteristic pattern of surface uplift/subsidence and crustal extension/shortening to occur due to the lithospheric deformation and dynamic/thermal forcing of the sublithospheric mantle. These features migrate with the progressive removal of the underlying lithosphere. Model results for delamination are comparable with observables related to the geodynamic evolution of the Southeast Carpathians since 10 Ma: the mantle structure inferred by seismic tomography, migrating patterns of uplift (>1.5 km) and subsidence (>2 km) in the region, crustal thinning in the Carpathian hinterland and thickening at the Focsani depression, and regional extension in the Carpathian corner (e.g., opening of Brasov basin) correlating with volcanism (e.g., Harghita and Persani volcanics) in the last 3 Myr.

  1. A 3-D Geodynamic Model of Strain Partitioning in Southern California

    NASA Astrophysics Data System (ADS)

    Ye, J.; Liu, M.; Lin, F.

    2012-12-01

    In southern California, strain resulting from the relative motion between the Pacific and the North American plates is partitioned in a complex system of transcurrent, transcompressional, and transtensional faults. High-precision GPS measurements in this region have enabled kinematic modeling of the present-day strain partitioning between major faults in southern California. However, geodynamic models are needed to understand the cause of strain partitioning and to determine strain in regions where faults are blind or diffuse. We have developed a regional-scale geodynamic model of strain partitioning in southern California. This 3-D viscoelasto-plastic finite element model incorporates first-order fault geometry of the major active faults in the region. The model domain includes an elastoplastic upper crust on top of a viscoelastic lower lithospheric layer. Deformation is driven by the relative motion between the Pacific and the North American plates, imposed as a displacement boundary condition. Plastic deformation both within the fault zones and in the unfaulted surrounding crust is calculated. Our results show that the Big Bend of the San Andreas Fault, and other geometric complexity of faults in southern California, plays a major role in strain partitioning. The observed variations of strain portioning in southern California can be explained by the geometric configuration of fault systems relative to the relative plate motion, without appealing to basal traction of a flowing lower lithosphere. The model predicts concentrated plastic strain under the reverse fault systems in the Transverse Ranges and the young and diffuse faults in the Eastern California Shear Zone across the Mojave Desert, where a number damaging earthquakes occurred in the past decades.

  2. Understanding the physics of the Yellowstone magmatic system with geodynamic inverse modelling

    NASA Astrophysics Data System (ADS)

    Reuber, Georg; Kaus, Boris

    2017-04-01

    The Yellowstone magmatic system is one of the largest magmatic systems on Earth. Thus, it is important to understand the geodynamic processes that drive this very complex system on a larger scale ranging from the mantle plume up to the shallow magma chamber in the upper crust. Recent geophysical results suggest that two distinct magma chambers exist: a shallow, presumably felsic chamber and a deeper and partially molten chamber above the Moho [1]. Why melt stalls at different depth levels above the Yellowstone plume, whereas dikes cross-cut the whole lithosphere in the nearby Snake River Plane is puzzling. Therefore, we employ lithospheric-scale 2D and 3D geodynamic models to test the influence of different model parameters, such as the geometry of the magma chamber, the melt fraction, the rheological flow law, the densities and the thermal structure on their influence on the dynamics of the lithosphere. The melt content and the rock densities are obtained by consistent thermodynamic modelling of whole rock data of the Yellowstone stratigraphy. We present derivations in the stress field around the Yellowstone plume, diking areas and different melt accumulations. Our model predictions can be tested with available geophysical data (uplift rates, melt fractions, stress states, seismicity). By framing it in an inverse modelling approach we can constrain which parameters (melt fractions, viscosities, geometries) are consistent with the data and which are not. [1] Huang, Hsin-Hua, et al. "The Yellowstone magmatic system from the mantle plume to the upper crust." Science 348.6236 (2015): 773-776.

  3. Putting Phase Equilibria into Geodynamic Models: An Equation of State Approach (Invited)

    NASA Astrophysics Data System (ADS)

    Connolly, J.

    2009-12-01

    The use of free energy minimization codes to calculate the proportions and properties of minerals and consequently bulk rock properties is now commonplace in geophysical modeling. In effect such applications imply the existence of an equation of state, which is the optimized free energy as a function of its independent variables, for the rocks of interest. The essential feature of the equation of state is that all thermodynamic properties can be derived from it, a feature that requires that its derivatives are continuous. The equation of state may be calculated dynamically within the larger framework of a geodynamic code or it may be implemented statically via tables that are calculated prior to the solution of the geodynamic application. The virtues of static implementation is its extreme simplicity, computational efficiency, and that the finite resolution of the table assures that the equation of state is numerically differentiable for any choice of independent state variables. However, the memory required to store the requisite multidimensional tables may necessitate dynamic implementations for problems involving multi-component mass transfer, e.g., as in reactive melt transport. Paradoxically, the unlimited accuracy of dynamic solutions creates a potential numerical instability, the Stefan problem, for geodynamic governing equations formulated in terms of pressure and temperature. This instability arises because the derivatives of an equation of state for a polyphase aggregate as a function of pressure and temperature are singular at the conditions of a low order phase transformation. An equation of state as a function of specific entropy, specific volume and chemical composition eliminates this difficulty and, additionally, leads to a robust formulation of the energy and mass conservation equations. In this formulation, energy and mass conservation furnish evolution equations for entropy and volume and the equation of state serves as an update rule for

  4. Post-breakup burial and exhumation of passive continental margins: nine propositions to inform geodynamic models

    NASA Astrophysics Data System (ADS)

    Green, Paul F.; Duddy, Ian; Japsen, Peter; Chalmers, James; Bonow, Johan

    2017-04-01

    Despite many years of study, the processes involved in the post-breakup development of passive margins remain poorly understood. Integration of apatite fission track analysis (AFTA) and stratigraphic landscape analysis (SLA) at a number of margins has provided new insights into the development of elevated passive continental margins (EPCMs). In particular, these studies have highlighted the importance of integrating evidence from the preserved rock record with information on the deposition and erosional removal of rock units which are no longer present ("missing section"). From these studies we have formulated nine propositions regarding the formation of EPCMs and the nature of the controlling processes, viz: 1: EPCMs are not the inevitable consequence of rifting and breakup 2: Elevated topography at present-day EPCMs developed long after breakup 3: Similar EPCM landscapes at different margins suggest similar controlling processes 4: EPCMs undergo episodic burial and exhumation rather than slow monotonic denudation, both before rifting and after breakup 5: Post-breakup exhumation at continental margins is not restricted to elevated onshore regions 6: Post-breakup burial and exhumation have affected low lying margins as well as EPCMs 7: Episodic km-scale exhumation and re-burial also affects cratonic regions 8: Exhumation events show a broad level of synchroneity across continents and oceans and correlate with plate boundary events and changes in plate motions. 9: EPCMs are located where there is an abrupt, lateral change in crustal or lithospheric thickness These propositions imply that positive and negative vertical motions at passive margins are controlled by plate-scale processes. Many of these key aspects are absent from current geodynamic models of passive margin development. Understanding the processes that control vertical movements at passive continental margins requires development of realistic geodynamic models that honour these propositions.

  5. MLDs, LABs, and Moho's, Oh My! Using Geodynamical Models to Guide Interpretations of Geophysical Observations

    NASA Astrophysics Data System (ADS)

    Cooper, C. M.; Miller, M. S.

    2014-12-01

    As we peer deeper and in more detail into cratonic lithosphere, intriguing structures arise to peak our curiosity and imagination. Seismic discontinuity imaging reveals anomalous features that appear as depths (~100-160 km) that appear to be shallower than the base of the tomographically inferred cratonic lithosphere (~150-300 km). These are now been known as mid-lithospheric discontinuities (MLD). Magnetotelluric data shows regions of low resistivity suggesting regions of hydration or presence of carbon in graphite form. But how do we interpret these observations and how do we use them to learn more about craton formation and evolution? Some explanations for these anomalies include melt accumulation, the lithosphere-asthenosphere boundary (LAB), and phase transitions. We propose that many of the structures might actually be related to the initial formation of the cratonic lithosphere. We use a combination of geodynamic models and observations of the depths and orientations of mid-lithospheric seismic discontinuities from a compilation of recent receiver function observations within various regions of cratonic lithosphere around the world and new results from the West African Craton to test whether some of the imaged structure can be attributed to the initial formation of thickened cratonic lithosphere. The formation of thick, cratonic lithosphere should introduce complex structures that could then be preserved within the long-lived regions (to then be later captured by eager geophysicists). We performed numerical simulations of the thickening of lithosphere. We considered two types of thickening - either a process akin to (1) thrust stacking or (2) viscous thickening of the lithospheric material.. In particular, we looked to delineate regions that showed regions with mid-lithospheric discontinuities occurring at variable depths and orientations. Our geodynamic models provide an explanation for the observation that some cratonic regions exhibit mid

  6. Stratigraphic and Geologic Constraints on Geodynamic Models of North America Since the Cretaceous

    NASA Astrophysics Data System (ADS)

    Spasojevic, S.; Gurnis, M. C.

    2007-12-01

    Stratigraphic and sea level data along with plate motions and mantle tomographic images are used as constraints on inverse and forward models of mantle convection beneath North America. Using plate reconstruction with continuously closed plate polygons (developed using the GPlates program), we compute forward and inverse models of mantle convection with the finite element method (CitcomS). With plate motions, seismic tomography is used to estimate mantle initial conditions using an adjoint of the energy equation, as described by Liu and Gurnis during this meeting. For North America, we developed a set of forward and inverse regional geodynamic models for last 100 million years, with plate movements consistent with global paleogeographic models. We used sediment isopachs, paleoshorelines, and tectonic subsidence curves as the primary stratigraphic and geologic constraints. Tectonic subsidence history for North America was the main constraint for inverse models. In forward mantle convection models, we used the prediction of dynamic topography, along with published eustatic curves, to model sediment isopachs, paleoshorelines, and tectonic subsidence. Modeling results are than compared to stratigraphic and geologic observations, and models are updated iteratively. In a fixed North American frame of reference, our models indicate that a dynamic topography low moved eastward from 100 million years to the present, due to of the descent of the Farallon slab as the plate moved westward. During the Cretaceous, the dynamic topography low was located in the middle of North American continent. During this period, eustatic sea-level reached its maximum and when combined with a dynamic topography low, caused a substantial inundation of North America, creating the Western Interior Seaway. At the present time, the dynamic topography low is located in the eastern United States, and we argue that this region is experiencing tectonic subsidence. This tectonic subsidence can explain

  7. Using Interactive Visualization to Analyze Solid Earth Data and Geodynamics Models

    NASA Astrophysics Data System (ADS)

    Kellogg, L. H.; Kreylos, O.; Billen, M. I.; Hamann, B.; Jadamec, M. A.; Rundle, J. B.; van Aalsburg, J.; Yikilmaz, M. B.

    2008-12-01

    The geological sciences are challenged to manage and interpret increasing volumes of data as observations and simulations increase in size and complexity. Major projects such as EarthScope and GeoEarthScope are producing the data needed to characterize the structure and kinematics of Earth's surface and interior at unprecedented resolution. At the same time, high-performance computing enables high-precision and fine- detail simulation of geodynamics processes, complementing the observational data. To facilitate interpretation and analysis of these datasets, to evaluate models, and to drive future calculations, we have developed methods of interactive visualization with a special focus on using immersive virtual reality (VR) environments to interact with models of Earth's surface and interior. VR has traditionally been used primarily as a presentation tool allowing active navigation through data. Reaping the full intellectual benefits of immersive VR as a tool for accelerated scientific analysis requires building on the method's strengths, that is, using both 3D perception and interaction with observed or simulated data. Our approach to VR takes advantage of the specialized skills of geoscientists who are trained to interpret geological and geophysical data generated from field observations. Interactive tools allow the scientist to explore and interpret geodynamic models, tomographic models, and topographic observations, while feature extraction tools support quantitative measurement of structures that emerge from numerical simulations or field observations. The use of VR technology enables us to improve our interpretation of crust and mantle structure and of geodynamical processes. Mapping tools based on computer visualization allow virtual "field studies" in inaccessible regions, and an interactive tool allows us to construct digital fault models for use in numerical models. Using the interactive tools on a high-end platform such as an immersive virtual reality

  8. Testing geodynamic models of lowermost mantle flow with a regional shear wave splitting data set

    NASA Astrophysics Data System (ADS)

    Ford, H. A.; Long, M. D.

    2015-12-01

    Global flow models rely on a number of assumptions, including composition, temperature, viscosity, and deformation mechanism. In the upper mantle, flow models and their associated assumptions can be tested and refined with observations of seismic anisotropy, which is treated as a proxy for flow direction. Beneath the transition zone, direct observations of seismic anisotropy are scarce, except for in the lowermost ~250 km of the mantle. In this study, we utilize a comprehensive, previously published (Ford et al., 2015) shear wave splitting study in order to test a three-dimensional global geodynamic flow model (Walker et al., 2011). Our study focuses on a region of the lowermost mantle along the eastern edge of the African Superplume beneath the Afar region. We find that our observations are fit by a model which invokes slip along the (010) plane of post-perovskite with flow directed down and to the southwest. Critically, we demonstrate the ability of a regional data set to interrogate models of lower mantle flow.

  9. Oedometer test as a benchmark for geodynamic models involving strain-weakening plasticity

    NASA Astrophysics Data System (ADS)

    Choi, E.; Lee, C.

    2016-12-01

    Strain-weakening plasticity is frequently used in geodynamic modeling to induce strain localization that is useful for representing faults, shear zones or plate boundaries. However, implementations of strain-weakening plasticity are rarely verified against known solutions, making it difficult to compare model results from different numerical methods. Devising suitable benchmarks appears necessary for promoting the practice of verifying numerical solutions for strain localization. In this study, we present a simple problem in which an analytic or at least semi-analytic solution is available for strain-weakening plasticity. Derived from the classical oedometer test, the benchmark assumes that three parameters of the Mohr-Coulomb plastic model, internal friction angle, dilation angle and cohesion, are a linear function of an internal scalar variable representing the amount of permanent plastic strain. We show how solutions are derived under this setting and use them for benchmarking numerical solutions from DES3D, an open-source finite element code for tectonic modeling, as well as COMSOL Multiphysics, a commercial finite element package for multiphysics simulations. We also discuss caveats as to comparing solutions from the two different modeling codes against the proposed benchmark.

  10. Geodynamic models of convergent margin tectonics: transition from rifted margin to overthrust belt and consequences for foreland-basin development

    SciTech Connect

    Stockmal, G.S.; Beaumont, C.; Boutilier, R.

    1986-02-01

    A quantitative geodynamic model for overthrusting of a passive continental margin during attempted continental subduction demonstrates the mechanical and thermal coupling between overthrust loads, the lithosphere, and the associated foreland basin. The model treated the lithosphere as a two-dimensional nonuniform elastic plate whose strength is controlled thermally. The thermal and flexural evolution of a margin is followed from initial rifting and passive-margin development, through overthrusting and foreland-basin deposition, to postdeformational erosion.

  11. Sink or swim? Geodynamic and petrological model constraints on the fate of Archaean primary crust

    NASA Astrophysics Data System (ADS)

    Kaus, B.; Johnson, T.; Brown, M.; VanTongeren, J. A.

    2013-12-01

    Ambient mantle potential temperatures in the Archaean were significantly higher than 1500 °C, leading to a high percent of melting and generating thick MgO-rich primary crust underlain by highly residual mantle. However, the preserved volume of this crust is low suggesting much of it was recycled. Here we couple calculated phase equilibria for hydrated and anhydrous low to high MgO crust compositions and their complementary mantle residues with 2-D numerical geodynamic models to investigate lithosphere dynamics in the early Earth. We show that, with increasing ambient mantle potential temperature, the density of primary crust increases more dramatically than the density of residual mantle decreases and the base of MgO-rich primary crust becomes gravitationally unstable with respect to the underlying mantle even when fully hydrated. To study this process we use geodynamic models that include the effects of melt extraction, crust formation and depletion of the mantle in combination with laboratory-constrained dislocation and diffusion creep rheologies for the mantle. The models show that the base of the gravitationally unstable lithosphere delaminates through relatively small-scale Rayleigh-Taylor instabilities, but only if the viscosity of the mantle lithosphere is sufficiently low. Thickening of the crust above upwelling mantle and heating at the base of the crust are the main mechanisms that trigger the delamination process. Scaling laws were developed that are in good agreement with the numerical simulations and show that the key parameters that control the instability are the density contrast between crust and underlying mantle lithosphere, the thickness of the unstable layer and the effective viscosity of the upper mantle. Depending on uncertainties in the melting relations and rheology (hydrous or anhydrous) of the mantle, this process is shown to efficiently recycle the crust above potential temperatures of 1550-1600 °C. However, below these temperatures

  12. Global paleo-lithospheric models for geodynamical analysis of plate reconstructions

    NASA Astrophysics Data System (ADS)

    Quevedo, L.; Morra, G.; Müller, R. D.

    2012-12-01

    We present a general framework to generate time-dependent global subduction history models from kinematic plate reconstructions and explore their associated coupled plate-mantle dynamic behaviour. Slabs are constructed by advecting material into the mantle by prescribing its radial velocity and following the absolute tangential motion of the subducting plate. A simple geodynamic scenario where plates and slabs define isopycnic and isoviscous regions in an homogeneous or layered mantle was explored using the boundary element method-based software BEMEarth. The resulting dynamic behaviour was used to predict the absolute plate motion directions for the present day and a particular mid-cretaceous (125 Ma) kinematic model. We show how the methodology can be used to compare and revise kinematic reconstructions based on their effect on the balance of plate driving forces and the resulting Euler poles of subducting plates. As an example we compare the Farallon plate dynamics at 125 Ma in a global model with two reconstructions in the context of the evolution of the Western North American Cordillera. Our results suggest a method to identify episodes of absolute plate motions that are inconsistent with the expected plate dynamics.

  13. Reconciling laboratory and observational models of mantle rheology in geodynamic modelling

    NASA Astrophysics Data System (ADS)

    King, Scott D.

    2016-10-01

    Experimental and geophysical observations constraining mantle rheology are reviewed with an emphasis on their impact on mantle geodynamic modelling. For olivine, the most studied and best-constrained mantle mineral, the tradeoffs associated with the uncertainties in the activation energy, activation volume, grain-size and water content allow the construction of upper mantle rheology models ranging from nearly uniform with depth to linearly increasing from the base of the lithosphere to the top of the transition zone. Radial rheology models derived from geophysical observations allow for either a weak upper mantle or a weak transition zone. Experimental constraints show that wadsleyite and ringwoodite are stronger than olivine at the top of the transition zone; however the uncertainty in the concentration of water in the transition zone precludes ruling out a weak transition zone. Both observational and experimental constraints allow for strong or weak slabs and the most promising constraints on slab rheology may come from comparing inferred slab geometry from seismic tomography with systematic studies of slab morphology from dynamic models. Experimental constraints on perovskite and ferropericlase strength are consistent with general feature of rheology models derived from geophysical observations and suggest that the increase in viscosity through the top of the upper mantle could be due to the increase in the strength of ferropericlase from 20-65 GPa. The decrease in viscosity in the bottom half of the lower mantle could be the result of approaching the melting temperature of perovskite. Both lines of research are consistent with a high-viscosity lithosphere, a low viscosity either in the upper mantle or transition zone, and high viscosity in the lower mantle, increasing through the upper half of the lower mantle and decreasing in the bottom half of the lower mantle, with a low viscosity above the core. Significant regions of the mantle, including high

  14. Geodynamics Branch research report, 1982

    NASA Technical Reports Server (NTRS)

    Kahn, W. D. (Editor); Cohen, S. C. (Editor)

    1983-01-01

    The research program of the Geodynamics Branch is summarized. The research activities cover a broad spectrum of geoscience disciplines including space geodesy, geopotential field modeling, tectonophysics, and dynamic oceanography. The NASA programs which are supported by the work described include the Geodynamics and Ocean Programs, the Crustal Dynamics Project, the proposed Ocean Topography Experiment (TOPEX) and Geopotential Research Mission. The individual papers are grouped into chapters on Crustal Movements, Global Earth Dynamics, Gravity Field Model Development, Sea Surface Topography, and Advanced Studies.

  15. Simulation of late Cenozoic South American flat-slab subduction using geodynamic models with data assimilation

    NASA Astrophysics Data System (ADS)

    Hu, Jiashun; Liu, Lijun; Hermosillo, Armando; Zhou, Quan

    2016-03-01

    The formation mechanisms of flat slabs in South America remain unclear. To quantitatively evaluate the earlier proposed mechanisms, we simulate the post-100 Ma subduction history below South America using 4-D geodynamic models by progressively incorporating plate kinematics, seafloor ages and key tectonic features including the buoyant oceanic crust, continental cratons, oceanic plateaus (i.e. the inferred Inca plateau, subducting Nazca Ridge and Juan Fernandez Ridge), as well as deformable trench profiles according to recent geological reconstructions. We find that, in the absence of an overriding plate and subducting buoyancy features, the seafloor age affects slab dip angle by controlling the slab's mechanical strength (i.e., the resistance to bending) and negative buoyancy (integrated positive density anomaly that enhances bending). Our models show that slab strength dominates its buoyancy at age >30 Ma and the opposite for younger ages. The existence of a thick overriding plate reduces the slab dip by increasing dynamic suction, and individual cratonic roots further lead to along-trench variations of dip angle reduction. While dynamic suction from the overriding plate generates a permanent reduction of the long-wavelength slab dip angle, it is the final addition of subducting oceanic plateau and aseismic ridges that produces the transient and localized flat-slabs as observed. These results suggest that all mechanisms except the buoyancy features affect the slab dip only at large spatial scales. Our best-fit model with all the above tectonic features included provides a good match to both the upper mantle Benioff zones and the temporal evolution of volcanic arcs since the mid-Miocene. The imperfect match of the Peruvian flat-slab is likely associated with the uncertain 3-D configuration of the Amazonian craton.

  16. The seismic cycle at subduction thrusts: benchmarking geodynamic numerical simulations and analogue models

    NASA Astrophysics Data System (ADS)

    van Dinther, Y.; Gerya, T.; Corbi, F.; Funiciello, F.; Mai, P. M.; Dalguer, L. A.

    2012-04-01

    The physics governing the long-term seismic cycle in subduction zones remains poorly understood due to its spatial inaccessibility, complex tectonics and geometry, and the limited observation time. However, modeling approaches for large-scale subduction and small-scale dynamic rupture processes are well developed, and could help to overcome limited seismic observations for improved studies of the long-term seismic cycle at subduction thrusts. Such a continuum mechanic, geodynamic model includes a more realistic geometry and rheology with spontaneously developing faults, but also needs to transfer large spatial and temporal modeling scales such that short seismic events are resolved. We deploy a continuum mechanic numerical method that involves a plane-strain finite-difference scheme with marker-in-cell technique to solve the conservation of momentum, mass, and energy for a visco-elasto-plastic rheology. The simulated laboratory setup constitutes a triangular, visco-elastic crustal wedge that is underlain by a restricted, velocity-weakening zone. Both are driven toward a backstop by a subducting, straight slab. We benchmark our geodynamic numerical approach to a novel gelatin lab experiment that shows a cyclic seismic pattern. Our results demonstrate that the fluid-dynamic, viscous-elasto-plastic code simulates a series of regular rapid, short, elastic seismic events if velocity-weakening friction is incorporated. During the inter-seismic period the seismogenic zone subducts with the slab, thus focusing stresses near its down-dip end. Once material strength is exceeded, the seismogenic zone fails and ruptures predominantly in up-dip direction, thereby causing a short, rapid reversal of wedge displacements and acceleration of reversed velocities. After this stress release, healing (increase of friction coefficient) is essential to build up stresses for generating the next earthquake. Velocity strengthening in aseismogenic regions assists a) to limit the rupture up

  17. The long-term seismic cycle at subduction thrusts: benchmarking geodynamic numerical simulations and analogue models

    NASA Astrophysics Data System (ADS)

    van Dinther, Y.; Gerya, T.; Corbi, F.; Funiciello, F.; Mai, P. M.; Dalguer, L. A.

    2011-12-01

    The physics governing the long-term seismic cycle in subduction zones remains elusive, largely due to its spatial inaccessibility, complex tectonic and geometric setting, and the short observational time span. To improve our understanding of the physics governing this seismic cycle, we benchmark a geodynamic numerical approach with a novel laboratory model. In this work we quantify and compare periodicity and source parameters of slip events (earth-quakes and gel-quakes) as a function of fault rheology (i.e. frictional properties), subduction velocity, slab dip, and seismogenic zone width. Our fluid-dynamic numerical method involves a plane-strain finite-difference scheme with marker-in-cell technique to solve the conservation of momentum, mass, and energy for a visco-elasto-plastic rheology. The simulated gelatin laboratory setup constitutes a triangular, visco-elastic crustal wedge on top of a straight subducting slab that includes a seismogenic zone. Numerical and analogue results show a regular and roughly comparable periodicity of short, rapid wedge velocity reversals. Ruptures nucleating mainly around the bottom of the seismogenic zone, and propagating upward, cause a distinct and rapid drop in stress within the wedge. To mimic the short duration, high speed and regularity of the analogue results, the numerical method requires a form of steady-state velocity-weakening friction for acceleration, and healing. The necessity of including a variable state component into the numerical simulations is subject of ongoing work. Finally, we extend this analysis by observing the role of different friction laws in large-scale, geometrically more realistic models.

  18. Geodynamic background of the 2008 Wenchuan earthquake based on 3D visco-elastic numerical modelling

    NASA Astrophysics Data System (ADS)

    Liu, Chang; Zhu, Bojing; Yang, Xiaolin; Shi, Yaolin

    2016-03-01

    The 2008 Wenchuan earthquake (Mw7.9) occurred in the Longmen Shan fault zone. The stress change and crustal deformation during the accumulation period is computed using 3D finite element modelling assuming visco-elastic rheology. Our results support that the eastward movement of the Tibetan Plateau resulting from the India-Eurasia collision is obstructed at the Longmen Shan fault zone by the strong Yangtze craton. In response, the Tibetan ductile crust thickens and accumulates at the contact between the Tibetan Plateau and the Sichuan Basin. This process implies a strong uplift with the rate of about 1.8 mm/a of the upper crust and induces a stress concentration nearly at the bottom of the Longmen Shan fault zone. We believe that the stress concentration in the Longmen Shan fault zone provides a very important geodynamic background of the 2008 Wenchuan earthquake. Using numerical experiments we find that the key factor controlling this stress concentration process is the large viscosity contrast in the middle and lower crusts between the Tibetan Plateau and the Sichuan Basin. The results show that large viscosity contrast in the middle and lower crusts accelerates the stress concentration in the Longmen Shan fault zone. Fast moving lower crustal flow accelerates this stress accumulation process. During the inter-seismic period, spatially the maximum stress accumulation rate of the eastern margin of the Tibetan Plateau is located nearly at the bottom of the brittle upper crust of the Longmen Shan fault zone. The spatial distribution of the stress accumulation along the strike of the Longmen Shan fault zone is as follows: the normal stress decreases while the shear stress increases from southwest to northeast along the Longmen Shan fault zone. This stress distribution explains the thrust motion in the SW and strike-slip motion in the NE during the 2008 Wenchuan earthquake.

  19. Paleogene retroarc flexural basin beneath the Neogene Pannonian Basin: A geodynamic model

    NASA Astrophysics Data System (ADS)

    Tari, G.; Báldi, T.; Báldi-Beke, M.

    1993-11-01

    The Neogene (Middle Miocene-Recent) Pannonian Basin is superimposed on an earlier Paleogene (Middle Eocene-Early Miocene) basin complex as a result of back-arc extension. Although the stratigraphy of the latter is very well known due to raw material exploration, its formation and structural evolution is much less understood. A transtensional origin was generally proposed for the Paleogene Basin of Hungary, assuming an origin analogous to that of the overlying Neogene Pannonian Basin. We suggest an alternative geodynamic scenario for the development of the Paleogene basin complex, as we think that the observations are better understood in terms of a retroarc foredeep basin model. According to this, a flexural basin developed south of the backthrust inner West Carpathian units. The thrust load resulted in a generally deep, underfilled "flysch" basin during Middle Eocene-Early Oligocene times. In the Late Oligocene-Early Miocene predominantly shallow marine and continental deposition occurred indicating the gradual cessation of thrusting in the adjacent thrust-fold belt and the beginning of "molasse" sedimentation. Throughout the whole Paleogene, a shift can be observed of the bathyal, dominantly siliciclastic (in the axis of the foredeep) and neritic, partly carbonate (in the foreland flank of the foredeep) facies belts. This migration of the Middle Eocene-Early Miocene depocenters of the HPB (Hungarian Paleogene Basin) to the east-northeast in present-day coordinates is the result of two processes: (1) the advancement of backthrusting to the southeast; (2) along-strike shift of thrusting to the northeast. While a thin-skinned thrust front can be reconstructed for the Late Eocene (Buda Anticline), the Diósjenö-Hurbanovo line is interpreted as the result of a major thick-skinned thrusting event at the base of the NP24 zone ( $˜31 Ma). The subsidence pattern, the distinct depositional environments and the structural observations can be more easily integrated into a

  20. NASA Geodynamics Program

    NASA Technical Reports Server (NTRS)

    1984-01-01

    Activities and achievements for the period of May 1983 to May 1984 for the NASA geodynamics program are summarized. Abstracts of papers presented at the Conference are inlcuded. Current publications associated with the NASA Geodynamics Program are listed.

  1. NASA geodynamics program: Bibliography

    NASA Technical Reports Server (NTRS)

    1990-01-01

    The Seventh Geodynamics Program report summarizes program activities and achievements during 1988 and 1989. Included is a 115 page bibliography of the publications associated with the NASA Geodynamics Program since its initiation in 1979.

  2. A geodynamic model of subduction evolution to explain Australian plate acceleration and deceleration during the latest Cretaceous-Early Cenozoic

    NASA Astrophysics Data System (ADS)

    Schellart, Wouter P.

    2017-04-01

    The northern margin of the Australian plate, in the region of present-day New Guinea, was characterized by a large north dipping subduction zone consuming a marginal basin during the latest Cretaceous (Maastrichtian) and Early Cenozoic. Observational data imply that the subduction zone was active at 71-50 Ma, and suggest that it was responsible for plate acceleration from 1 to 7 cm/yr between 66 and 59 Ma, and plate deceleration from 7 to 0 cm/yr between 52 and 49 Ma. A numerical model of buoyancy-driven subduction is presented to simulate the latest Cretaceous-Early Cenozoic geodynamic setting of the New Guinea region and to test if the rates of plate acceleration and deceleration can be ascribed to the progressive evolution of a subducting slab, from an initial transient subduction phase to the terminal stage of subduction involving slab detachment. The geodynamic model can reproduce the first-order plate velocity evolution of the Australian plate and demonstrates that plate velocity increases and decreases of the order of 5 cm/yr, due to transient early and terminal subduction phases, respectively, can occur over periods lasting only a few Myr.

  3. Advantages of a conservative velocity interpolation (CVI) scheme for particle‐in‐cell methods with application in geodynamic modeling

    PubMed Central

    Agrusta, Roberto; van Hunen, Jeroen

    2015-01-01

    Abstract The particle‐in‐cell method is generally considered a flexible and robust method to model the geodynamic problems with chemical heterogeneity. However, velocity interpolation from grid points to particle locations is often performed without considering the divergence of the velocity field, which can lead to significant particle dispersion or clustering if those particles move through regions of strong velocity gradients. This may ultimately result in cells void of particles, which, if left untreated, may, in turn, lead to numerical inaccuracies. Here we apply a two‐dimensional conservative velocity interpolation (CVI) scheme to steady state and time‐dependent flow fields with strong velocity gradients (e.g., due to large local viscosity variation) and derive and apply the three‐dimensional equivalent. We show that the introduction of CVI significantly reduces the dispersion and clustering of particles in both steady state and time‐dependent flow problems and maintains a locally steady number of particles, without the need for ad hoc remedies such as very high initial particle densities or reseeding during the calculation. We illustrate that this method provides a significant improvement to particle distributions in common geodynamic modeling problems such as subduction zones or lithosphere‐asthenosphere boundary dynamics. PMID:27840594

  4. Basic research for the geodynamics program

    NASA Technical Reports Server (NTRS)

    Mueller, I. I.

    1982-01-01

    Work performed and data obtained in geodynamic research is reported. The purpose was to obtain utilization of: (1) laser and very long baseline interferometry (VLBI); (2) range difference observation in geodynamics; (3) development of models for ice sheet and crustal deformations. The effects of adopting new precession, nutation and equinox corrections on the terrestrial reference frame are investigated.

  5. Plateau Uplift, Erosion, and Geodynamic Forcing in Southern Africa from Integration of Landscape Evolution Modeling with Geologic and Thermochronologic Constraints

    NASA Astrophysics Data System (ADS)

    Stanley, J. R.; Braun, J.; Flowers, R. M.

    2016-12-01

    The southern African plateau is a dominant feature of African topography but there is considerable debate about when and how it formed. Cretaceous kimberlite activity and the presence of a large low shear seismic velocity province (LLSVP) in the deep mantle below southern Africa have lead many to propose uplift related to mantle processes. Better constraints on the timing of uplift have the potential to constrain the nature of the LLSVP and the source of support for southern Africa's anomalous elevations. However, surface uplift is difficult to detect directly in the geologic record and the relationships between mantle sourced uplift and erosion are not necessarily direct. Here, we use a landscape evolution model combined with data constraining the spatiotemporal erosion patterns across southern Africa to explore how topographic development and erosion are related. We integrate a highly efficient landscape evolution model (FastScape, Braun and Willett, 2013) and a thermal module with a large apatite (U-Th)/He (AHe) thermochronologic dataset, sedimentary flux volumes for the major offshore basins, and geologic observations to address these questions. We used inversion methods based on the Neighborhood Algorithm to investigate how data is best simulated by the model while varying model parameters related to plateau uplift and the physical characteristics of the eroding material. Results from the inversions show that the data are sufficient to constrain many model parameters. Additionally, we show that the combination of different types of data, and in particular the spatiotemporal erosion information from the AHe thermochronologic results, is valuable for constraining many of these parameters. We show that the geometry and physical characteristics of the overlying sedimentary basin, as well as the characteristics of the geodynamic forcing, have significant control on plateau erosion patterns. It is therefore important to consider both geodynamics and surface controls

  6. Reconstructing palaeo-volcanic geometries using a Geodynamic Regression Model (GRM): Application to Deception Island volcano (South Shetland Islands, Antarctica)

    NASA Astrophysics Data System (ADS)

    Torrecillas, C.; Berrocoso, M.; Felpeto, A.; Torrecillas, M. D.; Garcia, A.

    2013-01-01

    This article describes a reconstruction made of the palaeo-volcanic edifice on Deception Island (South Shetland Islands, Antarctica) prior to the formation of its present caldera. Deception Island is an active Quaternary volcano located in the Bransfield Strait, between the South Shetland Islands and the Antarctic Peninsula. The morphology of the island has been influenced mainly by the volcanic activity but geodynamics and volcanic deformation have also contributed. A volcanic reconstruction method, the Geodynamic Regression Model (GRM), which includes a terrain deformation factor, is proposed. In the case of Deception Island, the directions of this deformation are NW-SE and NE-SW, and match both the observed deformation of the Bransfield Strait and the volcanic deformation monitored over the last 20 years in the island, using Global Navigation Satellite System (GNSS) techniques. Based on these data, possible volcanic deformation values of 5-15 mm/yr in these directions have been derived. A possible coastline derived from a current bathymetry is transformed, according to values for the chosen date, to obtain the palaeo-coastline of Deception Island of 100 k years ago. Topographic, geomorphologic, volcanological and geological data in a GIS system have been considered, for computation of the outside caldera slope, palaeo-coastline, palaeo-summit height and palaeo digital elevation model (DEM). The result is a 3D palaeo-geomorphological surface model of a volcano, reaching 640 m in height, with an increase of 4 km3 in volume compared to the current edifice, covering 4 km2 more surface area and the method reveals the previous existence of parasite volcanoes. Two photorealistic images of the island are obtained by superposition of textures extracted from a current Quick Bird satellite image also. This technique for reconstructing the terrain of an existing volcano could be useful for analysing the past and future geomorphology of this island and similar locations.

  7. Orogenesis of the Oman Mountains - a new geodynamic model based on structural geology, plate reconstructions and thermochronology

    NASA Astrophysics Data System (ADS)

    Grobe, Arne; Virgo, Simon; von Hagke, Christoph; Ralf, Littke; Urai, Janos L.

    2017-04-01

    Ophiolite obduction is an integral part of mountain building in many orogens. However, because the obduction stage is usually overprinted by later tectonic events, obduction geodynamics and its influence on orogenesis are often elusive. The best-preserved ophiolite on Earth is the Semail Ophiolite, Oman Mountains. 350 km of ophiolite and the entire overthrusted margin sequence are exposed perpendicular to the direction of obduction along the northeastern coast of the Sultanate of Oman. Despite excellent exposure, it has been debated whether early stages of obduction included formation of a micro-plate, or if the Oman Mountains result from collision of two macro-plates (e.g. Breton et al., 2004). Furthermore, different tectonic models for the Oman Mountains exist, and it is unclear how structural and tectonic phases relate to geodynamic context. Here we present a multidisciplinary approach to constrain orogenesis of the Oman Mountains. To this end, we first restore the structural evolution of the carbonate platform in the footwall of the Semail ophiolite. Relative ages of nine structural generations can be distinguished, based on more than 1,500 vein and fault overprintings. Top-to-S overthrusting of the Semail ophiolite is witnessed by three different generations of bedding confined veins in an anticlockwise rotating stress field. Rapid burial induced the formation of overpressure cells, and generation and migration of hydrocarbons (Fink et al., 2015; Grobe et al., 2016). Subsequent tectonic thinning of the ophiolite took place above a top-to-NNE crustal scale, ductile shear zone, deforming existing veins and forming a cleavage in clay-rich layers. Ongoing extension formed normal- to oblique-slip faults and horst-graben structures. This was followed by NE-SW oriented ductile shortening, the formation of the Jebel Akhdar anticline, potentially controlled by the positions of the horst-graben structures. Exhumation in the Cenozoic was associated with low angle normal

  8. Tectonic drivers of the Wrangell block: Insights on fore-arc sliver processes from 3-D geodynamic models of Alaska

    NASA Astrophysics Data System (ADS)

    Haynie, K. L.; Jadamec, M. A.

    2017-07-01

    Intracontinental shear zones can play a key role in understanding how plate convergence is manifested in the upper plate in regions of oblique subduction. However, the relative role of the driving forces from the subducting plate and the resisting force from within intracontinental shear zones is not well understood. Results from high-resolution, geographically referenced, instantaneous 3-D geodynamic models of flat slab subduction at the oblique convergent margin of Alaska are presented. These models investigate how viscosity and length of the Denali fault intracontinental shear zone as well as coupling along the plate boundary interface modulate motion of the Wrangell block fore-arc sliver and slip across the Denali fault. Models with a weak Denali fault (1017 Pa s) and strong plate coupling (1021 Pa s) were found to produce the fastest motions of the Wrangell block (˜10 mm/yr). The 3-D models predict along-strike variation in motion along the Denali fault, changing from dextral strike-slip motion in the eastern segment to oblique convergence toward the fault apex. Models further show that the flat slab drives oblique motion of the Wrangell block and contributes to 20% (models with a short fault) and 28% (models with a long fault) of the observed Quaternary slip rates along the Denali fault. The 3-D models provide insight into the general processes of fore-arc sliver mechanics and also offer a 3-D framework for interpreting hazards in regions of flat slab subduction.

  9. Recurrence interval of the 2008 Mw 7.9 Wenchuan earthquake inferred from geodynamic modelling stress buildup and release

    NASA Astrophysics Data System (ADS)

    Liu, Chang; Dong, Peiyu; Shi, Yaolin

    2017-10-01

    The destructive 2008 Mw 7.9 Wenchuan earthquake ruptured the Longmen Shan (LMS) fault zone and devastated cities in Sichuan province, China. Estimates of the recurrence interval of the large earthquake is important to understand the feature of seismic activity and to analyze the seismic hazard in the fault area. In this research we introduce the method of geodynamic modelling to estimate the recurrence interval of the Mw7.9 earthquake based on the basic physics of earthquakes-stress buildup and release on fault. The inter-seismic stress accumulation prior to the 2008 Wenchuan earthquake is extracted from our previous study, which developed 3D finite element visco-elastic lithospheric model of the LMS fault zone. The co-seismic stress release and the post-seismic stress relaxation of the earthquake are simulated through dislocation source models. The recurrence interval, which is the duration needed to accumulate the magnitude of the stress drop of the Mw7.9 earthquake, is estimated to be about 4200-6500 years. Sensitivities of the estimated recurrence interval relying on model dependent parameters, such as the viscosity and slip models, are discussed. This research provides a preferred method to estimate recurrence interval of large earthquake in fault zone.

  10. Subduction metamorphism in the Himalayan ultrahigh-pressure Tso Morari massif: An integrated geodynamic and petrological modelling approach

    NASA Astrophysics Data System (ADS)

    Palin, Richard M.; Reuber, Georg S.; White, Richard W.; Kaus, Boris J. P.; Weller, Owen M.

    2017-06-01

    The Tso Morari massif is one of only two regions where ultrahigh-pressure (UHP) metamorphism of subducted crust has been documented in the Himalayan Range. The tectonic evolution of the massif is enigmatic, as reported pressure estimates for peak metamorphism vary from ∼2.4 GPa to ∼4.8 GPa. This uncertainty is problematic for constructing large-scale numerical models of the early stages of India-Asia collision. To address this, we provide new constraints on the tectonothermal evolution of the massif via a combined geodynamic and petrological forward-modelling approach. A prograde-to-peak pressure-temperature-time (P-T-t) path has been derived from thermomechanical simulations tailored for Eocene subduction in the northwestern Himalaya. Phase equilibrium modelling performed along this P-T path has described the petrological evolution of felsic and mafic components of the massif crust, and shows that differences in their fluid contents would have controlled the degree of metamorphic phase transformation in each during subduction. Our model predicts that peak P-T conditions of ∼2.6-2.8 GPa and ∼600-620 ∘C, representative of 90-100 km depth (assuming lithostatic pressure), could have been reached just ∼3 Myr after the onset of subduction of continental crust. This P-T path and subduction duration correlate well with constraints reported for similar UHP eclogite in the Kaghan Valley, Pakistan Himalaya, suggesting that the northwest Himalaya contains dismembered remnants of what may have been a ∼400-km-long UHP terrane comparable in size to the Western Gneiss Region, Norway, and the Dabie-Sulu belt, China. A maximum overpressure of ∼0.5 GPa was calculated in our simulations for a homogeneous crust, although small-scale mechanical heterogeneities may produce overpressures that are larger in magnitude. Nonetheless, the extremely high pressures for peak metamorphism reported by some workers (up to 4.8 GPa) are unreliable owing to conventional thermobarometry

  11. Using low temperature thermochronology to decipher the surface history of the Superior craton and test geodynamic models

    NASA Astrophysics Data System (ADS)

    Sturrock, C. P.; Flowers, R. M.; Zhong, S.; Metcalf, J. R.; Kohn, B. P.

    2016-12-01

    The epeirogenic history of cratonic continental interiors can be a useful constraint or test for geodynamic models, but has historically been difficult to investigate due to the absence of stratigraphic sections for large areas of crystalline basement. Low-temperature thermochronologic methods provide a way to reconstruct past episodes of burial and denudation for areas devoid of sedimentary cover. New apatite (U-Th)/He (AHe) and apatite fission track (AFT) data from a 1400km NW-SE transect in the Archaean Superior Province of the Canadian Shield record a spatially variable thermal history for the craton in Paleozoic and Mesozoic times. Dates range from 600­­­­­­±60 Ma (AHe) and 529­±48 Ma (AFT) in the west to 184±14 Ma (AHe) and 174±9 Ma (AFT) in the east. Inverse thermal history models of these data coupled with geologic constraints show pronounced heating and cooling episodes in the Paleozoic and Mesozoic. Due to the lack of significant volcanism or other tectonic activity in the Superior Province during this time, the observed heating and cooling episodes are most likely associated with intervals of burial and denudation that varied in magnitude across the craton. Overall, both Paleozoic and Mesozoic peak temperatures are higher in the eastern than the western Superior craton, with eastern Superior samples requiring minimum peak Paleozoic temperatures of 37-130°C. Peak temperatures did not exceed 100°C from the middle to late Mesozoic through the Tertiary. Making the simplified assumption of a 25°C/km geothermal gradient and 0°C surface temperature, burial in some areas must have been at least 2-5km in the Paleozoic and was <4km in the Mesozoic. These burial and denudation patterns do not correlate with global sea level changes, making dynamic topography a good candidate for a driving mechanism. Ongoing work will compare these long wavelength uplift and subsidence histories with dynamic topography predictions from geodynamic models.

  12. Geodynamic models of a Yellowstone plume and its interaction with subduction and large-scale mantle circulation

    NASA Astrophysics Data System (ADS)

    Steinberger, B. M.

    2012-12-01

    Yellowstone is a site of intra-plate volcanism, with many traits of a classical "hotspot" (chain of age-progressive volcanics with active volcanism on one end; associated with flood basalt), yet it is atypical, as it is located near an area of Cenozoic subduction zones. Tomographic images show a tilted plume conduit in the upper mantle beneath Yellowstone; a similar tilt is predicted by simple geodynamic models: In these models, an initially (at the time when the corresponding Large Igneous Province erupted, ~15 Myr ago) vertical conduit gets tilted while it is advected in and buoyantly rising through large-scale flow: Generally eastward flow in the upper mantle in these models yields a predicted eastward tilt (i.e., the conduit is coming up from the west). In these models, mantle flow is derived from density anomalies, which are either inferred from seismic tomography or from subduction history. One drawback of these models is, that the initial plume location is chosen "ad hoc" such that the present-day position of Yellowstone is matched. Therefore, in another set of models, we study how subducted slabs (inferred from 300 Myr of subduction history) shape a basal chemically distinct layer into thermo-chemical piles, and create plumes along its margins. Our results show the formation of a Pacific pile. As subduction approaches this pile, the models frequently show part of the pile being separated off, with a plume rising above this part. This could be an analog to the formation and dynamics of the Yellowstone plume, yet there is a mismatch in location of about 30 degrees. It is therefore a goal to devise a model that combines the advantages of both models, i.e. a fully dynamic plume model, that matches the present-day position of Yellowstone. This will probably require "seeding" a plume through a thermal anomaly at the core-mantle boundary and possibly other modifications. Also, for a realistic model, the present-day density anomaly derived from subduction should

  13. A High-resolution 3D Geodynamical Model of the Present-day India-Asia Collision System

    NASA Astrophysics Data System (ADS)

    Kaus, B.; Baumann, T.

    2015-12-01

    We present a high-resolution, 3D geodynamic model of the present-day India-Asia collision system. The model is separated into multiple tectonic blocks, for which we estimate the first order rheological properties and the impact on the dynamics of the collision system. This is done by performing systematic simulations with different rheologies to minimize the misfit to observational constraints such as the GPS-velocity field. The simulations are performed with the parallel staggered grid FD code LaMEM using a numerical resolution of at least 512x512x256 cells to resolve dynamically important shear zones reasonably well. A fundamental part of this study is the reconstruction of the 3D present-day geometry of Tibet and the adjacent regions. Our interpretations of crust and mantle lithosphere geometry are jointly based on a globally available shear wave tomography (Schaeffer and Lebedev, 2013) and the Crust 1.0 model (Laske et al. http://igppweb.ucsd.edu/~gabi/crust1.html). We regionally refined and modified our interpretations based on seismicity distributions and focal mechanisms and incorporated regional receiver function studies to improve the accuracy of the Moho in particular. Results suggest that we can identify at least one "best-fit" solution in terms of rheological model properties that reproduces the observed velocity field reasonably well, including the strong rotation of the GPS velocity around the eastern syntax of the Himalaya. We also present model co-variances to illustrate the trade-offs between the rheological model parameters, their respective uncertainties, and the model fit. Schaeffer, A.J., Lebedev, S., 2013. Global shear speed structure of the upper mantle and transition zone. Geophysical Journal International 194, 417-449. doi:10.1093/gji/ggt095

  14. NASA geodynamics program

    NASA Technical Reports Server (NTRS)

    1980-01-01

    The history and development of the geodynamics program are described, in addition to accomplishments and plans for the future years activities. Extramural grant titles are listed for general research, Lageos investigations, and Magsat investigations.

  15. Fundamental studies in geodynamics

    NASA Technical Reports Server (NTRS)

    Anderson, D. L.; Hager, B. H.; Kanamori, H.

    1981-01-01

    Research in fundamental studies in geodynamics continued in a number of fields including seismic observations and analysis, synthesis of geochemical data, theoretical investigation of geoid anomalies, extensive numerical experiments in a number of geodynamical contexts, and a new field seismic volcanology. Summaries of work in progress or completed during this report period are given. Abstracts of publications submitted from work in progress during this report period are attached as an appendix.

  16. Geodynamics: Introduction and Background

    NASA Technical Reports Server (NTRS)

    1984-01-01

    An overview is given of the field of geodynamics and its major scientific questions. The NASA geodynamics program is described as well as its status and accomplishments projected by 1988. Federal coordination and international cooperation in monitoring tectonic plate motion, polar motion, and Earth rotation are mentioned. The development of a GPS receiver for civilian geodesy and results obtained using satellite laser ranging and very long baseline interferometry in measuring crustal dynamics, global dynamics, and the geopotential field are reported.

  17. Geodynamic Modeling of Planetary Ice-Oceans: Evolution of Ice-Shell Thickness in Convecting Two-Phase Systems

    NASA Astrophysics Data System (ADS)

    Allu Peddinti, D.; McNamara, A. K.

    2016-12-01

    Along with the newly unveiled icy surface of Pluto, several icy planetary bodies show indications of an active surface perhaps underlain by liquid oceans of some size. This augments the interest to explore the evolution of an ice-ocean system and its surface implications. The geologically young surface of the Jovian moon Europa lends much speculation to variations in ice-shell thickness over time. Along with the observed surface features, it suggests the possibility of episodic convection and conduction within the ice-shell as it evolved. What factors would control the growth of the ice-shell as it forms? If and how would those factors determine the thickness of the ice-shell and consequently the heat transfer? Would parameters such as tidal heating or initial temperature affect how the ice-shell grows and to what significance? We perform numerical experiments using geodynamical models of the two-phase ice-water system to study the evolution of planetary ice-oceans such as that of Europa. The models evolve self-consistently from an initial liquid ocean as it cools with time. The effects of presence, absence and magnitude of tidal heating on ice-shell thickness are studied in different models. The vigor of convection changes as the ice-shell continues to thicken. Initial modeling results track changes in the growth rate of the ice-shell as the vigor of the convection changes. The magnitude and temporal location of the rate change varies with different properties of tidal heating and values of initial temperature. A comparative study of models is presented to demonstrate how as the ice-shell is forming, its growth rate and convection are affected by processes such as tidal heating.

  18. Including the effects of elastic compressibility and volume changes in geodynamical modeling of crust-lithosphere-mantle deformation

    NASA Astrophysics Data System (ADS)

    de Monserrat, Albert; Morgan, Jason P.

    2016-04-01

    Materials in Earth's interior are exposed to thermomechanical (e.g. variations in stress/pressure and temperature) and chemical (e.g. phase changes, serpentinization, melting) processes that are associated with volume changes. Most geodynamical codes assume the incompressible Boussinesq approximation, where changes in density due to temperature or phase change effect buoyancy, yet volumetric changes are not allowed, and mass is not locally conserved. Elastic stresses induced by volume changes due to thermal expansion, serpentinization, and melt intrusion should cause 'cold' rocks to brittlely fail at ~1% strain. When failure/yielding is an important rheological feature, we think it plausible that volume-change-linked stresses may have a significant influence on the localization of deformation. Here we discuss a new Lagrangian formulation for "elasto-compressible -visco-plastic" flow. In this formulation, the continuity equation has been generalised from a Boussinesq incompressible formulation to include recoverable, elastic, volumetric deformations linked to the local state of mean compressive stress. This formulation differs from the 'anelastic approximation' used in compressible viscous flow in that pressure- and temperature- dependent volume changes are treated as elastic deformation for a given pressure, temperature, and composition/phase. This leads to a visco-elasto-plastic formulation that can model the effects of thermal stresses, pressure-dependent volume changes, and local phase changes. We use a modified version of the (Miliman-based) FEM code M2TRI to run a set of numerical experiments for benchmarking purposes. Three benchmarks are being used to assess the accuracy of this formulation: (1) model the effects on density of a compressible mantle under the influence of gravity; (2) model the deflection of a visco-elastic beam under the influence of gravity, and its recovery when gravitational loading is artificially removed; (3) Modelling the stresses

  19. Testing geodynamic models of plume-ridge interaction against surface wave anisotropy observed along the Reykjanes Ridge

    NASA Astrophysics Data System (ADS)

    Gallego, A.; Ito, G.; Dunn, R.

    2012-12-01

    We use 3D geodynamic models of plume-ridge interaction to understand the origin of the anomalous seismic structure in the shallowest 150 km of the upper mantle below the Reykjanes Ridge as sensed by Rayleigh and Love waves [Gaherty, 2001; Gaherty & Dunn, 2007; Delorey et al., 2007]. The anomalies include unusually low shear-wave velocities centered on the ridge and low-amplitude, positive (Vsh > Vsv) radial anisotropy beneath the Reykjanes Ridge separating two zones of negative (Vsv > Vsh) anisotropy 100-200 km wide on both sides of the ridge. There is relatively good consensus that the Icelandic plume is influencing the region; however, the mantle flow pattern that controls the observed anisotropic structure remains inconclusive. Geodynamic models were used to compute mantle flow and lattice preferred orientation (LPO), from which we predicted surface wave phase velocities. Then we inverted the synthetic data to recover the along-axis average, 2-D cross-section of shear velocity structure across the Reykjanes Ridge as was done by Delorey et al. [2007]. This as well as the other previous seismic studies was based on surface waves propagating nearly parallel to the Reykjanes Ridge; therefore this azimuthal effect was incorporated in our calculations. The first case tests a previously proposed hypothesis in which the buoyancy of interstitial melt produces vigorous upwelling beneath the ridge axis and downwelling limbs on the sides of the ridge axis where vertically aligned LPO leads to the observed negative anisotropy. Model results show that although the hypothesized downwellings indeed produce negative anisotropy on the sides of the ridge axis, the upwelling beneath the ridge produces strong negative anisotropy that is not observed beneath the Reykjanes Ridge. The second set of models simulate a hot mantle plume beneath the ridge axis and low viscosities in the shallowest 150 km of the upper mantle, resulting in strong mantle flow along the ridge axis. This group

  20. Quantitative analysis of surface deformation and ductile flow in complex analogue geodynamic models based on PIV method.

    NASA Astrophysics Data System (ADS)

    Krýza, Ondřej; Lexa, Ondrej; Závada, Prokop; Schulmann, Karel; Gapais, Denis; Cosgrove, John

    2017-04-01

    Recently, a PIV (particle image velocimetry) analysis method is optical method abundantly used in many technical branches where material flow visualization and quantification is important. Typical examples are studies of liquid flow through complex channel system, gas spreading or combustion problematics. In our current research we used this method for investigation of two types of complex analogue geodynamic and tectonic experiments. First class of experiments is aimed to model large-scale oroclinal buckling as an analogue of late Paleozoic to early Mesozoic evolution of Central Asian Orogenic Belt (CAOB) resulting from nortward drift of the North-China craton towards the Siberian craton. Here we studied relationship between lower crustal and lithospheric mantle flows and upper crustal deformation respectively. A second class of experiments is focused to more general study of a lower crustal flow in indentation systems that represent a major component of some large hot orogens (e.g. Bohemian massif). The most of simulations in both cases shows a strong dependency of a brittle structures shape, that are situated in upper crust, on folding style of a middle and lower ductile layers which is influenced by rheological, geometrical and thermal conditions of different parts across shortened domain. The purpose of PIV application is to quantify material redistribution in critical domains of the model. The derivation of flow direction and calculation of strain-rate and total displacement field in analogue experiments is generally difficult and time-expensive or often performed only on a base of visual evaluations. PIV method operates with set of images, where small tracer particles are seeded within modeled domain and are assumed to faithfully follow the material flow. On base of pixel coordinates estimation the material displacement field, velocity field, strain-rate, vorticity, tortuosity etc. are calculated. In our experiments we used velocity field divergence to

  1. Present Day Hot Spot Melting Inferred from Geodynamics and Thermodynamics Modeling and the Thermal History of the Mantle

    NASA Astrophysics Data System (ADS)

    Tirone, M.; Ganguly, J.

    2011-12-01

    Hot spot melting is the end-product of a complex sequence of processes that most likely starts at the CMB boundary. To provide a complete description and a better constrained understanding of the melting process from the petrological and geophysical point of view, two requirements appear to be essential. 1) accurate knowledge of the physico-chemical and thermodynamic properties of the mantle, and characterization of the thermal and geodynamic conditions for the generation and evolution of a thermal plume. 2) development of a geodynamic numerical procedure that incorporates the properties of the mantle and is capable of simulate the thermal evolution of a plume and the petrological evolution of the melting process. The thermodynamic approach is best suited to accomplish the latter objective. By following these requirements, the model allows us to compute several features that can be independently compared with petrological and geophysical observations which ultimately provide a validation for the whole procedure. The viscosity and the thermal conditions leading to the formation of a thermal plume are retrieved from a separate study of the thermal history of the mantle that is mainly constrained by the requirement for melting in the upper mantle in the past and recent time (session DI19, contribution entitled: A Viscosity Model for the Mantle Based on Diffusion in Minerals and Constrained by the Thermal History and Melting of the Mantle). The main topic of this contribution is the final stage of the plume evolution, that is the the thermal structure and melting in a hot spot setting, focusing in particular on the magmatism associated to the Hawaiian-Emperor seamount chain. The numerical study is a work in progress that reveals several key features. Perhaps the most important aspect that emerge from the modeling work is the formation of periodic instabilities and the thermal erosion of the base of the lithosphere which are mainly induced by the formation and transport

  2. Geodynamic modeling of the capture and release of a plume conduit by a migrating mid-ocean ridge

    NASA Astrophysics Data System (ADS)

    Hall, P. S.

    2011-12-01

    plates over the relatively stationary, long-lived conduits of mantle plumes. However, paleomagnetic data from the Hawaii-Emperor Seamount Chain suggests that the Hawaiian hotspot moved rapidly (~40 mm/yr) between 81 - 47 Ma [Tarduno et al., 2003]. Recently, Tarduno et al. [2009] suggested that this period of rapid motion might be the surface expression of a plume conduit returning to a largely vertical orientation after having been captured and tilted as the result of being "run over" by migrating mid-ocean ridge. I report on a series of analog geodynamic experiments designed to characterize the evolution of a plume conduit as a mid-ocean ridge migrates over. Experiments were conducted in a clear acrylic tank (100 cm x 70 cm x 50 cm) filled with commercial grade high-fructose corn syrup. Plate-driven flow is modeled by dragging two sheets of Mylar film (driven by independent DC motors) in opposite directions over the surface of the fluid. Ridge migration is achieved by moving the point at which the mylar sheets diverge using a separate motor drive. Buoyant plume flow is generated using a small electrical heater placed at the bottom of the tank. Plate velocities and ridge migration rate are controlled and plume temperature monitored using LabView software. Experiments are recorded using digital video which is then analyzed using digital image analysis software to track the position and shape of the plume conduit throughout the course of the experiment. The intersection of the plume conduit with the surface of the fluid is taken as an analog for the locus of hotspot volcanism and tracked as a function of time to obtain a hotspot migration rate. Results show that the plume conduit experiences significant tilting immediately following the passage of the migrating ridge.

  3. A new strain rate model for the Great Basin and its application to tectonic and geodynamic studies

    NASA Astrophysics Data System (ADS)

    Kreemer, C.; Blewitt, G.; Hammond, W. C.; Coolbaugh, M. F.

    2004-12-01

    The Great Basin in the western United States covers a large portion of the diffuse PA-NA plate boundary zone. Yet the seismic potential of its many faults as well as the evolution of, and the driving forces behind, the deformation remain largely unknown or disputed. To advance our understanding it is important to quantify the spatial distribution of the rate, style and direction of the present-day deformation field. GPS velocity measurements are the single most important input to fulfill this objective, and many data are now available from continuous (e.g., BARGEN network) and campaign style measurements (USGS and others). We use the Haines and Holt technique to present a new strain rate model, which is superior in its use of the latest GPS solutions and a denser model grid. Furthermore, the release of the 2003 USGS fault database makes it possible to use geologic data (i.e., slip rate and/or fault geometry) either as an additional constraint in or as a comparison with models based on the interpolation of GPS velocities alone. The ultimate aim of this work is; 1) to compare present-day style and rate of deformation with finite strain markers to place constraints on the Quaternary evolution of deformation, particularly in the northern Walker Lane, 2) to use objective means in distinguishing potential rigid blocks, 3) to identify zones of transient deformation, 4) to further develop the observed relationship between shear strain rate, fault orientation and geothermal output, and 5) to improve geodynamic models by comparing modeled present-day strain rate directions with finite strain orientations in the middle to lower crust as shown in metamorphic complexes and in the lithosphere as inferred from seismic anisotropy. For this presentation we will discuss the data synthesis as well as the resolution and reliability of the model. Furthermore, a few examples will be highlighted to underline the potential of the model in addressing the goals described above. Finally, a

  4. The geoid constraint in global geodynamics: viscosity structure, mantle heterogeneity models and boundary conditions.

    NASA Astrophysics Data System (ADS)

    Thoraval, C.; Richards, M. A.

    1997-10-01

    The authors address several of the most straightforward problems inherent in geoid modelling, namely the issues of viscosity structure resolution, uncertainties in appropriate boundary conditions, and differences among mantle heterogeneity models. A robust feature of all models is a lower-mantle viscosity at least a factor of 30 greater than that of the upper mantle, but there is little resolution with regard to finer details such as lithospheric or uppermost mantle ("low-viscosity zone") viscosity. Ironically, free-slip boundary conditions result in the best fits to the geoid in all cases, but all boundary conditions exhibit predictable trade-offs with the uppermost-mantle viscosity. Models with a single viscosity layer representing the lower mantle yield similar dynamic topography estimates of the order of 700-1000 m in amplitude, regardless of the finer details of upper-mantle viscosity structure, boundary conditions or input heterogeneity models. Comparing mantle heterogeneity models based on two independent seismological determinations (Harvard and Berkeley models) and on the history of subduction, the authors find that these models are virtually indistinguishable regarding inferences of mantle viscosity structure and amplitude of dynamic topography, and in terms of the effects of different boundary conditions. Uncertainties concerning which type of boundary condition is appropriate are much more important than which mantle heterogeneity model is chosen. Given other uncertainties in modelling the geoid, particularly the strong effects due to lateral viscosity variations for intermediate (<10,000 km) wavelengths, the authors conclude that the class of dynamic geoid models explored so far cannot reliably elucidate the details of upper-mantle viscosity structure.

  5. Integrating Geochemical and Geodynamic Numerical Models of Mantle Evolution and Plate Tectonics

    NASA Astrophysics Data System (ADS)

    Tackley, P. J.; Xie, S.

    2001-12-01

    The thermal and chemical evolution of Earth's mantle and plates are inextricably coupled by the plate tectonic - mantle convective system. Convection causes chemical differentiation, recycling and mixing, while chemical variations affect the convection through physical properties such as density and viscosity which depend on composition. It is now possible to construct numerical mantle convection models that track the thermo-chemical evolution of major and minor elements, and which can be used to test prospective models and hypotheses regarding Earth's chemical and thermal evolution. Model thermal and chemical structures can be compared to results from seismic tomography, while geochemical signatures (e.g., trace element ratios) can be compared to geochemical observations. The presented, two-dimensional model combines a simplified 2-component major element model with tracking of the most important trace elements, using a tracer method. Melting is self-consistently treated using a solidus, with melt placed on the surface as crust. Partitioning of trace elements occurs between melt and residue. Decaying heat-producing elements and secular cooling of the mantle and core provide the driving heat sources. Pseudo-plastic yielding of the lithosphere gives a first-order approximation of plate tectonics, and also allows planets with a rigid lid or intermittent plate tectonics to be modeled simply by increasing the yield strength. Preliminary models with an initially homogeneous mantle show that regions with a HIMU-like signature can be generated by crustal recycling, and regions with high 3He/4He ratios can be generated by residuum recycling. Outgassing of Argon is within the observed range. Models with initially layered mantles will also be investigated. In future it will be important to include a more realistic bulk compositional model that allows continental crust as well as oceanic crust to form, and to extend the model to three dimensions since toroidal flow may alter

  6. Investigating the presence of post-perovskite and large-scale chemical variations in Earth's lower mantle using tomographic-geodynamic model comparisons.

    NASA Astrophysics Data System (ADS)

    Koelemeijer, Paula; Ritsema, Jeroen; Deuss, Arwen; Davies, Rhodri; Schuberth, Bernhard

    2016-04-01

    Tomographic models of the Earth's mantle consistently image two large provinces of low shear-wave velocities (LLSVPs) in the lowermost mantle beneath Africa and the Pacific. Seismic studies also find an increase in the ratio of shear-wave velocity (Vs) to compressional-wave velocity (Vp) variations, accompanied by a significant negative correlation between shear-wave and bulk-sound velocity (Vc) variations, both of which are also observed in the recent SP12RTS model. The LLSVPs have consequently been suggested to represent intrinsically dense piles of thermochemical material. Alternatively, they have been interpreted as poorly imaged clusters of thermal plumes, with the deep mantle post-perovskite (pPv) phase invoked as explanation for the high Vs/Vp ratios and Vs-Vc anti-correlation. Geodynamical calculations of thermal plumes and thermochemical piles predict a fundamentally different style of mantle convection, interface topographies and CMB heat flow. However, to interpret tomographic images using these high-resolution models, the limited resolving power of seismic tomography has to be accounted for. Here, we interpret the observed seismic characteristics of SP12RTS by comparing the velocity structures to synthetic tomography images derived from 3D mantle convection models. As in previous studies, geodynamic models are converted to seismic velocities using mineral physics constraints and subsequently convolved with the tomographic resolution operator. In contrast to these studies, where generally only the shear-wave velocity structure has been compared, we use both the Vs and Vp resolution operator of SP12RTS to allow direct comparisons of the resulting velocity ratios and correlations. We use geodynamic models with and without pPv and/or chemical variations to investigate the cause of the high Vs/Vp ratio and Vs-Vs anti-correlation. Although the tomographic filtering significantly affects the synthetic tomography images, we demonstrate that the patterns

  7. Joint seismic-geodynamic-mineral physical modelling of African geodynamics: A reconciliation of deep-mantle convection with surface geophysical constraints

    SciTech Connect

    Forte, A M; Quere, S; Moucha, R; Simmons, N A; Grand, S P; Mitrovica, J X; Rowley, D B

    2008-08-22

    Recent progress in seismic tomography provides the first complete 3-D images of the combined thermal and chemical anomalies that characterise the unique deep mantle structure below the African continent. With these latest tomography results we predict flow patterns under Africa that reveal a large-scale, active hot upwelling, or superplume, below the western margin of Africa under the Cape Verde Islands. The scale and dynamical intensity of this West African superplume (WASP) is comparable to that of the south African superplume (SASP) that has long been assumed to dominate the flow dynamics under Africa. On the basis of this new tomography model, we find the dynamics of the SASP is strongly controlled by chemical contributions to deep mantle buoyancy that significantly compensate its thermal buoyancy. In contrast, the WASP appears to be entirely dominated by thermal buoyancy. New calculations of mantle convection incorporating these two superplumes reveal that the plate-driving forces due to the flow generated by the WASP is as strong as that due to the SASP. We find that the chemical buoyancy of the SASP exerts a strong stabilising control on the pattern and amplitude of shallow mantle flow in the asthenosphere below the southern half of the African plate. The asthenospheric flow predictions provide the first high resolution maps of focussed upwellings that lie below the major centres of Late Cenozoic volcanism, including the Kenya domes and Hoggar massif that lies above a remnant plume head in the upper mantle. Inferences of sublithospheric deformation from seismic anisotropy data are shown to be sensitive to the contributions of chemical buoyancy in the SASP.

  8. A review of analogue modelling of geodynamic processes: Approaches, scaling, materials and quantification, with an application to subduction experiments

    NASA Astrophysics Data System (ADS)

    Schellart, Wouter P.; Strak, Vincent

    2016-10-01

    We present a review of the analogue modelling method, which has been used for 200 years, and continues to be used, to investigate geological phenomena and geodynamic processes. We particularly focus on the following four components: (1) the different fundamental modelling approaches that exist in analogue modelling; (2) the scaling theory and scaling of topography; (3) the different materials and rheologies that are used to simulate the complex behaviour of rocks; and (4) a range of recording techniques that are used for qualitative and quantitative analyses and interpretations of analogue models. Furthermore, we apply these four components to laboratory-based subduction models and describe some of the issues at hand with modelling such systems. Over the last 200 years, a wide variety of analogue materials have been used with different rheologies, including viscous materials (e.g. syrups, silicones, water), brittle materials (e.g. granular materials such as sand, microspheres and sugar), plastic materials (e.g. plasticine), visco-plastic materials (e.g. paraffin, waxes, petrolatum) and visco-elasto-plastic materials (e.g. hydrocarbon compounds and gelatins). These materials have been used in many different set-ups to study processes from the microscale, such as porphyroclast rotation, to the mantle scale, such as subduction and mantle convection. Despite the wide variety of modelling materials and great diversity in model set-ups and processes investigated, all laboratory experiments can be classified into one of three different categories based on three fundamental modelling approaches that have been used in analogue modelling: (1) The external approach, (2) the combined (external + internal) approach, and (3) the internal approach. In the external approach and combined approach, energy is added to the experimental system through the external application of a velocity, temperature gradient or a material influx (or a combination thereof), and so the system is open

  9. The use of the Finite Element method for the earthquakes modelling in different geodynamic environments

    NASA Astrophysics Data System (ADS)

    Castaldo, Raffaele; Tizzani, Pietro

    2016-04-01

    Many numerical models have been developed to simulate the deformation and stress changes associated to the faulting process. This aspect is an important topic in fracture mechanism. In the proposed study, we investigate the impact of the deep fault geometry and tectonic setting on the co-seismic ground deformation pattern associated to different earthquake phenomena. We exploit the impact of the structural-geological data in Finite Element environment through an optimization procedure. In this framework, we model the failure processes in a physical mechanical scenario to evaluate the kinematics associated to the Mw 6.1 L'Aquila 2009 earthquake (Italy), the Mw 5.9 Ferrara and Mw 5.8 Mirandola 2012 earthquake (Italy) and the Mw 8.3 Gorkha 2015 earthquake (Nepal). These seismic events are representative of different tectonic scenario: the normal, the reverse and thrust faulting processes, respectively. In order to simulate the kinematic of the analyzed natural phenomena, we assume, under the plane stress approximation (is defined to be a state of stress in which the normal stress, sz, and the shear stress sxz and syz, directed perpendicular to x-y plane are assumed to be zero), the linear elastic behavior of the involved media. The performed finite element procedure consist of through two stages: (i) compacting under the weight of the rock successions (gravity loading), the deformation model reaches a stable equilibrium; (ii) the co-seismic stage simulates, through a distributed slip along the active fault, the released stresses. To constrain the models solution, we exploit the DInSAR deformation velocity maps retrieved by satellite data acquired by old and new generation sensors, as ENVISAT, RADARSAT-2 and SENTINEL 1A, encompassing the studied earthquakes. More specifically, we first generate 2D several forward mechanical models, then, we compare these with the recorded ground deformation fields, in order to select the best boundaries setting and parameters. Finally

  10. Constraining Cretaceous subduction polarity in eastern Pacific from seismic tomography and geodynamic modeling

    NASA Astrophysics Data System (ADS)

    Liu, Lijun

    2014-11-01

    Interpretation of recent mantle seismic images below the America ignited a debate on the Cretaceous subduction polarity in the eastern Pacific Ocean. The traditional view is that the massive vertical slab wall under eastern North America resulted from an eastward Farallon subduction. An alternative interpretation attributes this prominent seismic structure to a westward subduction of the North American Plate against a stationary intraoceanic trench. Here I design quantitative subduction models to test these two scenarios, using their implied plate kinematics as velocity boundary conditions. Modeling results suggest that the westward subduction scenario could not produce enough slab volume as seismic images reveal, as is due to the overall slow subduction rate (~2.5 cm/yr). The results favor the continuous eastward Farallon subduction scenario, which, with an average convergence rate of >10 cm/yr prior to the Eocene, can properly generate both the volume and the geometry of the imaged lower mantle slab pile. The eastward subduction model is also consistent with most Cretaceous geological records along the west coast of North America.

  11. Techniques to achieve geodynamic self-consistency in data-assimilation models of mantle convection

    NASA Astrophysics Data System (ADS)

    Liu, L.; Stegman, D. R.

    2012-04-01

    Recent models of mantle convection that incorporate data-assimilation such as paleogeography reconstructions of plate boundary locations, the history of global plate motions used as surface velocity boundary conditions and paleo-age of seafloor as a proxy for oceanic plate thickness, have been employed to generate mantle thermal structures that can be directly compared to present-day mantle structure as inferred from seismic tomography. However, previous models contained significant mismatch, particularly in areas with complex tectonic histories such as western North America. We present several techniques used in some recent models (Liu and Stegman, EPSL, 2011) that achieve an unprecedented level of agreement between modeled thermal mantle structure and several recent tomography models using EarthScope's USArray data. In particular, these models are able to forward predict a rupture in the subducting Farallon-Juan de Fuca slab that laterally tears open across the face of the slab and allows an asthenospheric upwelling to occur (Liu and Stegman, Nature, 2012). The surface projection of the tear's development agrees remarkably well with the temporal-spatial evolution of Steens-Columbia River Basalt volcansim. To achieve this level of agreement, there are four major technical aspects, all of which work in concert and are critical for success: 1) a weak hinge is prescribed as the region behind the trench 2) a low-viscosity wedge that helps to reduce coupling to the surface 3) a pseudo-free surface boundary condition consisting of a layer of "sticky air" that allows for more natural plate bending and single-sided subduction 4) because the convective system (including the tectonic plates) are separated from the surface velocity boundary condition, we introduce a phase change that allows the "sticky air" to be viscous enough for the surface plate motions applied above to actually drive the plates below. Since the bending of the plate is driven by the negative buoyancy of

  12. Constraining the Location of the Azores Plume Using Mantle Geodynamical Models

    NASA Astrophysics Data System (ADS)

    Georgen, J. E.

    2016-12-01

    In many cases, pinpointing the location of a plume conduit in the upper mantle remains elusive. This can be particularly true where plumes upwell in settings with complex plate boundary geometry, such as near an oceanic ridge-ridge-ridge triple junction (TJ). In such locations, lithospheric and crustal accretion processes can affect the shape, thickness, and other characteristics of plume-generated bathymetric plateaus. This study focuses on the Azores TJ region. Several lines of evidence, including seafloor geochemistry data, depth anomalies, and seismic topography, suggest that geological processes in the Azores TJ region are affected by a nearby plume. However, with respect to the location of the plume conduit and spatial distribution of plume material in the upper mantle, results can be ambiguous. This study investigates the dynamical interactions between a plume and a ridge-ridge-ridge TJ using a suite of steady-state, three-dimensional finite element models. Using a parameter space approach, models vary plume diameter, plume location (i.e., both azimuth and distance to the TJ), and the treatment of mantle viscosity. The numerical domain is similar to the Azores region with respect to plume flux, generalized ridge geometry, and spreading rate. Results show how properties of the calculated seafloor plateau are sensitive to the relative position of the plume conduit and TJ. For example, one way of assessing the effect of plume conduit position is to calculate normalized area, the spatial dispersion of a plume at specific depth (selected to be 50 km) divided by the area occupied by the same plume when it is located under the TJ. In one case, moving the plume from the TJ to an intraplate position 100 km away reduces the normalized area to 55%. Results from the suite of numerical models are compared to observed patterns of Azores seafloor depth to constrain the likely location of the plume in the upper mantle.

  13. The Multi-factor Predictive Seis &Gis Model of Ecological, Genetical, Population Health Risk and Bio-geodynamic Processes In Geopathogenic Zones

    NASA Astrophysics Data System (ADS)

    Bondarenko, Y.

    I. Goal and Scope. Human birth rate decrease, death-rate growth and increase of mu- tagenic deviations risk take place in geopathogenic and anthropogenic hazard zones. Such zones create unfavourable conditions for reproductive process of future genera- tions. These negative trends should be considered as a protective answer of the com- plex biosocial system to the appearance of natural and anthropogenic risk factors that are unfavourable for human health. The major goals of scientific evaluation and de- crease of risk of appearance of hazardous processes on the territory of Dnipropetrovsk, along with creation of the multi-factor predictive Spirit-Energy-Information Space "SEIS" & GIS Model of ecological, genetical and population health risk in connection with dangerous bio-geodynamic processes, were: multi-factor modeling and correla- tion of natural and anthropogenic environmental changes and those of human health; determination of indicators that show the risk of destruction structures appearance on different levels of organization and functioning of the city ecosystem (geophys- ical and geochemical fields, soil, hydrosphere, atmosphere, biosphere); analysis of regularities of natural, anthropogenic, and biological rhythms' interactions. II. Meth- ods. The long spatio-temporal researches (Y. Bondarenko, 1996, 2000) have proved that the ecological, genetic and epidemiological processes are in connection with de- velopment of dangerous bio-geophysical and bio-geodynamic processes. Mathemat- ical processing of space photos, lithogeochemical and geophysical maps with use of JEIS o and ERDAS o computer systems was executed at the first stage of forma- tion of multi-layer geoinformation model "Dnipropetrovsk ARC View GIS o. The multi-factor nonlinear correlation between solar activity and cosmic ray variations, geophysical, geodynamic, geochemical, atmospheric, technological, biological, socio- economical processes and oncologic case rate frequency, general and primary

  14. Deformation of the Western Caribbean: Insights from Block and Geodynamic Models of Geodetic, Seismic and Geologic Data

    NASA Astrophysics Data System (ADS)

    La Femina, P. C.; Geirsson, H.; Kobayashi, D.

    2012-12-01

    Cocos - Caribbean convergence along the Middle America Trench, including subduction of the Cocos Ridge and seamount domain, and Nazca - Caribbean oblique convergence along the South Panama Deformed Belt have resulted in complex plate boundary zone deformation since Miocene - Pliocene time. Plate boundary evolution and upper plate deformation in the western Caribbean is well studied and indicates, 1) Quaternary migration of the volcanic arc toward the back-arc northwest of the Cocos Ridge; 2) Pleistocene to present northwestward motion of the Central American Fore Arc (CAFA); 3) Quaternary to present deformation within the Central Costa Rica Deformed Belt; 4) Miocene-Pliocene cessation of volcanism and uplift of the Cordillera de Talamanca inboard the ridge; 5) Quaternary to present shortening across the fore-arc Fila Costeña fold and thrust belt and back-arc North Panama Deformed Belt (NPDB); 6) Quaternary to present outer fore-arc uplift above the seamount domain (Nicoya Peninsula), and above (Osa Peninsula) and flanking (Burica Peninsula) the ridge; and 7) Quaternary to present faulting along the Sona-Azuero and Canal Discontinuity fault systems. We investigate the dynamic effects of Cocos and Nazca convergence along the entire Central American margin, and the implications on western Caribbean plate boundary evolution with a new GPS derived three-dimensional (horizontal and vertical) velocity field and kinematic block and geodynamic models. Specifically, we test the hypotheses that the Cocos Ridge is the main driver for upper plate deformation and that there is an independent Panama block. Our model results provide new Euler vectors for the CAFA and Panama block, rates of relative plate and block motions in the region, and constraints on interseismic coupling along the Middle America Trench and other major block bounding fault systems. These results are compared to existing geophysical and geologic data for the region and add insights into the rates of

  15. Continental Collision, Oceanic Subduction and Related Geodynamical Processes: a Numerical Modeling Perspective

    NASA Astrophysics Data System (ADS)

    Faccenda, M.; Gerya, T.; Burlini, L.; Chakraborty, S.

    2008-05-01

    Collisional and subduction zones are sites on the Earth surface where two continents collide or an oceanic plate descends into the mantle, respectively. Aside these gross scale phenomena, a wide variety of other small scale geological processes take place at the same time. The study of these processes is crucial for the understanding of the subduction/collision history and for the interpretation of geophysical data that, in turn, give informations about the present day structure of these areas. In the recent years, coupled petrological-thermomechanical numerical models have been used to study processes occurring at collision/subduction settings. We use I2VIS code with realistic visco-plastic rheologies (Gerya and Yuen, 2003) to model subduction zones characterized by an early oceanic subduction followed by continental collision. Collision between two continents includes mountain chains building, continental crust recycling in the mantle and exhumation of HP-UHP metamorphic rocks. In case of plate decoupling, asthenospheric mantle wedges between the continents triggering the retreating and delamination of the converging continental plate. In order to investigate hydration and subsequent dehydration of the slab, we also performed 2D numerical models of a spontaneously bending oceanic plate using I2ELVIS code that account for visco-elasto-plastic rheologies (Gerya and Yuen, 2007). At the outer rise, bending-related slab faulting occurs and provides a pathway for water percolation in the slab. Faults generally deep trenchward, but antithetic faults are also common. As the slab subducts, serpentinized faults acquire a sub-vertical position; on the other hand, pressure and temperature increase so that hydrous phases become unstable and elevated pore fluid pressure build up allowing to brittle deformation at big depths. Results are consistent with intermediate-depth earthquakes distribution and confirm the now well accepted theory that dehydration of the slab as the main

  16. Generation of felsic crust in the Archean: a geodynamic modeling perspective

    NASA Astrophysics Data System (ADS)

    Sizova, Elena; Gerya, Taras; Stüwe, Kurt; Brown, Michael

    2015-04-01

    The relevance of contemporary tectonics to the formation of the Archean terrains is a matter of vigorous debate. Higher mantle temperatures and higher radiogenic heat production in the past would have impacted on the thickness and composition of the oceanic and continental crust. As a consequence of secular cooling, there is generally no modern analog to assist in understanding the tectonic style that may have operated in the Archean. For this reason, well-constrained numerical modeling, based on the fragmentary evidence preserved in the geological record, is the most appropriate tool to evaluate hypotheses of Archean crust formation. The main lithology of Archean terrains is the sodic tonalite-trondhjemite-granodiorite (TTG) suite. Melting of hydrated basalt at garnet-amphibolite to eclogite facies conditions is considered to be the dominant process for the generation of the Archean TTG crust. Taking into account geochemical signatures of possible mantle contributions to some TTGs, models proposed for the formation of Archean crust include subduction, melting at the bottom of thickened continental crust and fractional crystallization of mantle-derived melts under water-saturated conditions. We evaluated these hypotheses using a 2D coupled petrological-thermomechanical numerical model with initial conditions appropriate to the Eoarchean-Mesoarchean. As a result, we identified three tectonic settings in which intermediate to felsic melts are generated by melting of hydrated primitive basaltic crust: 1) delamination and dripping of the lower primitive basaltic crust into the mantle; 2) local thickening of the primitive basaltic crust; and, 3) small-scale crustal overturns. In addition, we consider remelting of the fractionated products derived from underplated dry basalts as an alternative mechanism for the formation of some Archean granitoids. In the context of a stagnant lid tectonic regime which is intermittently terminated by short-lived subduction, we identified

  17. A new free-surface stabilization algorithm for geodynamical modelling: Theory and numerical tests

    NASA Astrophysics Data System (ADS)

    Andrés-Martínez, Miguel; Morgan, Jason P.; Pérez-Gussinyé, Marta; Rüpke, Lars

    2015-09-01

    The surface of the solid Earth is effectively stress free in its subaerial portions, and hydrostatic beneath the oceans. Unfortunately, this type of boundary condition is difficult to treat computationally, and for computational convenience, numerical models have often used simpler approximations that do not involve a normal stress-loaded, shear-stress free top surface that is free to move. Viscous flow models with a computational free surface typically confront stability problems when the time step is bigger than the viscous relaxation time. The small time step required for stability (< 2 Kyr) makes this type of model computationally intensive, so there remains a need to develop strategies that mitigate the stability problem by making larger (at least ∼10 Kyr) time steps stable and accurate. Here we present a new free-surface stabilization algorithm for finite element codes which solves the stability problem by adding to the Stokes formulation an intrinsic penalization term equivalent to a portion of the future load at the surface nodes. Our algorithm is straightforward to implement and can be used with both Eulerian or Lagrangian grids. It includes α and β parameters to respectively control both the vertical and the horizontal slope-dependent penalization terms, and uses Uzawa-like iterations to solve the resulting system at a cost comparable to a non-stress free surface formulation. Four tests were carried out in order to study the accuracy and the stability of the algorithm: (1) a decaying first-order sinusoidal topography test, (2) a decaying high-order sinusoidal topography test, (3) a Rayleigh-Taylor instability test, and (4) a steep-slope test. For these tests, we investigate which α and β parameters give the best results in terms of both accuracy and stability. We also compare the accuracy and the stability of our algorithm with a similar implicit approach recently developed by Kaus et al. (2010). We find that our algorithm is slightly more accurate

  18. Research program of the Geodynamics Branch

    NASA Technical Reports Server (NTRS)

    Kahn, W. D. (Editor); Cohen, S. C. (Editor); Boccucci, B. S. (Editor)

    1986-01-01

    This report is the Fourth Annual Summary of the Research Program of the Geodynamics Branch. The branch is located within the Laboratory for Terrestrial Physics of the Space and Earth Sciences Directorate of the Goddard Space Flight Center. The research activities of the branch staff cover a broad spectrum of geoscience disciplines including: tectonophysics, space geodesy, geopotential field modeling, and dynamic oceanography. The NASA programs which are supported by the work described in this document include the Geodynamics and Ocean Programs, the Crustal Dynamics Project and the proposed Ocean Topography Experiment (TOPEX). The reports highlight the investigations conducted by the Geodynamics Branch staff during calendar year 1985. The individual papers are grouped into chapters on Crustal Movements and Solid Earth Dynamics, Gravity Field Modeling and Sensing Techniques, and Sea Surface Topography. Further information on the activities of the branch or the particular research efforts described herein can be obtained through the branch office or from individual staff members.

  19. Sn Attenuation Model in Tibetan Region and its Geodynamic Implications to Plateau Formation

    NASA Astrophysics Data System (ADS)

    Zhao, L.; Xie, X. B.; Fan, N.; Yao, Z.

    2014-12-01

    We collected 23,940 tangential broadband regional seismic records with their ray paths cross the Tibetan plateau. The waveforms are selected based on criteria that these earthquakes were located in the crust, with magnitudes ranging 3.5-6.6, and epicentral distances 200-2000 km. We extract Sn waveforms using a 0.7 km/s group-velocity window around the IASP91 arrival times, and collect the noise in an equal-length time window before the first arriving P wave. By correcting Sn spectra with the noise, we obtain the source-station amplitudes between 0.05 and 10.0 Hz. Both dual- and single-station data are used in the joint inversion for the Sn Q distribution and Sn-wave excitation functions. The wave paths are calculated using the CRUST1.0 model, and the source radiation patterns are obtained from the Harvard CMT. Strong Sn attenuations are observed in the Tibetan plateau, particularly in its northern part, which are correlated with strong Lg wave attenuations in this area. The part of the Tibetan plateau with elevations above 4,000 m has an average Sn Q of 210. On the contrast, regions surrounding the Tibetan plateau are mostly characterized by high Q values except for Yungui plateau, where a relatively low Q of 203 is observed. The dynamic processes of plateau formation are accompanied by strong thermal activities. The temperature variations affect both material rheology and seismic velocity and attenuation. Thus, seismic attenuations may serve as indicators for material flow. We use attenuation data to constrain the flow pattern in the low crust and uppermost mantle. Combining the Lg- and Sn-wave Q models with other geophysical data, a lower-crustal flow channel is found from north Tibet to east and then towards the southeast along the western edge of the rigid Sichuan basin. This work was supported by the National Natural Science Foundation of China (grants 41374065, 41174048).

  20. A consistent geodynamic model for predicting the velocity and plate-internal deformation of Eurasia

    NASA Astrophysics Data System (ADS)

    Govers, Rob; Garcia-Sancho, Candela; Warners-Ruckstuhl, Karin; van der Burgt, Janneke; Wortel, Rinus

    2015-04-01

    The motion and deformation of tectonic plates is driven by gravity and resisted by frictional forces. In principle it should thus be possible to build mechanical models that reproduce plate velocities and surface deformation. Here we present a new approach that overcomes many of the previous obstacles to achieving this goal. Our approach to quantify the forces is based on mechanical equilibrium of the whole Eurasian plate, meaning that an increase in, for instance collision, forces must be matched by other plate tectonic forces. We first focus on present-day Eurasia. We include basal tractions from a global convection model, lithospheric body forces, and edge forces resulting from the interaction of the Eurasian plate with neighboring plates. The resulting force distribution is constrained by observed plate motion and by stress observations. Eurasia's stress field turns out to be most sensitive to the distribution of collision forces on the plate's southern margin and, to a lesser extent, to lithospheric density structure and normal pressure from mantle flow. Stress observations require collision forces on the India-Eurasia boundary of 7.0 - 10.5 TN/m. A similar analysis is performed for Eurasia at 20 Ma and 40 Ma. Plate geometry is taken from the global Lausanne (Stampfli) reconstruction, as are plate velocities and oceanic ages. Lithospheric body forces are accounted for in a simplified way because we lack detailed enough information on the plate scale topography. For the Miocene, we find ˜1.2 TN/m for the collision force on the India-Eurasia boundary. In the Eocene, the collision force we find is ˜0.4 TN/m. We conclude that the magnitude of the collision force on Tibet increased significantly after 20 Ma: from 40-20 Ma, the plate contact force on the India/Tibet plate boundary segment was of the same order of magnitude as resistive forces on subduction plate boundaries elsewhere. Our timing of the collision force on Eurasia, is substantially younger than the

  1. Geodynamical evolution of the Southern Carpathians: inferences from computational models of lithospheric gravitational instability

    NASA Astrophysics Data System (ADS)

    Lorinczi, Piroska; Houseman, Gregory

    2010-05-01

    The Carpathians are a geologically young mountain chain which, together with the Alps and the Dinarides, surround the extensional Pannonian and Transylvanian basins of Central Europe. The tectonic evolution of the Alpine-Carpathian-Pannonian system was controlled by convergence between the Adriatic and European plates, by the extensional collapse of thickened Alpine crust and by the retreat of the Eastern Carpathians driven by either a brief episode of subduction or by gravitational instability of the continental lithospheric mantle. The Southeast corner of the Carpathians has been widely studied due to its strong seismic activity. The distribution and rate of moment release of this seismic activity provides convincing evidence of a mantle drip produced by gravitational instability of the lithospheric mantle developing beneath the Vrancea region now. The question of why gravitational instability is strongly evident beneath Vrancea and not elsewhere beneath the Southern Carpathians is unresolved. Geological and geophysical interpretations of the Southern Carpathians emphasise the transcurrent deformation that has dominated recent tectonic evolution of this mountain belt. We use computational models of gravitational instability in order to address the question of why the instability appears to have developed strongly only at the eastern end of this mountain chain. We use a parallelised 3D Lagrangean-frame finite deformation algorithm, which solves the equations of momentum and mass conservation in an incompressible viscous fluid, assuming a non-linear power-law that relates deviatoric stress and strain-rate. We consider a gravitationally unstable system, with a dense mantle lithosphere overlying a less dense asthenosphere, subject to boundary conditions which simulate the combination of shear and convergence that are thought to have governed the evolution of the South Carpathians. This program (OREGANO) allows 3D viscous flow fields to be computed for spatially

  2. Geodynamical model of oil-gas and mineral deposits using RS&GIS Western Uzbekistan

    NASA Astrophysics Data System (ADS)

    Sidorova, I.

    2006-05-01

    This paper deals with the application of complex study of Remote Sensing images and deep Lithospheric structures to the knowledge of spatial interrelation between regional lineaments and oil-gas and mineral deposits in Uzbekistan. Deciphering of structural units of Uzbekistan territory using space ASTER images allows us to reveal regional, deeprooted lineament, extending in latitudinal direction over Uzbekistan territory and neighboring countries. Thus lineament could penetrate the Earth up to deep Lithosphere layers, inheriting a position of old fault-lineament systems which origin related to Paleocene tectonic processes. The most extended latitudinal lineament is the "Transregional lineament of Central Asia" located within 42-44N zone. It stretches for more than 2000km from Sultan-Uvais mountains (Karakalpakstan), through Kyzylkums and Nurata mountains (Uzbekistan), Turkestan-Alay and Atbashi-Inychek mountains (Kyrgyzstan), to Chinese border with possible extension along the Chinese Tien-Shan. The main objective is to associate the surface «indicators» as geological, geophysical and tectonic base of data using RS&GIS with the purpose toidentify the occurrence special geoobjects of economic interest. Additionally, it will be possible to evaluate geospatial distributions of these altered zones related to morphological structures using Digital Elevation Modelling/DEM/ products of ASTER images. RS&GIS methods were used to determine the interrelations of the volcanic and granitic rocks distribution-mineralization-alteration with the faults-lineaments, circular structures. The alteration zones, the tectonic lines and the Circular structures related to the cones and calderas determined these methods and checked by group truth studies may be target areas to explore for some new oil-gas and ore deposits. As a result, our investigations envelops more then 10 deposits in Western Uzbekistan.In conclusion, it is necessary to note that such structures are well-known in the

  3. Computational Infrastructure for Geodynamics (CIG)

    NASA Astrophysics Data System (ADS)

    Gurnis, M.; Kellogg, L. H.; Bloxham, J.; Hager, B. H.; Spiegelman, M.; Willett, S.; Wysession, M. E.; Aivazis, M.

    2004-12-01

    Solid earth geophysicists have a long tradition of writing scientific software to address a wide range of problems. In particular, computer simulations came into wide use in geophysics during the decade after the plate tectonic revolution. Solution schemes and numerical algorithms that developed in other areas of science, most notably engineering, fluid mechanics, and physics, were adapted with considerable success to geophysics. This software has largely been the product of individual efforts and although this approach has proven successful, its strength for solving problems of interest is now starting to show its limitations as we try to share codes and algorithms or when we want to recombine codes in novel ways to produce new science. With funding from the NSF, the US community has embarked on a Computational Infrastructure for Geodynamics (CIG) that will develop, support, and disseminate community-accessible software for the greater geodynamics community from model developers to end-users. The software is being developed for problems involving mantle and core dynamics, crustal and earthquake dynamics, magma migration, seismology, and other related topics. With a high level of community participation, CIG is leveraging state-of-the-art scientific computing into a suite of open-source tools and codes. The infrastructure that we are now starting to develop will consist of: (a) a coordinated effort to develop reusable, well-documented and open-source geodynamics software; (b) the basic building blocks - an infrastructure layer - of software by which state-of-the-art modeling codes can be quickly assembled; (c) extension of existing software frameworks to interlink multiple codes and data through a superstructure layer; (d) strategic partnerships with the larger world of computational science and geoinformatics; and (e) specialized training and workshops for both the geodynamics and broader Earth science communities. The CIG initiative has already started to

  4. An Empirical Approach to Simulating the Development of Various Olivine Fabric and Associated Seismic Anisotropy in Complex Geodynamic Flow Models

    NASA Astrophysics Data System (ADS)

    Miller, K. J.; Montesi, L. G.

    2009-12-01

    Kevin J. Miller; Laurent G.J. Montési strat944@umd.edu ; montesi@umd.edu Department of Physics, Department of Geology University of Maryland, College Park, MD 20742, United States The detection of seismic anisotropy has become one of the most useful tools for characterizing flow in the Earth’s upper mantle. Thus, it is crucial for geodynamic models to include predictions of anisotropy so that their relevance for the Earth can be easily evaluated. Rigorous fabric development models, which utilize the deformation and rotation of a large number of grains, have already been created for the purpose of analyzing flow models. Such models include D-REX. However, it is important to have simpler tools that provide rapidly first order prediction of mantle fabric and anisotropy. The simplest proxy for anisotropy is provided by the instantaneous flow field, with the fast axis of olivine oriented along the direction for shear. More rigorously, it is possible to integrate finite strain and associate the fast axis of olivine with the direction of maximum elongation. However, the recognition that different fabric types can dominate in different regions of the mantle motivates a more general, albeit empirical model of fabric development. Our empirical approach is motivated as follows: 1) The intensity of the fabric should grow proportionally with the strain rate; 2) The fast, intermediate, and low axes of the crystals should rotate and align towards target directions related to the principal axes of strain rate. To achieve these goals, we developed a 4-step algorithm: 1) The flow field is decomposed into strain rate and rotation rate tensors; 2) We determine the eigenvalues and eigenvectors of the instantaneous strain rate tensor; 3) We switch the order of these eigenvalues, recombining them to produce a fabric development tensor; 4) We return the fabric development tensor to the global reference frame and add the rotation rate tensor. After integration along flow lines, this

  5. Self-consistent Synthetic Mantle Discontinuities From Joint Modeling of Geodynamics and Mineral Physics and Their Effects on the 3D Global Wave Field

    NASA Astrophysics Data System (ADS)

    Schuberth, B.; Piazzoni, A.; Bunge, H.; Igel, H.; Steinle-Neumann, G.; Moder, C.; Oeser, J.

    2007-12-01

    Our current understanding of mantle structure and dynamics is to a large part based on inversion of seismic data resulting in tomographic images and on direct analysis of a wide range of seismic phases such as Pdiff, PcP, ScS SdS etc. For solving inverse problems, forward modeling is needed to obtain a synthetic dataset for a given set of model parameters. In this respect, great progress has been made over the last years in the developement of sophisticated numerical full waveform modeling tools. However, the main limitation in the application of this new class of techniques for the forward problem of seismology is the lack of accurate predictions of mantle heterogeneity that allow us to test hypotheses about Earth's mantle. Such predictive models should be based on geodynamic and mineralogical considerations and derived independently of seismological observations. Here, we demonstrate the feasibility of joining forward simulations from geodynamics, mineral physics and seismology to obtain earth-like seismograms. 3D global wave propagation is simulated for dynamically consistent thermal structures derived from 3D mantle circulation modeling (e.g. Bunge et al. 2002), for which the temperatures are converted to seismic velocities using a recently published, thermodynamically self-consistent mineral physics approach (Piazzoni et al. 2007). Assuming a certain, fixed mantle composition (e.g. pyrolite) our mineralogic modeling algorithm computes the stable phases at mantle pressures for a wide range of temperatures by system Gibbs free energy minimization. Through the same equations of state that model the Gibbs free energy, we compute elastic moduli and density for each stable phase assemblage at the same P-T conditions. One straightforward application of this approach is the study of the seismic signature of synthetic mantle discontinuities arising in such models, as the temperature dependent phase transformations occuring at around 410 Km and 660 Km depth are

  6. A geodynamic model of the evolution of the Arctic basin and adjacent territories in the Mesozoic and Cenozoic and the outer limit of the Russian Continental Shelf

    NASA Astrophysics Data System (ADS)

    Laverov, N. P.; Lobkovsky, L. I.; Kononov, M. V.; Dobretsov, N. L.; Vernikovsky, V. A.; Sokolov, S. D.; Shipilov, E. V.

    2013-01-01

    The tectonic evolution of the Arctic Region in the Mesozoic and Cenozoic is considered with allowance for the Paleozoic stage of evolution of the ancient Arctida continent. A new geodynamic model of the evolution of the Arctic is based on the idea of the development of upper mantle convection beneath the continent caused by subduction of the Pacific lithosphere under the Eurasian and North American lithospheric plates. The structure of the Amerasia and Eurasia basins of the Arctic is shown to have formed progressively due to destruction of the ancient Arctida continent, a retained fragment of which comprises the structural units of the central segment of the Arctic Ocean, including the Lomonosov Ridge, the Alpha-Mendeleev Rise, and the Podvodnikov and Makarov basins. The proposed model is considered to be a scientific substantiation of the updated Russian territorial claim to the UN Commission on the determination of the Limits of the Continental Shelf in the Arctic Region.

  7. Global rates of mantle serpentinization and H2 production at oceanic transform faults in 3-D geodynamic models

    NASA Astrophysics Data System (ADS)

    Rüpke, Lars H.; Hasenclever, Jörg

    2017-07-01

    Previous studies have estimated that mantle serpentinization reactions generate H2 at a rate of 1010-1012 mol/yr along the global mid-ocean ridge (MOR) system. Here we present results of 3-D geodynamic simulations that predict rates of additional mantle serpentinization and H2 production at oceanic transform faults (OTF). We find that the extent and rate of mantle serpentinization increases with OTF length and is maximum at intermediate slip rates of 5 to 10 cm/yr. The additional global OTF-related production of H2 is found to be between 6.1 and 10.7 × 1011 mol/yr, which is comparable to the predicted background MOR rate of 4.1-15.0 × 1011 mol H2/yr. This points to oceanic transform faults as potential sites of intense fluid-rock interaction, where chemosynthetic life could be sustained by serpentinization reactions.

  8. 3-D geodynamic models of the India-Eurasia collision zone: investigating the role of lithospheric strength variation Sarah Bischoff and Lucy Flesch EAPS, Purdue University

    NASA Astrophysics Data System (ADS)

    Bischoff, S. H.; Flesch, L. M.

    2013-12-01

    The India-Eurasia collision zone is the largest zone of continental deformation on the Earth's surface. A proliferation of geodetic, seismic, and geologic data across the zone provides a unique opportunity for constraining geodynamic models and increasing our understanding of mountain building and plateau growth. We present a 3-D, spherical, Stokes flow, finite volume, geodynamic model of the India-Eurasia collision. Lithospheric volume is constrained by seismic data. Continuous surface velocities, inferred from GPS and Quaternary fault slip data, are used to approximate velocity boundary conditions. We assume a stress-free surface, and free-slip along the model base. Model viscosity varies with depth and is calculated assuming the laterally-varying, depth-averaged viscosities of Flesch et al. (2001) and a cratonic Indian plate. Laterally the model extends from the southern tip of India northward to the Tian Shan, and from the Pamir Mountains eastward to the South China block. Vertically the model volume extends to a depth of 100 km, and is divided into three layers: upper crust, lower crust, and upper-lithospheric mantle. We use COMSOL Multiphysics (www.comsol.com) to investigate the role of vertical viscosity variation on surface deformation by holding the dynamics constant, adjusting the viscosity substructure, and determining the resultant stress and velocity fields. Solved model surface velocities are compared to the observed surface velocities inferred from GPS and Quaternary fault slip rates. A two-layer model employing laterally-variant viscosity estimates throughout the crust and mantle is ineffective at replicating the observed force balance. The weak crustal viscosities necessary for attaining the observed clockwise rotation around the eastern Himalayan syntaxis also result in erroneous southward velocities in southern Tibet, driven by excessive gravitational collapse. Strengthening crustal viscosities balances the boundary/body forces and allows for

  9. Research activities of the Geodynamics Branch

    NASA Technical Reports Server (NTRS)

    Kahn, W. D. (Editor); Cohen, S. C. (Editor)

    1984-01-01

    A broad spectrum of geoscience disciplines including space geodesy, geopotential field modeling, tectonophysics, and dynamic oceanography are discussed. The NASA programs, include the Geodynamics and Ocean Programs, the Crustal Dynamics Project, the proposed Ocean Topography Experiment (TOPEX), and the Geopotential Research Mission (GRM). The papers are grouped into chapters on Crustal Movements, Global Earth Dynamics, Gravity Field Model Development, Sea Surface Topography, and Advanced Studies.

  10. GLOBAL DISASTERS: Geodynamics and Society

    NASA Astrophysics Data System (ADS)

    Vikulina, Marina; Vikulin, Alexander; Semenets, Nikolai

    2013-04-01

    The problem of reducing the damage caused by geodynamic and social disasters is a high priority and urgent task facing the humanity. The vivid examples of the earthquake in Japan in March 2011 that generated a new kind of threat - the radiation pollution, and the events in the Arabic world that began in the same year, are dramatic evidences. By the middle of this century, the damage from such disastrous events is supposed to exceed the combined GDP of all countries of the world. The database of 287 large-scale natural and social disasters and global social phenomena that have occurred in the period of II B.C.E. - XXI A.D. was compiled by the authors for the first time. We have proposed the following phenomenological model: the scale of disasters over the time does not decrease, there is a minimum of accidents in the XV century; the numbers of accidents have cycles lasting until the first thousand years, natural and social disasters in the aggregate are uniformly distributed in time, but separately natural and social disasters are nonuniform. Thus, due to the evaluation, a 500-year cycle of catastrophes and 200-300 and 700-800-year periodicities are identified. It is shown that catastrophes are grouped into natural and social types by forming clusters. The hypothesis of the united geo-bio-social planetary process is founded. A fundamentally new feature of this research is the assumptions about the statistical significance of the biosphere and the impact of society on the geodynamic processes. The results allow to formulate a new understanding of global disaster as an event the damage from which the humanity will be unable to liquidate even by means of the total resource potential and the consequence of which may turn into the irreversible destruction of civilization. The correlation between the natural and social phenomena and the possible action mechanism is suggested.

  11. Geodynamic models of terrane accretion: Testing the fate of island arcs, oceanic plateaus, and continental fragments in subduction zones

    NASA Astrophysics Data System (ADS)

    Tetreault, J. L.; Buiter, S. J. H.

    2012-08-01

    Crustal growth at convergent margins can occur by the accretion of future allochthonous terranes (FATs), such as island arcs, oceanic plateaus, submarine ridges, and continental fragments. Using geodynamic numerical experiments, we demonstrate how crustal properties of FATs impact the amount of FAT crust that is accreted or subducted, the type of accretionary process, and the style of deformation on the overriding plate. Our results show that (1) accretion of crustal units occurs when there is a weak detachment layer within the FAT, (2) the depth of detachment controls the amount of crust accreted onto the overriding plate, and (3) lithospheric buoyancy does not prevent FAT subduction during constant convergence. Island arcs, oceanic plateaus, and continental fragments will completely subduct, despite having buoyant lithospheric densities, if they have rheologically strong crusts. Weak basal layers, representing pre-existing weaknesses or detachment layers, will either lead to underplating of faulted blocks of FAT crust to the overriding plate or collision and suturing of an unbroken FAT crust. Our experiments show that the weak, ultramafic layer found at the base of island arcs and oceanic plateaus plays a significant role in terrane accretion. The different types of accretionary processes also affect deformation and uplift patterns in the overriding plate, trench migration and jumping, and the dip of the plate interface. The resulting accreted terranes produced from our numerical experiments resemble observed accreted terranes, such as the Wrangellia Terrane and Klamath Mountain terranes in the North American Cordilleran Belt.

  12. Laser Geodynamics Satellite (LAGEOS)

    NASA Image and Video Library

    2016-05-04

    This 1975 NASA video highlights the development of LAser GEOdynamics Satellite (LAGEOS I) developed at NASA's Marshall Space Flight Center in Huntsville, Alabama. LAGEOS I is a passive satellite constructed from brass and aluminum and contains 426 individual precision reflectors made from fused silica glass. The mirrored surface of the satellite was designed to reflect laser beams from ground stations for accurate ranging measurements. LAGEOS I was launched on May 4, 1976 from Vandenberg Air Force Base, California. The two-foot diameter, 900-pound satellite orbited the Earth from pole to pole, measuring the movements of the Earth's surface relative to earthquakes, continental drift, and other geophysical phenomena. Scientists at NASA's Marshall Space Flight Center in Huntsville, Alabama came up with the idea for the satellite and built it at the Marshall Center.

  13. 3-D geodynamic models of the India-Eurasia collision zone: Guiding numerical models with seismic and MT observations

    NASA Astrophysics Data System (ADS)

    Bischoff, S. H.; Flesch, L. M.

    2015-12-01

    Piecing together the uplift and growth of the Tibetan Plateau requires a robust understanding of the present-day dynamics of the India-Eurasia collision zone. To aid in the understanding of mountain building and plateau growth, we developed a 3D finite element model of the Tibetan Plateau following Flesch and Bendick (2012). Our model is based on the vast collection of published geophysical data and employs COMSOL Multiphysics (www.comsol.com). We assume model material properties from the wide variety of published seismic and MT studies, incorporated with an updated, vertically averaged, effective viscosity distribution from Flesch et al. (2001). We test potential relationships between conductance/seismic velocity and strength (viscosity) by modeling strength difference contacts at imaged interfaces. We quantify fitness of candidate 3D viscosity functions by comparing solved model surface velocities to observed surface velocities inferred from GPS and Quaternary fault slip rates. The model geometry incorporates Earth curvature and extends eastward from 65° to 110°E, northward from 15° to 45°N, and vertically down to 100 km below sea level. The physics of deformation is governed by the Stokes equations describing incompressible Newtonian fluid flow. Boundary conditions consist of free slip across the bottom surface (representing the lithosphere-asthenosphere boundary) and moving edge walls constrained by a GPS-derived, continuous velocity field. Model results indicate a tradeoff between crust and mantle dominant strength. Best-fit models are achieved by a combination of strong crust/upper mantle with additional strain accommodation in localized weak zones.

  14. Geodynamic and Geochemical Modeling of Mantle Processes along the Southwest Indian Ridge at 35°-40°E: A Hotspot-Mid-Ocean Ridge Interaction Region

    NASA Astrophysics Data System (ADS)

    Larson, M. O.; Okino, K.; Montesi, L.

    2014-12-01

    Mantle convection can be regarded as the superposition of two convective models: aplate mode and a plume mode. Geodynamic modeling of these regimes has grantedinsight into surface features, and tells us about the mantle processes in a system largelydevoid of observables. Our study of the 35°-40°E segment of the Southwest Indian Ridge(SWIR) seeks to link geochemical and geological observations with the underlying mantleprocesses.Both plate and plume modes interact and combine at the SWIR 35°-40°E segment. Themid-ocean ridge itself is a manifestation of the plate tectonics mode of mantle convection.The slow opening rate and obliquity of this segment should lead to low volcanic activityalong this segment. However, this segment is the point along the SWIR closest to theMarion hotspot, a manifestation of the plume mode of mantle convection. When interactingwith the mid-ocean ridges, hotspots like the Azores, Iceland, Galápagos, and Rodriguezproduce distinctive patterns, such as propagating rifts, triple junctions, and enriched MORBsignatures. The Marion hotspot does not have a similar effect on the SWIR even thoughit is associated with a bathymetric high and residual mantle Bouguer anomaly low. Anotable feature along the ridge is a V-shaped bathymetric anomaly around one of the non-transform discontinuities (NTD).As for the SWIR 10°-16°E area (Montési et al., 2011) geodynamics modeling predictsmagma focusing to highly segmented non-transform oblique segments (NTOS) along theridge. However, geophysical observations show a thinning crust at these regions. Modelingwithout the segmentation along the oblique segments shows much better agreement withthe observations. So either the NTOS are a crustal structure that does not influence mantleupwelling, melt extraction parameters vary along the ridge, or the density of the crust isanomalous in NTOS due to a different fractionation history.We will incorporate whole rock chemistry (including trace element, & REEs

  15. Testing geodynamic models for surface uplift of the central Andean plateau through volcanic glass paleoaltimetry and basin analysis in southern Peru

    NASA Astrophysics Data System (ADS)

    Sundell, K. E., II; Saylor, J. E.; Villarreal, D. P.; Horton, B. K.

    2014-12-01

    Differentiating between geodynamic models describing the formation mechanism(s) of the central Andean plateau (CAP) requires information concerning the timing and location of basin formation, crustal deformation, and surface uplift. All models involve the removal of lithospheric mantle, and typically fall into one of two end-members: 1) slow, continuous uplift (km over 10s of Myr) involving protracted removal of mantle lithosphere through ablative subduction or thermal weakening that is predicted to be coincident with crustal shortening, or 2) punctuated uplift (km over Myr) driven by rapid wholesale or piecemeal foundering of a dense lithospheric root, likely post-dating major crustal shortening. However, these models are not mutually exclusive, nor must any one geodynamic mechanism describe the entire history of the formation of the CAP, an area spanning ~1800 km N-S by up to 500 km E-W, comprised of multiple physiographic regions of differing compositional and geophysical characteristics resulting from protracted orogenesis. We present new stratigraphic, stable isotopic, and geochronologic data for temporally overlapping yet spatially separate Cenozoic intermontane basins in the northern CAP to evaluate the contribution of these end-member scenarios to the formation of the CAP. Data span multiple physiographic regions of the CAP, including basins near Puquio (Western Cordillera), the Huacochullo basin (western Altiplano margin), and the Macusani and Crucero basins of the Cordillera de Carabaya (Eastern Cordillera). The magnitude of paleoelevation changes is reconstructed from δD values of volcanic glass, while timing is constrained by zircon U-Pb geochronology. Initial results indicate early, rapid, high-magnitude surface uplift from initially low elevations in the Western Cordillera but a later, lower-magnitude pulse of uplift from initially moderate elevations in the Eastern Cordillera. This diachronous uplift history, together with published reports of

  16. Palaeoproterozoic (1.83 Ga) zircons in a Bajocian (169 Ma) granite within a Middle Jurassic ophiolite (Rubiku, central Albania): a challenge for geodynamic models

    NASA Astrophysics Data System (ADS)

    Kryza, Ryszard; Beqiraj, Arjan

    2014-04-01

    Two distinct zircon populations, 1,827 ± 17 and 169 ± 2 Ma in age, have been found in the Rubiku granite dyke in the Middle Jurassic Mirdita ophiolite in central Albania. The old inherited zircons represent a homogeneous population formed during a discrete Palaeoproterozoic, likely magmatic, zircon crystallization event. These older zircons were likely incorporated, in large part, into the granite magma that crystallized broadly at the time of the ophiolite emplacement (around 169 Ma). The limited data available do not allow for the construction of an unequivocal petrogenetic model, though several palaeotectonic scenarios are discussed as possible settings for the granite formation. The models refer to recent findings of old inherited zircons in rocks at recent mid-ocean ridge settings, but also consider likely contributions of crustal materials to primary basic ophiolitic magmas within supra-subduction settings and subsequent accretion/collision circumstances. The presence of old zircons in much younger rocks within ophiolite successions runs counter to geodynamic models of interaction between the oceanic lithosphere and continental crust, but constraining their genesis would require further systematic studies on these old inherited zircons, both in mafic (if present) and in felsic rocks of the ophiolites.

  17. Is the Okavango Delta the terminus of the East African Rift System? Towards a new geodynamic model: Geodetic study and geophysical review

    NASA Astrophysics Data System (ADS)

    Pastier, Anne-Morwenn; Dauteuil, Olivier; Murray-Hudson, Michael; Moreau, Frédérique; Walpersdorf, Andrea; Makati, Kaelo

    2017-08-01

    The Okavango Graben (OG) has been considered as the terminus of the southwestern branch of the East African Rift System (EARS) since the 1970s based on fault morphology and early seismic and geophysical data. Thus it has been assumed to be an incipient rifting zone, analogous to the early stage of mature rifts in the EARS. Recent geodetic data and geophysical studies in the area bring new insights into the local crust and lithosphere, mantle activity and fault activity. In this study, we computed the velocities for three permanent GPS stations surrounding the graben and undertook a review of the new geophysical data available for the area. The northern and southern blocks of the graben show an exclusively low strike-slip displacement rate of about 1mm/year, revealing the transtensional nature of this basin. The seismic record of central and southern Africa was found to be instrumentally biased for the events recorded before 2004 and the OG may not represent the most seismically active area in Botswana anymore. Moreover, no significant lithosphere and crustal thinning is found in the tectonic structure nor any strong negative Bouguer anomaly and surface heat flux. Thus the OG does not match the classical model for a rifting zone. We propose a new geodynamic model for the deformation observed west of the EARS based on accommodation of far-field deformation due to the differential extension rates of the EARS and the displacement of the Kalahari craton relative to the Nubian plate.

  18. Preliminary northeast Asia geodynamics map

    USGS Publications Warehouse

    Parfenov, Leonid M.; Khanchuk, Alexander I.; Badarch, Gombosuren; Miller, Robert J.; Naumova, Vera V.; Nokleberg, Warren J.; Ogasawara, Masatsugu; Prokopiev, Andrei V.; Yan, Hongquan

    2003-01-01

    This map portrays the geodynamics of Northeast Asia at a scale of 1:5,000,000 using the concepts of plate tectonics and analysis of terranes and overlap assemblages. The map is the result of a detailed compilation and synthesis at 5 million scale and is part of a major international collaborative study of the Mineral Resources, Metallogenesis, and Tectonics of Northeast Asia conducted from 1997 through 2002 by geologists from earth science agencies and universities in Russia, Mongolia, Northeastern China, South Korea, Japan, and the USA. This map is the result of extensive geologic mapping and associated tectonic studies in Northeast Asia in the last few decades and is the first collaborative compilation of the geology of the region at a scale of 1:5,000,000 by geologists from Russia, Mongolia, Northeastern China, South Korea, Japan, and the USA. The map was compiled by a large group of international geologists using the below concepts and definitions during collaborative workshops over a six-year period. The map is a major new compilation and re-interpretation of pre-existing geologic maps of the region. The map is designed to be used for several purposes, including regional tectonic analyses, mineral resource and metallogenic analysis, petroleum resource analysis, neotectonic analysis, and analysis of seismic hazards and volcanic hazards. The map consists of two sheets. Sheet 1 displays the map at a scale of 1:5,000,000, explanation. Sheet 2 displays the introduction, list of map units, and source references. Detailed descriptions of map units and stratigraphic columns are being published separately. This map is one of a series of publications on the mineral resources, metallogenesis, and geodynamics,of Northeast Asia. Companion studies and other articles and maps , and various detailed reports are: (1) a compilation of major mineral deposit models (Rodionov and Nokleberg, 2000; Rodionov and others, 2000; Obolenskiy and others, in press a); (2) a series of

  19. From Geodynamics to Simplicity

    NASA Astrophysics Data System (ADS)

    Anderson, D. L.

    2002-12-01

    Mantle convection and plate tectonics are often thought as synonymous. Convection is sometimes treated as the driver or plate tectonics is viewed as simply a manifestation of mantle convection. Mantle plumes are regarded as supplying some of the elements missing in the plate tectonic and mantle convection paradigms, such as island chains, swells and large igneous provinces. An alternate view is motivated by Prigogine's concept of far-from-equilibrium self-organization ( SOFFE), not to be confused with Bak's self-organized criticality ( SOC) . In a SOFFE system the components interact, and the system is small compared to the outside world to which it is open. There must be multiple possible states and dissipation is important. Such a system is sensitive to small changes. Rayleigh-Benard convection in a container with isothermal walls is such a self-organizing system ; the driving bouyancy and the dissipation ( viscosity ) are in the fluid. In Marangoni convection the driving forces ( surface tension ) and dissipation are in the surface film and this organizes the surface and the underlying fluid. The mantle provides energy and matter to the interacting plate system but forces in the plates drive and dissipate the energy. Thus, plate tectonics may be a SOFFEE system that drives convection,as are systems cooled from above, in general. If so, plates will reorganize as boundary conditions change ; incipient plate boundaries will emerge as volcanic chains at tensile regions. Plates are defined as regions of lateral compression ( force chains ), rather than strength, and they are ephemeral. The plate system, rather than mantle viscosity, will modulate mantle cooling. The supercontinent cycle, with episodes of reorganization and massive magmatism, may be a manifestation of this far-from-equilibrium, driven from above, system. Geodynamics may be simpler than we think. Plate tectonics is certainly a more powerful concept once the concepts of rididity, elasticity, homogeneity

  20. Basic research for the geodynamics program

    NASA Technical Reports Server (NTRS)

    1986-01-01

    Further development of utility program software for analyzing final results of Earth rotation parameter determination from different space geodetic systems was completed. Main simulation experiments were performed. Results and conclusions were compiled. The utilization of range-difference observations in geodynamics is also examined. A method based on the Bayesian philosophy and entropy measure of information is given for the elucidation of time-dependent models of crustal motions as part of a proposed algorithm. The strategy of model discrimination and design of measurements is illustrated in an example for the case of crustal deformation models.

  1. The NASA Geodynamics Program: An overview

    NASA Technical Reports Server (NTRS)

    1983-01-01

    This NASA Geodynamics Program overview collectively examines the history, scientific basis, status, and results of the NASA Program and outlines plans for the next five to eight years. It is intended as an informative nontechnical discussion of geodynamics research.

  2. Basic research for the geodynamics program

    NASA Technical Reports Server (NTRS)

    Mueller, I. I.

    1985-01-01

    The current technical objectives for the geodynamics program consist of (1) optimal utilization of laser and Very Long Baseline Interferometry (VLBI) observations for reference frames for geodynamics; (2) utilization of range difference observations in geodynamics; and (3) estimation techniques in crustal deformation analysis.

  3. Kinematic analysis of recent and active faults of the southern Umbria-Marche domain, Northern Apennines, Italy: geological constraints to geodynamic models

    NASA Astrophysics Data System (ADS)

    Pasqui, Valeria; Viti, Marcello; Mantovani, Enzo

    2013-04-01

    strain field. The coexistence of extensional and strike-slip regimes, in principle difficult to achieve, may be explained in the framework of a transtensional deformation model where extensional components, normal to the main NW-directed structural trends, are associated to left-lateral strike-slip movements parallel to the main NW-directed structural trends. Critical for the evaluation of the internal consistency of a deformation model for the brittle upper crustal levels is the definition of the kinematics of active faults. In this study we illustrate the preliminary results of a kinematic analysis carried out along 20, exceptionally well exposed, recent and active fault surfaces cropping out in the southernmost portion of the Umbria-Marche belt adjacent to its termination against the the Latium-Abruzzi domain to the East. The collected data indicate that the investigated faults reflect a kinematically oblique character, and that development of these structures may be explained in the framework of a left-dominated transtensional strain field. More important, the data indicate that fault kinematic analysis is an effective tool in testing geodynamic models for actively deforming crustal domains.

  4. The evolution of Hadean-Eoarchaean geodynamics

    NASA Astrophysics Data System (ADS)

    O'Neill, C.; Debaille, V.

    2014-11-01

    Geodynamic modelling of Hadean/Eoarchaean tectonics typically requires higher rates of internal heat production, and higher mantle temperatures, in models that possess temperature-dependent viscosity and a yield criterion. In such models under Hadean conditions, for a wide range of geodynamic configurations and modelling approaches, subduction has a propensity to fail. This has led to the suggestion that the predominant tectonic regime in the Hadean was stagnant-lid convection, with intermittent recycling events. Various lines of evidence support this suggestion, from i) the long mixing time of mantle isotopic anomalies or compositional heterogeneities, such as 142Nd, 182W, and platinum group elements, to ii) the long residence time of the Hadean protolith to the Jack Hills zircons, and iii) thermal evolution models, which typically require lower heat flux in the past to avoid the "Archaean thermal catastrophe". The framework provided by stagnant lid, or episodic overturn, convection, iv) provides an explanation for the formation of early Archaean TTGs and greenstones, and v) explains the interleaving arc-plume sequence observed in many Archaean terranes, suggesting subduction initiation events may have been common, increasing their preservation potential. Implications include a low magnetic field strength in the Hadean, which is consistent with emerging paleointensity data from these times.

  5. Overriding plate deformation and variability of fore-arc deformation during subduction: Insight from geodynamic models and application to the Calabria subduction zone

    NASA Astrophysics Data System (ADS)

    Chen, Zhihao; Schellart, Wouter P.; Duarte, João. C.

    2015-10-01

    In nature, subducting slabs and overriding plate segments bordering subduction zones are generally embedded within larger plates. Such large plates can impose far-field boundary conditions that influence the style of subduction and overriding plate deformation. Here we present dynamic laboratory models of progressive subduction in three-dimensional space, in which the far-field boundary conditions at the trailing edges of the subducting plate (SP) and overriding plate (OP) are varied. Four configurations are presented: Free (both plates free), SP-Fixed, OP-Fixed, and SP-OP-Fixed. We investigate their impact on the kinematics and dynamics of subduction, particularly focusing on overriding plate deformation. The results indicate that the variation in far-field boundary conditions has an influence on the slab geometry, subduction partitioning, and trench migration partitioning. Our models also indicate that in natural (narrow) subduction zones, assuming a homogeneous overriding plate, the formation of back-arc basins (e.g., Tyrrhenian Sea, Aegean Sea, and Scotia Sea) is generally expected to occur at a comparable location (250-700 km from the trench), irrespective of the boundary condition. In addition, our models indicate that the style of fore-arc deformation (shortening or extension) is influenced by the mobility of the overriding plate through controlling the force normal to the subduction zone interface (trench suction). Our geodynamic model that uses the SP-OP-Fixed setup is comparable to the Calabria subduction zone with respect to subduction kinematics, slab geometry, trench curvature, and accretionary configuration. Furthermore, the model can explain back-arc and fore-arc extension at the Calabria subduction zone since the latest middle Miocene as a consequence of subduction of the narrow Calabrian slab and the immobility of the subducting African plate and overriding Eurasian plate. This setting induced strong trench suction, driving fore-arc extension, and

  6. Geodynamic Models of Plume-Ridge Interaction in the Indian Ocean and its Effect on the Crustal Thickness of the Réunion Hotspot Track

    NASA Astrophysics Data System (ADS)

    Bredow, E.; Gassmöller, R.; Dannberg, J.; Steinberger, B.

    2016-12-01

    The Réunion mantle plume had a first impact on the Earth's surface when the plume head approached the base of the lithosphere around 67 million years ago and the first vigorous volcanic eruptions created the Deccan Traps in India, one of the largest flood basalt provinces in the world. During this period, the Indian plate may have been accelerated by the uprising plume head, leading to a northeastward plate motion with a unique velocity of up to 18 cm/year. The hotspot track, generally considered to be created by the plume tail impinging on the moving plates, comprises the volcanic chains of the Laccadives, Maldives and Chagos on the Indian plate and the Southern Mascarene Plateau on the African plate. It has been divided by seafloor spreading, since the Central Indian Ridge has passed over the plume approximately 50 million years ago, leading to intensive and continuing plume-ridge interaction. Considering the whole geodynamic history of the plume up to its currently active position underneath the island of Réunion, we set up three-dimensional regional convection models of the upper mantle using the mantle convection code ASPECT (Advanced Solver for Problems in Earth's ConvecTion). In order to study this specific plume, we prescribe the global flow field from a coarser global model at the side boundaries and bottom of the box model and the reconstructed tectonic plate velocities at the uppermost 200 km while a plume inflow is enforced at the bottom. Furthermore, we extended the code to import varying lithosphere thickness values at the side boundaries to compare realistic lithosphere models with simple constant lithosphere thickness models. Finally, we compare the amount and pattern of the resulting crustal thickness produced by the plume with present-day topographic maps to constrain plume properties such as the excess temperature and buoyancy flux. Special focus is placed on how the ridge geometry helps generating the distinctive gap in the hotspot track

  7. Geophysical-petrological modeling of the lithosphere beneath the Cantabrian Mountains and the North-Iberian margin: geodynamic implications

    NASA Astrophysics Data System (ADS)

    Pedreira, David; Afonso, Juan Carlos; Pulgar, Javier A.; Gallastegui, Jorge; Carballo, Alberto; Fernàndez, Manel; Garcia-Castellanos, Daniel; Jiménez-Munt, Ivone; Semprich, Julia; García-Moreno, Olga

    2015-08-01

    Cenozoic contractional deformation in the North-Iberian continental margin (southern Bay of Biscay) led to the uplift of the Cantabrian Mountains and the northward subduction of part of the thick continental crust, down to at least 55 km depth beneath the coastline, and perhaps even 30-40 km deeper. In order to provide a more constrained model of this unique structure and gain insight into the factors controlling its evolution, we performed an integrated geophysical-petrological modeling of the lithosphere along a 470 km-long, N-S transect down to 400 km depth. The methodology used allows for fitting gravity anomalies, geoid undulations, surface heat flow, elevation and seismic velocities with a realistic distribution of densities and seismic velocities in the mantle and the subducting lower crust, which are dependent on chemical composition, pressure and temperature. Two models are presented, with variable maximum depth for the crustal root: 60 km (Model A) and 90 km (Model B). Results indicate that both models are feasible from the geophysical point of view, but the shallower root agrees slightly better with tomographic results. The thickness of the thermal lithosphere in Model A varies from 125-145 km south of the Cantabrian Mountains to 170 km beneath the crustal root and 135-140 km beneath the central part of the Bay of Biscay. Model B requires a thicker thermal lithosphere beneath the crustal root (205 km). Low seismic velocities beneath the Bay of Biscay Moho and in the mantle wedge above the crustal root are explained by the addition of 1-2 wt% of water. Input from dehydration reactions in the subducting lower crust is ruled out in Model A and has a very minor influence in Model B. We therefore interpret the water to have percolated from the seafloor during the formation of the margin in the Mesozoic. A later basaltic underplating was also inferred. A tentative evolutionary model (to a great extent governed by these petrological processes) is proposed

  8. Geophysical and petrological modelling of the structure and composition of the crust and upper mantle in complex geodynamic settings: The Tyrrhenian Sea and surroundings

    NASA Astrophysics Data System (ADS)

    Panza, G. F.; Peccerillo, A.; Aoudia, A.; Farina, B.

    2007-01-01

    structure shows a rigid body dipping westward, a feature that continues southward, up to the eastern Aeolian arc. In contrast, at Ischia the upper mantle contains a shallow low-velocity layer ( Vs = 3.5-4.0 km/s) just beneath a thin but complex crust. The western Aeolian arc and Ustica sit over an upper mantle with Vs ˜ 4.2-4.4 km/s, although a rigid layer ( Vs = 4.55 km/s) from about 80 to 150 km occurs beneath the western Aeolian arc. In Sardinia, no significant differences in the LAS structure are detected from north to south. The petrological-geochemical signatures of Italian volcanoes show strong variations that allow us to distinguish several magmatic provinces. These often coincide with mantle sectors identified by Vs tomography. For instance, the Roman volcanoes show remarkable similar petrological and geochemical characteristics, mirroring similar structure of the LAS. The structure and geochemical-isotopic composition of the upper mantle change significantly when we move to the Stromboli-Campanian volcanoes. The geochemical signatures of Ischia and Procida volcanoes are similar to other Campanian centres, but Sr-Pb isotopic ratios are lower marking a transition to the backarc mantle of the Central Tyrrhenian Sea. The structural variations from Stromboli to the central (Vulcano and Lipari) and western Aeolian arc are accompanied by strong variations of geochemical signatures, such as a decrease of Sr-isotope ratios and an increase of Nd-, Pb-isotope and LILE/HFSE ratios. The dominance of mafic subalkaline magmatism in the Tyrrhenian Sea basin denotes large degrees of partial melting, well in agreement with the soft characteristics of the uppermost mantle in this area. In contrast, striking isotopic differences of Plio-Quaternary volcanic rocks from southern to northern Sardinia does not find a match in the LAS geophysical characteristics. The combination of petrological and geophysical constraints allows us to propose a 3D schematic geodynamic model of the

  9. The intraplate Mw 7 Machaze earthquake in Mozambique: Improved point source model, stress drop, and geodynamic implications

    NASA Astrophysics Data System (ADS)

    Attanayake, Januka; Fonseca, João F. B. D.

    2016-05-01

    The February 22nd 2006 Mw = 7 Machaze earthquake is one of the largest, if not the largest, earthquakes reported since 1900 within Continental Africa. This large continental intraplate event has important implications to our understanding of tectonics and strong ground motion prediction locally and in the global context. Thus, accurate estimates of source parameters of this earthquake are important. In this study, we inverted the complete azimuthally distributed high frequency (0.05-2 Hz) P waveform dataset available for a best-fitting point source model and obtained stress drop estimates assuming different theoretical rupture models from spectral fitting. Our best-fitting point source model confirms steep normal faulting, has strike = 173° (309°), dip = 73° (23°), rake = -72° (-132°), and shows a 12%-4% improvement in waveform fit compared to previous models, which translates into an error minimization. We attribute this improvement to higher order reverberations near the source region that we took in to account and the excellent azimuthal coverage of the dataset. Preferred stress drop estimates assuming a rupture velocity = 0.9 x shear wave velocity (Vs) are between 11 and 15 MPa though, even higher stress drop estimates are possible for rupture velocities lower than 0.9Vs. The estimated stress drop is significantly higher than the global stress drop average of intraplate earthquakes, but is consistent with stress drop estimated for some intra-continental earthquakes elsewhere. The detection of a new active structure that appears to terminate in Machaze, its step-like geometry, and lithospheric strength all favors a hypothesis of stress concentration in the source region, which is likely the cause of this event and the higher than average stress drop.

  10. Investigating the magnitude of lower crustal flow and impact on surface deformation patterns in Tibet using 3-D geodynamic models

    NASA Astrophysics Data System (ADS)

    Bischoff, S. H.; Flesch, L. M.

    2016-12-01

    Differential flow in the lower crust of Tibet has been invoked to explain features in the region, including uniform plateau elevation, crustal thickness/topographic gradients, and uplift without observed shortening. Here, we use 3-D finite element modeling to test impacts of assumed lower crustal viscosities on deformation patterns in the India-Eurasia collision zone. We simulate instantaneous lithospheric deformation with Stokes flow using COMSOL Multiphysics (www.comsol.com). Our model geometry ranges eastward from the Pamir to Sichuan, northward from the southern tip of India to the Tien Shan, and vertically downward from the Earth's surface to 100 km below sea level. We divide model geometry into four domains: Indian lithosphere, Eurasian upper crust, lower crust, and upper mantle. Seismic and magnetotelluric study results guide inclusion of subducted Indian and Burma slabs along with our targeted weak lower crust. Within the larger Eurasian lower crust domain, weak lower crust is restricted to a zone bounded clockwise by the Himalayan Frontal Thrust, Karakorum, Altyn-Tagh, Kunlun, Longmen Shan, and onset of lower elevations along the plateau's southeastern margin. From top to bottom, vertical bounds of the zone are constrained by a constant 20 km below sea level and the shallower of either the top of the Indian slab or Moho. Strength is approximated via 3-D maps of effective viscosity constrained by the vertically-averaged lithospheric estimates of Flesch et al. [2001]. We forward model lower crust effective viscosities on the order of 1018 to 1022 Pa•s and inspect resulting horizontal and vertical deformation patterns. Results suggest that effective viscosities of less than 1020 Pa•s are required for both appreciable differential mass flux through lower crustal flow as well as decoupled lower crustal flow from the upper crust or mantle. Movement of the lower crust is partitioned within weaker fault zones. Effective viscosities of 1020 Pa•s or less

  11. Geodynamic models assist in determining the South Loyalty Basin's slab location and its implications for regional topography

    NASA Astrophysics Data System (ADS)

    Clark, Stuart R.

    2010-05-01

    In the Western Pacific, two competing kinematic reconstructions exist: one with wholly westward subduction of the Pacific plate at what is now the Tonga-Kermadec trench and one combining a degree of eastward subduction under what has been termed the New Caledonia trench. New seismological observations indicate that eastward subduction could explain the existence of a fast anomaly, the hyothesised South Loyalty Basin slab, below the 660km transition zone distinct from the fast anomaly aligned with the Tonga-Kermadec slab. A plate reconstruction dated from the suggested initiation of New Caledonia subduction in the Eocene has been developed. This reconstruction is then used to predict the thermal history of the region and together provide kinematic and thermal boundary conditions for a regional mantle convection model. The model-predicted location of the South Loyalty Basin slab's location will be presented along with the location's dependence on the mantle rheological parameters and the hotspot reference frame. The implications for the topography of the region will also be discussed.

  12. How fault evolution changes strain partitioning and fault slip rates in Southern California: Results from geodynamic modeling

    NASA Astrophysics Data System (ADS)

    Ye, Jiyang; Liu, Mian

    2017-08-01

    In Southern California, the Pacific-North America relative plate motion is accommodated by the complex southern San Andreas Fault system that includes many young faults (<2 Ma). The initiation of these young faults and their impact on strain partitioning and fault slip rates are important for understanding the evolution of this plate boundary zone and assessing earthquake hazard in Southern California. Using a three-dimensional viscoelastoplastic finite element model, we have investigated how this plate boundary fault system has evolved to accommodate the relative plate motion in Southern California. Our results show that when the plate boundary faults are not optimally configured to accommodate the relative plate motion, strain is localized in places where new faults would initiate to improve the mechanical efficiency of the fault system. In particular, the Eastern California Shear Zone, the San Jacinto Fault, the Elsinore Fault, and the offshore dextral faults all developed in places of highly localized strain. These younger faults compensate for the reduced fault slip on the San Andreas Fault proper because of the Big Bend, a major restraining bend. The evolution of the fault system changes the apportionment of fault slip rates over time, which may explain some of the slip rate discrepancy between geological and geodetic measurements in Southern California. For the present fault configuration, our model predicts localized strain in western Transverse Ranges and along the dextral faults across the Mojave Desert, where numerous damaging earthquakes occurred in recent years.

  13. Configuration of geological domains and geodynamic evolution of the Africa-Eurasia plate boundary off SW Iberia revisited based on seismic velocity and density models

    NASA Astrophysics Data System (ADS)

    Martínez-Loriente, Sara; Sallarès, Valentí; Gràcia, Eulàlia; Bartolome, Rafael; Ranero, César

    2015-04-01

    We present a new classification of geological (basement) domains at the Africa-Eurasia plate boundary offshore SW Iberia, together with a regional geodynamic reconstruction spanning from the Mesozoic extension to the Neogene-to-present-day convergence. It is based on seismic velocity and density models along two regional wide-angle seismic transects, one running NW-SE from the Tagus to the Seine abyssal plains, and the other running N-S from S Portugal to the Seine Abyssal Plain, combined with previously available information. The seismic velocity and density structure at the Seine Abyssal Plain and the internal Gulf of Cadiz indicates the presence of a highly heterogeneous oceanic crust, similar to that described in ultra-slow spreading centers, whereas in the Horseshoe and Tagus abyssal plains, the basement structure resembles that of exhumed mantle sections identified in the Northern Atlantic margin. The integration of all this new information allows defining the presence of three oceanic domains off SW Iberia: (1) the Seine Abyssal Plain domain, generated during the first stages of slow seafloor spreading in the NE segment of the Central Atlantic (Early Jurassic); (2) the Gulf of Cadiz domain, made of oceanic crust generated in the Alpine-Tethys spreading system between Iberia and Africa, which was coeval with the formation of the Seine Abyssal Plain domain and lasted up to the North Atlantic continental break-up (Late Jurassic); and (3) the Gorringe Bank domain, mainly made of rocks exhumed from the mantle with little synchronous magmatism, which formed during the first stages of North Atlantic opening (Early Cretaceous). Our models suggest that the Seine Abyssal Plain and Gulf of Cadiz domains are separated by the Lineament South strike-slip fault, whereas the Gulf of Cadiz and Gorringe Bank domains appear to be limited by a deep thrust fault located at the center of the Horseshoe Abyssal Plain, which coincides with the seismicity cluster nucleated in the

  14. Revisiting the factors which control the angle of shear bands in geodynamic numerical models of brittle deformation

    NASA Astrophysics Data System (ADS)

    Thieulot, Cedric

    2017-04-01

    In this work I present Finite Element numerical simulations of brittle deformation in two-dimensional Cartesian systems subjected to compressional or extensional kinematical boundary conditions with a basal velocity discontinuity. The rheology is visco-plastic and is characterised by a cohesion and an angle of internal friction (Drucker-Prager type). I will explore the influence of the following factors on the recovered shear band angles when the angle of internal friction is varied: a) element type (quadrilateral vs triangle), b) element order, c) continuous vs discontinous pressure, d) visco-plasticity model implementation, e) the nonlinear tolerance value, f) the use of markers, g) Picard vs Newton-Raphson, h) velocity discontinuity nature. I will present these results in the light of already published literature (e.g. Lemiale et al, PEPI 171, 2008; Kaus, Tectonophysics 484, 2010).

  15. Source modeling of the 2015 Mw 7.8 Nepal (Gorkha) earthquake sequence: Implications for geodynamics and earthquake hazards

    USGS Publications Warehouse

    McNamara, Daniel E.; Yeck, William; Barnhart, William D.; Schulte-Pelkum, V.; Bergman, E.; Adhikari, L. B.; Dixit, Amod; Hough, S.E.; Benz, Harley M.; Earle, Paul

    2017-01-01

    The Gorkha earthquake on April 25th, 2015 was a long anticipated, low-angle thrust-faulting event on the shallow décollement between the India and Eurasia plates. We present a detailed multiple-event hypocenter relocation analysis of the Mw 7.8 Gorkha Nepal earthquake sequence, constrained by local seismic stations, and a geodetic rupture model based on InSAR and GPS data. We integrate these observations to place the Gorkha earthquake sequence into a seismotectonic context and evaluate potential earthquake hazard.Major results from this study include (1) a comprehensive catalog of calibrated hypocenters for the Gorkha earthquake sequence; (2) the Gorkha earthquake ruptured a ~ 150 × 60 km patch of the Main Himalayan Thrust (MHT), the décollement defining the plate boundary at depth, over an area surrounding but predominantly north of the capital city of Kathmandu (3) the distribution of aftershock seismicity surrounds the mainshock maximum slip patch; (4) aftershocks occur at or below the mainshock rupture plane with depths generally increasing to the north beneath the higher Himalaya, possibly outlining a 10–15 km thick subduction channel between the overriding Eurasian and subducting Indian plates; (5) the largest Mw 7.3 aftershock and the highest concentration of aftershocks occurred to the southeast the mainshock rupture, on a segment of the MHT décollement that was positively stressed towards failure; (6) the near surface portion of the MHT south of Kathmandu shows no aftershocks or slip during the mainshock. Results from this study characterize the details of the Gorkha earthquake sequence and provide constraints on where earthquake hazard remains high, and thus where future, damaging earthquakes may occur in this densely populated region. Up-dip segments of the MHT should be considered to be high hazard for future damaging earthquakes.

  16. Tectonic Evolution of the Cretaceous Sava-Klepa Massif, Former Yugoslav Republic of Macedonia, based on field observations and microstructural analysis - Towards a new geodynamic Model

    NASA Astrophysics Data System (ADS)

    Altmeyer, Tobias; Peternell, Mark; Prelević, Dejan; Köpping, Jonas

    2016-04-01

    The Balkan Peninsula was formed during the Mesozoic collision of Gondwana and Eurasia, associated with the closure of the Neo-Tethyan Ocean. As a result, two ophiolitic belts were formed: Dinaride-Hellenide ophiolitic belt in the southwest and the Vardar ophiolitic belt in the northeast. The bulk of Balkan ophiolites originated in the Jurassic (Robertson & Karamata, 1994), and only recently the Late Cretaceous Sava-zone ophiolites are discovered. Ophiolit-like outcrops of Mount Klepa in the Central Macedonia represents a part of Late Cretaceous oceanic lithosphere within the Sava Zone, comprising of pillow lavas, sheet flows, columns, hyaloclastites, dikes as well as cumulates. In this study we investigate the geodynamic setting and evolution of the Late Cretaceous Klepa Massif. Our working hypotheses we want to test is that Klepa Massif represents a new ocean opened through rifting after the closure of Tethyan ocean(s) and collision of Europe and Gondwana already in the Late Jurassic to Early Cretaceous. This hypothesis contradicts the accepted model suggesting that Sava ophiolites represent a relic of the Neo-Tethyan Ocean that closed in the Late Cretaceous. During detailed structural geology field studies, the ophiolitic rock sequence of Klepa Mountain area was mapped in several profiles and about 60 rock samples were taken. These field data in addition to the north-south trending outcrops of the Klepa ophiolite and the north-south trending shear zones which bound the Klepa basalt, lead to the assumption of the existence of a pull apart basin. With the help of microstructural analyses we will determine the deformation history and temperatures which also will be confirmed by the analyses of calcite twins (Ferril et al., 2004). Quartz grain size analysis of quartz bearing rocks, were used for stress piezometry. Furthermore, quartz crystal geometry and crystallographic orientations, which were measured with the Fabric Analyser G60 (Peternell et al., 2010), reveal

  17. Fundamental studies in geodynamics

    NASA Technical Reports Server (NTRS)

    Anderson, D. L.

    1980-01-01

    Progress in modeling instantaneous plate kinematics is reviewed, with emphasis on recently developed models of present day plate motions derived by the systematic inversion of globally distributed data sets. Rivera plate motions, the Caribbean South American boundary, Indian plate deformation, Pacific-North America, seismicity and subduction processes, and the study of slow earthquakes and free oscillations are discussed.

  18. Geodynamics map of northeast Asia

    USGS Publications Warehouse

    Parfenov, Leonid M.; Khanchuk, Alexander I.; Badarch, Gombosuren; Miller, Robert J.; Naumova, Vera V.; Nokleberg, Warren J.; Ogasawara, Masatsugu; Prokopiev, Andrei V.; Yan, Hongquan

    2013-01-01

    This map portrays the geodynamics of Northeast Asia at a scale of 1:5,000,000 using the concepts of plate tectonics and analysis of terranes and overlap assemblages. The map is the result of a detailed compilation and synthesis at 5 million scale and is part of a major international collaborative study of the mineral resources, metallogenesis, and tectonics of northeast Asia conducted from 1997 through 2002 by geologists from earth science agencies and universities in Russia, Mongolia, northeastern China, South Korea, Japan, and the USA.

  19. Yellowstone Hotspot Geodynamics

    NASA Astrophysics Data System (ADS)

    Smith, R. B.; Farrell, J.; Massin, F.; Chang, W.; Puskas, C. M.; Steinberger, B. M.; Husen, S.

    2012-12-01

    The Yellowstone hotspot results from the interaction of a mantle plume with the overriding N. America plate producing a ~300-m high topographic swell centered on the Late Quaternary Yellowstone volcanic field. The Yellowstone area is dominated by earthquake swarms including a deadly M7.3 earthquake, extraordinary high heat flow up to ~40,000 mWm-2, and unprecedented episodes of crustal deformation. Seismic tomography and gravity data reveal a crustal magma reservoir, 6 to 15 km deep beneath the Yellowstone caldera but extending laterally ~20 km NE of the caldera and is ~30% larger than previously hypothesized. Kinematically, deformation of Yellowstone is dominated by regional crustal extension at up to ~0.4 cm/yr but with superimposed decadal-scale uplift and subsidence episodes, averaging ~2 cm/yr from 1923. From 2004 to 2009 Yellowstone experienced an accelerated uplift episode of up to 7 cm/yr whose source is modeled as magmatic recharge of a sill at the top of the crustal magma reservoir at 8-10-km depth. New mantle tomography suggest that Yellowstone volcanism is fed by an upper-mantle plume-shaped low velocity body that is composed of melt "blobs", extending from 80 km to 650 km in depth, tilting 60° NW, but then reversing tilt to ~60° SE to a depth of ~1500 km. Moreover, images of upper mantle conductivity from inversion of MT data reveal a high conductivity annulus around the north side of the plume in the upper mantle to resolved depths of ~300 km. On a larger scale, upper mantle flow beneath the western U.S. is characterized by eastward flow beneath Yellowstone at 5 cm/yr that deflects the plume to the west, and is underlain by a deeper zone of westerly return flow in the lower mantle reversing the deflection of the plume body to the SE. Dynamic modeling of the Yellowstone plume including a +15 m geoid anomaly reveals low excess plume temperatures, up to 150°K, consistent with a weak buoyancy flux of ~0.25 Mg/s. Integrated kinematic modeling of GPS

  20. Geodesy and geodynamics

    NASA Astrophysics Data System (ADS)

    Whitten, Charles A.

    1986-11-01

    Man's interest in the dynamics of the earth's crust goes back several centuries. Ekman recently pointed out the theory of post-glacial uplift in Fennoscandia. In the 15th century, towns along the Baltic-Sea experienced receding of the sea. In this century, Bowie had started a program for repeating surveys in seismically active regions. Wegeners' hypothesis of Continental Drift aroused the interest of scientists. In January 1985, Walter Sullivan traced the evolution from Wegener's continental drift through plate tectonics to the latest suggestion of the formation of continents from "terranes". Spatial techniques. Laser Ranging, VLBI, GPS have given geodesists the ability to monitor continental drift, intracontinental deformations and other phenomena. Along faults, such as the San Andreas Fault, the conventional geodetic approach to deformation has been to use a linear concept, except for episodic events such as earthquakes and so on. Wayne Thatcher's model on the declining strain rate is justified if sufficient geodetic data, well distributed, are available. Strain components can be computed from distortion patterns which might develop when an earlier survey is adjusted to be made consistent with a later survey. There exists a correlation of the movement of the instantaneous pole of rotation with the energy release of all earthquakes.

  1. A westward propagating slab tear model for Late Triassic Qinling Orogenic Belt geodynamic evolution: Insights from the petrogenesis of the Caoping and Shahewan intrusions, central China

    NASA Astrophysics Data System (ADS)

    Hu, Fangyang; Liu, Shuwen; Zhang, Wanyi; Deng, Zhengbin; Chen, Xu

    2016-10-01

    Late Triassic granitoid intrusions are widespread in the South Qinling Belt (SQB), providing excellent subjects to understand the geodynamic evolution of the Qinling Orogenic Belt and the collision between the North China Craton (NCC) and Yangtze Craton (YZC). This study shows newly obtained geological, geochemical and zircon U-Pb-Hf isotopic data of the Caoping and Shahewan intrusions, revealing that the Caoping intrusion consists of 215 Ma fined-grained granites, and 221-215 Ma porphyritic and coarse to medium-grained tonalites, granodiorites and monzogranites, which assemble with coeval mafic magmatic enclaves (MMEs). The Shahewan intrusion is composed of 215-210 Ma porphyritic granodiorites and monzogranites, which also assemble with coeval MMEs. The fine-grained granites from the Caoping intrusion are characterized by high SiO2, Rb and (La/Yb)N ratio, but low MgO, CaO and Sc contents, with εHf(t) values of - 8.6 to + 4.3 and TDM2(Hf) ages of 883-1596 Ma, suggesting that they are mainly derived from partial melting of the Meso- to Neoproterozoic metagreywackes. The porphyritic and coarse to medium-grained granitoid rocks from both Caoping and Shahewan intrusions are characterized by higher MgO, CaO, Sc, Mg# values, but low SiO2, Rb contents and (La/Yb)N ratio, with εHf(t) values of - 0.7 to + 2.8 and TDM2(Hf) values of 961-1158 Ma, suggesting that they are mainly formed by magma mixing between melts that were derived from Meso- to Neoproterozoic basement rocks of the SQB and metasomatized lithospheric mantle. The MMEs from Caoping and Shahewan intrusions are characterized by low SiO2, Sr/Y ratio, high MgO, K2O, Rb, Sc, total REE contents, with εHf(t) values of + 0.5 to + 6.1 and TDM(Hf) values of 661-846 Ma, suggesting that they are produced by partial melting of metasomatized lithospheric mantle. The rapakivi-like textures of the rocks from Shahewan intrusion may be caused by continued underplating and injection of mafic magma resulting in higher

  2. At the craton edge: Geodynamic evolution of the southern Canadian Cordillera

    NASA Astrophysics Data System (ADS)

    DiCaprio, L.; Eaton, D. W. S.

    2016-12-01

    In the southern Canadian Cordillera, the thermal and mechanical interface with the craton may influence the geodynamic evolution of the lithosphere-asthenosphere system. Evidence including recent Rayleigh-wave tomography studies suggest that, beneath the southern Canadian Cordillera, the mantle lithosphere is virtually absent. Here, the boundary between craton and Cordillera also marks a step change in measured surface heat flux and a westward termination of magnetic anomalies. This study provides a numerical simulation of lithospheric-mantle removal by geodynamic processes that include delamination, viscous erosion, and mantle dripping. An additional constraint to the geodynamic model comes from thermochronologic data demonstrating long wavelength uplift of the cordilleran plateau in the Eocene. We have developed a suite of 2D visco-plastic models of a transect through the southern Canadian Cordillera and North American Craton. Sensitivity tests elucidate a range of geodynamic models that are consistent with tomographic results and the observed uplift history.

  3. Scientific Data Analysis and Software Support: Geodynamics

    NASA Technical Reports Server (NTRS)

    Klosko, Steven; Sanchez, B. (Technical Monitor)

    2000-01-01

    The support on this contract centers on development of data analysis strategies, geodynamic models, and software codes to study four-dimensional geodynamic and oceanographic processes, as well as studies and mission support for near-Earth and interplanetary satellite missions. SRE had a subcontract to maintain the optical laboratory for the LTP, where instruments such as MOLA and GLAS are developed. NVI performed work on a Raytheon laser altimetry task through a subcontract, providing data analysis and final data production for distribution to users. HBG had a subcontract for specialized digital topography analysis and map generation. Over the course of this contract, Raytheon ITSS staff have supported over 60 individual tasks. Some tasks have remained in place during this entire interval whereas others have been completed and were of shorter duration. Over the course of events, task numbers were changed to reflect changes in the character of the work or new funding sources. The description presented below will detail the technical accomplishments that have been achieved according to their science and technology areas. What will be shown is a brief overview of the progress that has been made in each of these investigative and software development areas. Raytheon ITSS staff members have received many awards for their work on this contract, including GSFC Group Achievement Awards for TOPEX Precision Orbit Determination and the Joint Gravity Model One Team. NASA JPL gave the TOPEX/POSEIDON team a medal commemorating the completion of the primary mission and a Certificate of Appreciation. Raytheon ITSS has also received a Certificate of Appreciation from GSFC for its extensive support of the Shuttle Laser Altimeter Experiment.

  4. Basic research for the geodynamics program

    NASA Technical Reports Server (NTRS)

    1984-01-01

    Some objectives of this geodynamic program are: (1) optimal utilization of laser and VLBI observations as reference frames for geodynamics, (2) utilization of range difference observations in geodynamics, and (3) estimation techniques in crustal deformation analysis. The determination of Earth rotation parameters from different space geodetic systems is studied. Also reported on is the utilization of simultaneous laser range differences for the determination of baseline variation. An algorithm for the analysis of regional or local crustal deformation measurements is proposed along with other techniques and testing procedures. Some results of the reference from comparisons in terms of the pole coordinates from different techniques are presented.

  5. International GPS Service for Geodynamics

    NASA Technical Reports Server (NTRS)

    Zumberge, J. F. (Editor); Urban, M. P. (Editor); Liu, R. (Editor); Neilan, R. E. (Editor)

    1996-01-01

    This 1995 annual report of the IGS International GPS (Global Positioning System) Service for Geodynamics - describes the second operational year of the service. It provides the many IGS contributing agencies and the rapidly growing user community with essential information on current organizational and technical matters promoting the IGS standards and products (including organizational framework, data processing strategies, and statistics showing the remarkable expansion of the GPS monitoring network, the improvement of IGS performance, and product quality). It also introduces important practical concepts for network densification by integration of regional stations and the combination of station coordinate solutions. There are groups of articles describing general aspects of the IGS, the Associate Analysis Centers (AACs), Data Centers, and IGS stations.

  6. Fuzzy Logic Modelling and Hidden Geodynamic Parameters of Earth: What is the role of Fluid Pathaways and Hydrothermal Stages on the Mineralization Variations of Kozbudaklar Pluton over Southern Uludag

    NASA Astrophysics Data System (ADS)

    Kocaturk, Huseyin; Kumral, Mustafa

    2016-04-01

    Plate tectonics is one of the most illustrated theory and biggest geo-dynamic incident on earth surface and sub-surface for the earth science. Tectonic settlement, rock forming minerals, form of stratigraphy, ore genesis processes, crystal structures and even rock textures are all related with plate tectonic. One of the most known region of Turkey is Southern part of Uludaǧ and has been defined with three main lithological union. Region is formed with metamorphics, ophiolites and magmatic intrusions which are generally I-type granodiorites. Also these intrusion related rocks has formed and altered by high grade hydrothermal activity. This study approaches to understand bigger to smaller frameworks of these processes which between plate tectonics and fluid pathways. Geodynamic related fuzzy logic modelling is present us compact conclusion report about structural associations for the economic generations. Deformation structures and fluid pathways which related with plate tectonics progressed on our forearc system and each steps of dynamic movements of subducting mechanism has been seemed affect both hydrothermal stages and mineral variations together. Types of each deformation structure and mineral assemblages has characterized for flux estimations which can be useful for subsurface mapping. Geoanalytical results showed us clear characteristic stories for mutual processes. Determined compression and release directions on our map explains not only hydrothermal stages but also how succesion of intrusions changes. Our fuzzy logic models intersect sections of physical and chemical interactions of study field. Researched parameters like mafic minerals and enclave ratios on different deformation structures, cross sections of structures and relative existing sequence are all changes with different time periods like geochemical environment and each vein. With the combined informations in one scene we can transact mineralization processes about region which occurs in

  7. Study of a close-grid geodynamic measurement system

    NASA Technical Reports Server (NTRS)

    1977-01-01

    The Clogeos (Close-Grid Geodynamic Measurement System) concept, a complete range or range-rate measurement terminal installed in a satellite in a near-polar orbit with a network of relatively simple transponders or retro-reflectors on the ground at intervals of 0.1 to 10 km was reviewed. The distortion of the grid was measured in three dimensions to accuracies of + or - 1 cm with important applications to geodynamics, glaciology, and geodesy. User requirements are considered, and a typical grid, designed for earthquake prediction, was laid out along the San Andreas, Hayward, and Calaceras faults in southern California. The sensitivity of both range and range-rate measurements to small grid motions was determined by a simplified model. Variables in the model are satellite altitude and elevation angle plus grid displacements in latitude, and height.

  8. The NASA Geodynamics Program report, 1981

    NASA Technical Reports Server (NTRS)

    1982-01-01

    The activities of the NASA Geodynamics Program in 1981 both in achieving improved measurement precision and in establishing the foundation for the acquisition and analysis of scientific data are discussed.

  9. Cultural and Technological Issues and Solutions for Geodynamics Software Citation

    NASA Astrophysics Data System (ADS)

    Heien, E. M.; Hwang, L.; Fish, A. E.; Smith, M.; Dumit, J.; Kellogg, L. H.

    2014-12-01

    Computational software and custom-written codes play a key role in scientific research and teaching, providing tools to perform data analysis and forward modeling through numerical computation. However, development of these codes is often hampered by the fact that there is no well-defined way for the authors to receive credit or professional recognition for their work through the standard methods of scientific publication and subsequent citation of the work. This in turn may discourage researchers from publishing their codes or making them easier for other scientists to use. We investigate the issues involved in citing software in a scientific context, and introduce features that should be components of a citation infrastructure, particularly oriented towards the codes and scientific culture in the area of geodynamics research. The codes used in geodynamics are primarily specialized numerical modeling codes for continuum mechanics problems; they may be developed by individual researchers, teams of researchers, geophysicists in collaboration with computational scientists and applied mathematicians, or by coordinated community efforts such as the Computational Infrastructure for Geodynamics. Some but not all geodynamics codes are open-source. These characteristics are common to many areas of geophysical software development and use. We provide background on the problem of software citation and discuss some of the barriers preventing adoption of such citations, including social/cultural barriers, insufficient technological support infrastructure, and an overall lack of agreement about what a software citation should consist of. We suggest solutions in an initial effort to create a system to support citation of software and promotion of scientific software development.

  10. The present geodynamics of Albania

    NASA Astrophysics Data System (ADS)

    Koçi, Rexhep; Dushi, Edmond; Begu, Enkela; Bozo, Rrezart

    2017-04-01

    Geological structure of Albania comprises different formations widely varying in age beginning since the Paleozoic era to Quaternary. From the tectonic stand point Albanides belongs to folded Alpine belt, representing a particular node in the geology of the Mediterranean Alps. Albanian geological environment have a long and complicated history. It is folded and dissected by many tectonic faults. During the Alpine geological evolution of Albanides, an imbricated tectonic thrusting system, with considerable amplitude, has been developed in the outer part, while a series of normal faults have been developed in the inner part. The convergence of the geological structures is southwest oriented, from inner to external tectonic area, associated by mass displacement. These displacements can be observed nowadays from geodynamic measurements, of the GPS networks in Albania, and the surrounding. GPS data for Albanian territory, recorded during a 10-years period, in reference to the Eurasia and Apulia plates, reveal an important pre-Pliocene compression of the outer Albanides, including Sazani, Ionian and Kruja zones, undergoing a major post-Pliocene shortening in the western side. The outer Albanides are structured by infringements of over-thrust and up-thrust type, by NNW-SSE oriented folds, which in some cases are dislocated by transverse faults, of NE orientation. Actual results from GPS measurements of the points located in outer Albanides show a displacement towards west and northwest in relation to Eurasia, and southwest in relation to Apulia block. From numerous focal mechanisms solutions (FMS) of shallow earthquakes it results a horizontal compression dominating along the Adriatic collision contact. Active tectonics in this area is reflected from historical and instrumental strong earthquakes. Quite often, they are generated from the activation of tectonic faults, which in turn are responsible for this seismic activity of the country. Referring to the historical data

  11. Geodynamic contributions to global climatic change

    NASA Technical Reports Server (NTRS)

    Bills, Bruce G.

    1992-01-01

    Orbital and rotational variations perturb the latitudinal and seasonal pattern of incident solar radiation, producing major climatic change on time scales of 10(exp 4)-10(exp 6) years. The orbital variations are oblivious to internal structure and processes, but the rotational variations are not. A program of investigation whose objective would be to explore and quantify three aspects of orbital, rotational, and climatic interactions is described. An important premise of this investigation is the synergism between geodynamics and paleoclimate. Better geophysical models of precessional dynamics are needed in order to accurately reconstruct the radiative input to climate models. Some of the paleoclimate proxy records contain information relevant to solid Earth processes, on time scales which are difficult to constrain otherwise. Specific mechanisms which will be addressed include: (1) climatic consequences of deglacial polar motion; and (2) precessional and climatic consequences of glacially induced perturbations in the gravitational oblateness and partial decoupling of the mantle and core. The approach entails constructing theoretical models of the rotational, deformational, radiative, and climatic response of the Earth to known orbital perturbations, and comparing these with extensive records of paleoclimate proxy data. Several of the mechanisms of interest may participate in previously unrecognized feed-back loops in the climate dynamics system. A new algorithm for estimating climatically diagnostic locations and seasons from the paleoclimate time series is proposed.

  12. On the geodynamics of the Aegean rift

    NASA Astrophysics Data System (ADS)

    Agostini, Samuele; Doglioni, Carlo; Innocenti, Fabrizio; Manetti, Piero; Tonarini, Sonia

    2010-06-01

    The Aegean rift is considered to be either a classic backarc basin, or the result of the westward escape of Anatolia, or the effect of a gravitational collapse of an over-thickened lithosphere. Here these models are questioned. We alternatively present a number of geodynamic and magmatic constraints suggesting a simple model for the genesis of the extension as being related to the differential advancement of the upper lithosphere over a heterogeneous lower African plate. The Greek microplate overrides the Ionian oceanic segment of the African plate faster than the Anatolian microplate over the thicker Levantine more continental segment. This setting is evidenced by GPS-velocity gradient in the hangingwall of the Hellenic-Cyprus subduction system and requires a zone of rifting splitting the hangingwall into two microplates. This mechanism is unrelated to the replacement of retreated slab by the asthenosphere as typically occurs in the backarc of west-directed subduction zones. The supposed greater dehydration of the Ionian segment of the slab is providing a larger amount of fluids into the low velocity channel at the top of the asthenosphere, allowing a faster decoupling between the Greek microplate and the underlying mantle with respect to the Anatolian microplate. Slab ruptures associated with the differential retreat controlled by the inherited lithospheric heterogeneities in the lower plate and the proposed upwelling of the mantle suggested by global circulation models would explain the occurrence and coexistence of slab-related and slab-unrelated magmatism.

  13. Basic research for the geodynamics program

    NASA Technical Reports Server (NTRS)

    1991-01-01

    The mathematical models of space very long base interferometry (VLBI) observables suitable for least squares covariance analysis were derived and estimatability problems inherent in the space VLBI system were explored, including a detailed rank defect analysis and sensitivity analysis. An important aim is to carry out a comparative analysis of the mathematical models of the ground-based VLBI and space VLBI observables in order to describe the background in detail. Computer programs were developed in order to check the relations, assess errors, and analyze sensitivity. In order to investigate the estimatability of different geodetic and geodynamic parameters from the space VLBI observables, the mathematical models for time delay and time delay rate observables of space VLBI were analytically derived along with the partial derivatives with respect to the parameters. Rank defect analysis was carried out both by analytical and numerical testing of linear dependencies between the columns of the normal matrix thus formed. Definite conclusions were formed about the rank defects in the system.

  14. The Computational Infrastructure for Geodynamics as a Community of Practice

    NASA Astrophysics Data System (ADS)

    Hwang, L.; Kellogg, L. H.

    2016-12-01

    Computational Infrastructure for Geodynamics (CIG), geodynamics.org, originated in 2005 out of community recognition that the efforts of individual or small groups of researchers to develop scientifically-sound software is impossible to sustain, duplicates effort, and makes it difficult for scientists to adopt state-of-the art computational methods that promote new discovery. As a community of practice, participants in CIG share an interest in computational modeling in geodynamics and work together on open source software to build the capacity to support complex, extensible, scalable, interoperable, reliable, and reusable software in an effort to increase the return on investment in scientific software development and increase the quality of the resulting software. The group interacts regularly to learn from each other and better their practices formally through webinar series, workshops, and tutorials and informally through listservs and hackathons. Over the past decade, we have learned that successful scientific software development requires at a minimum: collaboration between domain-expert researchers, software developers and computational scientists; clearly identified and committed lead developer(s); well-defined scientific and computational goals that are regularly evaluated and updated; well-defined benchmarks and testing throughout development; attention throughout development to usability and extensibility; understanding and evaluation of the complexity of dependent libraries; and managed user expectations through education, training, and support. CIG's code donation standards provide the basis for recently formalized best practices in software development (geodynamics.org/cig/dev/best-practices/). Best practices include use of version control; widely used, open source software libraries; extensive test suites; portable configuration and build systems; extensive documentation internal and external to the code; and structured, human readable input formats.

  15. Continental geodynamics and mineral exploration - the Western Australian perspective

    NASA Astrophysics Data System (ADS)

    Gessner, Klaus; Murdie, Ruth; Yuan, Huaiyu; Brisbout, Lucy; Sippl, Christian; Tyler, Ian; Kirkland, Chris; Wingate, Michael; Johnson, Simon; Spaggiari, Catherine; Smithies, Hugh; Lu, Yongjun; Gonzalez, Chris; Jessell, Mark; Holden, Eun-Jung; Gorczyk, Weronika; Occhipinti, Sandra

    2017-04-01

    The exploration for mineral resources and their extraction has been a fundamental human activity since the dawn of civilisation: Geology is everywhere - ore deposits are rare. Most deposits were found at or near Earth's surface, often by chance or serendipity. To meet the challenge of future demand, successful exploration requires the use of advanced technology and scientific methods to identify targets at depth. Whereas the use and development of high-tech exploration, extraction and processing methods is of great significance, understanding how, when and where dynamic Earth systems become ore-forming systems is a difficult scientific challenge. Ore deposits often form by a complex interplay of coupled physical processes with evolving geological structure. The mineral systems approach states that understanding the geodynamic and tectonic context of crustal scale hydrothermal fluid flow and magmatism can help constrain the spatial extent of heat and mass transport and therefore improve targeting success in mineral exploration. Tasked with promoting the geological assets of one of the World's largest and most resource-rich jurisdictions, the Geological Survey of Western Australia is breaking new ground by systematically collecting and integrating geophysical, geological and geochemical data with the objective to reveal critical ties between lithospheric evolution and mineral deposits. We present examples where this approach has led to fundamental reinterpretations of Archean and Proterozoic geodynamics and the nature of tectonic domains and their boundaries, including cases where geodynamic modelling has played an important role in testing hypotheses of crustal evolution.

  16. Advanced cyberinfrastructure for research in Geodynamics

    NASA Astrophysics Data System (ADS)

    Manea, Marina; Constantin Manea, Vlad

    2010-05-01

    Today's scientists need access to new information technology capabilities, able to perform high-resolution complex computing simulations in a reasonable time frame. Sophisticated simulation tools allow us to study phenomena that can never be observed or replicated by standard laboratory experiments. Modeling complex natural processes in general, and numerical computation in particular, represents today an essential need of research, and all modern research centers benefit from a computing center of one form or another. The combined power of hardware and sophisticated software, visualization tools, and scientific applications produced and used by interdisciplinary research teams make possible nowadays to advance the frontiers of science and to pose new key scientific questions. Cyberinfrastructure integrates hardware for high speed computing, a collection of highly specialized software and tools, and a powerful visualization tool. A new interdisciplinary research domain is emerging at the interface of geosciences and computing with essential inputs from geology and geophysics. In this study we show how to rapidly deploy a low-cost high-performance computing cluster (HPCC) and a 3D visualization system that can be used both in teaching and research in geosciences. Also, we present several geodynamic simulations performed with such systems.

  17. Plume connection of carbonatites: geodynamic Implication

    NASA Astrophysics Data System (ADS)

    Kogarko, Liya; Veselovskiy, Roman

    2017-04-01

    Geodynamic position of the carbonatites is actively discussed question during the last decades. Some researches link their formation with ascend of the large volumes of mantle melts from the CMB. There is certain evidence for temporal and spatial correlation of the carbonatites and LIPs, whose origin is certainly related with mantle plumes [1], as it was shown for carbonatites of the Polar Siberia (Maymecha- Kotuy province) which were formed simultiniusly with the Siberian superplume 250 Ma [2]. We used the recent absolute plate kinematic model [2] to reconstruct locations of Phanerozoic carbonatites at the time of their origin (Fig. 1). We have found that 118 out of 180 carbonatites (66%) are projecting onto central or peripheral parts of African Large Low Shear-wave Velocity Province and this can be viewed as an evidence for linking the carbonatites with mantle plumes. [1] Ernst R.E. Large Igneous Provinces. Cambridge University Press. 2014. 666 p [2]. Kogarko L., Zartman R.(2007) Min Petrol.89,113-132 [3] Torsvik T.H. et al. (2014) Proceedings of the National Academy of Sciences of the United States.111 ,8735-8740. Supported by RSCF grant 15- 17-30019.

  18. Effects of differentiation on the geodynamics of the early Earth

    NASA Astrophysics Data System (ADS)

    Piccolo, Andrea; Kaus, Boris; White, Richard; Johnson, Tim

    2016-04-01

    Archean geodynamic processes are not well understood, but there is general agreement that the mantle potential temperature was higher than present, and that as a consequence significant amounts of melt were produced both in the mantle and any overlying crust. This has likely resulted in crustal differentiation. An early attempt to model the geodynamic effects of differentiation was made by Johnson et al. (2014), who used numerical modeling to investigate the crust production and recycling in conjunction with representative phase diagrams (based on the inferred chemical composition of the primary melt in accordance with the Archean temperature field). The results of the simulations show that the base of the over-thickened primary basaltic crust becomes gravitational unstable due to the mineral assemblage changes. This instability leads to the dripping of dense material into the mantle, which causes an asthenospheric return flow, local partial melting and new primary crust generation that is rapidly recycled in to mantle. Whereas they gave important insights, the previous simulations were simplified in a number of aspects: 1) the rheology employed was viscous, and both elasticity and pressure-dependent plasticity were not considered; 2) extracted mantle melts were 100% transformed into volcanic rocks, whereas on the present day Earth only about 20-30% are volcanic and the remainder is plutonic; 3) the effect of a free surface was not studied in a systematic manner. In order to better understand how these simplifications affect the geodynamic models, we here present additional simulations to study the effects of each of these parameters. Johnson, T.E., Brown, M., Kaus, B., and VanTongeren, J.A., 2014, Delamination and recycling of Archaean crust caused by gravitational instabilities: Nature Geoscience, v. 7, no. 1, p. 47-52, doi: 10.1038/NGEO2019.

  19. Geodynamics - Tracking satellites to monitor global change

    NASA Technical Reports Server (NTRS)

    Beutler, Gerhard; Morgan, Peter; Neilan, Ruth E.

    1993-01-01

    The major goals and organizational structure of the International GPS Geodynamics Service (IGS), a new Navstar satellite tracking service, are described. IGS activities are aimed at providing the scientific community with data on GPS orbits accurate enough for performing regional and local GPS analysis and daily earth rotation information.

  20. Geodynamics - Tracking satellites to monitor global change

    SciTech Connect

    Beutler, G.; Morgan, P.; Neilan, R.E. Canberra Univ. JPL, Pasadena, CA )

    1993-02-01

    The major goals and organizational structure of the International GPS Geodynamics Service (IGS), a new Navstar satellite tracking service, are described. IGS activities are aimed at providing the scientific community with data on GPS orbits accurate enough for performing regional and local GPS analysis and daily earth rotation information.

  1. A petrological view of early Earth geodynamics

    NASA Astrophysics Data System (ADS)

    Herzberg, C.

    2003-04-01

    Xenoliths of low T Archean cratonic mantle consist mostly of harzburgite and lherzolite with geochemical depletions that are characterisitc of igneous residues. Many authors have identified the complementary magmas as komatiites. This model is re-examined in light of work presented in Herzberg & O'Hara (2002) and found to be problematic. Munro-type alumina-undepleted komatiites from Alexo, Pyke Hill, and other locations often contain olivine phenocrysts with maximum Mg# \\cong 94. Residues of fractional melting would consist of pure dunite having Mg# = 97-98, but these are not observed. Residues of equilibrium melting would also be pure dunite with Mg# = 94, but these are also not observed. Olivines with Mg# = 94 are found in rare harzburgites, indicating that residues of alumina-undepleted komatiite have either been overprinted by subsequent magmatism or they have been geodynamically eroded. Alumina-undepleted komatiites can be successfully modeled with a primary magma containing 30% MgO produced by 0.5 mass fractions of equilibrium melting of depleted peridotite. A hot plume interpretation is consistent with both the petrology and helium isotopic compositions of alumina-undepleted komatiites. But what about cratonic mantle? The FeO and MgO contents of residues of fertile mantle peridotite formed by both equilibrium and fractional melting can be predicted and applied to xenoliths of cratonic mantle in most cases. Application to xenoliths from the Kaapvaal and Slave cratons is not possible owing to a second stage of Opx enrichment, but results can be applied to most xenoliths from Siberia, Tanzania, Somerset Island, and east Greenland as they contain less than 45% SiO_2. These xenoliths are very similar to residues produced by fractional melting. Pressures of initial melting were mostly 3 to 5 GPa, but can be as high 7 GPa. Pressures of final melting were highly variable and can be as low as 1 GPa. Potential temperatures (T_P) were typically 1450 to 1600oC and

  2. Geodynamic Research at the Department of Planetary Geodesy, SRC PAS

    NASA Astrophysics Data System (ADS)

    Brzeziński, Aleksander; Jóźwik, Mieczysław; Kaczorowski, Marek; Kalarus, Maciej; Kasza, Damian; Kosek, Wiesław; Nastula, Jolanta; Szczerbowski, Zbigniew; Wińska, Małgorzata; Wronowski, Roman; Zdunek, Ryszard; Zieliński, Janusz B.

    2016-06-01

    The Department of Planetary Geodesy of the Space Research Centre PAS has been conducting research on a broad spectrum of problems within a field of global dynamics of the Earth. In this report we describe the investigations on selected subjects concerning polar motion (modeling and geophysical interpretation of the Chandler wobble, hydrological excitation of seasonal signals, search for optimal prediction methods), tectonic activity in the region of the Książ Geodynamic Laboratory of the SRC, and finally the new joint Polish-Italian project GalAc analyzing feasibility and usefulness of equipping second-generation Galileo satellites with accelerometers.

  3. Establishing geodetic-geodynamic parameters using lunar laser range measurements

    NASA Astrophysics Data System (ADS)

    Ballani, L.

    The state of the art of lunar laser range measurements is reviewed. The transit time of the signals is simulated to determine if the effects of the final signal speed should be taken into account, and modeling of the signal time delay is treated in the frame of earth-moon dynamics. Results concerning coordinates and distances of laser stations in the United States, USSR and Austria, and essential UTO and UT1 analyses are presented. Conditions for establishing the geodetic-geodynamic parameters are determined, and preliminary estimations are made.

  4. Geodynamic evidence for a chemically depleted continental tectosphere.

    PubMed

    Forte, A M; Perry, H K

    2000-12-08

    The tectosphere, namely the portions of Earth's mantle lying below cratons, has a thermochemical structure that differs from average suboceanic mantle. The tectosphere is thought to be depleted in its basaltic components and to have an intrinsic buoyancy that balances the mass increase associated with its colder temperature relative to suboceanic mantle. Inversions of a large set of geodynamic data related to mantle convection, using tomography-based mantle flow models, indicate that the tectosphere is chemically depleted and relatively cold to 250 kilometers depth below Earth's surface. The approximate equilibrium between thermal and chemical buoyancy contributes to cratonic stability over geological time.

  5. Software and Algorithms for Solving Computational Geodynamic Problems using Next Generation Hardware

    NASA Astrophysics Data System (ADS)

    Zheng, Liang; Gerya, Taras

    2014-05-01

    Numerical geodynamic modeling is typically based on solving a series of partial differential equations which describe the long-term behavior of the solid visco-elasto-brittle/plastic Earth as a highly viscous incompressible fluid with strongly variable non-Newtonian viscosity. Coding for solving geodynamic equations is catching up with the advance of modern high performance computing. In the past five years, newly developed many-core computing technology, including GPU (Graphics Processing Unit) and MIC (Many Integrated Core), has also been utilized for geodynamic modeling. However, the lack of easy-to-expand or easy-to-use geo-computing toolkits limits the high performance software catching up with the endless updating of high performance hardware. In this presentation, we will firstly show two examples of the implementation of solving geodynamic problems based on Stokes and continuity equations with strongly variable viscosity using many-core hardware, with a specific focus on the GPU. The first example is a geometric multi-grid (GMG) solver, which solves a synthetic sinking cube problem using a staggered grid finite difference discretization. The second example is a preconditioned minimal residual (MINRES) solver for incompressible Stokes flow problem with many viscous inclusions which is discretized using the finite element method. Through these two implementation examples, we will analyze the cost of coding and running advantages and disadvantages of the two kinds of coding methodologies, and in a hope to discuss a potential general coding flowchart for solving geodynamic equations using many-core devices. Finally, a software stack based many-core computing framework oriented to geodynamic modeling is proposed for the future.

  6. Eclogites and their geodynamic interpretation: a history

    NASA Astrophysics Data System (ADS)

    Godard, Gaston

    2001-09-01

    -to-eclogite transition could not coincide with a sharp Mohorovičić discontinuity. Before plate tectonics, high-pressure belts were interpreted as remnants of ophiolite-bearing "geosynclines", metamorphosed by loading during thrust faulting. After the acceptance of plate tectonics, around 1970, the same high-pressure Alpine-type belts came to be considered as former oceanic crust, transformed into eclogite within subduction zones, and subsequently incorporated into mountain belts. Surprisingly, formation of eclogite in "subsidence" zones (i.e. subduction zones) had already been envisaged as early as 1931 by Holmes, the inventor of a convection-current theory. In the 1980s, many authors tried to apply the model of Alpine-type high-pressure belts to eclogites enclosed within the gneisses of ancient orogens, but the question remains obscure nowadays. These eclogites have been involved in the "in situ versus foreign" controversy and in the unresolved enigma of ultrahigh-pressure metamorphism. The latter came under scrutiny in 1984 after the discovery of coesite and diamond in some eclogite-facies rocks. It has been a matter of considerable interest during the last two decades. Currently, the debate is focused on the geodynamic mechanisms responsible for the exhumation of these rocks, a question that will probably remain unresolved for part of the coming century.

  7. Geodynamics Studies in the active seismic regions in Egypt

    NASA Astrophysics Data System (ADS)

    Mohamed, A. S.

    2003-04-01

    The recent crustal movement studies have a great role for evaluating the geodynamics of the seismo-active areas in the country. The crustal deformations must be in mind where it connecting significantly with the human life and its resources. From the historical point of view and recent instrumental records, there are some seismo-active areas in Egypt, where some significant earthquakes gad been occurred in different places. The special tectonic features in Egypt, Cairo, Aswan, Red Sea, Sinia and Nile Delta regions are the territories of a high seismic risk, which have to be monitored by up-to date technologies. The investigations of the seismic events and interpretations led to evaluate the seismic hazard for disaster prevention and for the safety of the dense populated areas and the vital national projects as the High Dam. In addition to the monitoring of the seismic events, the most powerful technique of satellite geodesy GPS will be used where geodetic networks are covering such seismic-active areas, around Nasser Lake, gulf of Suez, Cairo, Sinai and the Nile Delta. The main goal of these studies are monitoring of the crustal deformations associated with the earthquake occurrence in these seismo-active areas in order to study its geodynamical behavior and reducing the earthquake losses. The results of these movements at all networks in Egypt represent the form of the dynamic models for the deformations occurred during the different epochs of measurements. The final compiled output from the seismological and geodetic analysis will threw lights upon the geodynamical regime of these seismo-active areas.

  8. Appraisal of geodynamic inversion results: a data mining approach

    NASA Astrophysics Data System (ADS)

    Baumann, T. S.

    2016-11-01

    Bayesian sampling based inversions require many thousands or even millions of forward models, depending on how nonlinear or non-unique the inverse problem is, and how many unknowns are involved. The result of such a probabilistic inversion is not a single `best-fit' model, but rather a probability distribution that is represented by the entire model ensemble. Often, a geophysical inverse problem is non-unique, and the corresponding posterior distribution is multimodal, meaning that the distribution consists of clusters with similar models that represent the observations equally well. In these cases, we would like to visualize the characteristic model properties within each of these clusters of models. However, even for a moderate number of inversion parameters, a manual appraisal for a large number of models is not feasible. This poses the question whether it is possible to extract end-member models that represent each of the best-fit regions including their uncertainties. Here, I show how a machine learning tool can be used to characterize end-member models, including their uncertainties, from a complete model ensemble that represents a posterior probability distribution. The model ensemble used here results from a nonlinear geodynamic inverse problem, where rheological properties of the lithosphere are constrained from multiple geophysical observations. It is demonstrated that by taking vertical cross-sections through the effective viscosity structure of each of the models, the entire model ensemble can be classified into four end-member model categories that have a similar effective viscosity structure. These classification results are helpful to explore the non-uniqueness of the inverse problem and can be used to compute representative data fits for each of the end-member models. Conversely, these insights also reveal how new observational constraints could reduce the non-uniqueness. The method is not limited to geodynamic applications and a generalized MATLAB

  9. Geodynamics of Bending-related Normal Faults in Subducting Plates

    NASA Astrophysics Data System (ADS)

    Zhou, Z.; Lin, J.

    2016-12-01

    We investigated bending-related normal faults in subducting plates along several subduction zones through analyzing high-resolution multibeam bathymetry data and geodynamic modeling. The investigated systems include the Tonga, Izu-Bonin-Mariana, Japan, Middle America, Chile, and Puerto Rico trenches. Investigation was focused on spatial variations in normal faulting patterns from trench axes to the outer rise regions. Results of analyses revealed several key observations: (1) Most bending-related normal faults are sub-parallel to the local and regional strikes of the trench axis, including regions of significant trench-axis curvatures. (2) For trenches of significant oblique subduction components, e.g., Tonga and Puerto Rico trenches, the strikes of normal faults still remain sub-parallel to the trench axes. (3) Normal faults could be identified near outer-rise region, but normal faults with relatively large throws are generally located much closer to the trench axis, in regions of relatively large topographic slope. (4) Normal faults can cut through most of the seamounts near trench axes. We speculate that near-trench normal faults are generated by extensional stress due to plate bending and gravity sliding. Geodynamic models are being developed to investigate how near-trench normal faults evolve subjected to various tectonic forces at subduction zones, including subduction-induced plate bending, slab pulling, gravity sliding, and seamount loading, etc.

  10. Metastability of Subducted Slabs in the Mantle Transition Zone: A Collaborative Geodynamic, Petrologic, and Seismological Approach

    NASA Astrophysics Data System (ADS)

    Garber, J. M.; Billen, M. I.; Duncan, M. S.; Roy, C.; Ibourichene, A. S.; Olugboji, T.; Celine, C.; Rodríguez-González, J.; Grand, S. P.; Madrigal, P.; Sandiford, D.; Valencia-Cardona, J. J.

    2016-12-01

    Subducted slabs exhibit a range of geometries in the mantle transition zone. Studies of this phenomenon suggest that olivine and/or pyroxene metastability may profoundly alter the slab density profile, leading to slab flattening (e.g., King et al., 2015) and potentially yielding a resolvable seismological signature (e.g., Kawakatsu and Yoshioka, 2011; Yoshioka et al., 2015). Such metastability may also be critical for deep earthquake generation. Geodynamic modelling of this process is typically done with a simplified petrologic model of the downgoing slab, whereas petrologic studies of phase assemblages in subducted slabs typically impose an idealized geodynamic model with an unrealistic thermal structure. Connecting these two approaches should lead to a better understanding of the consequences of metastable assemblages on subducting slabs. Here, we present a new methodology that combines geodynamic, seismic and petrologic approaches to assess the impact of mineral metastability on dynamic subduction models, developed in a collaborative effort begun at the 2016 NSF CIDER summer program in Santa Barbara, CA. We use two parallel approaches to extrapolate equilibrium rock properties to metastable regions and impose these data on extracted time-slices from robust thermo-mechanical geodynamic models, allowing us to quantify the density and buoyancy changes in the slab that result from considering metastable phase assemblages. Our preliminary results suggest that metastable assemblages can yield a 10-30% density decrease over the subducted slab relative to an equilibrium reference model. We then generate a seismic velocity profile of the slab, and compute waveforms based on the 2D finite-difference method (e.g., Vidale & Helmberger, 1987) to determine whether metastable phases could reasonably be detected by different seismic approaches. Continuing analyses will be aimed at coupling the evolution of geodynamic models with phase metastability to model the feedback between

  11. Precise geodynamic measurements in South America

    NASA Astrophysics Data System (ADS)

    Groten, E.

    First high precision gravity measurements carried out in 1984 were repeated in November 1987 when in a wider frame, ranging from Santa Cruz de la Sierra (Bolivia) down to Santiago de Chile and Mendoza (Argentina), a regional densified network in Northern Chile was observed. The carefully monumented regional network extends from the earthquake-active coastal area in Chile up to Salta in Argentina. The repeated measurements are considered as a first step in a longtime study where geometric vertical control will be provided by GPS-measurements. Additional geodynamic information is provided by parallel seismic and other observations. Special interest arose from the fact that briefly after the first observations in 1984 significant earthquake deformation occurred in the area of Mendoza and Santiago de Chile. As far as gravimetry is concerned, all possible error sources are being carefully considered where also absolute measurements in view of scaling errors are planned. Reference is being made with respect to those areas which appear to be decoupled from the well known uplift of the High Andes. A detailed discussion and analysis of gravimetric data is presented. Correlation with geodynamic phenomena is studied. Future prospects of the general concept "GPS-gravimetry" as a geodynamic tool for studying vertical phenomena are interpreted.

  12. Geodynamics of melting in the Asthenosphere

    NASA Astrophysics Data System (ADS)

    Gaillard, F.; Richard, G. C. M.; Massuyeau, M.; Hashim, L.; Sifre, D.; Tarits, P.

    2016-12-01

    At geological time-scales, the mantle behaves as a high Rayleigh number fluid, i.e., thermal convection takes place and produces cells circulating at variable sizes and speeds. A lot of effort has been made to understand the upwelling part of these cells occurring underneath ridges and hotspots where they give birth to volcanoes. Nevertheless, local passive (adiabatic) sub-lithospheric mantle upwellings are likely to be more widespread and even common below oceanic plates. Just like under volcanoes, mantle is expected to undergo decompression melting in these concealed upwelling regions but the magma produced may be trapped and not have any volcanic expression. Here, we intend to discuss the fate of these deep melts and try to present a broad view of their geophysical and geochemical expressions. In our analyses, we model mantle melting that is favored by two critical parameters: high temperatures and/or elevated concentrations of H2O and CO2. It is frequently modeled as a chemical process in a static system, where thermodynamics is used to define the quantity of melts produced as a function of temperature and volatile contents. On the other hand, fluid mechanics tell us that the melt produced having low viscosity and low density tends to migrate away from its solid source at a rate depending on a variety of physical parameters; permeability and density/viscosity contrasts being the most influent. Combining thermodynamics and fluid mechanics, we show that CO2-H2O melts tend to focus at the lithosphere-asthenosphere boundary, where melt contents can reach 1-2%. This can easily explain many geophysical observations on the LVZ. The magnitude of the geophysical signal at the LVZ is related to convection (upwelling) in the asthenosphere; upwelling produces decompression-melting and the melt tends to accumulate below the impermeable lithosphere. The lithosphere-asthenosphere boundary must be featured by a strong and focused weakening where strain localizations enable

  13. Geodynamic evolution of early Mesozoic sedimentary basins in eastern Australia

    NASA Astrophysics Data System (ADS)

    Rosenbaum, G.; Babaahmadi, A.; Esterle, J.

    2014-12-01

    Eastern Australia is covered by a series of continental sedimentary basins deposited during the Triassic and Jurassic, but the geodynamic context of these basins is not fully understood. Using gridded aeromagnetic data, seismic reflection data, geological maps, digital elevation models, and field observations, we conducted a structural synthesis aimed at characterizing major structures and deformation style in the Triassic-Jurassic sedimentary basins of eastern Australia. Our results show evidence for four alternating episodes of rifting and contractional events during the Triassic. Two major episodes of rifting, characterized by syn-sedimentary steep normal faults and bimodal volcanism, resulted in the development of the Early-Middle Triassic Esk-Nymboida Rift System and the early Late Triassic Ipswich Basin. Faults in the Esk-Nymboida Rift System have been controlled by a pre-existing oroclinal structure. Each phase of rifting was followed by a contractional event, which produced folds, reverse faults and unconformities in the basins. Since the latest Late Triassic, thermal subsidence led to the deposition of continental sediments in the Clarence-Moreton Basin, which continued until the Early Cretaceous. We suggest that the geodynamic control on the alternating episodes of rifting and contraction during the Triassic in eastern Australia was ultimately related to plate boundary migration and switches between trench retreat and advance.

  14. Geodynamical aspects of the Hoggar Shield (Algeria) from Aeromagnetic data

    NASA Astrophysics Data System (ADS)

    Bournas, N.; Hamoudi, M.; Galdeano, A.; Ouzegane, K.; Kienast, J. R.

    2003-04-01

    The Hoggar is a wide region situated in the central part of northwest Africa. It represents the main component of the Tuareg shield, which is a part of the Panafrican Transaharan belt. The Hoggar is mainly composed of metamorphic rocks formed during the Panafrican orogeny and is crossed by several north-south mega-shear zones separating crustal blocks with different lithology. This region has been covered by a regional airborne magnetic survey carried out during the seventies. The survey was flown using a cesium magnetometer with a 2 km flight line spacing and a constant terrain clearance of 150 meters above the ground. Comprehensive processing and interpretation procedures including digital filtering and inversion techniques of the aeromagnetic data are presented in this work. The synergetic analysis of the aeromagnetic data with the geological considerations, has been very useful to clearly identifying the principal structural features of this region. The obtained results confirm the proposed earlier geodynamical model, in which the 4°50 and the 8°30 mega shears have played a major role in the geodynamical evolution of the Hoggar during the Panafrican event. On the other hand, the interpretation of the aeromagnetic anomalies suggests the existence of a NW-SE rifting zone affecting the whole region.

  15. Coupling geodynamic earthquake cycles and dynamic ruptures

    NASA Astrophysics Data System (ADS)

    van Zelst, Iris; van Dinther, Ylona; Gabriel, Alice-Agnes; Heuret, Arnauld

    2016-04-01

    Studying the seismicity in a subduction zone and its effects on tsunamis requires diverse modelling methods that span spatial and temporal scales. Hundreds of years are necessary to build the stresses and strengths on a fault, while consequent earthquake rupture propagation is determined by both these initial fault conditions and the feedback of seismic waves over periods of seconds up to minutes. This dynamic rupture displaces the sea floor, thereby causing tsunamis. The aim of the ASCETE (Advanced Simulations of Coupled Earthquake and Tsunami Events) project is to study all these aspects and their interactions. Here, we present preliminary results of the first aspects in this modelling chain: the coupling of a seismo-thermo-mechanical (STM) code to the dynamic rupture model SeisSol. STM models of earthquake cycles have the advantage of solving multiple earthquake events in a self-consistent manner concerning stress, strength and geometry. However, the drawback of these models is that they often lack in spatial or temporal resolution and do not include wave propagation. In contrast, dynamic rupture models solve for frictional failure coupled to seismic wave propagation. We use the software package SeisSol (www.seissol.org) based on an ADER-DG discretization allowing high-order accuracy in space and time as well as flexible tetrahedral meshing. However, such simulations require assumptions on the initial fault stresses and strengths and its geometry, which are hard to constrain due to the lack of near-field observations and the complexity of coseismic conditions. By adapting the geometry as well as the stress and strength properties of the self-consistently developing non-finite fault zones from the geodynamic models as initial conditions for the dynamic rupture models, the advantages of both methods are exploited and modelling results may be compared. Our results show that a dynamic rupture can be triggered spontaneously and that the propagating rupture is

  16. Lithospheric Stress and Geodynamics: History, Accomplishments and Challenges

    NASA Astrophysics Data System (ADS)

    Richardson, R. M.

    2016-12-01

    The kinematics of plate tectonics was established in the 1960s, and shortly thereafter the Earth's stress field was recognized as an important constraint on the dynamics of plate tectonics. Forty years ago the 1976 Chapman Conference on the Stress in the Lithosphere, which I was fortunate to attend as a graduate student, and the ensuing 1977 PAGEOPH Stress in the Earth publication's 28 articles highlighted a range of datasets and approaches that established fertile ground for geodynamic research ever since. What are the most useful indicators of stress? Do they measure residual or tectonic stresses? Local or far field sources? What role does rheology play in concentrating deformation? Great progress was made with the first World Stress Map in 1991 by Zoback and Zoback, and the current version (2016 release with 42,348 indicators) remains a tremendous resource for geodynamic research. Modeling sophistication has seen significant progress over the past 40 years. Early applications of stress to dynamics involved simple lithospheric flexure, particularly at subduction zones, Hawaii, and continental foreland basin systems. We have progressed to full 3-D finite element models for calculating the flexure and stress associated with loads on a crust and mantle with realistic non-linear viscoelastic rheology, including frictional sliding, low-temperature plasticity, and high-temperature creep. Initial efforts to use lithospheric stresses to constrain plate driving forces focused on a "top-down" view of the lithosphere. Such efforts have evolved to better include asthenosphere-lithosphere interactions, have gone from simple to complicated rheologies, from 2-D to 3-D, and seek to obtain a fully thermo-mechanical model that avoids relying on artificial boundary conditions to model plate dynamics. Still, there are a number of important issues in geodynamics, from philosophy (when are more complicated models necessary? can one hope to identify "the" answer with modeling, or only

  17. Is uplift of volcano clusters in the Tohoku Volcanic Arc, Japan, driven by magma accumulation in hot zones? A geodynamic modeling study

    NASA Astrophysics Data System (ADS)

    George, Ophelia A.; Malservisi, Rocco; Govers, Rob; Connor, Charles B.; Connor, Laura J.

    2016-06-01

    In many volcanic arcs, the rate of tectonic uplift cannot be explained by lithospheric plate motion alone but may be associated with dynamic uplift. Buoyant forces associated with underplated magma bodies lift the upper crust and leads to relatively high rates of topographic change. One such region is northern Honshu, Japan, where Quaternary volcano clusters are spatially associated with uplifted crust and isostatic gravity anomalies. Axisymmetric inversion of Bouguer gravity data for the Sengan volcano cluster shows that these gravity anomalies can be modeled by 30 km radius bodies emplaced at ˜15 km depth. Axisymmetric, finite element models, generated using GTECTON, of a layered Earth representative of the Tohoku crust indicate that the deformation of these midcrustal intrusions produces elevated topography on the surface directly above the intrusion that is bounded by a shallow peripheral trough. The wavelengths of vertical deformation produced by these bodies are sensitive to the thickness of the models' elastic layer and relatively insensitive to the models' rheology. This suggests that the amplitude of the vertical deformation represents a trade-off between the size of the intrusion and the thickness of the elastic layer and is less strongly influenced by the rheology of the lithosphere into which the bodies are emplaced. Our results are consistent with hot zone and hot finger models for the arc and indicate that Tohoku Volcanic Arc features such as gravity anomalies and uplifted basement are related to crustal magma intrusions and hot zones rather than directly related to mantle processes.

  18. Geodynamics--where are we and what lies ahead?

    PubMed

    Drake, C L; Maxwell, J C

    1981-07-03

    The introduction and evolution of the plate tectonics hypothesis during the past two decades has sparked the current renaissance of research in the earth sciences. An outgrowth of active geophysical and geological exploration of the oceans, the plate tectonics model has come under intense scrutiny by geologists, geochemists, and geophysicists who have attempted to apply the model to the origin and growth of continents, the generation of oceanic and continental crust, and the nature of the lithosphere, asthenosphere, and underlying mantle with respect to their evolution through time and to the driving mechanism or mechanisms for plate tectonics. The study of other terrestrial planets and moons has been helpful in understanding the earth model. The unequal distribution of geological features, both in the continents and oceans, emphasizes the need for ongoing studies of international scope such as the recently completed International Geodynamics Project and its successor, the International Lithosphere Program, both stressing studies related to the dynamics of the lithosphere.

  19. Magnetohydrodynamic Convection in the Outer Core and its Geodynamic Consequences

    NASA Technical Reports Server (NTRS)

    Kuang, Weijia; Chao, Benjamin F.; Fang, Ming

    2004-01-01

    The Earth's fluid outer core is in vigorous convection through much of the Earth's history. In addition to generating and maintaining Earth s time-varying magnetic field (geodynamo), the core convection also generates mass redistribution in the core and a dynamical pressure field on the core-mantle boundary (CMB). All these shall result in various core-mantle interactions, and contribute to surface geodynamic observables. For example, electromagnetic core-mantle coupling arises from finite electrically conducting lower mantle; gravitational interaction occurs between the cores and the heterogeneous mantle; mechanical coupling may also occur when the CMB topography is aspherical. Besides changing the mantle rotation via the coupling torques, the mass-redistribution in the core shall produce a spatial-temporal gravity anomaly. Numerical modeling of the core dynamical processes contributes in several geophysical disciplines. It helps explain the physical causes of surface geodynamic observables via space geodetic techniques and other means, e.g. Earth's rotation variation on decadal time scales, and secular time-variable gravity. Conversely, identification of the sources of the observables can provide additional insights on the dynamics of the fluid core, leading to better constraints on the physics in the numerical modeling. In the past few years, our core dynamics modeling efforts, with respect to our MoSST model, have made significant progress in understanding individual geophysical consequences. However, integrated studies are desirable, not only because of more mature numerical core dynamics models, but also because of inter-correlation among the geophysical phenomena, e.g. mass redistribution in the outer core produces not only time-variable gravity, but also gravitational core-mantle coupling and thus the Earth's rotation variation. They are expected to further facilitate multidisciplinary studies of core dynamics and interactions of the core with other

  20. Geodynamics branch data base for main magnetic field analysis

    NASA Technical Reports Server (NTRS)

    Langel, Robert A.; Baldwin, R. T.

    1991-01-01

    The data sets used in geomagnetic field modeling at GSFC are described. Data are measured and obtained from a variety of information and sources. For clarity, data sets from different sources are categorized and processed separately. The data base is composed of magnetic observatory data, surface data, high quality aeromagnetic, high quality total intensity marine data, satellite data, and repeat data. These individual data categories are described in detail in a series of notebooks in the Geodynamics Branch, GSFC. This catalog reviews the original data sets, the processing history, and the final data sets available for each individual category of the data base and is to be used as a reference manual for the notebooks. Each data type used in geomagnetic field modeling has varying levels of complexity requiring specialized processing routines for satellite and observatory data and two general routines for processing aeromagnetic, marine, land survey, and repeat data.

  1. Precision geodesy and geodynamics using Starlette laser ranging

    NASA Technical Reports Server (NTRS)

    Marsh, J. G.; Lerch, F. J.; Williamson, R. G.

    1985-01-01

    The French Starlette satellite, launched in February 1975, was the first satellite specifically designed to minimize the effects of nongravitational forces and to obtain the highest possible accuracy for laser range measurements. It has been found that Starlette represents a valuable complement to the U.S. geodetic satellites. In an analysis of Starlette laser ranging data conducted by Marsh and Williamson (1978), it was concluded that by tailoring a gravity model to a specific satellite and observation period, substantial improvements in data fits and, therefore, in orbit accuracy could be achieved. In the present analyses, a tailored gravity model has been derived for Starlette from the data acquired for the 4-year period, 1975-1978. Attention is given to the solution for geodetic and geodynamic parameters and polar motion.

  2. StagLab: Post-Processing and Visualisation in Geodynamics

    NASA Astrophysics Data System (ADS)

    Crameri, Fabio

    2017-04-01

    Despite being simplifications of nature, today's Geodynamic numerical models can, often do, and sometimes have to become very complex. Additionally, a steadily-increasing amount of raw model data results from more elaborate numerical codes and the still continuously-increasing computational power available for their execution. The current need for efficient post-processing and sensible visualisation is thus apparent. StagLab (www.fabiocrameri.ch/software) provides such much-needed strongly-automated post-processing in combination with state-of-the-art visualisation. Written in MatLab, StagLab is simple, flexible, efficient and reliable. It produces figures and movies that are both fully-reproducible and publication-ready. StagLab's post-processing capabilities include numerous diagnostics for plate tectonics and mantle dynamics. Featured are accurate plate-boundary identification, slab-polarity recognition, plate-bending derivation, mantle-plume detection, and surface-topography component splitting. These and many other diagnostics are derived conveniently from only a few parameter fields thanks to powerful image processing tools and other capable algorithms. Additionally, StagLab aims to prevent scientific visualisation pitfalls that are, unfortunately, still too common in the Geodynamics community. Misinterpretation of raw data and exclusion of colourblind people introduced with the continuous use of the rainbow (a.k.a. jet) colour scheme is just one, but a dramatic example (e.g., Rogowitz and Treinish, 1998; Light and Bartlein, 2004; Borland and Ii, 2007). StagLab is currently optimised for binary StagYY output (e.g., Tackley 2008), but is adjustable for the potential use with other Geodynamic codes. Additionally, StagLab's post-processing routines are open-source. REFERENCES Borland, D., and R. M. T. Ii (2007), Rainbow color map (still) considered harmful, IEEE Computer Graphics and Applications, 27(2), 14-17. Light, A., and P. J. Bartlein (2004), The end of

  3. Geodynamics of the Earth's Inner Core From Seismology

    NASA Astrophysics Data System (ADS)

    Tkalcic, Hrvoje

    2013-04-01

    Despite its small volume, the Earth's inner core plays a crucial role in outer core fluid motions and the geodynamo, which generates the Earth's magnetic field. Understanding energy exchange across the liquid core boundaries, helps to better understand planetary formation, the workings of the Earth's magnetic field and the age of the inner core, the time capsule to understanding Earth's past, present and future. A volume of seismic observations has dramatically increased and its analysis reveals challenging constraints on inner- and outer core heterogeneous structure, putting standard geodynamic models to test. This should not be surprising given that the inner core is buried deep below our feet and it represents a subject of study that is difficult to scrutinise due to a lack of experimentally controlled conditions. One controversial aspect in the current seismological research is the existence of elastic anisotropy in the inner core. I will show that due to inadequate volumetric coverage of the inner core, anisotropy's nature (strength and orientation of fast axes) is still an unresolved problem in seismology, especially in the context of recent advances in geodynamical modeling. This subject is widely open for further amendments, if not surprise turns in the existing paradigms. Another active area of seismological research is a dichotomy in seismic velocity (and seismic attenuation) that exists between the two hemispheres of the inner core, and this view is largely based on the travel times and amplitudes of body waves sampling the inner core in the equatorial region. The existence of this dichotomy has been explained in recent geodynamical models of the inner core, however most recent seismological studies demonstrate that the inner core does not have a simple hemispherical variation. While it appears that seismology still have a long way to go before the reconciliation of various results can be made, the characterization and mapping of heterogeneity in the

  4. Geodynamic environments of ultra-slow spreading

    NASA Astrophysics Data System (ADS)

    Kokhan, Andrey; Dubinin, Evgeny

    2015-04-01

    Ultra-slow spreading is clearly distinguished as an outstanding type of crustal accretion by recent studies. Spreading ridges with ultra-slow velocities of extension are studied rather well. But ultra-slow spreading is characteristic feature of not only spreading ridges, it can be observed also on convergent and transform plate boundaries. Ultra-slow spreading is observed now or could have been observed in the past in the following geodynamic environments on divergent plate boundaries: 1. On spreading ridges with ultra-slow spreading, both modern (f.e. Gakkel, South-West Indian, Aden spreading center) and ceased (Labrador spreading center, Aegir ridge); 2. During transition from continental rifting to early stages of oceanic spreading (all spreading ridges during incipient stages of their formation); 3. During incipient stages of formation of spreading ridges on oceanic crust as a result of ridge jumps and reorganization of plate boundaries (f.e. Mathematicians rise and East Pacific rise); 4. During propagation of spreading ridge into the continental crust under influence of hotspot (Aden spreading center and Afar triple junction), under presence of strike-slip faults preceding propagation (possibly, rift zone of California Bay). Ultra-slow spreading is observed now or could have been observed in the past in the following geodynamic environments on transform plate boundaries: 1. In transit zones between two "typical" spreading ridges (f.e. Knipovich ridge); 2. In semi strike-slip/extension zones on the oceanic crust (f.e. American-Antarctic ridge); 3. In the zones of local extension in regional strike-slip areas in pull-apart basins along transform boundaries (Cayman trough, pull-apart basins of the southern border of Scotia plate). Ultra-slow spreading is observed now or could have been observed in the past in the following geodynamic environments on convergent plate boundaries: 1. During back-arc rifting on the stage of transition into back-arc spreading (central

  5. Application of space technology to geodynamics.

    PubMed

    Flinn, E A

    1981-07-03

    Measurements of the movement and deformation of tectonic plates are needed for many research areas in geodynamics, but observations with adequate accuracy and frequency of measurement are not feasible if classical geodetic methods are used. Long-baseline microwave interferometry and laser ranging to Earth satellites are among the new techniques that have been developed within the past decade to make the required measurements. Fixed and mobile stations using both these methods have been constructed in several countries and are now being used in an internationally coordinated research program. Baseline length accuracy better than 2 to 3 centimeters (1 standard deviation) is expected within the next 5 years.

  6. Newton Solver Stabilization for Stokes Solvers in Geodynamic Problems

    NASA Astrophysics Data System (ADS)

    Fraters, Menno; Bangerth, Wolfgang; Thieulot, Cedric; Spakman, Wim

    2017-04-01

    The most commonly used method by the geodynamical community for solving non-linear equations is the Picard fixed-point iteration. However, the Newton method has recently gained interest within this community because it formally leads to quadratic convergence close to the solution as compared to the global linear convergence of the Picard iteration. In mantle dynamics, a blend of pressure and strain-rate dependent visco-plastic rheologies is often used. While for power-law rheologies the Jacobian is guaranteed to be Symmetric Positive Definite (SPD), for more complex (compressible) rheologies, the Jacobian may become non-SPD. Here we present a new method for efficiently enforce the Jacobian to be SPD, necessary for our current highly efficient Stokes solvers, with a minimum loss in convergence rate. Furthermore, we show results for both incompressible and compressible models.

  7. Arctic region: new model of geodynamic history

    NASA Astrophysics Data System (ADS)

    Nikishin, Anatoly; Kazmin, Yuriy; Malyshev, Nikolay; Morozov, Andrey; Petrov, Eugene

    2014-05-01

    Basement of the Arctic shelf areas is characterizes with a complex structure. Age of the defined domains is early Pre-Cambrian, Neoproterozoic to Cambrian (Timanian and Baykalian), early-middle Paleozoic (Caledonian) and late Paleozoic (Uralian, Taimyrian and Ellesmerian). Mesozoic deformations affected Novaya Zemlya, Southern Taimyr and southern parts of the Laptev Sea, the East Siberian Sea, and the Chukchi Sea regions. There are several Paleozoic rift-postrift basins. The North Kara Basin and the Timan-Pechora Basin was formed during the early Ordovician time as subduction-related back-arc rift systems. The East-Barents Basin has the same origin but the age of its formation is late Devonian. Carboniferous rifting took place in the Norwegian part of the Barents Sea, the Chukchi Sea (Hanna Trough Basin) and the Sverdrup Basin. There are also rift-postrift basins of the Mesozoic age. Late Permian to Early Triassic rifting took place in the South Kara Basin; it was connected with both collapse of the Uralian Orogen and activity of the Siberian mantle plume. Aptian to Albian rifting was affected with really big area in the Laptev Sea, the East Siberian Sea and the Chukchi Sea right after the De-Long plume-related magmatic event. Paleogene (mainly Eocene) rifting was also widely spread in these areas. The Arctic Ocean consists of three main domains: the Canada Basin, Alpha-Mendeleev-Podvodnikov-Makarov domain, and the Eurasia Basin. The Canada Basin is a typical oceanic one. There are many uncertainties in the definition of spreading age, but in accordance with the prevalent point of view, it should be early Cretaceous, Neocomian. Alpha-Mendeleev-Podvodnikov-Makarov domain is an enigmatic region. We propose the following scenario for the formation of this domain: Aptian to Cenomanian plume-related large-scale intraplate basalt magmatism was followed by Albian to late Cretaceous rifting. Few axes of rifting were nearly orthogonal to the pre-existing one in the Canada Basin. The Alpha-Mendeleev Ridge is a rifted continental terrane covered by pre-rift basalts. The Eurasian Basin is a small oceanic one. Defined age of spreading is 56-0 Ma. The basin is characterized by a very slow spreading rate. Eocene to recent sediments covers the system of prominent linear ranges and valleys of former mid-oceanic ridge. The Lomonosov Ridge is a well known continental terrane dissected by Neogene-Quaternary faults. New data shows that the area of the Lomonosov and the Alpha-Mendeleev ridges was affected by strong Neogene to recent extension or transtension tectonics with the formation of numerous normal faults and related topographic highs and valleys. Recent bathymetry of these ridges is a result of this Neogene to recent tectonics. Our report is based on a new set of seismic lines in the Russian part of the Arctic region.

  8. A Geodynamical Perspective on the Subduction of Cocos and Rivera plates beneath Mexico and Central America

    NASA Astrophysics Data System (ADS)

    Constantin Manea, Vlad; Manea, Marina; Ferrari, Luca

    2013-04-01

    The Middle America subduction zone (MASZ) is one of the world most complex convergent margins as it involves the subduction of the Rivera and Cocos young oceanic plates beneath the North American and Caribbean plates and is bounded by the Gulf of California rift and the Panama slab window. Characterized by contorted and unusual slab geometry, irregularly distributed seismicity and volcanism, exceptionally large slow slip events (SSE) and non-volcanic tremors (NVT), this subduction system represents a great natural laboratory for better understanding geodynamic processes at a fundamental level. Based on a solid observational foundation, and incorporating the latest experimental results into a coherent geodynamical framework, we shed light on the main processes controlling the subduction system evolution in this region. The tectonics, volcanism, slab geometry and segmentation along the margin are reviewed from a geodynamical perspective. We proposed and discussed a series of evolutionary scenarios for the Mexican and Central American subduction zones, providing a coherent starting base for future geodynamical modeling studies tailored to this active margin. We discuss comparatively the recently discovered SSEs and NVTs along the MASZ, and try to differentiate among the proposed mechanisms responsible for these observations. Finally we discuss the recent seismic anisotropy observations in a geodynamic context, offering an integrated view of mantle flow pattern along the entire active margin. Although the MASZ as a whole may be considered a fairly complicated region with many unusual features and sometimes controversial interpretations, its complexity and unusual characteristics can improve our knowledge about the linkage between deep and surface processes associated with subduction zone dynamics.

  9. A geodynamical perspective on the subduction of Cocos and Rivera plates beneath Mexico and Central America

    NASA Astrophysics Data System (ADS)

    Manea, V. C.; Manea, M.; Ferrari, L.

    2013-12-01

    The Middle America subduction zone (MASZ) is one of the world’ most complex convergent margins as it involves the subduction of the Rivera and Cocos young oceanic plates beneath the North American and Caribbean plates and is bounded by the Gulf of California rift and the Panama slab window. Characterized by contorted and unusual slab geometry, irregularly distributed seismicity and volcanism, exceptionally large slow slip events (SSE) and non-volcanic tremors (NVT), this subduction system represents a great natural laboratory for better understanding geodynamic processes at a fundamental level. Based on a solid observational foundation, and incorporating the latest experimental results into a coherent geodynamical framework, we shed light on the main processes controlling the subduction system evolution in this region. The tectonics, volcanism, slab geometry and segmentation along the margin are reviewed from a geodynamical perspective. We proposed and discussed a series of evolutionary scenarios for the Mexican and Central American subduction zones, providing a coherent starting base for future geodynamical modeling studies tailored to this active margin. We discuss comparatively the recently discovered SSEs and NVTs along the MASZ, and try to differentiate among the proposed mechanisms responsible for these observations. Finally we discuss the recent seismic anisotropy observations in a geodynamic context, offering an integrated view of mantle flow pattern along the entire active margin. Although the MASZ as a whole may be considered a fairly complicated region with many unusual features and sometimes controversial interpretations, its complexity and unusual characteristics can improve our knowledge about the linkage between deep and surface processes associated with subduction zone dynamics.

  10. A Geodynamical Perspective on the Subduction of Cocos and Rivera plates beneath Mexico and Central America

    NASA Astrophysics Data System (ADS)

    Manea, V.; Manea, M.; Ferrari, L.

    2013-05-01

    The Middle America subduction zone (MASZ) is one of the world most complex convergent margins as it involves the subduction of the Rivera and Cocos young oceanic plates beneath the North American and Caribbean plates and is bounded by the Gulf of California rift and the Panama slab window. Characterized by contorted and unusual slab geometry, irregularly distributed seismicity and volcanism, exceptionally large slow slip events (SSE) and non-volcanic tremors (NVT), this subduction system represents a great natural laboratory for better understanding geodynamic processes at a fundamental level. Based on a solid observational foundation, and incorporating the latest experimental results into a coherent geodynamical framework, we shed light on the main processes controlling the subduction system evolution in this region. The tectonics, volcanism, slab geometry and segmentation along the margin are reviewed from a geodynamical perspective. We proposed and discussed a series of evolutionary scenarios for the Mexican and Central American subduction zones, providing a coherent starting base for future geodynamical modeling studies tailored to this active margin. We discuss comparatively the recently discovered SSEs and NVTs along the MASZ, and try to differentiate among the proposed mechanisms responsible for these observations. Finally we discuss the recent seismic anisotropy observations in a geodynamic context, offering an integrated view of mantle flow pattern along the entire active margin. Although the MASZ as a whole may be considered a fairly complicated region with many unusual features and sometimes controversial interpretations, its complexity and unusual characteristics can improve our knowledge about the linkage between deep and surface processes associated with subduction zone dynamics.

  11. Lithosphere-scale geodynamics in the Rhodope: assumptions and implications

    NASA Astrophysics Data System (ADS)

    Moulas, Evangelos; Burg, Jean-Pierre; Kostopoulos, Dimitrios; Schenker, Filippo

    2014-05-01

    The Rhodope Metamorphic Complex (RMC) is a synmetamorphic nappe stack located in the hinterland of the Hellenide orogen which is part of the Alpine-Himalayan chain. Advances in analytical instrumentation in petrology over the last 10 years made possible the documentation of high-to ultrahigh-pressure conditions in this complex. Despite the wealth of petrologic P-T-t data and the multitude of generic models on the evolution of the RMC, only few geodynamic restorations project long enough back in time to cover the entire life span of the orogen since the Jurassic. There are many reasons for the different (and often contrasting) models proposed for the RMC that deserve to be mentioned. Here, we present the different reconstructions published together with the assumptions on which they were built and their geodynamic implications. We then proceed to carefully assess those implications individually from the mineral to the lithosphere scale. Our assessment poses important constrains on the pressure, temperature and deformation history of the complex on a regional scale that cannot be satisfied by all reconstructions. Such constrains involve the length of the subducting plate, the thermal histories of the metamorphic rocks, the age response of the isotopic systems and last, but not least, the structural record of km-scale movements that can be identified in the field. In addition, the presence of ultrahigh-pressure rocks is restricted to shear zones all across the RMC and this requires an explanation. We examine the possibility of non-lithostatic pressure variations within crustal-scale ductile shear zones.

  12. A Feasibility Study of Space VLBI for Geodesy and Geodynamics

    NASA Astrophysics Data System (ADS)

    Kulkarni, Madhav Narayan

    1992-01-01

    Space Very Long Baseline Interferometry (VLBI) is an extension of the ground based VLBI to the space. With the launching of two or more Space VLBI satellites in the future, Space VLBI observations will be available for astrometric, geodetic and geodynamic applications. This new technique holds potential for various important applications including monitoring Earth rotation and interconnection of the reference frames used in geodesy and geodynamics. The aim of this feasibility study has been to investigate the possibility of precise estimation of geodetic parameters, with emphasis on the Earth rotation parameters (ERP's), from Space VLBI observations. A brief description of the Space VLBI technique, it's possible applications, and the Space VLBI missions being planned has been given. Estimability analysis to investigate the estimability of geodetic parameters from Space VLBI observations has been carried out and a simplified mathematical model is derived in terms of estimable parameters. Results of sensitivity analysis carried out to study the sensitivity of the Space VLBI observables to the geodetic parameters of interest, including the number of these parameters and random errors in their a priori values, have been presented. Some of the dominant systematic effects including atmospheric refraction, solar radiation pressure and relativistic effects have also been investigated. Simulation studies have been carried out to study the influence of these systematic effects and a priori information on the estimation of the Earth rotation parameters. The results from the simulation studies indicate that it may be possible to use the Space VLBI technique for monitoring Earth rotation and polar motion, only if the orbital systematic effects can be modeled to a high degree of accuracy (or the satellites can be tracked, with high accuracy, independently), and precise a priori information on station coordinates from other sources is used. A brief description of the Space VLBI

  13. Applying multi-resolution numerical methods to geodynamics

    NASA Astrophysics Data System (ADS)

    Davies, David Rhodri

    Computational models yield inaccurate results if the underlying numerical grid fails to provide the necessary resolution to capture a simulation's important features. For the large-scale problems regularly encountered in geodynamics, inadequate grid resolution is a major concern. The majority of models involve multi-scale dynamics, being characterized by fine-scale upwelling and downwelling activity in a more passive, large-scale background flow. Such configurations, when coupled to the complex geometries involved, present a serious challenge for computational methods. Current techniques are unable to resolve localized features and, hence, such models cannot be solved efficiently. This thesis demonstrates, through a series of papers and closely-coupled appendices, how multi-resolution finite-element methods from the forefront of computational engineering can provide a means to address these issues. The problems examined achieve multi-resolution through one of two methods. In two-dimensions (2-D), automatic, unstructured mesh refinement procedures are utilized. Such methods improve the solution quality of convection dominated problems by adapting the grid automatically around regions of high solution gradient, yielding enhanced resolution of the associated flow features. Thermal and thermo-chemical validation tests illustrate that the technique is robust and highly successful, improving solution accuracy whilst increasing computational efficiency. These points are reinforced when the technique is applied to geophysical simulations of mid-ocean ridge and subduction zone magmatism. To date, successful goal-orientated/error-guided grid adaptation techniques have not been utilized within the field of geodynamics. The work included herein is therefore the first geodynamical application of such methods. In view of the existing three-dimensional (3-D) spherical mantle dynamics codes, which are built upon a quasi-uniform discretization of the sphere and closely coupled

  14. Present-day geodynamics of the northern North American Cordillera

    NASA Astrophysics Data System (ADS)

    Finzel, Emily S.; Flesch, Lucy M.; Ridgway, Kenneth D.

    2014-10-01

    Diffuse continental deformation results from interactions at plate boundaries, buoyancy forces generated by gradients in gravitational potential energy, and loads applied to the base of the lithosphere. Using finite element models, we calculate a deviatoric stress field associated with buoyancy forces, and then perform an iterative inversion to calculate deviatoric stress fields associated with boundary forces in the northern North American Cordillera. Our results reveal the presence of two distinct geodynamic domains. In the outboard domain, approximately equal magnitudes of boundary and buoyancy forces can account for the observed deformation along the Aleutian megathrust. In contrast, large boundary forces related to subduction of the Pacific and Yakutat slabs dominate the force-balance in south-central Alaska and combine with relatively small buoyancy forces to reproduce the observed kinematic indicators. In the inboard domain, encompassed by interior and northern Alaska and western Canada, boundary and buoyancy forces alone cannot reproduce the observed deformation. Therefore, we infer that deviatoric stresses due to basal tractions from a deeper mantle convection cell contribute to surface deformation in the inboard domain. Low effective lithospheric viscosity in south-central Alaska and the balancing effect of an independent geodynamic system driven by basal tractions in northern Alaska combine to confine the anomalously large Yakutat-related boundary deviatoric stresses to south-central Alaska. Deviatoric stresses associated with flat-slab subduction of the Yakutat microplate are a factor of two greater than boundary force estimates for the Andean and Indian-Eurasian convergent margins, where buoyancy and boundary forces are roughly equal in magnitude and dominate the force-balance.

  15. Geodynamic evolution of the Earth over 600 Ma: implications for palaeo-climatic indicators

    NASA Astrophysics Data System (ADS)

    Hochard, C.; Vérard, C.

    2011-12-01

    During the last decades numerous local reconstructions were developed by the Geodynamic School of Lausanne. They participated to the elaboration of a 600Ma to present global plate tectonics model* based on field geology and controlled by geometric and kinematic constraints. Plate tectonics principles and lithospheric behaviour were applied to the model that drastically differs from the continental drift approach (i.e. based on palaeomagnetic data). Step after step lithospheric plates were reconstructed by adding or removing oceanic material (symbolized by synthetic isochrones) to major continents. The geodynamic evolution obtained is thus physically coherent and covers the whole surface of the Earth for the Phanerozoic. In the present contribution, we detail the basic tectonic features making up the model and the way they can be tested against the main palaeoclimatic indicators. Using synthetic isochrones, we developed a series of ocean lithosphere age maps. Based on plate rotation poles we computed velocity maps showing accretion and convergence rates. Converting ages into lithosphere thicknesses we quantified the volume of subducting material. Such tectonic parameters can be compared with the evolution of chemical proxies (e.g. CO2, δ18O, 87Sr/86Sr, Mg/Ca, SO4) offering a different way to decipher long-term climate changes. * This work was carried out as part of work done within the research program of the University of Lausanne on the Stampfli geodynamic model, model which is now owned by Neftex Petroleum Consultants Ltd. and is now attached to the "Neftex Earth Model ".

  16. Magmatism and Geodynamics of Eastern Turkey

    NASA Astrophysics Data System (ADS)

    Keskin, Mehmet; Oyan, Vural; Sharkov, Evgenii V.; Chugaev, Andrey V.; Genç, Ş. Can; Ünal, Esin; Aysal, Namık; Duru, Olgun; Kavak, Orhan

    2013-04-01

    phan volcanoes) and plateaus (e.g. The Erzurum-Kars Plateau) around the Mediterranean region. Our melting models indicate that there is a temporal change in source characteristics across the collision zone from a garnet-dominated deeper mantle-source during the Miocene to a spinel-dominated shallower source during the Quaternary. Our AFC and EC-AFC models reveal that the importance of the AFC process decreased broadly in time while each volcano experienced a unique replenishment and fractionation history. On the basis of the results from our geochemical data and petrologic models, we argue that the temporal and spatial changes in the chemistry of volcanics across the region are the reflections of the geodynamic events that controlled the movement and interaction of mantle domains with contrasting geochemical, isotopic and mineralogical identities. Compositions of some of the primitive magmas were further modified via interactions with the lithospheric mantle and/or crustal material coupled with fractionation en route to the surface.

  17. An efficient and general approach for implementing thermodynamic phase equilibria information in geophysical and geodynamic studies

    NASA Astrophysics Data System (ADS)

    Afonso, Juan Carlos; Zlotnik, Sergio; Díez, Pedro

    2015-10-01

    We present a flexible, general, and efficient approach for implementing thermodynamic phase equilibria information (in the form of sets of physical parameters) into geophysical and geodynamic studies. The approach is based on Tensor Rank Decomposition methods, which transform the original multidimensional discrete information into a separated representation that contains significantly fewer terms, thus drastically reducing the amount of information to be stored in memory during a numerical simulation or geophysical inversion. Accordingly, the amount and resolution of the thermodynamic information that can be used in a simulation or inversion increases substantially. In addition, the method is independent of the actual software used to obtain the primary thermodynamic information, and therefore, it can be used in conjunction with any thermodynamic modeling program and/or database. Also, the errors associated with the decomposition procedure are readily controlled by the user, depending on her/his actual needs (e.g., preliminary runs versus full resolution runs). We illustrate the benefits, generality, and applicability of our approach with several examples of practical interest for both geodynamic modeling and geophysical inversion/modeling. Our results demonstrate that the proposed method is a competitive and attractive candidate for implementing thermodynamic constraints into a broad range of geophysical and geodynamic studies. MATLAB implementations of the method and examples are provided as supporting information and can be downloaded from the journal's website.

  18. Geodynamic Inversion to Constrain the Nonlinear Rheology of the Lithosphere

    NASA Astrophysics Data System (ADS)

    Kaus, B.; Baumann, T.

    2015-12-01

    The rheology of the lithosphere is of key importance for the physics of the lithosphere. Yet, it is probably the most uncertain parameter in geodynamics as experiments have to be extrapolated to geological conditions and as existing geophysical methods such as EET estimation make simplifying assumptions about the structure of the lithosphere. Here, we therefore discuss a new method that employs thermo-mechanical lithospheric-scale forward models of the lithosphere using a realistic initial geometry constructed from geophysical data sets. We employ experimentally determined creep-laws for the various parts of the lithosphere, but assume that the parameters of these creep-laws as well as the temperature structure of the lithosphere are uncertain. This is used as a priori information to formulate a Bayesian inverse problem that employs topography, gravity, horizontal and vertical surface velocities to invert for the unknown material parameters and temperature structure. In order to test the general methodology, we first perform a geodynamic inversion of a synthetic forward model of intraoceanic subduction with known parameters. This requires solving an inverse problem with 14-16 parameters, depending on whether temperature is assumed to be known or not. With the help of a massively parallel direct-search combined with a Markov Chain Monte Carlo method, solving the inverse problem becomes feasible. Results show that the rheological parameters and particularly the effective viscosity structure of the lithosphere can be reconstructed in a probabilistic sense. This also holds, with somewhat larger uncertainties, for the case where the temperature distribution is parametrized. Finally, we apply the method to a cross-section of the India-Asia collision system. In this case, the number of parameters is larger, which requires solving around 1.9 × 106 forward models. The resulting models fit the data within their respective uncertainty bounds, and show that the Indian mantle

  19. Geodynamical implication of delamination on felsic crust generation during the Archean

    NASA Astrophysics Data System (ADS)

    Piccolo, Andrea; Kaus, Boris; Palin, Richard; White, Richard; Johnson, Tim

    2017-04-01

    The geodynamic processes that were active during the Archean remain enigmatic. On the basis of geochemical and geological data, several working hypotheses exist, which suggest that the most crucial unsolved problems are: a) when and how was felsic crust generated and did this have geodynamic implications? b) how did cratonic lithosphere form and survive? c) did plate tectonics exist? Here, we test the feasibility of some of these hypothesis with a modeling approach, in which we couple chemical evolution and melt extraction using state-of-the art mafic thermodynamic melting models with a viscoelastoplastic geodynamic finite element code. In our simulations, we test the effect of rheology of the mafic crust, melt weakening, the amount of intrusion, and the amount of melt extraction on the geodynamic deformation mode. Our simulations show that under particular conditions, a plate like behavior occurs for a short amount of time, but also that the most stable mode of crustal recycling during the Archean is delamination of the eclogitic/restitic mafic crust. Delamination of the lower crust occurs rapidly and completely destroys the lithospheric mantle, putting the hot asthenosphere in direct contact with the mafic crust, which inducing a continuous generation of felsic crust. Continuous crustal delamination triggers significant mantle melting and thus mafic crust generation, and produces a cold crust similar to the recently proposed heat pipe model. This results in rapid mantle cooling, which suggest that the average cooling rate of the Earth has not been constant but rather fluctuated with time. Our results show that delamination processes has several implication on felsic crust production and on the preservation of the lithospheric mantle. Providing useful insight to understand the close relation between crust and mantle.

  20. Exploring problems in tectonics and geodynamics with seismology

    NASA Astrophysics Data System (ADS)

    Walker, Kristoffer T.

    I demonstrate in two different studies how seismology can be a powerful tool for exploring and testing tectonic/geodynamic problems. In the first study, I analyze, model, and interpret a deep marine seismic reflection/refraction, magnetics, gravity, and bathymetric profile collected across the Bristol Bay basin, a back-arc basin in the southeast Bering Sea. I test three leading models for basin subsidence, and show that the basin evolved due to both faulting and flexural subsidence associated with extension and volcanic loading of the arc. The second study is an investigation of mantle fabrics around hotspots (Eifel, Hawaii, and eastern Nevada) and beneath part of the East African Plateau (Tanzania and Kenya). I analyze, model, and interpret the splitting of teleseismic shear-waves that originate from earthquakes to determine the orientation and magnitude of seismic velocity anisotropy, which allows me to place constraints on the orientation, magnitude, and depth of mantle deformation fabrics. I show that the fabrics around hotspots are explained best as a result of current deformation associated with parabolic asthenospheric flow (PAF), the horizontal asthenospheric flow associated with the interaction of gravitationally spreading plume material with an asthenosphere that is being dragged in the direction of plate motion. The success of the PAF model in fitting the data suggests that strong anisotropy exists in the asthenosphere, which means that dislocation creep is an important deformation mechanism beneath some hotspots. It also suggests that plume-lithosphere interaction is dominated by laminar flow. Perhaps the most important implication is that shear-wave splitting can be used as a diagnostic to test between upwelling and non-upwelling sources for mantle hotspots, and can provide estimates of geodynamic parameters beneath regions of thin mantle lithosphere. Splitting beneath the East African Plateau appears to be due to asthenospheric anisotropy associated

  1. Late Cenozoic Basin Architecture in Central Turkey: Geodynamic Implications

    NASA Astrophysics Data System (ADS)

    Gurbuz, A.; Kazanci, N.

    2014-12-01

    The Lake Tuz basin is the largest intracontinental basin in Turkey and has hydrocarbon and industrial mineral reserves. Thus, there are several studies particularly intended for the pre-Neogene geology of the basin. However, there is not any detailed study related to the geological units of Neogene and Quaternary periods. This study aims to exhibit facies features of these units within spatial and temporal distributions according to field studies. In the other hand, the region has modelled through stratigraphically by computing more than 250 borehole data within 3D GeoScientific Information System. In light of obtained model, basement topographies of Neogene and Quaternary units has revealed. The model indicate high amounts of sedimentation during the Mio-Pliocene with a southward increasing thickness of a freshwater lake basin while it is a shallow saline lake basin today that regressed towards the north during the Plio-Quaternary. The combination of these results with regional geological and geophysical data (i.e. gravity and crustal thickness) allows geodynamic implications for central Turkey. The spatio-temporal variations of Late Cenozoic units reflect the main effect of endogenic forces that were caused due to lithospheric slab break-off and following asthenospheric upwelling under central Turkey.

  2. Singular Spectrum Analysis in Astrometry and Geodynamics

    NASA Astrophysics Data System (ADS)

    Vityazev, V. V.; Miller, N. O.; Prudnikova, E. Ja.

    2010-10-01

    The paper presents the possibilities of the Singular Spectrum Analyses on the examples of its application to several astrometric and geodynamic time series. The comparisons of results obtained by other often used methods (Fourier transform, Wavelet Transform, different filter methods) are given. The Singular Spectrum Analyses method was used for the investigation of the Chandler wobble (CW), which was extracted from the IERS Pole coordinates and latitude variations at Pulkovo. The CW amplitude and phase variations were examined by means of the Hilbert transform. The main conclusion which can be made from this study is: we have found two epochs of deep CW amplitude decreases near 1850 and 2005, which are also accompanied by a large phase jump, similar to well known event in 1920s. The investigation of first latitude observations at Pulkovo (1840-1855) was executed with the aim to gain and analyse the sum of Chandler and annual components from very small quantity of very noisy observations. The SSA is applied for investigation of the zenith troposphere delay time-series derived from observations of several VLBI stations. Combined IVS time-series of the zenith wet and total troposphere delays obtained in IGG were used for analysis. For all stations under consideration the non-linear trends and the seasonal components with annual and semiannual periods were found. Some interesting peculiarities were found to be individual for every stations. Comparison of the trends with meteorological parameters is also presented.

  3. High Speed Networking and Large-scale Simulation in Geodynamics

    NASA Technical Reports Server (NTRS)

    Kuang, Weijia; Gary, Patrick; Seablom, Michael; Truszkowski, Walt; Odubiyi, Jide; Jiang, Weiyuan; Liu, Dong

    2004-01-01

    Large-scale numerical simulation has been one of the most important approaches for understanding global geodynamical processes. In this approach, peta-scale floating point operations (pflops) are often required to carry out a single physically-meaningful numerical experiment. For example, to model convective flow in the Earth's core and generation of the geomagnetic field (geodynamo), simulation for one magnetic free-decay time (approximately 15000 years) with a modest resolution of 150 in three spatial dimensions would require approximately 0.2 pflops. If such a numerical model is used to predict geomagnetic secular variation over decades and longer, with e.g. an ensemble Kalman filter assimilation approach, approximately 30 (and perhaps more) independent simulations of similar scales would be needed for one data assimilation analysis. Obviously, such a simulation would require an enormous computing resource that exceeds the capacity of a single facility currently available at our disposal. One solution is to utilize a very fast network (e.g. 10Gb optical networks) and available middleware (e.g. Globus Toolkit) to allocate available but often heterogeneous resources for such large-scale computing efforts. At NASA GSFC, we are experimenting with such an approach by networking several clusters for geomagnetic data assimilation research. We shall present our initial testing results in the meeting.

  4. High Speed Networking and Large-scale Simulation in Geodynamics

    NASA Technical Reports Server (NTRS)

    Kuang, Weijia; Gary, Patrick; Seablom, Michael; Truszkowski, Walt; Odubiyi, Jide; Jiang, Weiyuan; Liu, Dong

    2004-01-01

    Large-scale numerical simulation has been one of the most important approaches for understanding global geodynamical processes. In this approach, peta-scale floating point operations (pflops) are often required to carry out a single physically-meaningful numerical experiment. For example, to model convective flow in the Earth's core and generation of the geomagnetic field (geodynamo), simulation for one magnetic free-decay time (approximately 15000 years) with a modest resolution of 150 in three spatial dimensions would require approximately 0.2 pflops. If such a numerical model is used to predict geomagnetic secular variation over decades and longer, with e.g. an ensemble Kalman filter assimilation approach, approximately 30 (and perhaps more) independent simulations of similar scales would be needed for one data assimilation analysis. Obviously, such a simulation would require an enormous computing resource that exceeds the capacity of a single facility currently available at our disposal. One solution is to utilize a very fast network (e.g. 10Gb optical networks) and available middleware (e.g. Globus Toolkit) to allocate available but often heterogeneous resources for such large-scale computing efforts. At NASA GSFC, we are experimenting with such an approach by networking several clusters for geomagnetic data assimilation research. We shall present our initial testing results in the meeting.

  5. Structural Analysis and Geodynamic Implications of Tessera Terrain, Venus

    NASA Astrophysics Data System (ADS)

    Hansen, V. L.; Willis, J. J.

    1996-03-01

    Understanding processes of tessera formation is fundamental to Venus tectonic and geodynamic models. We examined tessera terrain in Ishtar Terra, crustal plateaus, and as inliers within the plains using high-resolution Magellan SAR imagery. We describe several major types of tesseraeeach found in specific geologic or geomorphic regions. Fold and S-C tessera terrain are found only in Ishtar Terra; lava flow and basin-and-dome terrains reside within the interior of crustal plateaus, whereas folded ribbon terrain and extended folded terrain comprise margins of crustal plateaus; and star terrain lies within central Phoebe. Inliers are divisible into fracture-dominated and graben-dominated tesserae, which may represent ancient flooded coronae-chasmata and crustal plateaus, respectively. Thus tesserae might form in several tectonic environments, including as a result of (1) subsurface flow in Ishtar Terra, (2) as sequences of surface-layer extension and contraction in crustal plateaus, (3) as highly-extended, previously-deformed crustal plateaus which have deflated or sunken, and become flooded and thus preserved as large plains inliers, and (4) as densely-fractured surface layersfractured as a result of corona and chasma formationwhich have since sunken and become flooded, and thus preserved as isolated, scattered, highly-fractured inliers. If these models of formation are correct, tesserae would not form a global onion skin; they would not represent a globally synchronous unit; they would not record a single period of deformation; and it would not infer a single mechanism for tesserae formation.

  6. Geodynamic Effects of Ocean Tides: Progress and Problems

    NASA Technical Reports Server (NTRS)

    Richard, Ray

    1999-01-01

    Satellite altimetry, particularly Topex/Poseidon, has markedly improved our knowledge of global tides, thereby allowing significant progress on some longstanding problems in geodynamics. This paper reviews some of that progress. Emphasis is given to global-scale problems, particularly those falling within the mandate of the new IERS Special Bureau for Tides: angular momentum, gravitational field, geocenter motion. For this discussion I use primarily the new ocean tide solutions GOT99.2, CSR4.0, and TPXO.4 (for which G. Egbert has computed inverse-theoretic error estimates), and I concentrate on new results in angular momentum and gravity and their solid-earth implications. One example is a new estimate of the effective tidal Q at the M_2 frequency, based on combining these ocean models with tidal estimates from satellite laser ranging. Three especially intractable problems are also addressed: (1) determining long-period tides in the Arctic [large unknown effect on the inertia tensor, particularly for Mf]; (2) determining the global psi_l tide [large unknown effect on interpretations of gravimetry for the near-diurnal free wobble]; and (3) determining radiational tides [large unknown temporal variations at important frequencies]. Problems (2) and (3) are related.

  7. Geodynamic and metabolic cycles in the Hadean

    NASA Astrophysics Data System (ADS)

    Russell, M. J.; Arndt, N. T.

    2005-04-01

    High-degree melting of hot dry Hadean mantle at ocean ridges and plumes resulted in a crust about 30km thick, overlain in places by extensive and thick mafic volcanic plateaus. Continental crust, by contrast, was relatively thin and mostly submarine. At constructive and destructive plate boundaries, and above the many mantle plumes, acidic hydrothermal springs at ~400°C contributed Fe and other transition elements as well as P and H2 to the deep ocean made acidulous by dissolved CO2 and minor HCl derived from volcanoes. Away from ocean ridges, submarine hydrothermal fluids were cool (≤100°C), alkaline (pH ~10), highly reduced and also H2-rich. Reaction of solvents in this fluid with those in ocean water was catalyzed in a hydrothermal mound, a natural self-restoring flow reactor and fractionation column developed above the alkaline spring. The mound consisted of brucite, Mg-rich clays, ephemeral carbonates, Fe-Ni sulfide and green rust. Acetate and glycine were the main products, some of which were eluted to the ocean. The rest, along with other organic byproducts were retained and concentrated within Fe-Ni sulfide compartments. These compartments, comprising the natural hydrothermal reactor, consisted partly of greigite (Fe5NiS8). It was from reactions between organic modules confined within these inorganic compartments that the first prokaryotic organism evolved. These acetogenic precursors to the bacteria diversified and migrated down the mound and into the ocean floor to inaugurate the "deep biosphere". Once there they were protected from cataclysmic heating events caused by large meteoritic impacts. Geodynamic forces led to the eventual obduction of the deep biosphere into the photic zone where, initially protected by a thin veneer of sediment, the use of solar energy was mastered and photosynthesis emerged. The further evolution to oxygenic photosynthesis was effected as catalytic [Mn,Ca]-bearing molecules that otherwise would have been interred in

  8. Geodynamic and metabolic cycles in the Hadean

    NASA Astrophysics Data System (ADS)

    Russell, M. J.; Arndt, N. T.

    2004-09-01

    High-degree melting of hot dry Hadean mantle at ocean ridges and plumes resulted in a crust about 30km thick, overlain in places by extensive and thick mafic volcanic plateaus. Continental crust, by contrast, was relatively thin and mostly submarine. At constructive and destructive plate boundaries, and above the many mantle plumes, acidic hydrothermal springs at ~400°C contributed Fe and other transition elements as well as P and H2 to the deep ocean made acidulous by dissolved CO2 and minor HCl derived from volcanoes. Away from ocean ridges, submarine hydrothermal fluids were cool (≤100°C), alkaline (pH ~10), highly reduced and also H2-rich. Reaction of solvents in this fluid with those in ocean water was catalyzed in a hydrothermal mound, a natural self-restoring flow reactor and fractionation column made up of carbonates and freshly precipitated Fe-Ni sulfide and greenrust pores and bubbles, developed above the alkaline spring. Acetate and the amino acetate glycine were the main products, much of which was eluted to the ocean. Other organic byproducts were retained, concentrated and reacted within the compartments. These compartments comprising the natural hydrothermal reactor consisted partly of greigite (Fe5NiS8). It was from reactions between organic modules confined within these inorganic compartments that the first prokaryotic organism evolved. These acetogenic precursors to the Bacteria diversified and migrated down the mound and into the ocean floor to inaugurate the "deep biosphere". Once there the Bacteria, and the recently differentiated Archaea, were protected from cataclysmic heating events caused by large bolide impacts. Geodynamic forces led to the eventual obduction of the deep biosphere into the photic zone where, initially protected by a thin veneer of sediment, the use of solar energy was mastered and photosynthesis emerged. The further evolution to oxygenic photosynthesis was effected as catalytic [CaMn4+] bearing molecules that otherwise

  9. Tightly Coupled Geodynamic Systems: Software, Implicit Solvers & Applications

    NASA Astrophysics Data System (ADS)

    May, D.; Le Pourhiet, L.; Brown, J.

    2011-12-01

    The generic term "multi-physics" is used to define physical processes which are described by a collection of partial differential equations, or "physics". Numerous processes in geodynamics fall into this category. For example, the evolution of viscous fluid flow and heat transport within the mantle (Stokes flow + energy conservation), the dynamics of melt migration (Stokes flow + Darcy flow + porosity evolution) and landscape evolution (Stokes + diffusion/advection over a surface). The development of software to numerically investigate processes that are described through the composition of different physics components are typically (a) designed for one particular set of physics and are never intended to be extended, or coupled to other processes (b) enforce that certain non-linearity's (or coupling) are explicitly removed from the system for reasons of computational efficiency, or due the lack of a robust non-linear solver (e.g. most models in the mantle convection community). We describe a software infrastructure which enables us to easily introduce new physics with minimal code modifications; tightly couple all physics without introducing splitting errors; exploit modern linear/non-linear solvers and permit the re-use of monolithic preconditioners for individual physics blocks (e.g. saddle point preconditioners for Stokes). Here we present a number of examples to illustrate the flexibility and importance of using this software infra-structure. Using the Stokes system as a prototype, we show results illustrating (i) visco-plastic shear banding experiments, (ii) how coupling Stokes flow with the evolution of the material coordinates can yield temporal stability in the free surface evolution and (iii) the discretisation error associated with decoupling Stokes equation from the heat transport equation in models of mantle convection with various rheologies.

  10. ELEFANT: a user-friendly multipurpose geodynamics code

    NASA Astrophysics Data System (ADS)

    Thieulot, C.

    2014-07-01

    A new finite element code for the solution of the Stokes and heat transport equations is presented. It has purposely been designed to address geological flow problems in two and three dimensions at crustal and lithospheric scales. The code relies on the Marker-in-Cell technique and Lagrangian markers are used to track materials in the simulation domain which allows recording of the integrated history of deformation; their (number) density is variable and dynamically adapted. A variety of rheologies has been implemented including nonlinear thermally activated dislocation and diffusion creep and brittle (or plastic) frictional models. The code is built on the Arbitrary Lagrangian Eulerian kinematic description: the computational grid deforms vertically and allows for a true free surface while the computational domain remains of constant width in the horizontal direction. The solution to the large system of algebraic equations resulting from the finite element discretisation and linearisation of the set of coupled partial differential equations to be solved is obtained by means of the efficient parallel direct solver MUMPS whose performance is thoroughly tested, or by means of the WISMP and AGMG iterative solvers. The code accuracy is assessed by means of many geodynamically relevant benchmark experiments which highlight specific features or algorithms, e.g., the implementation of the free surface stabilisation algorithm, the (visco-)plastic rheology implementation, the temperature advection, the capacity of the code to handle large viscosity contrasts. A two-dimensional application to salt tectonics presented as case study illustrates the potential of the code to model large scale high resolution thermo-mechanically coupled free surface flows.

  11. Operations of the International GPS Geodynamics Service (IGS)

    NASA Technical Reports Server (NTRS)

    Beutler, G.; Neilan, R.; Mueller, I.

    1993-01-01

    This paper focuses on the operations, organization, and interfaces of the International GPS Geodynamics Service (IGS) which is expected to contribute to geodesy for many years to come. It briefly summarizes the history of the IGS, reports on IGS '92 campaign activities, and describes the current IGS terms of reference and proposal status.

  12. Constraining Mantle Heterogeneities with Joint Inversions of Seismic, Geodynamic, and Mineral Physics Data

    NASA Astrophysics Data System (ADS)

    Lu, C.; Grand, S. P.; Forte, A. M.; Simmons, N. A.

    2014-12-01

    Two outstanding goals of solid earth geophysics are to determine the chemical structure of the Earth and to understand the dynamics of its interior. The dynamics of the mantle are controlled by density variations and combined knowledge of density structure and seismic velocities provide the strongest constraints on chemical heterogeneity. Unfortunately, most of the traditional geophysical methods such as seismic tomography and geodynamic modeling alone cannot adequately resolve the density structure within the mantle. Thus, seismic, geodynamic and mineral physics joint inversion methods have been applied to better understand the dynamics of the mantle in recent years (e.g. Simmons et al. 2010). In these joint inversions, P wave and S wave travel times, as well as four convection-related geodynamic observations (free air gravity, tectonic plate motion, dynamic topography, and the excess ellipticity of the core-mantle boundary) can be used to produce 3-D models of density and seismic velocities simultaneously. The approach initially attempts to find a model that assuming temperature controls lateral variations in mantle properties and then to consider more complicated lateral variations that account for the presence of chemical heterogeneity to further fit data. Here we present new joint inversion results include 50% more new S wave travel time data than in previous work and geodynamic data that extend to larger spherical harmonic degrees. In addition, temperature derivatives of P and S velocity and density have been determined using an updated mineral physics dataset. For the first time we include non-linear anelastic temperature effects on velocities in the joint inversion. The anelastic effects decrease the required high density component within the lower mantle superplumes. The hypothesis that temperature variations explain most observed heterogeneity within the mantle is consistent with our data. Reference: Simmons, N. A., A. M. Forte, L. Boschi, and S. P. Grand

  13. Planetary cores: a geodynamic perspective (Invited)

    NASA Astrophysics Data System (ADS)

    Nimmo, F.

    2010-12-01

    How can measurements of planetary core materials improve our understanding of their geodynamical behaviour? Here I will focus on three aspects of this questions: 1) core formation; 2) the growth and rheology of solid cores; 3) dynamo activity. Core formation occurs either due to the heat generated by short-lived nuclides (for small bodies) or due to gravitational energy released during impacts (for large bodies) [1]. Core formation results in elemental fractionation; such fractionation depends on P,T and oxygen fugacity [2], and for Earth-mass bodies occurs as a succession of discrete events. Experimental measurements of siderophile element partition coefficients are necessary to infer conditions during accretion, though these inferences are non-unique [3]. Core formation may also lead to isotopic fractionation of elements such as Si [4] and Fe [5], although the latter in particular is currently uncertain and merits further experimental investigation. Core solidification depends on the slopes of the adiabat and melting curve, and on the concentration and nature of the light element(s) present [6,7]. Solidification may proceed from outside in (for small bodies) or from inside out (for larger bodies); the solid may be either lighter or heavier than the fluid, depending on the core composition. Thus, core solidification is complex and poorly understood; for instance, Ganymede and Mercury’s cores may be in a completely different solidification regime to that of the Earth [8,9]. Solidification can also vary spatially, giving rise to inner core seismological structure [10,11]. The viscosity of a solid inner core is an important and poorly constrained parameter [12] which controls core deformation, core-mantle coupling and tidal heating. Super-Earths probably lack solid inner cores [13], though further high-P experimental data are needed. Core dynamos are usually thought to be driven by compositional or thermal buoyancy [14] , with the former effect dominant for small

  14. Geodynamic Evolution of the Banda Sea Region

    NASA Astrophysics Data System (ADS)

    Kaymakci, N.; Decker, J.; Orange, D.; Teas, P.; Van Heiningen, P.

    2013-12-01

    We've carried out a large on- and offshore study in Eastern Indonesia to characterize the major structures and to provide constraints on the Neogene geodynamic evolution of the Banda Sea region. The onshore portion utilized remote sensing data and published geology. We tied the onshore to the offshore using recently acquired high resolution bathymetric data (16m and 25m bin size) and 2D seismic profiles that extend from Sulawesi in the west to Irian Jaya in the east across the northern part of the Banda Arc. We interpret the northern boundary of the 'Birds Head' (BH) of Papua, the Sorong Fault, to be a sinistral strike-slip fault zone with a minimum of 48 km displacement over the last few million years. The western boundary fault of Cendrawasih Basin defines the eastern boundary of BH and corresponds to the Wandamen Peninsula which comprises high pressure metamorphic rocks, including eclogite and granulite facies rocks, with exhumation ages from 4 to 1 Ma. Earthquake focal mechanism solutions indicate that the eastern boundary of BH is linked with a large scale offshore normal fault which we suggest may be related to the exhumation of the Wandamen Peninsula. The eastern boundary of Cendrawasih Basin is defined by a large transpressive belt along which BH is decoupled from the rest of Papua / Irian Jaya. This interpretation is supported by recent GPS studies. We propose that the BH and the Pacific plate are coupled, and therefore the Birds Head is therefore completely detached from Irian Jaya. Furthermore, Aru Basin, located at the NE corner of Banda Arc, is a Fault-Fault-Transform (FFT) type triple junction. According to available literature information the Banda Sea includes three distinct basins with different geologic histories; the North Banda Sea Basin (NBSB) was opened during 12-7 Ma, Wetar-Damar Basin (WDB) during 7-3.5 Ma and Weber Basin (WB) 3-0 Ma. Our bathymetric and seismic data indicated that the NBSB and Weber Basin lack normal oceanic crust and are

  15. Geophysical Monitoring of Geodynamic Processes of Central Armenia Earth Crust

    NASA Astrophysics Data System (ADS)

    Avetyan, R.; Pashayan, R.

    2016-12-01

    The method of geophysical monitoring of earth crust was introduced. It allows by continuous supervision to track modern geodynamic processes of Armenia. Methodological practices of monitoring come down to allocation of a signal which reflects deformation of rocks. The indicators of deformations are not only deviations of geophysical indicators from certain background values, but also parameters of variations of these indicators. Data on changes of parameters of barometric efficiency and saw tooth oscillations of underground water level before seismic events were received. Low-amplitude periodic fluctuations of water level are the reflection of geodynamic processes taking place in upper levels of earth crust. There were recorded fluctuations of underground water level resulting from luni-solar tides and enabling to control the systems of borehole-bed in changes of voluminous deformations. The slow lowering (raising) of underground water level in the form of trend reflects long-period changes of stress-deformative state of environment. Application of method promotes identification of medium-term precursors on anomalous events of variations of geomagnetic field, change of content of subsoil radon, dynamics of level of underground water, geochemistry and water temperature. Increase of activity of geodynamic processes in Central Armenian tectonic complex is observed to change macro component Na+, Ca2+, Mg2-, CL-, SO42-, HCO3-, H4SiO4, pH and gas - CO2 structure of mineral water. Modern geodynamic movements of earth crust of Armenia are the result of seismic processes and active geodynamics of deep faults of longitudinal and transversal stretching. Key Words: monitoring, hydrogeodynamics, geomagnetic field, seismicity, deformation, earth crust

  16. Vertically Coherent Deformation in Tibet and Its Geodynamic Implications

    NASA Astrophysics Data System (ADS)

    Liu, M.; Sandvol, E. A.; Yang, Y.; Ceylan, S.

    2009-12-01

    One important discovery from intensive studies of the Tibetan Plateau in the past decade is the apparent agreement between the strain fields of the Tibetan crust and the upper mantle. The geodynamic implications of this vertically coherent deformation (VCD) is currently being debated. Some have interpreted it as indicating a strong mechanical coupling between the crust and the mantle lithosphere, which is discordant with the evidence of a weak, flowing lower crust under Tibet. Here we present new datasets of the crustal and inferred mantle strain fields in the Tibetan Plateau, and explore their controlling factors in a three-dimensional viscous flow model. We recalculated the crustal strain field from updated GPS data, and measured shear wave splitting from the new data sets generated by nearly 250 stations in eastern Tibet, and combined these results with surface wave tomography to constrain the three dimensional anisotropic structure in the Tibetan plateau, including the Rayleigh wave azimuthal anisotropy in the lower crust. While the pattern of shear wave splitting from this new and expanded datasets is in general agreement with previous results, we found important local variations, especially across the Bangong-Nujing suture zone, and significant azimuthal anisotropy in the lower crust. These variations indicate lithospheric heterogeneities between various terrains within the plateau. Our numerical results show that the general coherence between crustal and mantle deformation can be attributed to the particular tectonic boundary conditions around the Tibetan Plateau which force both crustal and mantle material to flow coherently eastward as the consequence of the Indo-Asian collision. In this case the Tibetan VCD is consistent with a weak and flowing lower crust.

  17. Tectonics and geodynamics of the Eastern Venezuelan Ranges

    SciTech Connect

    Roure, F. ); Passalacqua, H. ); Gou, I. )

    1993-02-01

    The eastern Venezuelan Ranges result from oblique convergence along the South American-Caribbean plate boundary, whose main surface expression is the El Pilar dextral strike-slip fault. Crustal scale balanced cross-sections have been here completed from available surface and subsurface data across this major transfer zone which links the oceanic subduction of the Lesser Antilles with the continental subduction of the Andes. The present geometries of the sectons show a major discrepancy between the cover and basement lengths, which could be explained by tectonic inheritance from the Tethyan margin. A careful analysis of both the chronostratigraphy and the internal geometry of the foredeep and piggy-back syntectonic deposits are also used to establish the kinematics of each individual structure. Basement involved is postulated for the Pirital Thrust which cuts previously emplaced cover structures like the El Furrial structural unit. Reactivation of ancient thrust faults occurs also at the rear of the Pirital out-of-sequence thrust in the west. As in the Alps or the Pyrenees, a high density intracrustal wedge is required to fit the gravimetric high imaged north of the Serrania; the solutions require a deep crustal root beneath the belt and a north-dipping South American Moho. A consistent geodynamical model, involving the north-dipping subduction of at least 70 km of South American continental lithosphere is thus proposed. An important strain partitioning occurs along the El Pilar Fault and underneath the deep crustal indenter (backstop), which decouples the south-verging allochthon of the Serrania from the north-dipping subducted South American lithosphere and from the eastward-migrating metamorphic belt.

  18. Geodynamic Evolution of the Northeastern South China Sea

    NASA Astrophysics Data System (ADS)

    Yeh, Y.; Sibuet, J.; Hsu, S.; Liu, C.

    2008-12-01

    We present a geodynamic evolution model of the northeastern South China Sea (SCS) updated the kinematic context based on a re-interpretation and analysis of all available magnetic data. Using the latest available multi-channel seismic data, two significant tectonic phases T1 and T2 were identified in the northeastern SCS. T1 is a slight tensional tectonic event and T2 is a major compressive event. In the absence of the drilling data in the deep basin, the identification of the magnetic anomalies, the age of major unconformities at ODP Sites 1146 and 1148 drilled on the northeastern SCS margin as well as a re- interpretation of the tectonic subsidence curve based on drilled holes in the west Taiwan basins provided age constraints for dating these two tectonic events. Tensional phase T1 is characterized by tilted blocks and fan-shaped deposits developed shortly (8-10 Ma) after the onset of SCS oceanic domain (37.8 Ma). It corresponds to the first ENE-WSW to E-W change in spreading directions, which occurred around chron C10 (~28.7 Ma). Tectonic phase T2 is characterized by the uplift of ENE-WSW rift features and NE-SW transverse features associated with the major plate reorganization in East Asia and a northeast shift of the Ryukyu subduction zone from the Luzon-Ryukyu transform plate boundary (LRTPB) to east of the present- day position of Taiwan, which occurred 17-18 Ma ago. As the T2 intra-plate compressive deformation only occurred south of the LRTPB, we suggest that the slab pull effect of the dead slab might have been transmitted to the oceanic crust south of the already inactive LRTPB.

  19. Izanagi-Pacific Ridge Subduction and its Geodynamic Consequences

    NASA Astrophysics Data System (ADS)

    Müller, R. D.; Whittaker, J. M.; Sdrolias, M.

    2007-12-01

    As part of a global plate tectonic model for 140 Ma to the present we present a revised plate reconstruction for the western Pacific and investigate its geodynamic consequences. In our plate model, mid-ocean ridge subduction beneath southern Japan occurs at 60-55 Ma, 20 million years later than proposed for Kula-Pacific or Farallon- Izanagi ridge subduction. The difference arises because Izanagi-Pacific (I-P) spreading ceases in previous models after 110 Ma while our model incorporates continued spreading until the I-P ridge subducts beneath eastern Asia at 60-55 Ma. We regard cessation of spreading at the I-P ridge between 110 and 80 Ma as unlikely as the Izanagi plate was undergoing rapid motion, driven by net slab-pull force, from the north-northwest, immediately prior to the proposed spreading cessation. Metamorphism of the Ryoke Belt in southern Japan has previously been attributed to Kula-Pacific ridge subduction at 85 Ma, but the high-T/low-P Ryoke Belt cannot be uniquely linked to a ridge subduction event. We propose that sub-parallel subduction of the I-P mid-ocean ridge beneath Japan at 60-55 Ma resulted in nearly simultaneous slab break-off along the length of the Japanese trench (approximately 2700 km). Geological evidence for this model includes cessation of a major accretion phase in the late Cretaceous, emplacement of the Okitsu Melange due to subduction of hot, buoyant material at 55 Ma, and cross-cutting fault fabrics that indicate a counter-clockwise rotation in relative plate motions between Eurasia and the I-P plate, consistent with palaeothermal and palaeopressure data, some time between 55 and 34 Ma. Rapid subduction of the I-P ridge, over a vast distance, may have triggered a chain reaction of tectonic plate reorganizations. With complete subduction of the I-P ridge at 55 Ma, forces acting on the western edge of the Pacific Plate would have changed from ridge-push to slab pull, changing Pacific absolute plate motions from northwest to west. A

  20. Linking geodynamics and geophysical inversion with multiobservable probabilistic tomography

    NASA Astrophysics Data System (ADS)

    Afonso, Juan Carlos; Rawlinson, Nicholas; Yang, Yingjie; Zlotnik, Sergio; Ortega, Olga

    2017-04-01

    Our recent work (Afonso et al., 2013a,b; 2016) has demonstrated that multiobservable probabilistic tomography offers a sound method to characterize the thermochemical structure of the lithosphere and upper mantle and opens exiting new opportunities for deep-Earth imaging. In this method, all physical and chemical parameters defining an Earth model are linked together by fundamental thermodynamic relations, rather than by ad hoc empirical assumptions. This allows us to directly invert for the fundamental variables defining the physical state of the Earth's interior, namely, temperature, pressure, and major-element composition using a multitude of data sets with complementary strengths: body wave teleseismic data, surface wave phase dispersion data, gravity anomalies, long-wavelength gravity gradients, geoid height, receiver functions, absolute elevation, and surface heat flow data. In this probabilistic inversion scheme, traditional tomographic images of physical parameters such as 3-D seismic velocity become a "free" by-product. However, our tomographic images are, by design, also thermodynamically compatible with all the other inverted observables instead of satisfying one type of data set only. This is important, as any model deemed representative of the real physical state of the Earth's interior should pass the test of explaining other geophysical data sets as well. Inverting for "geodynamic" parameters such as viscosity or convection-related topography in 3D within this multiobservable probabilistic inverse framework is a major challenge, mainly due to the computational cost of solving the Stokes equations; we are not aware of previous attempts to do so with a probabilistic approach. However, recent advances on Reduced Order Modelling and Proper Generalized Decompositions have allowed us to overcome the traditional difficulties and create a probabilistic inversion framework that not only inverts for the physical state of the mantle but also for dynamic

  1. Applications of Geodesy to Geodynamics, an International Symposium

    NASA Technical Reports Server (NTRS)

    Mueller, I. I. (Editor)

    1978-01-01

    Geodetic techniques in detecting and monitoring geodynamic phenomena are reviewed. Specific areas covered include: rotation of the earth and polar motion; tectonic plate movements and crustal deformations (space techniques); horizontal crustal movements (terrestrial techniques); vertical crustal movements (terrestrial techniques); gravity field, geoid, and ocean surface by space techniques; surface gravity and new techniques for the geophysical interpretation of gravity and geoid undulation; and earth tides and geodesy.

  2. Automated Testing Infrastructure and Result Comparison for Geodynamics Codes

    NASA Astrophysics Data System (ADS)

    Heien, E. M.; Kellogg, L. H.

    2013-12-01

    The geodynamics community uses a wide variety of codes on a wide variety of both software and hardware platforms to simulate geophysical phenomenon. These codes are generally variants of finite difference or finite element calculations involving Stokes flow or wave propagation. A significant problem is that codes of even low complexity will return different results depending on the platform due to slight differences in hardware, software, compiler, and libraries. Furthermore, changes to the codes during development may affect solutions in unexpected ways such that previously validated results are altered. The Computational Infrastructure for Geodynamics (CIG) is funded by the NSF to enhance the capabilities of the geodynamics community through software development. CIG has recently done extensive work in setting up an automated testing and result validation system based on the BaTLab system developed at the University of Wisconsin, Madison. This system uses 16 variants of Linux and Mac platforms on both 32 and 64-bit processors to test several CIG codes, and has also recently been extended to support testing on the XSEDE TACC (Texas Advanced Computing Center) Stampede cluster. In this work we overview the system design and demonstrate how automated testing and validation occurs and results are reported. We also examine several results from the system from different codes and discuss how changes in compilers and libraries affect the results. Finally we detail some result comparison tools for different types of output (scalar fields, velocity fields, seismogram data), and discuss within what margins different results can be considered equivalent.

  3. Numerical Geodynamic Experiments of Continental Collision: Past and Present

    NASA Astrophysics Data System (ADS)

    Gray, Robert

    -lithospheric mantle to upwell and come into contact with the thickened upper crust. When sedimentation is imposed subduction-like consumption of the subducting plate remains stable. Using numerical geodynamic models, I studied the influence of the pressure-dependence of viscosity on tectonic deformation during collision. At low activation volumes, high convergence rates, and low to moderate initial Moho temperatures the subduction style of mantle lithosphere deformation is dominant. At low activation volumes, high convergence rates, and high initial Moho temperatures distributed pure-shear style deformation occurs. At low activation volumes, low convergence rate, and moderate to high initial Moho temperatures the mantle lithosphere prefers a convective removal style of deformation. Increasing the activation volume of mantle material in either of these three cases changes the style of mantle lithosphere deformation because its viscosity increases non-linearly.

  4. Chapter 4: Regional magnetic domains of the Circum-Arctic: A framework for geodynamic interpretation

    USGS Publications Warehouse

    Saltus, R.W.; Miller, E.L.; Gaina, C.; Brown, P.J.

    2011-01-01

    We identify and discuss 57 magnetic anomaly pattern domains spanning the Circum-Arctic. The domains are based on analysis of a new Circum-Arctic data compilation. The magnetic anomaly patterns can be broadly related to general geodynamic classification of the crust into stable, deformed (magnetic and nonmagnetic), deep magnetic high, oceanic and large igneous province domains. We compare the magnetic domains with topography/bathymetry, regional geology, regional free air gravity anomalies and estimates of the relative magnetic 'thickness' of the crust. Most of the domains and their geodynamic classification assignments are consistent with their topographic/bathymetric and geological expression. A few of the domains are potentially controversial. For example, the extent of the Iceland Faroe large igneous province as identified by magnetic anomalies may disagree with other definitions for this feature. Also the lack of definitive magnetic expression of oceanic crust in Baffin Bay, the Norwegian-Greenland Sea and the Amerasian Basin is at odds with some previous interpretations. The magnetic domains and their boundaries provide clues for tectonic models and boundaries within this poorly understood portion of the globe. ?? 2011 The Geological Society of London.

  5. Global radial anisotropy in the Earth's mantle: new constraints from seismology and geodynamics

    NASA Astrophysics Data System (ADS)

    Ferreira, Ana MG; Faccenda, Manuele; Chang, Sung-Joon; Sturgeon, William; Schardong, Lewis

    2017-04-01

    When combined with information from mineral physics and geodynamics, seismic anisotropy is one of the most direct ways to constrain mantle deformation and flow. However, it can be challenging to image it globally due to limited data's sensitivity and difficulties in separating shallow and deep Earth signals. In this presentation we review recent developments in the global seismic imaging and interpretation of radially anisotropic mantle structure. We show that it is highly beneficial to invert simultaneously for mantle and crustal structure using multiple datasets, notably: (i) short-period group velocity data with strong sensitivity to the crust; and, (ii) surface wave overtone measurements sensitive to the transition zone and uppermost lower mantle. Moreover, we show that comparisons between anisotropy tomography and combined micro- and macro-flow geodynamic simulations help constrain the Earth's mineralogy and the patterns of mantle convection. As a case study, we present new results highlighting the ubiquitous presence of anisotropy in the uppermost lower mantle beneath subduction zones. These observations are consistent with 3-D numerical models of deformation from subducting slabs and the associated lattice preferred orientation of bridgmanite produced by a combination of dislocation and diffusion creep mechanisms.

  6. A Geodynamic Grand Challenge: Time-Reversed Mantle Convection Reconstructions From Tomographic Images of Present-Day Mantle Structure

    NASA Astrophysics Data System (ADS)

    Glisovic, P.; Forte, A. M.; Moucha, R.

    2009-12-01

    One of the most complex challenges in current geodynamics research is the reconstruction of the past evolution of 3-D mantle temperature structure from seismic tomographic images of present-day lateral heterogeneity in the mantle. Early efforts to address this problem have been based on backward advection approximations based on the assumption that mantle convection is a very-high Rayleigh number process (e.g. Forte & Mitrovica 1997; Steinberger & O'Connell 1997). Over the past decade further progress has been achieved and new techniques have been proposed, such as the 4-D variational (Bunge et al. 2003) and quasi-reversible (Ismail-Zadeh et al. 2007) approaches. An enduring challenge is the construction of time-reversed mantle convection simulations that yield maximum consistency with a wide suite of surface geodynamic constraints on mantle rheology and 3-D structure inferred from seismic tomography. Resolving this outstanding problem is of crucial importance, because a successful reconstruction of the time-dependent, 3-D mantle convective structure in the geological past provides unique insights into the origin and evolution of a number of fundamental surface processes that include topography changes, eustatic sea level variations, state of stress in the lithosphere, and Earth rotation variations. A key concern in these reconstructions is quantifying the inherent uncertainties and the implications for surface geodynamic observables. We will explore these issues and compare the efficacy of different backward convection techniques using a new mantle convection model based on recent joint seismic-geodynamic tomography inversions (Simmons et al., GJI, 2009).

  7. Fluidity: a fully-unstructured adaptive mesh computational framework for geodynamics

    NASA Astrophysics Data System (ADS)

    Kramer, S. C.; Davies, D.; Wilson, C. R.

    2010-12-01

    Fluidity is a finite element, finite volume fluid dynamics model developed by the Applied Modelling and Computation Group at Imperial College London. Several features of the model make it attractive for use in geodynamics. A core finite element library enables the rapid implementation and investigation of new numerical schemes. For example, the function spaces used for each variable can be changed allowing properties of the discretisation, such as stability, conservation and balance, to be easily varied and investigated. Furthermore, unstructured, simplex meshes allow the underlying resolution to vary rapidly across the computational domain. Combined with dynamic mesh adaptivity, where the mesh is periodically optimised to the current conditions, this allows significant savings in computational cost over traditional chessboard-like structured mesh simulations [1]. In this study we extend Fluidity (using the Portable, Extensible Toolkit for Scientific Computation [PETSc, 2]) to Stokes flow problems relevant to geodynamics. However, due to the assumptions inherent in all models, it is necessary to properly verify and validate the code before applying it to any large-scale problems. In recent years this has been made easier by the publication of a series of ‘community benchmarks’ for geodynamic modelling. We discuss the use of several of these to help validate Fluidity [e.g. 3, 4]. The experimental results of Vatteville et al. [5] are then used to validate Fluidity against laboratory measurements. This test case is also used to highlight the computational advantages of using adaptive, unstructured meshes - significantly reducing the number of nodes and total CPU time required to match a fixed mesh simulation. References: 1. C. C. Pain et al. Comput. Meth. Appl. M, 190:3771-3796, 2001. doi:10.1016/S0045-7825(00)00294-2. 2. B. Satish et al. http://www.mcs.anl.gov/petsc/petsc-2/, 2001. 3. Blankenbach et al. Geophys. J. Int., 98:23-28, 1989. 4. Busse et al. Geophys

  8. Testing Absolute Plate Reference Frames and the Implications for the Generation of Geodynamic Mantle Heterogeneity Structure

    NASA Astrophysics Data System (ADS)

    Shephard, G. E.; Bunge, H.; Schuberth, B. S.; Müller, D.; Talsma, A.; Moder, C.

    2010-12-01

    Several absolute reference frames for Cretaceous-Tertiary plate tectonic reconstructions have been proposed over the last decade. They include reference frames based on hotspot tracks displaying age progression, and assuming either fixed or moving hotspots, as well as palaeomagnetically-based reference frames, a subduction reference frame and hybrid reference frames. All these alternative reference frames imply a particular history of the location of subduction zones through time, the associated subduction history, and the evolution of mantle heterogeneity via the mixing of subducted slab material with the mantle. Therefore it is possible to evaluate the observed distribution of subducted slab material in the mantle versus that predicted by a forward geodynamic model in which the plate kinematic history given by a particular absolute plate is coupled with a mantle convection model. We present a comparison of five alternative absolute plate motion models in terms of their consequences for global deep mantle structure by utilizing the 3-D spherical finite element mantle convection code TERRA, coupled with the global plate tectonic reconstruction software GPlates. We impose global palaeo-plate boundaries and plate velocities back to 140 Ma as surface boundary conditions for each absolute rotation model and forward model the associated subduction history. The correlation of seismic tomography with the predicted present-day mantle structure from each of plate models is then assessed using well-imaged slabs. We will present and discuss a comparison of geodynamically predicted mantle heterogeneity and seismic tomography to infer the robustness of each absolute reference frame through time, thus providing additional constraints for the integration of plate tectonics and mantle dynamics.

  9. Monitoring deep geodynamic processes within Vrancea intermediate-depth seismic zone by geodetic means

    NASA Astrophysics Data System (ADS)

    Besutiu, Lucian; Zlagnean, Luminita

    2015-04-01

    mechanism exclusively in the Vrancea seismic zone support the assumption. Recent studies on the Vrancea echoes of 2013 Galati-Izvoarele quake swarm have also confirmed our hypotheses. Based on numerical modelling of the geodynamic process, an estimate of the stretching rate has been obtained, fully consistent with results inferred from studies on the seismic energy released by the Vrancea intermediate earthquakes. Concluding remarks Looking further, the sinking of the Vrancea lithosphere into the upper mantle (and consequent crust stretching, appropriately reflected in the non-tidal gravity change) appears as an ongoing geodynamic process, tightly connected to the intermediate-depth seismicity generated within the lithosphere penetrating the upper mantle by thermo-baric accommodation phenomena. Time series provided by repeated gravity observations conducted on the above-mentioned infrastructure for about ten years have clearly revealed: (i) the persistence of the gravity lowering, and (ii) some apparent connection between the rate of the gravity change, and the amount of seismic energy released by intermediate-depth earthquakes. Acknowledgements. The research has been partly performed through CYBERDYNE project, funded through the EU structural programme (contract #184/2010).

  10. Putting the Dynamics in Chemical Geodynamics

    NASA Astrophysics Data System (ADS)

    Spiegelman, M.; Katz, R. F.; Kelemen, P. B.; Fang, Y.; Collier, M.; Holtzman, B.

    2007-12-01

    An outstanding goal for both geochemists and geophysicists is to understand how to use the wide range of proxy geochemical (and geophysical) data to make useful inferences about the current and past dynamics of the planet. To relate data to dynamics, however, requires models that include the fundamental processes that affect chemical variability: i.e. source heterogeneity, chemical fractionation (melting/reactions), chemical transport and mixing. In particular, most models of chemical evolution do not include explicit fluid or magma transport and questions remain as to how much observed chemical variability can be attributed to magma dynamics. We discuss recent developments and models that suggest that at least some of the observed variability arises from transport processes. Driven by field observations, experiments and computational models, there is an emerging picture of partially molten regions as highly localized, channelized plumbing systems. Computations suggest that melt localization can arise from both chemical/physical and purely mechanical instabilities and can provide non-trivial mixing pathways through the mantle. Questions remain as to how the different instabilities interact and which may be dominant in the mantle. Regardless, a highly localized melt transport system can lead to significant trace element (and U-series) variability and fractionation even for a homogeneous source. Recent work extends these results to consider the interaction of a channelized melt system with a heterogeneous source and suggests that small scale spatial variations in partitioning can lead to significant scatter in the ratios of highly incompatible elements (Fang, Spiegelman & Kelemen). Current work is extending these approaches to try to understand the variability of major elements and reaction in open systems (Collier, Kelemen & Spiegelman) Looking forward, the integration of magma dynamics and small-scale localization into global mantle dynamics presents a major

  11. On the solvability of incompressible Stokes with viscoplastic rheologies in geodynamics

    NASA Astrophysics Data System (ADS)

    Spiegelman, Marc; May, Dave A.; Wilson, Cian R.

    2016-06-01

    Plasticity/failure is an essential ingredient in geodynamics models as earth materials cannot sustain unbounded stresses. However, many questions remain as to appropriate models of plasticity as well as effective solvers for these strongly nonlinear systems. Here we present some simplified model problems designed to elucidate many of the issues involved for the description and solution of viscoplastic problems as currently used in geodynamic modeling. We consider compression and extension of a viscoplastic layer overlying an isoviscous layer and introduce a single plastic yield criterion which includes the most commonly used viscoplasticity models: von Mises, depth-dependent von Mises, and Drucker-Prager. We show that for all rheologies considered, successive substitution schemes (aka Picard iteration) often stall at large values of the nonlinear residual, producing spurious solutions. However, combined Picard-Newton schemes can be effective for rheologies that are independent of the dynamic pressure. Difficulties arise when solving incompressible Stokes problems for rheologies that depend on the dynamic pressure such as Drucker-Prager viscoplasticity. Analysis suggests that incompressible Stokes can become ill-posed when the dependence of the deviatoric stress tensor on dynamic pressure (i.e., |∂τ/∂p'|) becomes large. We demonstrate empirically that, in these cases, Newton solvers can fail by introducing spurious shear bands and discuss the consequence of interpreting the results of nonconverged computations. Even for problems where solvers converge, Drucker-Prager viscoplasticity can produce dynamic pressures that deviate significantly from lithostatic and both the velocity and pressure fields should be evaluated to determine whether solutions are geologically reasonable.

  12. Geodynamics of oroclinal bending: Insights from the Mediterranean

    NASA Astrophysics Data System (ADS)

    Rosenbaum, Gideon

    2014-12-01

    The Alpine Orogen in the Mediterranean region exhibits a series of orogenic curvatures (oroclines). The evolution of these oroclines is relatively well constrained by a plethora of geophysical and geological data, and therefore, their origin can inform us on the fundamental processes controlling oroclinal bending. Here, a synthesis of the geometry of Mediterranean oroclines, followed by a discussion on their geodynamic origin is presented. The geometrical synthesis is based on a new classification of Mediterranean oroclines, which defines a first-order orocline (Adriatic Orocline) by the general northward-convex shape of the Alpine Orogen from Cyprus to Gibraltar. Superimposed on the limbs of this orocline, are second-, third- and fourth-order oroclines. The major process that led to the formation of the Adriatic Orocline is the indentation of Adria into Europe, whereas second- and third-order oroclines (e.g., Western Mediterranean and Gibraltar oroclines, respectively) were primarily controlled by a combination of trench retreat and slab tearing. It appears, therefore, that the geodynamics of Mediterranean oroclines has been entirely dependent on plate boundary migration and segmentation, as expressed in the interlinked processes of indentation, trench retreat and slab tearing. The relative contribution of specific geodynamic processes, and their maturity, could be inferred from geometrical characteristics, such as the amplitude-to-width ratio, the orientation of the curvature (convex or concave) relative to the convergence vector, and their geometrical relationship with backarc extensional basins (e.g., in the concave side of the orocline). Based on the information from the Mediterranean oroclines, it is concluded that oroclinal bending commonly involves lithospheric-scale processes, and is not restricted to thin-skinned deformation. However, contrary to previous suggestions that assume that the whole lithosphere can buckle, there is no clear evidence that such

  13. International GPS (Global Positioning System) Service for Geodynamics

    NASA Technical Reports Server (NTRS)

    Zumberge, J. F. (Editor); Liu, R. (Editor); Neilan, R. E. (Editor)

    1995-01-01

    The International GPS (Global Positioning System) Service for Geodynamics (IGS) began formal operation on January 1, 1994. This first annual report is divided into sections, which mirror different aspects of the service. Section (1) contains general information, including the history of the IGS, its organization, and the global network of GPS tracking sites; (2) contains information on the Central Bureau Information System; (3) describes the International Earth Rotation Service (IERS); (4) details collecting and distributing IGS data in Data Center reports; (6) describes how the IGS Analysis Centers generate their products; (7) contains miscellaneous contributions from other organizations that share common interests with the IGS.

  14. Geodynamic evolution of the western Mediterranean basin since the Late Cretaceous

    NASA Astrophysics Data System (ADS)

    Romagny, Adrien; Jolivet, Laurent; Augier, Romain; Bessière, Eloise; Gumiaux, Charles

    2016-04-01

    The western Mediterranean basin results from the convergence between Africa and Eurasia and from related interactions between an undetermined number of macroplates and microplates during the Late Cretaceous. Various and very different models proposed during the last thirty years attempted to explain the geodynamic evolution of this area (e.g. Carminati et al., 2012; Schettino and Turco, 2011; Handy et al., 2010; Jolivet et al., 2006). However, none of those models are totally satisfactory, especially when regarding the Gibraltar arc region. The western Mediterranean constitutes a unique laboratory to study interactions between surface deformations and crustal and mantle processes (slab roll-back, slab break-off, delamination, etc.). The goal of this study is to understand how these deep processes are coupled to crustal evolution during the collision between Africa and Eurasia. In this context, two different approaches will be undertaken. Firstly, using GPlates software (Boyden et al., 2011), kinematic reconstructions will be performed based on stratigraphic, metamorphic, magmatic, structural and paleomagnetic data. These reconstructions will be made from the Present to the Late Cretaceous and using the principle of rigid polygons which enables deformation of areas between polygons. Realizing these reconstructions backward allows to be free from any preconceived geodynamic model. The principle of rigid polygons helps avoiding problems due to rough approximations linked to rigid blocks. Secondly, obtained results will be used to constrain 4D numerical modelling (space and time) of the western Mediterranean subduction zone evolution since the Late Cretaceous. The influence of different primordial parameters (rheological and thermal stratification of the upper and lower plates, convergence rates, presence of weak zones, etc.) will be tested. The results will be compared to natural data (surface velocity field, thermal anomalies, temporal and spatial evolution of the

  15. Basic research for the geodynamics program

    NASA Technical Reports Server (NTRS)

    1983-01-01

    Laser systems deployed in satellite tracking were upgraded to accuracy levels where biases from systematic unmodelled effects constitute the basic factor that prohibits extraction of the full amount of information contained in the observations. Taking into consideration that the quality of the instrument advances at a faster pace compared to the understanding and modeling of the physical processes involved, one can foresee that in the near future when all lasers are replaced with third generation ones the limiting factor for the estimated accuracies will be the aforementioned biases. Therefore, for the reduction of the observations, methods should be deployed in such a way that the effect of the biases will be kept well below the noise level. Such a method was proposed and studied. This method consists of using the observed part of the satellite pass and converting the laser ranges into range differences in hopes that they will be less affected by biases in the orbital models, the reference system, and the observations themselves.

  16. The Tell-Rif belt in the geodynamic frame of the West Mediterranean

    NASA Astrophysics Data System (ADS)

    Leprêtre, Rémi; Frizon de Lamotte, Dominique; Combier, Violaine; Gorini, Christian; Eschard, Remi

    2017-04-01

    The Tell-Rif (Tell in Algeria and Tunisia; Rif in Morocco) or Maghrebides is the orogenic system fringing the West Mediterranean basins to the south. This system comprises 3 major tectonic-paleogeographic zones from north to south: (1) the internal zones (AlKaPeCa for Alboran, Kabylies, Peloritan, Calabria) originated from the former northern European margin of the Maghrebian Tethys (MT); (2) the "flyschs zone" regarded as the former sedimentary cover of the MT and (3) the external zones, the former southern African passive margin of the MT. In the geodynamic frame of the West Mediterranean basins formation, the Tell-Rif is interpreted as the direct result of the progressive closure of the MT until the collision between AlKaPeCa and Africa at 17 Ma and the propagation of the deformation within Africa. Such a scenario gives a consistent explanation for the off-shore geodynamics and is now shared by almost all the authors. Nevertheless, all the geodynamic models do not integrate recent developments regarding the geology the Tell-Rif. In particular, the following points must be integrated in any models: (1) The importance of pre-Late Oligocene (pre-30 Ma) contractional events not only in the Atlas System, where they are well established, but also in the Tell-Rif system, where their effects are often ignored or minimized; (2) The existence of MP-BT metamorphic rocks associated with fragments of ophiolites in the Eastern External Rif and likely in the Western External Tell suggesting that the southern Maghrebian Tethys margin is more complicated than what could be expected for a single linear oceanic domain; (3) The presence over the Rif and western Tell of wide Miocene basins developed along with the ones of the West Mediterranean Basins. Among these basins, the Cheliff Basin occupies a large part of the western Tell in Algeria. These elements must be taken into account for a reassessment of the complex relationships between the West Mediterranean Basins and the

  17. Geodynamics of Cenozoic deformation in central Asia

    NASA Technical Reports Server (NTRS)

    Liu, H.-S.

    1981-01-01

    This paper presents a study of the tectonic stresses in central Asia based on an interpretation of satellite gravity data for mantle convection and supplemented with published fault plane solutions of earthquakes. Northwest-southeast to north-south compressional stresses exist in the Tien Shan region where reverse faulting dominates. The maximum compressive stress is oriented approximately northeast-southwest in the regions of Altai and southern Mongolia. Farther north, compressive stress gives way to tensional stress which causes normal faulting in the Baikal rift system. It is also shown that all of the tectonic stresses in the Tibetan plateau and Himalayan frontal thrust are related to the convection-generated stress patterns inferred from satellite gravity data. These results suggest that the complex crustal deformation in central Asia can be convincingly described by the deformation of the lithosphere on top of the up- and down-welling asthenospheric material beneath it. This observational fact may not only upset the simple view of the fluid crustal model of the Tibetan plateau, but also provide some useful constraints for the future development of deformation theory of continental crust.

  18. Geodynamics of Cenozoic deformation in central Asia

    NASA Technical Reports Server (NTRS)

    Liu, H.-S.

    1981-01-01

    This paper presents a study of the tectonic stresses in central Asia based on an interpretation of satellite gravity data for mantle convection and supplemented with published fault plane solutions of earthquakes. Northwest-southeast to north-south compressional stresses exist in the Tien Shan region where reverse faulting dominates. The maximum compressive stress is oriented approximately northeast-southwest in the regions of Altai and southern Mongolia. Farther north, compressive stress gives way to tensional stress which causes normal faulting in the Baikal rift system. It is also shown that all of the tectonic stresses in the Tibetan plateau and Himalayan frontal thrust are related to the convection-generated stress patterns inferred from satellite gravity data. These results suggest that the complex crustal deformation in central Asia can be convincingly described by the deformation of the lithosphere on top of the up- and down-welling asthenospheric material beneath it. This observational fact may not only upset the simple view of the fluid crustal model of the Tibetan plateau, but also provide some useful constraints for the future development of deformation theory of continental crust.

  19. Constraining the rheology of the lithosphere through joint geodynamic and gravity inversion

    NASA Astrophysics Data System (ADS)

    Baumann, T.; Kaus, B.; Popov, A.

    2013-12-01

    Understanding the physics of lithospheric deformation and continental collision requires good constraints on lithospheric rheology. Typically, rheology is determined from laboratory experiments on small rock samples, which are extrapolated to geological conditions - an extrapolation over 10 orders of magnitude in deformation rates. These laboratory experiments generally show that small changes in the composition of the rocks, such as adding a bit of water, can dramatically change its viscosity. Moreover, it is unclear which rock type gives the best mechanical description of, for example, the upper crust and whether a small sample is even appropriate to describe the large scale mechanical behavior of the crust. So the viscosity of the lithosphere is probably the least constrained parameter in geodynamics. Ideally, we thus need a new independent method that allows constraining the effective rheology of the lithosphere directly from geophysical data, which is the aim of this work. Our method uses the fact that the geodynamically controlling parameters of lithospheric deformation are its effective viscosity and density structure. By appropriately parameterising the rheological structure of the lithosphere we perform instantaneous forward simulations of present-day lithospheric deformation scenarios with a finite element method to compute the gravity field and surface velocities. The forward modelling results can be compared with observations such as Bouguer anomalies and GPS-derived surface velocities. More precisely, we automatize the forward modelling procedure with a Monte Carlo method, and in fact solve a joint geodynamic and gravity inverse problem. The resulting misfit can be illustrated as a function of rheological model parameters and a more detailed analysis allows constraining probabilistic parameter ranges. For a simplified setup with linear viscous rheologies we can demonstrate mathematically that a joint geodynamic-gravity inversion approach results in a

  20. Joint seismic-geodynamic-mineral physical constraints on heat flux across the CMB

    NASA Astrophysics Data System (ADS)

    Forte, A. M.; Moucha, R.; Simmons, N. A.; Grand, S. P.

    2009-05-01

    The dynamics and thermal evolution of the Earth's interior is strongly dependent on the relative contributions from internal heating in the mantle (due to radioactivity and secular cooling) and from bottom heating across the core-mantle boundary (CMB). The dynamical style of the thermal convective flow, in particular the relative importance of active, thermally buoyant upwellings and mantle cooling due to descending lithospheric plates is also strongly dependent on the amplitude of heat flux across the CMB. We are able to provide new constraints on the convectively maintained heat flux across the CMB thanks to recent progress in mapping the lateral variations in mantle temperature by jointly inverting global seismic and geodynamic data sets, in which mineral physical constraints on mantle thermal heterogeneity are also imposed (Simmons et al. 2009). We present here new models of the present-day global mantle convective flow predicted on the basis of the thermal and non-thermal (compositional) density perturbations derived from the new tomography model and using the inferences of depth-dependent, horizontally averaged mantle viscosity derived from joint inversions of glacial isostatic adjustment and mantle convection data (Forte and Mitrovica 2004). We employ this tomography- geodynamics based mantle convection model to explore the convective transport of mass (buoyancy flux) and heat (advected heat flux) across the lower and upper mantle. We show that the predictions of advected heat flux at the top of the seismic D" layer provide direct constraints on the heat flux across the core-mantle boundary (CMB). Our current best estimates of the present-day CMB heat flux are in excess of 10 TW. We present a sensitivity analysis showing the degree of robustness of this inference, depending on the inferred variation of mantle viscosity in the lower mantle. We also present new predictions of the present-day distribution of secular heating and cooling at different depths in

  1. Arctic geodynamics: Continental shelf and deep ocean geophysics. ERS-1 satellite altimetry: A first look

    NASA Technical Reports Server (NTRS)

    Anderson, Allen Joel; Sandwell, David T.; Marquart, Gabriele; Scherneck, Hans-Georg

    1993-01-01

    An overall review of the Arctic Geodynamics project is presented. A composite gravity field model of the region based upon altimetry data from ERS-1, Geosat, and Seasat is made. ERS-1 altimetry covers unique Arctic and Antarctic latitudes above 72 deg. Both areas contain large continental shelf areas, passive margins, as well as recently formed deep ocean areas. Until ERS-1 it was not possible to study these areas with satellite altimetry. Gravity field solutions for the Barents sea, portions of the Arctic ocean, and the Norwegian sea north of Iceland are shown. The gravity anomalies around Svalbard (Spitsbergen) and Bear island are particularly large, indicating large isostatic anomalies which remain from the recent breakup of Greenland from Scandinavian. Recently released gravity data from the Armed Forces Topographic Service of Russia cover a portion of the Barents and Kara seas. A comparison of this data with the ERS-1 produced gravity field is shown.

  2. Geodynamics in Modular Course System at Vienna High School

    NASA Astrophysics Data System (ADS)

    Pitzl-Reinbacher, Robert

    2017-04-01

    In Austria there are currently some major reforms concerning high school education underway. At our school, the Bundesgymnasium and Bundesrealgymnasium Draschestrasse, a school belonging to the Vienna Bilingual Schooling branch, we have developed a course system in which pupils can select courses and determine individually which areas of study they want to focus on. Specially devised courses have been developed which fit within the framework of natural and applied sciences but go beyond the basic curriculum in physics. Geodynamics is the title of one of these courses, with an emphasis on weather, climate and geodynamic processes of the earth's crust. The course „The restless earth" deals specifically with plate tectonics, vulcanism, formation of mountains and processes such as ocean currents and the physics involved. Apart from theoretical basics we use manifold media and approaches concerning visualization: graphics, map data taken from Google Maps, satellite pictures, and others. The knowledge acquired in this course is broadened and consolidated by means of excursions to the Vienna Natural History Museum where additional instructional materials and visual aids are on display. Based on this experience pupils are requested to hold presentations (individually or in groups) at the end of the course.

  3. Autonomous geodynamics of the Pamir-Tien Shan junction zone from seismology data

    NASA Astrophysics Data System (ADS)

    Lukk, A. A.; Shevchenko, V. I.; Leonova, V. G.

    2015-11-01

    The geodynamics of the Tajik Depression, the junction zone of the Pamirs and Tien Shan, is typically considered in the context of plate tectonic concept, which implies intense subhorizontal compression of the zone resulting from the subduction of the Indian and Eurasian lithospheric plates. This convergence has been reliably confirmed by the GPS measurements. However, the joint analysis of the geological structure, seismicity, and geodimeter measurements conducted during a few years at the Garm geodynamical testing site of the Schmidt Institute of Physics of the Earth, Russian Academy of Sciences, demonstrates a widening of the Tajik Depression instead of its shortening, as should be expected from the subhorizontal compression predominant in the present-day stress-state of this region. This conclusion, together with the data from the other regions, suggests that, along with the plate tectonic mechanisms, there are also other, local, autonomous drivers that contribute to the tectogenesis of this region. Besides, the probable existence of these autonomous sources within the Tajik Depression directly follows from the seismology data. Among them is the crustal spreading within the depression suggested by the seismotectonic displacements in the focal mechanisms of the earthquakes. These displacements are directed in different azimuths off the axial's most subsided part of the depression at a depth of 20-30 km. Above this region the distribution of seismotectonic deformations (STD) is chaotic. This pattern of deformation is barely accounted for by a simple model of subhorizontal compression of the Earth's crust in the region. In our opinion, these features of the seismotectonic deformation in the crust within the studied part of the Tajik Depression is probably associated with the gain in the volume of the rocks due to the inflow of the additional material, which is supplied from the bottom crust or upper mantle by the deep fluids. This increase in the rock volume

  4. Program of Geodynamic Investigation for the Site of a New Nuclear Power Plant in Hungary

    NASA Astrophysics Data System (ADS)

    Trosits, D.; Horvath, F.; Katona, T.; Gerstenkorn, A.

    2014-12-01

    Preparation of a new nuclear power plant project is going on in Hungary at Paks site. Although there is an operating plant at the site, comprehensive geological, geophysical investigation has to be implemented in accordance with Hungarian nuclear safety regulation and international norms for confirming the site acceptability and providing a neotectonic basis for site seismic hazard assessment. The scope, techniques and methods of investigations have to be adapted to the geotectonic environment of the site and Pannonian Basin as a whole. The poster presents a brief summary of the program and provides a detailed description of the seismic survey focusing on the 3D subsurface imaging that is the most important task of planned geophysical investigations. The 3D geophysical imaging provides essential geodynamic information to assess the capability of near site faults and for the seismic hazard analysis, as well as for the hydrogeological modeling. The planned seismic survey gives a unique dataset for understanding the spatial relationship between individual fault segments. The 3D survey allows predicting and characterization of deformations induced by recent lithospheric stresses that is crucial for assessing the tectonic stability of the area. 3D seismic survey has to be combined with appropriate 2D and 3D shallow seismic profiling. The obtained 3D seismic data are also used for numerical geodynamic modeling. Rheology of rocks fundamentally influences the frequency of seismic activity, i.e. the accumulation and release of seismic energy. Regarding this the Pannonian Basin has specific features: the crust is thin and thermal gradients are high. This implies the whole lithosphere can be considered rheologically weak and its behavior is mostly plastic. It is suspected that most of the fault zones in the Pannonian basin are restricted to the sedimentary fill and the uppermost crust, and rest of the lithosphere experiences aseismic deformation.

  5. Multiscale, multiphysics geomechanics for geodynamics applied to buckling instabilities in the middle of the Australian craton

    NASA Astrophysics Data System (ADS)

    Regenauer-Lieb, Klaus; Veveakis, Manolis; Poulet, Thomas; Paesold, Martin; Rosenbaum, Gideon; Weinberg, Roberto F.; Karrech, Ali

    2015-10-01

    We propose a new multi-physics, multi-scale Integrated Computational Materials Engineering framework for 'predictive' geodynamic simulations. A first multiscale application is presented that allows linking our existing advanced material characterization methods from nanoscale through laboratory-, field and geodynamic scales into a new rock simulation framework. The outcome of our example simulation is that the diachronous Australian intraplate orogenic events are found to be caused by one and the same process. This is the non-linear progression of a fundamental buckling instability of the Australian intraplate lithosphere subject to long-term compressive forces. We identify four major stages of the instability: (1) a long wavelength elasto-visco-plastic flexure of the lithosphere without localized failure (first 50 Myrs of loading); (2) an incipient thrust on the central hinge of the model (50-90 Myrs); (3) followed by a secondary and tertiary thrust (90-100 Myrs) 200 km away to either side of the central thrust; (4) a progression of subsidiary thrusts advancing towards the central thrust (? Myrs). The model is corroborated by multiscale observations which are: nano-micro CT analysis of deformed samples in the central thrust giving evidence of cavitation and creep fractures in the thrust; mm-cm size veins of melts (pseudotachylite) that are evidence of intermittent shear heating events in the thrust; and 1-10 km width of the thrust - known as the mylonitic Redbank shear zone - corresponding to the width of the steady state solution, where shear heating on the thrust exactly balances heat diffusion.

  6. Neogene stratigraphy and Andean geodynamics of southern Ecuador

    NASA Astrophysics Data System (ADS)

    Hungerbühler, Dominik; Steinmann, Michael; Winkler, Wilfried; Seward, Diane; Egüez, Arturo; Peterson, Dawn E.; Helg, Urs; Hammer, Cliff

    2002-01-01

    The present paper reviews Tertiary volcanic and sedimentary formations in the Inter-Andean region of southern Ecuador (between 2°S and 4°20'S) in order to develop a geodynamic model of the region. The formations occur in the southern shallow prolongation of the Inter-Andean Valley between the Cordillera Real to the east, and the Cordillera Occidental and Amotape-Tahuı´n Provinces to the west. One hundred fifty zircon fission-track analyses has established a detailed chronostratigraphy for the sedimentary and volcanic formations and several small intrusions. The Paleogene to early Miocene formations are dominated by intermediate and acidic volcanic and pyroclastic rocks. In addition, relics of Eocene continental sedimentary series have been identified. The Neogene sedimentary series lie unconformably on deformed and eroded metamorphic, sedimentary and volcanic formations. They were deposited in two stages, which are separated by a major unconformity dated at ≈10-9 Ma. (1) During the middle and early late Miocene (≈15-10 Ma) marginal marine deltaic, lagoonal, lacustrine and fluvial environments prevailed, which we group under the heading "Pacific Coastal sequences". They presumably covered a greater surface area in southern Ecuador than their present occurrence in small topographic depressions. We suggest that they were deposited in the shallow marine Cuenca and Loja Embayments. Deposition in a marginal marine environment is also supported by the occurrence of brackish water ostracods and other fauna. (2) Above the regional (angular) unconformity, the coastal facies are overlain by late Miocene (≈9-5 Ma) continental alluvial fan and fluvial facies which are in turn covered by mainly airborne volcanic material. They represent the "Intermontane sequences" of the basins of Cuenca, Girón-Santa Isabel, Nabón, Loja and Malacatos-Vilcabamba. Sedimentologic and stratigraphic results are used to discuss the tectonic setting of Neogene sedimentation in the forearc

  7. Miocene to Recent Magmatism and Geodynamics of Eastern Turkey

    NASA Astrophysics Data System (ADS)

    Keskin, M.; Sharkov, E. V.; Lebedev, V. A.; Chugaev, A. V.; Oyan, V.; Genc, S. C.; Unal, E.; Aysal, N.

    2012-04-01

    ) mantle source, while magmas of the later stages were derived from deeper (asthenospheric) sources. Based on the results of seismic tomography, tectonics and geochemical/isotopic studies of the volcanic successions, it has now been well established that both uplift and widespread volcanism across the region have a common reason: a major "slab-steepening and breakoff event beneath a large accretionary complex". After the collision, being unsupported by the subduction, the slab started to be steepened beneath the region. This possibly resulted in widening, invasion and upwelling of the mantle wedge beneath E Anatolian accretionary complex, followed by a widespread decompressional melting, generating voluminous magmas with an inherited subduction signature. The subducted slab broke off beneath the Bitlis-Pötürge massif ~10 Ma, causing the enriched asthenospheric mantle with no subduction component beneath the Arabian continent to flow to the north through a slab-window. This resulted in mixing between the subduction-modified E Anatolian and the Arabian asthenospheres. On the basis of the results from our geochemical/ geochronologic/isotopic data and petrologic models, we argue that the temporal and spatial changes in the chemistry of volcanics across the region are the artifacts of these geodynamic events that controlled the movement and interaction of mantle domains with contrasting geochemical, isotopic and mineralogical identities. Compositions of some of the primitive magmas were further modified via interactions with the lithospheric mantle and/or crustal material coupled with fractionation en route to the surface.

  8. An attempt to monitor tectonic forces in the Vrancea active geodynamic zone: The Baspunar experiment

    NASA Astrophysics Data System (ADS)

    Besutiu, Lucian; Zlagnean, Luminita; Plopeanu, Marin

    2013-04-01

    An alternative model attempting to explain the unusual sub-crustal seismicity occurring in the bending zone of East Carpathians within full intra-continental environment (the so-called Vrancea zone) has assumed the presence of a FFT unstable triple junction between the three lithospheric compartments joining the area: East European Plate (EEP), Intra-Alpine Microplate (IaP) and the Moesian Microplate (MoP). Geophysical imprints (e.g. EM data, potential fields, seismic tomography), and indirect geological evidence (e.g. absence of the volcanism associated to subduction zones, the unusual high Neogene tectonic subsidence, symmetry and normal faulting within compressional environment of Focsani basin) support the hypothesis. The above-mentioned model considers the intermediate-depth seismicity as the result of the thermo-baric-accommodation phenomena generated within the colder lithosphere collapsed into the hotter upper mantle. Therefore, the amount of seismic energy thus released should be related to the volume of the lithosphere brought into thermo-baric disequilibrium by sinking into the upper mantle. Vertical dynamics of the Vrancea unstable triple junction (VTJ) seems to be controlled by the both tangential tectonic forces driving the neighbouring plates and the gravitational pull created by the eclogitization of VTJ lower crust. But, while eclogitization provides a relatively constant force, acceleration of sinking is expected to be provided by changes in the tectonic forces acting on VTJ. As changes in tectonic forces should reflect in changes of the dynamics of lithospheric compartments, geodetic means were considered for helping in their monitoring. The Peceneaga-Camena Fault (PCF) is a major lithospheric contact separating MoP and EEP, starting from the W Black Sea basin to the Vrancea zone. Geological evidence advocate for its variable geodynamic behaviour during the time, both as left-lateral or right-lateral fault. Unfortunately, GPS campaigns, so far

  9. Geodynamics and intermediate-depth seismicity in Vrancea (the south-eastern Carpathians): Current state-of-the art

    NASA Astrophysics Data System (ADS)

    Ismail-Zadeh, Alik; Matenco, Liviu; Radulian, Mircea; Cloetingh, Sierd; Panza, Giuliano

    2012-03-01

    The Vrancea region of the south-eastern Carpathians is a remarkable site of intra-continental intermediate-depth seismicity. A large set of geological, geophysical, and geodetic observations has been accumulated for the last few decades and utilised to improve our knowledge of the shallow and deep structures beneath Vrancea, the crustal and mantle dynamics, and the linkage between deep and surface processes in the region. In this article we review geology and tectonics of the Vrancea region including post-collisional to recent deformations, syn- to post-collisional magmatism, and orogenic exhumation along the East and South Carpathians. The regional seismicity is analysed, and the recent seismic studies including reflection, refraction, body and surface wave tomography are reviewed. We discuss new geodetic measurements of horizontal and vertical movements in the region, geoelectric studies, density/gravity and thermal modelling. Qualitative and quantitative (including retrospective) geodynamic models developed for Vrancea are analysed. The knowledge of regional tectonics, geodynamics, seismicity, lithospheric deformation, and stress regime in the Vrancea earthquake-prone region assists in an assessment of strong ground motion, seismic hazard and risk. The earthquake simulation, seismic hazard, and earthquake forecasting models have also been reviewed providing a link between deep geodynamic processes and their manifestation on the surface. Finally we discuss unresolved problems in Vrancea in order to improve our understanding of the regional evolution, present tectonics, mantle dynamics, intermediate-depth seismicity, and surface manifestations of the lithosphere dynamics and to enhance our ability to forecast strong earthquakes in the Vrancea region. The problems to be solved include: (i) the origin of the high-velocity body revealed by seismic tomography studies (oceanic versus continental); (ii) the lithospheric scale mechanism driving the Miocene subsidence of

  10. Software Attribution for Geoscience Applications in the Computational Infrastructure for Geodynamics

    NASA Astrophysics Data System (ADS)

    Hwang, L.; Dumit, J.; Fish, A.; Soito, L.; Kellogg, L. H.; Smith, M.

    2015-12-01

    Scientific software is largely developed by individual scientists and represents a significant intellectual contribution to the field. As the scientific culture and funding agencies move towards an expectation that software be open-source, there is a corresponding need for mechanisms to cite software, both to provide credit and recognition to developers, and to aid in discoverability of software and scientific reproducibility. We assess the geodynamic modeling community's current citation practices by examining more than 300 predominantly self-reported publications utilizing scientific software in the past 5 years that is available through the Computational Infrastructure for Geodynamics (CIG). Preliminary results indicate that authors cite and attribute software either through citing (in rank order) peer-reviewed scientific publications, a user's manual, and/or a paper describing the software code. Attributions maybe found directly in the text, in acknowledgements, in figure captions, or in footnotes. What is considered citable varies widely. Citations predominantly lack software version numbers or persistent identifiers to find the software package. Versioning may be implied through reference to a versioned user manual. Authors sometimes report code features used and whether they have modified the code. As an open-source community, CIG requests that researchers contribute their modifications to the repository. However, such modifications may not be contributed back to a repository code branch, decreasing the chances of discoverability and reproducibility. Survey results through CIG's Software Attribution for Geoscience Applications (SAGA) project suggest that lack of knowledge, tools, and workflows to cite codes are barriers to effectively implement the emerging citation norms. Generated on-demand attributions on software landing pages and a prototype extensible plug-in to automatically generate attributions in codes are the first steps towards reproducibility.

  11. Geodynamics of the Dead Sea Fault: Do active faulting and past earthquakes determine the seismic gaps?

    NASA Astrophysics Data System (ADS)

    Meghraoui, Mustapha

    2014-05-01

    The ~1000-km-long North-South trending Dead Sea transform fault (DSF) presents structural discontinuities and includes segments that experienced large earthquakes (Mw>7) in historical times. The Wadi Araba and Jordan Valley, the Lebanese restraining bend, the Missyaf and Ghab fault segments in Syria and the Ziyaret Fault segment in Turkey display geometrical complexities made of step overs, restraining and releasing bends that may constitute major obstacles to earthquake rupture propagation. Using active tectonics, GPS measurements and paleoseismology we investigate the kinematics and long-term/short term slip rates along the DSF. Tectonic geomorphology with paleoseismic trenching and archeoseismic investigations indicate repeated faulting events and left-lateral slip rate ranging from 4 mm/yr in the southern fault section to 6 mm/yr in the northern fault section. Except for the northernmost DSF section, these estimates of fault slip rate are consistent with GPS measurements that show 4 to 5 mm/yr deformation rate across the plate boundary. However, recent GPS results showing ~2.5 mm/yr velocity rate of the northern DSF appears to be quite different than the ~6 mm/yr paleoseismic slip rate. The kinematic modeling that combines GPS and seismotectonic results implies a complex geodynamic pattern where the DSF transforms the Cyprus arc subduction zone into transpressive tectonics on the East Anatolian fault. The timing of past earthquake ruptures shows the occurrence of seismic sequences and a southward migration of large earthquakes, with the existence of major seismic gaps along strike. In this paper, we discuss the role of the DSF in the regional geodynamics and its implication on the identification of seismic gaps.

  12. 3-D seismic tomography of the lithosphere and its geodynamic implications beneath the northeast India region

    NASA Astrophysics Data System (ADS)

    Raoof, J.; Mukhopadhyay, S.; Koulakov, I.; Kayal, J. R.

    2017-05-01

    We have evolved 3-D seismic velocity structures in northeast India region and its adjoining areas to understand the geodynamic processes of Indian lithosphere that gently underthrusts under the Himalayas and steeply subducts below the Indo-Burma Ranges. The region is tectonically buttressed between the Himalayan arc to the north and the Indo-Burmese arc to the east. The tomographic image shows heterogeneous structure of lithosphere depicting different tectonic blocks. Though our results are limited to shallower depth (0-90 km), it matches well with the deeper continuation of lithospheric structure obtained in an earlier study. We observe low-velocity structure all along the Eastern Himalayas down to 70 km depth, which may be attributed to deeper roots/thicker crust developed by underthrusting of Indian plate. Parallel to this low-velocity zone lies a high-velocity zone in foredeep region, represents the Indian lithosphere. The underthrusting Indian lithosphere under the Himalayas as well as below the Indo-Burma Ranges is well reflected as a high-velocity dipping structure. The buckled up part of bending Indian plate in study region, the Shillong Plateau-Mikir Hills tectonic block, is marked as a high-velocity structure at shallower depth. The Eastern Himalayan Syntaxis, tectonic block where the two arcs meet, is identified as a high-velocity structure. The Bengal Basin, tectonic block to the south of Shillong Plateau, shows low velocity due to its thicker sediments. Based on the tomographic image, a schematic model is presented to elucidate the structure and geodynamics of Indian lithosphere in study region.

  13. Modelling phase-assemblage diagrams for magnesian metapelites in the system K2O-FeO-MgO-Al2O3-SiO2-H2O: geodynamic consequences for the Monte Rosa nappe, Western Alps

    NASA Astrophysics Data System (ADS)

    Le Bayon, R.; de Capitani, C.; Frey, M.

    2006-04-01

    Magnesian metamorphic rocks with metapelitic mineral assemblage and composition are of great interest in metamorphic petrology for their ability to constrain P- T conditions in terranes where metamorphism is not easily visible. Phase-assemblage diagrams for natural and model magnesian metapelites in the system KFMASH are presented to document how phase relationships respond to water activity, bulk composition, pressure and temperature. The phase assemblages displayed on these phase diagrams are consistent with natural mineral assemblages occurring in magnesian metapelites. It is shown that the equilibrium assemblages at high pressure conditions are very sensitive to a(H2O). Specifically, the appearance of the characteristic HP assemblage chloritoid-talc-phengite-quartz (with excess H2O) in the magnesian metapelites of the Monte Rosa nappe (Western Alps) is due to the reduction of a(H2O). Furthermore, the mineral assemblages are determined by the whole-rock FeO/(FeO+MgO) ratio and effective Al content X A as well as P and T. The predicted mineral associations for the low- and high- X A model bulk compositions of magnesian metapelites at high pressure are not dependent on the X A variations as they show a similar sequence of mineral assemblages. Above 20 kbar, the prograde sequence of assemblages associated with phengite (with excess SiO2 and H2O) for low- and high- X A bulk compositions of magnesian metapelites is: carpholite-chlorite → chlorite-chloritoid → chloritoid-talc → chloritoid-talc-kyanite → talc-garnet-kyanite → garnet-kyanite ± biotite. At low to medium P- T conditions, a low- X A stabilises the phengite-bearing assemblages associated with chlorite, chlorite + K-feldspar and chlorite + biotite while a high- X A results in the chlorite-phengite bearing assemblages associated with pyrophyllite, andalusite, kyanite and carpholite. A high- X A magnesian metapelite with nearly iron-free content stabilises the talc-kyanite-phengite assemblage at

  14. Seismotectonics and Neotectonics of the Gulfs of Gökova-Kuşadasi-Siǧacik and Surrounding Regions (SW Turkey): Earthquake Mechanisms, Source Rupture Modeling, Tsunami Hazard and Geodynamic Implications

    NASA Astrophysics Data System (ADS)

    Yolsal-Cevikbilen, Seda; Karaoglu, Özgür; Taymaz, Tuncay; Helvaci, Cahit

    2013-04-01

    The mechanical behavior of the continental lithosphere for the Aegean region is one of the foremost interesting geological disputes in earth sciences. The Aegean region provides complex tectonic events which produced a strong heterogeneity in the crust (i.e. large thrusts and exhumation shear zones or extensional detachments) as such in among most continental regions. In order to investigate mechanical reasons of the ongoing lithospheric-scale extension within the region, we must tackle all of the existing kinematic and dynamic agents: (1) roll back of the subduction slab and back arc extension; (2) westward extrusion of the Anatolian micro-plate; (3) block rotations of the Aegean region and western Anatolia; and (4) transtensional transform faults. Furthermore, seismological studies, particularly earthquake source mechanisms and rupture modeling, play important roles on deciphering the ongoing deformation and seismotectonic characteristics of the region. Recently, many moderate earthquakes occurred in the Gulfs of Gökova, Kuşadası, Sıǧacık and surroundings. In the present study, we examined source mechanisms and rupture histories of those earthquakes with Mw > 5.0 in order to retrieve the geometry of active faulting, source characteristics, kinematic and dynamic source parameters and current deformations of the region by using teleseismic body-waveform inversion of long-period P- and SH-waves, and broad-band P-waveforms recorded by GDSN and FDSN stations. We also checked first motion polarities of P- waveforms recorded at regional and teleseismic stations and applied several uncertainty tests to find the error limits of minimum misfit solutions. Inversion results revealed E-W directed normal faulting mechanisms with small amount of left lateral strike slip components in the Gulf of Gökova and NE-SW oriented right lateral strike slip faulting mechanisms in the Gulf of Sıǧacık. Earthquakes mostly have N-S and NW-SE directed T- axes directions which are

  15. The role of modern geodynamics in the transformation of the local erosion basis in the Arctic river systems

    NASA Astrophysics Data System (ADS)

    Shapovalova, Elizaveta

    2015-04-01

    To assess the impact of modern geodynamic processes in the erosion of river channels in the area of oil and gas field, located in the permafrost region the following studies were made: interpretation of satellite images to identify fault zones in the structure of the landscape oil and gas field, located in the subarctic zone; mathematical modeling of extensive and local subsidence in the found faults areas; field measurements within the territory of the field. These studies led to conclusions about influence of modern geodynamic processes on activization of erosive processes. Dimensions of the studied field is approximately 40*60 km. As a result of extensive sagging modeling on its territory for the period of the end of the development the sag depth of the Earth's surface equal to 90 cm was obtained. In this case, the slope of the Earth's surface with respect to the central part of the study area will be 4.5 * 10-5. This slope is comparable with the values of the average slope of lowland rivers. For example, for the Ob River it is 4 * 10-5. This case shows that the river flowing through the field, due to changes in the local erosion basis may be experiencing channel deformation in its central part. According to the observations and model calculations local subsidence of the Earth's surface in fault zones induced by mining, lead to the Earth's surface inclines order 7 * 10-5 - 1.2 * 10-3. Field observations in 2014 in areas where active faults identified revealed a number of factors of changes in the river channel. There were areas overdeepened channel, tear off and slipped down blocks of rocks, leading to the subsequent transformation of the channel, as well as additional thermal erosion gullies that increase the accumulation of sediments and alter the structure of the river network. The combination of modern geodynamics with thermokarst processes in perennial permafrost layer enhances erosion. This investigations have shown that the factor of modern geodynamics of

  16. Brittle Solvers: Lessons and insights into effective solvers for visco-plasticity in geodynamics

    NASA Astrophysics Data System (ADS)

    Spiegelman, M. W.; May, D.; Wilson, C. R.

    2014-12-01

    Plasticity/Fracture and rock failure are essential ingredients in geodynamic models as terrestrial rocks do not possess an infinite yield strength. Numerous physical mechanisms have been proposed to limit the strength of rocks, including low temperature plasticity and brittle fracture. While ductile and creep behavior of rocks at depth is largely accepted, the constitutive relations associated with brittle failure, or shear localisation, are more controversial. Nevertheless, there are really only a few macroscopic constitutive laws for visco-plasticity that are regularly used in geodynamics models. Independent of derivation, all of these can be cast as simple effective viscosities which act as stress limiters with different choices for yield surfaces; the most common being a von Mises (constant yield stress) or Drucker-Prager (pressure dependent yield-stress) criterion. The choice of plasticity model, however, can have significant consequences for the degree of non-linearity in a problem and the choice and efficiency of non-linear solvers. Here we describe a series of simplified 2 and 3-D model problems to elucidate several issues associated with obtaining accurate description and solution of visco-plastic problems. We demonstrate that1) Picard/Successive substitution schemes for solution of the non-linear problems can often stall at large values of the non-linear residual, thus producing spurious solutions2) Combined Picard/Newton schemes can be effective for a range of plasticity models, however, they can produce serious convergence problems for strongly pressure dependent plasticity models such as Drucker-Prager.3) Nevertheless, full Drucker-Prager may not be the plasticity model of choice for strong materials as the dynamic pressures produced in these layers can develop pathological behavior with Drucker-Prager, leading to stress strengthening rather than stress weakening behavior.4) In general, for any incompressible Stoke's problem, it is highly advisable to

  17. Geomorphology and Geodynamics at Crustal Boundaries within Asia and Africa

    NASA Technical Reports Server (NTRS)

    2004-01-01

    The release of SRTM images by NASA over the past two years year has been greeted by foreign Earth scientist's as "NASA's gift to the World". The goodwill that this has engendered in parts of Africa. India, Pakistan and Bangladesh, as scientists in those countries contemplated what many of them considered an unprovoked and unjustifiable US invasion of Iraq, cannot be underestimated. We have used SRTM images from Africa and India and elsewhere to examine aspects of tectonism, geodynamics and tsunami and earthquake hazards. Highlights of this research are itemized in this final report. One difficulty that has arisen is , of course, that the funding for the science lead the availability of the data by more than a year. and as a result many of the findings are as yet unpublished.

  18. Effects of turbulence on the geodynamic laser ranging system

    NASA Technical Reports Server (NTRS)

    Churnside, James H.

    1993-01-01

    The Geodynamic Laser Ranging System (GLRS) is one of several instruments being developed by the National Aeronautics and Space Administration (NASA) for implementation as part of the Earth Observing System in the mid-1990s (Cohen et al., 1987; Bruno et al., 1988). It consists of a laser transmitter and receiver in space and an array of retroreflectors on the ground. The transmitter produces short (100 ps) pulses of light at two harmonics (0.532 and 0.355 microns) of the Nd:YAG laser. These propagate to a retroreflector on the ground and return. The receiver collects the reflected light and measures the round-trip transit time. Ranging from several angles accurately determines the position of the retroreflector, and changes in position caused by geophysical processes can be monitored.

  19. Aconcagua peak geodynamics from GPS observations, Mendoza, Argentina: preliminary results

    NASA Astrophysics Data System (ADS)

    Mateo, M. L.; Lenzano, L. E.; Moreiras, S. M.

    2009-12-01

    In 2005, the SIGMA Program (Mount Aconcagua GNSS Research System) was implemented to investigate the geodynamics of the Aconcagua mountain region in the Central Andes. For this purpose, a continuously recording GPS station, ACON, was installed on the summit of Mount Aconcagua at 6.292 m a.s.l. The installation required special technology to support the equipment under extreme climatic conditions. The power supply system was optimized in 2008, so that a greater quantity of data could be recorded. This, in turn, will lead to more accurate estimates of displacement of the Aconcagua peak. Preliminary results from the ACON station indicate an average horizontal velocity of 0.023±0.0001 m/yr toward NE in 2 time windows between 2006 and 2008.

  20. Laser Geodynamics Satellite- B-roll footage (No Sound)

    NASA Image and Video Library

    2016-05-04

    This 1975 NASA video highlights the development of LAser GEOdynamics Satellite (LAGEOS I). LAGEOS I is a passive satellite constructed from brass and aluminum and contains 426 individual precision reflectors made from fused silica glass. The mirrored surface of the satellite was designed to reflect laser beams from ground stations for accurate ranging measurements. LAGEOS I was launched on May 4, 1976 from Vandenberg Air Force Base, California. The two-foot diameter, 900-pound satellite orbited the Earth from pole to pole, measuring the movements of the Earth's surface relative to earthquakes, continental drift, and other geophysical phenomena. Scientists at NASA's Marshall Space Flight Center in Huntsville, Alabama came up with the idea for the satellite and built it at the Marshall Center.

  1. Geodynamics of the Gibraltar Arc and the Alboran Sea region

    NASA Astrophysics Data System (ADS)

    Corsini, M.; Chalouan, A.; Galindo-Zaldivar, J.

    2014-07-01

    Located at the Westernmost tip of the Mediterranean sea, the Gibraltar Arc is a very complex zone. The Betics in Spain and the Rif belt in Morocco surround the Alboran sea characterized by a thinned continental crust. The geodynamic evolution of this region results from the convergence of African and Iberian margins since the Late Cretaceous. It is controlled both by plate convergence and mantle dynamics, which significantly impact on morphology, sedimentary environments, tectonics, metamorphism and magmatism. We present here the contents of the special issue on the Gibraltar Arc and nearby regions, following the workshop organized at the University Abdelmalek Essaadi of Tetouan in Morocco from 27 to 28 October, 2011. The goal of this international workshop was to have an overview of the actual advance in research concerning the Rif and Betics chains, the Alboran basin, and their influence on the Iberian and African forelands.

  2. Estimation of Geodetic and Geodynamical Parameters with VieVS

    NASA Technical Reports Server (NTRS)

    Spicakova, Hana; Bohm, Johannes; Bohm, Sigrid; Nilsson, tobias; Pany, Andrea; Plank, Lucia; Teke, Kamil; Schuh, Harald

    2010-01-01

    Since 2008 the VLBI group at the Institute of Geodesy and Geophysics at TU Vienna has focused on the development of a new VLBI data analysis software called VieVS (Vienna VLBI Software). One part of the program, currently under development, is a unit for parameter estimation in so-called global solutions, where the connection of the single sessions is done by stacking at the normal equation level. We can determine time independent geodynamical parameters such as Love and Shida numbers of the solid Earth tides. Apart from the estimation of the constant nominal values of Love and Shida numbers for the second degree of the tidal potential, it is possible to determine frequency dependent values in the diurnal band together with the resonance frequency of Free Core Nutation. In this paper we show first results obtained from the 24-hour IVS R1 and R4 sessions.

  3. Dependency of geodynamic parameters on the GNSS constellation

    NASA Astrophysics Data System (ADS)

    Scaramuzza, Stefano; Dach, Rolf; Beutler, Gerhard; Arnold, Daniel; Sušnik, Andreja; Jäggi, Adrian

    2017-07-01

    Significant differences in time series of geodynamic parameters determined with different Global Navigation Satellite Systems (GNSS) exist and are only partially explained. We study whether the different number of orbital planes within a particular GNSS contributes to the observed differences by analyzing time series of geocenter coordinates (GCCs) and pole coordinates estimated from several real and virtual GNSS constellations: GPS, GLONASS, a combined GPS/GLONASS constellation, and two virtual GPS sub-systems, which are obtained by splitting up the original GPS constellation into two groups of three orbital planes each. The computed constellation-specific GCCs and pole coordinates are analyzed for systematic differences, and their spectral behavior and formal errors are inspected. We show that the number of orbital planes barely influences the geocenter estimates. GLONASS' larger inclination and formal errors of the orbits seem to be the main reason for the initially observed differences. A smaller number of orbital planes may lead, however, to degradations in the estimates of the pole coordinates. A clear signal at three cycles per year is visible in the spectra of the differences between our estimates of the pole coordinates and the corresponding IERS 08 C04 values. Combinations of two 3-plane systems, even with similar ascending nodes, reduce this signal. The understanding of the relation between the satellite constellations and the resulting geodynamic parameters is important, because the GNSS currently under development, such as the European Galileo and the medium Earth orbit constellation of the Chinese BeiDou system, also consist of only three orbital planes.

  4. Towards Grid-Enabling the Global Geodynamics Project

    NASA Astrophysics Data System (ADS)

    Lumb, I.; Aldridge, K. D.

    2004-05-01

    The Global Geodynamics Project (GGP) allows Earth scientists to access a network of globally distributed superconducting gravimeters (SGs). By establishing standards around SG instrumentation and data, in concert with various bilateral agreements, the GGP ensures scientific and organizational integrity. Now in its second phase, the GGP is proactively engaging non-traditional disciplines - i.e., those outside the tidal gravimetry community. Although GGP has generated interest with geodynamicists, seismologists, and others, there are practicalities which inhibit engangement by these `non-specialists'. For example, to geodynamicists and seismologists, tidal, atmospheric, hydrologic and oceanic signals are all unwanted. This means that the processed GGP Data must undergo further, non-trivial reductions before it is useful for geodynamic and seismic purposes. The requirement to correlate data in time and space presents another example. Currently this is a manually intensive process that requires geodynamicists and seismologists to specify temporal (e.g., a period of time, an event in time) and/or spatial (e.g., global, regional, specific instruments) specifics to allow for further analysis. These and other examples suggest infrastructural opportunities for further enabling GGP scientists. With decided emphasis on Virtual Organizations, open standards and qualities of experience, Grid Computing has the potential to facilitate deeper degrees of collaboration within the context of the GGP. Through use cases which seek to identify core resonance effects at semi-diurnal periods (e.g., Lumb et al., AGU Monograph 72, 51-68, 1993) and earthquake activity, various opportunities for Grid-enabling the GGP are identified and prioritized. Because the High Energy Physics community has figured so significantly in the development of the World Wide Web and The Grid, a Grid-enabled GGP also has the potential to play a role in shaping the ongoing evolution of Grid Computing.

  5. Geodynamic Regimes of the Mantle - Constraints From a He-Inclusive Global Data Compilation

    NASA Astrophysics Data System (ADS)

    Class, C.; Goldstein, S. L.

    2007-12-01

    27 years after the introduction of Chemical Geodynamics by Allègre (1982), fundamental issues about the geodynamic evolution of the Earth's mantle remain to be resolved. Geophysical evidence for whole mantle convection combined with the difficulty to preserve mantle heterogeneity since the early Earth contrast with geochemical evidence for longterm isolation of parts of the Earth's mantle. Noble gases, in particular helium, remain central to this discussion with three contrasting models considered here: (1) The layered mantle by Allègre et al. (1983) with the lower mantle preserving high 3He/4He ratios since early Earth; (2) The D" layer model by Tolstikhin & Hofmann (1995) with D" preserving high 3He/4He ratios since early Earth; (3) The incompletely degassing mantle model of Class and Goldstein (1995) with depleted mantle domains in the lower mantle preserving high 3He/4He ratios since 1-2 Ga. Here we present new constraints from our updated He-inclusive global data compilation. Ocean island basalts show a correlation between 3He/4He and Th contents, consistent with He isotope ratios reflecting the radiogenic production rate of the variably enriched OIB mantle sources. A high 3He/4He - low Th component is required to explain the global systematics. Constraints on the Th-U content in the three models place tight constraints on the absolute and relative contribution from the high 3He/4He reservoir to OIB mantle sources. Both the layered mantle model and the D" model requires small and extremely uniform contributions of a few percent or permil respectively; contributions outside of this small range, even if slightly higher or lower, are inconsistent with the global OIB data. Only the incompletely degassing mantle model allows for variability in the scale of contributions from old depleted mantle preserving higher 3He/4He ratios and from sources having a variety of ages. This model is also consistent with the requirement of dominantly peridotitic mantle sources for

  6. The Deep Structure and 3D Thermo-geodynamics of the Caucasus by Geophysical Data.

    NASA Astrophysics Data System (ADS)

    Chelidze, T.; Gugunava, G.; Gamkrelidze, N.; Mindeli, P.; Kiria, J.; Ghonghadze, S.; Janovskaya, O.

    2012-04-01

    The Caucasus is a continental collision zone, representing a connecting link between the Western and Eastern parts of the Alpine-Himalayan Belt. The structure and geodynamics have been studied rather well in both of the above mentioned segments of Alpine-Himalayan Belt, but remained problematic on the Caucasus. Compilation of detailed digital geophysical data bases and their numerical interpretation by modern methods are needed for the quantitative solution of the problem of structure and tectonics of the Caucasus. The first steps in these directions are made in this paper. The Caucasus is crossed by deep seismic sounding profiles "Gali-Safaraliev" (from the West of East) and "Bakuriani-Stepnoe" (from The North to South). Besides, there are the measurements of gravitational and magnetic fields at different heights along these lines. Integrated interpretation of the set of these geophysical fields by modern geophysical technique supplemented by the existing geological data allows approaching closely the solution of problems, related to structure and evolution of Caucasus. Three-dimensional stationary and non-stationary geothermal and thermo-elastic models of the Caucasus and the Black and Caspian seas areas are developed and their geological interpretation is given. The temperature field has been defined for the period 410 Ma on the basis of the stationary model of the investigated region. The thermo-elastic equations were solved and both horizontal and vertical thermo-elastic displacements have been calculated on the basis of the thermal field using Hook's rheology. These models revealed a number of interesting features in the geodynamics of the region. Nevertheless, they did not give us an opportunity to consider the dynamics of models, taking into account the process of sedimentation. That is why afterwards, computations were carried out on the basis of a non-stationary thermal model beginning from the period of the sedimentary cover formation. Such approach

  7. On principles, methods and recent advances in studies towards a GPS-based control system for geodesy and geodynamics

    NASA Technical Reports Server (NTRS)

    Delikaraoglou, Demitris

    1989-01-01

    Although Very Long Baseline Interferometry (VLBI) and Satellite Laser Ranging (SLR) are becoming increasingly important tools for geodynamic studies, their future role may well be fulfilled by using alternative techniques such as those utilizing the signals from the Global Positioning System (GPS). GPS, without the full implementation of the system, already offers a favorable combination of cost and accuracy and has consistently demonstrated the capability to provide high precision densification control in the regional and local areas of the VLBI and SLR networks. This report reviews VLBI and SLR vis-a-vis GPS and outlines the capabilities and limitations of each technique and how their complementary application can be of benefit to geodetic and geodynamic operations. It demonstrates, albeit with a limited data set, that dual-frequency GPS observations and interferometric type analysis techniques make possible the modelling of the GPS orbits for several days with an accuracy of a few meters. The use of VLBI or SLR sites as fiducial stations together with refinements in the orbit determination procedures can greatly reduce the systematic errors in the GPS satellite orbits used to compute the positions of non-fiducial locations. In general, repeatability and comparison with VLBI of the GPS determined locations are of the order of between 2 parts in 10 to the 7th power and 5 parts in 10 to the 8th power for baseline lengths less than 2000 km. This report is mainly a synthesis of problems, assumptions, methods and recent advances in the studies towards the establishment of a GPS-based system for geodesy and geodynamics and is one phase in the continuing effort for the development of such a system. To some, including the author, it seems reasonable to expect within the next few years that more evidence will show GPS to be as a powerful and reliable a tool as mobile VLBI and SLR are today, but largely more economical.

  8. Geological and geodynamic reconstruction of the East Barents megabasin from analysis of the 4-AR regional seismic profile

    NASA Astrophysics Data System (ADS)

    Startseva, K. F.; Nikishin, A. M.; Malyshev, N. A.; Nikishin, V. A.; Valyushcheva, A. A.

    2017-07-01

    The article considers problems related to the geological structure and geodynamic history of sedimentary basins of the Barents Sea. We analyze new seismic survey data obtained in 2005-2016 to refine the geological structure model for the study area and to render it in more detail. Based on the data of geological surveys in adjacent land (Novaya Zemlya, Franz Josef Land, and Kolguev Island), drilling, and seismic survey, we identified the following geodynamic stages of formation of the East Barents megabasin: Late Devonian rifting, the onset of postrift sinking and formation of the deep basin in Carboniferous-Permian, unique (in terms of extent) and very rapid sedimentation in the Early Triassic, continued thermal sinking with episodes of inversion vertical movements in the Middle Triassic-Early Cretaceous, folded pressure deformations that formed gently sloping anticlines in the Late Cretaceous-Cenozoic, and glacial erosion in the Quaternary. We performed paleoreconstructions for key episodes in evolution of the East Barents megabasin based on the 4-AR regional profile. From the geometric modeling results, we estimated the value of total crustal extension caused by Late Devonian rifting for the existing crustal model.

  9. Geodynamics of the Eastern Pacific Region, Caribbean and Scotia Arcs. Volume 9

    SciTech Connect

    Cabre, R.

    1983-01-01

    This book analyze the geodynamic phenomena related to the interaction of the eastern Pacific with the Americas between Canada and the Antarctic peninsula. Studies include the Cordilleran arcs and Juan de Fuca plate.

  10. Constraining the rheology of the lithosphere through joint geodynamic and gravity inversion

    NASA Astrophysics Data System (ADS)

    Kaus, Boris; Baumann, Tobias; Popov, Anton

    2014-05-01

    Understanding the physics of lithospheric deformation requires good constraints on lithospheric rheology and in particular on the effective viscosity. Typically, rheology is determined from laboratory experiments on small rock samples, which are extrapolated to geological conditions - an extrapolation over 10 orders of magnitude in deformation rates. Ideally, we thus need a new independent method that allows constraining the effective rheology of the lithosphere directly from geophysical data, which is the aim of this work. Our method uses the fact that the geodynamically controlling parameters of lithospheric deformation are its effective viscosity and density structure. By appropriately parametrising the rheological structure of the lithosphere we perform instantaneous forward simulations of present-day lithospheric deformation scenarios with a finite element method to compute the gravity field as well as surface velocities. The forward modelling results can be compared with observations such as Bouguer anomalies and GPS-derived surface velocities. More precisely, we automatise the forward modelling procedure with a Markov-Chain Monte Carlo method, and in fact solve a joint geodynamic and gravity inverse problem. The resulting misfit can be illustrated as a function of rheological model parameters and a more detailed analysis allows constraining probabilistic parameter ranges. Yet, the lithosphere has non-linear rheologies that can be plastic or temperature-dependent powerlaw creep depending on stresses. As the thermal structure of the lithosphere is in general poorly constrained, and only affects the dynamics of the lithosphere in an indirect manner, we developed a parameterised rheology that excludes a direct temperature dependency. To test the accuracy of this approximation we perform lithospheric-scale collision forward models that incorporate a temperature-dependent visco-plastic rheology to create synthetic surface observations. In a second step, we deploy

  11. Geodynamic and Seismic Constraints on the Evolution of the Oceanic Lithosphere and Asthenosphere

    NASA Astrophysics Data System (ADS)

    Fahy, E. H.; Hall, P. S.; Dalton, C. A.; Faul, U.

    2011-12-01

    We report on a series of numerical geodynamic experiments undertaken to investigate the evolution the oceanic lithosphere and the characteristics of the underlying asthenosphere. In particular, we used the CitcomCU finite element package to model mantle flow beneath an oceanic plate. Experiments incorporated deformation by both diffusion creep and dislocation creep mechanisms, with experimentally constrained constants used for the relevant flow laws. We find that the use of flow laws appropriate for wet olivine aggregates leads to the formation of instabilities at the base of the thermal boundary layer corresponding to the lithosphere, which are not found in the experiments employing flow laws for dry olivine. These instabilities effectively thin the older portions of the thermal boundary layer, resulting in an average temperature structure closely resembling the GDH1 plate model [Stein and Stein, 1992] within the model domain. In contrast, the thermal structure of experiments in which instabilities do not form resembles resembles that of a half-space cooling model. Comparison of experimental results to seismic models of variations in shear wave velocity and shear attenuation with both depth and age within the oceanic upper mantle indicates that experiments in which instabilities occur provide a better match to seismic observations than do experiments without such instabilities.

  12. Seismic Velocity Structure of the Mantle beneath the Hawaiian Hotspot and Geodynamic Perspectives

    NASA Astrophysics Data System (ADS)

    Wolfe, C. J.; Laske, G.; Ballmer, M. D.; Ito, G.; Collins, J. A.; Solomon, S. C.; Rychert, C. A.

    2012-12-01

    Data from the PLUME deployments of land and ocean bottom seismometers have provided unprecedented new constraints on regional seismic structure of the mantle beneath the Hawaiian Islands and motivated a new generation of geodynamic models for understanding hotspot origins. Three-dimensional finite-frequency body-wave tomographic images of S- and P-wave velocity structure reveal an upper-mantle low-velocity anomaly beneath Hawaii that is elongated in the direction of the island chain and surrounded by a high-velocity anomaly in the shallow upper mantle that is parabolic in map view. Low velocities continue downward to the mantle transition zone between 410 and 660 km depth and extend into the topmost lower mantle southeast of Hawaii. Upper mantle structure from both S and P waves is asymmetric about the island chain, with lower velocities just southwest of the island of Hawaii and higher velocities to the east. Independent Rayleigh-wave tomography displays a similarly asymmetric structure in the lower lithosphere and asthenosphere, and also reveals a low-velocity anomaly (with horizontal dimensions of 100 by 300 km across and along the chain, respectively) beneath the hotspot swell that reaches to depths of at least 140 km. Shear-wave splitting observations dominantly reflect fossil lithospheric anisotropy, although a signature of asthenospheric flow also may be resolvable. S-to-P receiver function imaging of the lithosphere-asthenosphere boundary suggests shoaling from 100 km west of Hawaii to 80 km beneath the island, a pattern consistent with results from Rayleigh wave imaging. In terms of mantle plume geodynamic models, the broad upper-mantle low-velocity region beneath the Hawaiian Islands may reflect the "diverging pancake" at the top of the upwelling zone; the surrounding region of high velocities could represent a downwelling curtain of relatively cool sublithospheric material; and the low-velocity anomalies southeast of Hawaii in the transition zone and

  13. Constraining the rheology of the lithosphere through joint geodynamic and gravity inversion

    NASA Astrophysics Data System (ADS)

    Kaus, Boris; Baumann, Tobias; Popov, Anton

    2013-04-01

    In order to understand the physics of the lithospheric deformation and continental collision we need to have better constraints on its rheology and in particular on the effective viscosity of various parts of the lithosphere. Typically, rheology is determined from laboratory experiments on small rock samples, which are extrapolated to geological conditions - an extrapolation over 10 orders of magnitude in deformation rates. These laboratory experiments generally show that small changes in the composition of the rocks, such as adding a bit of water, can dramatically change its viscosity. Moreover, it is unclear which rocktype gives the best mechanical description of, for example, the upper crust and whether a small sample is even appropriate to describe the large scale mechanical behaviour of the crust (or whether this is rather controlled by heterogeneities such as fault zones and batholiths). So the viscosity of the lithosphere is probably the least constrained parameter in geodynamics and might vary over maybe 10 orders of magnitude. The concept of the effective elastic thickness is often used to make statements about the mechanical strength of the lithosphere. Whereas there is general agreement that the concept of EET works will in oceanic lithospheres, there are huge discrepancies in the EET for active collision belts in continental lithospheres, partly because the (mechanical) lithosphere at those locations is unlikely to be a thin elastic plate floating on a viscous mantle, but is rather multi-layered. Ideally, we thus need a new independent method that allows constraining the effective rheology of the lithosphere directly from geophysical data, which is the aim of this work. Our method uses the fact that geodynamically the controlling parameters of lithospheric deformation are its effective viscosity and density structure (which can both be depth-dependent). By performing a forward simulation with a lithospheric deformation code we can model both the gravity

  14. Influences of a ridge subduction on seismicity and geodynamics in the central Vanuatu arc.

    NASA Astrophysics Data System (ADS)

    Baillard, C.; Crawford, W. C.; Ballu, V.; Regnier, M. M.; Pelletier, B.; Garaebiti, E.

    2014-12-01

    The central part of the Vanuatu arc is characterized by the subduction of the d'Entrecasteaux ridge under the North Fiji Basin. This ridge influences directly the seismicity and the geodynamics in the proximal region. By analyzing the hypocenters from a local microseismic catalog (2008-2009) and global catalogs we show that the subduction interface, in the first 50 km depth, presents a small dipping angle where the ridge is subducting. This bump highlights the buoyancy of the ridge associated to the excess of fluids present in the seamount. This underplating could explain 20% to 60% of the vertical displacement estimated on the forearc islands from corals datations and that can reach a maximum of 6 mm/yr. The high concentration of hydrous minerals in the subducting ridge might also explain the important activity of intermediate depth earthquakes (half of the total activity in the studied region), we observed a very good correlation between the supposed extension of the ridge in depth and the location of these earthquakes. We propose that they are associated to crust minerals dehydration that causes hydrous fracturation trough preexistent faults. This dehydration process is maintained to a maximum depth of 190 km due to the high thermal parameter of the australian plate.Using the geometry of the Wadati-Benioff plane derived from earthquakes localisations, we established a 2D mechanical model to explain the horizontal interseismic displacement observed by GPS on islands of the upper plate. We show that the subduction interface alone cannot explain the GPS velocities observed, the system of thrust faults located below the back arc islands of Maewo and Pentecost, plays a major role in the region geodynamics and accommodate as much convergence as the subduction interface (between ~16 and 34 mm/yr). Using the model we were also able to explain the closing of the Aoba basin during interseismic phase (~25 mm/an). Finally, the mechanical model suggests the existence of a 23

  15. Geodynamic inversion to constrain the rheology of the lithosphere: What is the effect of elasticity?

    NASA Astrophysics Data System (ADS)

    Baumann, Tobias; Kaus, Boris; Thielmann, Marcel

    2016-04-01

    The concept of elastic thickness (T_e) is one of the main methods to describe the integrated strength of oceanic lithosphere (e.g. Watts, 2001). Observations of the Te are in general agreement with yield strength envelopes estimated from laboratory experiments (Burov, 2007, Goetze & Evans 1979). Yet, applying the same concept to the continental lithosphere has proven to be more difficult (Burov & Diament, 1995), which resulted in an ongoing discussion on the rheological structure of the lithosphere (e.g. Burov & Watts, 2006, Jackson, 2002; Maggi et al., 2000). Recently, we proposed a new approach, which constrains rheological properties of the lithosphere directly from geophysical observations such as GPS-velocity, topography and gravity (Baumann & Kaus, 2015). This approach has the advantage that available data sets (such as Moho depth) can be directly taken into account without making the a-priori assumption that the lithosphere is thin elastic plate floating on the mantle. Our results show that a Bayesian inversion method combined with numerical thermo-mechanical models can be used as independent tool to constrain non-linear viscous and plastic parameters of the lithosphere. As the rheology of the lithosphere is strongly temperature dependent, it is even possible to add a temperature parameterisation to the inversion method and constrain the thermal structure of the lithosphere in this manner. Results for the India-Asia collision zone show that existing geophysical data require India to have a quite high effective viscosity. Yet, the rheological structure of Tibet less well constrained and a number of scenarios give a nearly equally good fit to the data. Yet, one of the assumptions that we make while doing this geodynamic inversion is that the rheology is viscoplastic, and that elastic effects do not significantly alter the large-scale dynamics of the lithosphere. Here, we test the validity of this assumption by performing synthetic forward models and retrieving

  16. Crustal tomographic imaging and geodynamic implications toward south of Southern Granulite Terrain (SGT), India

    NASA Astrophysics Data System (ADS)

    Behera, Laxmidhar

    2011-09-01

    The crustal structure toward southern part of SGT is poorly defined leaving an opportunity to understand the tectonic and geodynamic evolution of this high-grade granulite terrain surrounded by major shear and tectonically disturbed zones like Achankovil Shear Zone (AKSZ) and Palghat Cauvery Shear Zone (PCSZ). To develop a geologically plausible crustal tectonic model depicting major structural elements, a comprehensive tomographic image was derived using deep-seismic-sounding data corroborated by Bouguer gravity modeling, coincident-reflection-seismic, heat-flow and available geological/geochronological informations along the N-S trending Vattalkundu-Kanyakumari geotransect. The final tectonic model represents large compositional changes of subsurface rocks accompanied by velocity heterogeneities with crustal thinning (44-36 km) and Moho upwarping from north to south. This study also reveals and successfully imaged anomalous zone of exhumation near AKSZ having transpression of exhumed rocks at mid-to-lower crustal level (20-30 km) with significant underplating and mantle upwelling forming a complex metamorphic province. The presence of shear zones with high-grade charnockite massifs in the upper-crust exposed in several places reveal large scale exhumation of granulites during the Pan-African rifting (~ 550 Ma) and provide important insights of plume-continental lithosphere interaction with reconstruction of the Gondwanaland.

  17. Chronological constraints on the Permian geodynamic evolution of eastern Australia

    NASA Astrophysics Data System (ADS)

    Li, Pengfei; Rosenbaum, Gideon; Vasconcelos, Paulo

    2014-03-01

    The New England Orogen in eastern Australia developed as a subduction-related orogen in the Late Devonian to Carboniferous, and was modified in the Permian by deformation, magmatism and oroclinal bending. The geodynamics associated with the development of the New England oroclines and the exact timing of major tectonic events is still enigmatic. Here we present new 40Ar/39Ar results from metasedimentary and volcanic rocks from the southern New England Orogen. Eight grains from four metasedimentary samples (Texas beds) that originated in the Late Devonian to Carboniferous accretionary wedge yielded reproducible plateau ages of ~ 293, ~ 280, ~ 270 and ~ 260 Ma. These results suggest a complex thermal history associated with multiple thermal events, possibly due to the proximity to Permian intrusions. Two samples from mafic volcanic rocks in the southernmost New England Orogen (Alum Mountain Volcanics and Werrie Basalt) yielded eruption ages of 271.8 ± 1.8 and 266.4 ± 3.0 Ma. The origin of these rocks was previously attributed to slab breakoff, following a period of widespread extension in the early Permian. We suggest that this phase of volcanism marked the transition from backarc extension assisted by trench retreat to overriding-plate contraction. The main phase of oroclinal bending has likely occurred during backarc extension in the early Permian, and terminated at 271-266 Ma with the processes of slab segmentation and breakoff.

  18. Global Biomass Variation and its Geodynamic Effects, 1982-1998

    NASA Technical Reports Server (NTRS)

    Rodell, M.; Chao, B. F.; Au, A. Y.; Kimball, J. S.; McDonald, K. C.

    2005-01-01

    Redistribution of mass near Earth's surface alters its rotation, gravity field, and geocenter location. Advanced techniques for measuring these geodetic variations now exist, but the ability to attribute the observed modes to individual Earth system processes has been hampered by a shortage of reliable global data on such processes, especially hydrospheric processes. To address one aspect of this deficiency, 17 yrs of monthly, global maps of vegetation biomass were produced by applying field-based relationships to satellite-derived vegetation type and leaf area index. The seasonal variability of biomass was estimated to be as large as 5 kg m(exp -2). Of this amount, approximately 4 kg m(exp -2) is due to vegetation water storage variations. The time series of maps was used to compute geodetic anomalies, which were then compared with existing geodetic observations as well as the estimated measurement sensitivity of the Gravity Recovery and Climate Experiment (GRACE). For gravity, the seasonal amplitude of biomass variations may be just within GRACE'S limits of detectability, but it is still an order of magnitude smaller than current observation uncertainty using the satellite-laser-ranging technique. The contribution of total biomass variations to seasonal polar motion amplitude is detectable in today's measurement, but it is obscured by contributions from various other sources, some of which are two orders of magnitude larger. The influence on the length of day is below current limits of detectability. Although the nonseasonal geodynamic signals show clear interannual variability, they are too small to be detected.

  19. Paradoxes of high and low velocities in modern geodynamics

    NASA Astrophysics Data System (ADS)

    Makarov, P. V.

    2016-11-01

    An analysis of the data on the vertical and horizontal movements of the Earth's crust obtained within recent 40 years has revealed paradoxical deviations of its deformations from the movements inherited from the past geological times. Currently, high local deformation velocities are observed both in the aseismic and seismically active regions. There are no clues to this phenomenon within the conventional concepts of geodynamics and mechanics of deformed solids. It is shown in this work that the paradoxes of high and low velocities could be solved if deformation processes taking place in the Earths' crust would be treated as the evolution of the stress-strain state of the loaded medium as a typical non-linear dynamic system. In this case, fracture develops in two stages—a comparatively slow quasi-stationary stage and a superfast catastrophic one, wherein the spatial localization of parameters is followed by the localization of the deformation process in time. This property is a fundamental characteristic of any non-linear dynamic systems.

  20. Global Biomass Variation and its Geodynamic Effects, 1982-1998

    NASA Technical Reports Server (NTRS)

    Rodell, M.; Chao, B. F.; Au, A. Y.; Kimball, J. S.; McDonald, K. C.

    2005-01-01

    Redistribution of mass near Earth's surface alters its rotation, gravity field, and geocenter location. Advanced techniques for measuring these geodetic variations now exist, but the ability to attribute the observed modes to individual Earth system processes has been hampered by a shortage of reliable global data on such processes, especially hydrospheric processes. To address one aspect of this deficiency, 17 yrs of monthly, global maps of vegetation biomass were produced by applying field-based relationships to satellite-derived vegetation type and leaf area index. The seasonal variability of biomass was estimated to be as large as 5 kg m(exp -2). Of this amount, approximately 4 kg m(exp -2) is due to vegetation water storage variations. The time series of maps was used to compute geodetic anomalies, which were then compared with existing geodetic observations as well as the estimated measurement sensitivity of the Gravity Recovery and Climate Experiment (GRACE). For gravity, the seasonal amplitude of biomass variations may be just within GRACE'S limits of detectability, but it is still an order of magnitude smaller than current observation uncertainty using the satellite-laser-ranging technique. The contribution of total biomass variations to seasonal polar motion amplitude is detectable in today's measurement, but it is obscured by contributions from various other sources, some of which are two orders of magnitude larger. The influence on the length of day is below current limits of detectability. Although the nonseasonal geodynamic signals show clear interannual variability, they are too small to be detected.

  1. Local, regional and global signals in longterm time series of gravity, tilt and strain at the Geodynamic Observatory Moxa/Germany

    NASA Astrophysics Data System (ADS)

    Jahr, T.; Kukowski, N.; Schindler, P.; Weise, A.; Jentzsch, G.

    2012-04-01

    For the past 15 years geodynamic signals in gravity, tilt and strain are recorded continuously at the Observatory Moxa in Thuringia/Germany. In the period range between minutes and years signals of interest are the free modes of the Earth, the tides, the polar motion with the Chandler Wobble up to the very long- and non-periodic effects. These global signals can be overlain or masked by local signals, caused by sources in the nearby surroundings of the observatory. These recorded local signals originate from fluctuations of meteorological and hydrological parameters as well as by anthropogenic effects. Modelling and elimination of the effects of environmental parameters in the time series are a great challenge for geodynamic observatories worldwide. For the past several years, the work at the Observatory Moxa is focusing on the separation of local, regional and global parts of the signals. Here, we present several signals in gravity, tilt and strain, e.g. barometric pressure, preciptation and groundwater level, separated from our time series, showing the broad application in geodynamics.

  2. Geodynamics of passive margins: insights from the DFG Schwerpunktprogramm SAMPLE for the South Atlantic and beyond

    NASA Astrophysics Data System (ADS)

    Bunge, Hans-Peter

    2016-04-01

    The DFG Priority Program SAMPLE (South Atlantic Margin Processes and Links with onshore Evolution: http://www.sample-spp.de/), which is to be completed 2016, has studied the evolution of the South Atlantic from its Cretaceous inception to the present day. The program has an explicit interdisciplinary focus, drawing on constraints from deep Earth geophysics, lithosphere and basin dynamics, petrology, landscape evolution and geodesy, thus linking processes that are commonly studied in isolation. Starting from the premise that passive margins are first-order geo-archives, the program has placed the South Atlantic opening history into an observational and theoretical context that considers seismic imaging, plate motion histories, uplift and subsidence events, magmatic and surface evolution, together with models of mantle convection and lithosphere dynamics. A primary lesson is that passive margins are active, displaying a range of vertical motion (i.e. dynamic topography) events, apparently correlated with plate motion changes, that do not conform to traditional rifting models of passive margins. I will summarize some observational results of the program, and place them into a geodynamic context.

  3. Detection of metastable olivine wedge in the western Pacific slab and its geodynamic implications

    NASA Astrophysics Data System (ADS)

    Jiang, Guoming; Zhao, Dapeng; Zhang, Guibin

    2015-01-01

    Seismic tomography and numerical simulations show that the western Pacific slab bends horizontally when it reaches the boundary between the upper mantle and lower mantle beneath northeast Asia. It is expected that a metastable olivine wedge (MOW) exists in the cold core of the slab because of a delayed phase transition from olivine to its high-pressure polymorphs. However, it is still debated whether the MOW actually exists or not, and even if it exists, its physical properties, such as seismic velocity and density, are still unclear. In this work we use high-quality arrival-time data of 17 deep earthquakes occurring within the Pacific slab under northeast Asia to study the detailed structure of the slab. The deep earthquakes are relocated precisely by applying a modified double-difference location method to arrival-time data recorded at both Chinese and Japanese stations. Based on the precise hypocentral locations, a forward modeling method and differential travel-time residuals data are used to estimate seismic velocity within the deep source zone, which can decrease or remove the influence of ambient velocity heterogeneities. Our results show that the MOW does exist within the Pacific slab under northeast Asia, and the MOW has a mean velocity anomaly of 7-9% lower than the iasp91 Earth model. The existence of MOW in the slab has important geodynamic implications. It can reduce the speed of slab subduction and affect the generation of deep earthquakes.

  4. Metamorphic pattern of the Cretaceous Celica Formation, SW Ecuador, and its geodynamic implications

    NASA Astrophysics Data System (ADS)

    Aguirre, Luis

    1992-04-01

    The volcanic rocks of the Cretaceous Celica Formation of southern Ecuador are affected by a weak although widespread alteration. The chemical study of the secondary chemical phases present in andesitic and basaltic lava flows reveals that this alteration corresponds to very low-grade metamorphism comprising the zeolite and the prehnite-pumpellyite facies. Main features of this metamorphism are: weak lithostatic pressure, moderate to steep thermal gradient, high ƒ O2, low value of the seawater/rock ratio and total absence of deformation. These characteristics are typically present in other volcanic suites of similar age and composition along the Andes and correspond to the pattern of metamorphism developed in extensional settings (diastathermal metamorphism) linked to various degrees of thinning of the continental crust. Based on this metamorphic pattern, a geodynamic model is proposed in which the Celica Formation is interpreted as an ensialic, aborted, marginal basin developed on strongly attenuated continental crust at the border of the South American plate. The relationship between the Ecuadorian and Colombian volcanic suites of Cretaceous age present along the Western Cordillera is discussed in the light of the model suggested.

  5. Geodynamic evolution and sedimentary infill of the northern Levant Basin: A source to sink-perspective

    NASA Astrophysics Data System (ADS)

    Hawie, N.

    2013-12-01

    quantities of clastic material into the Levant Basin: (1) the marginal canyons along the Levant Margin, (2) the Latakia region and the Palmyrides Basin (Syria) and (3) the Red Sea area and Nile Delta. Regional drainage system analysis was performed to estimate the contribution to the infill of the basin of the different sediment sources, and in particular, to estimate erosion of Nubian siliciclastic material, granitic Red Sea rift shoulders and Arabian Shield. A numerical stratigraphic forward model, Dionisos, was used to test these source-to-sink assumptions; a sensitivity analysis was then performed to understand better the impact of the different geodynamic and stratigraphic scenarios on the architecture and sedimentary infill of the Levant Basin, and thus on the expected petroleum systems of this frontier basin

  6. Crustal Accretion and Mantle Geodynamics at Microplates: Constraints from Gravity Analysis

    NASA Astrophysics Data System (ADS)

    Ames, K.; Georgen, J. E.; Dordevic, M. M.

    2013-12-01

    Oceanic crustal accretion occurs in a variety of locations, including mid-ocean ridges and back-arc spreading centers, and in unique settings within these systems, such as plate boundary triple junctions, intra-transform spreading centers, and microplates. This study focuses on crustal accretion and mantle geodynamics at microplates. The Easter and Juan Fernandez microplates are located in the South Pacific along the Pacific, Nazca and Antarctic plate boundaries. Both microplates formed 3-5 Ma and they are currently rotating clockwise at 15 deg/Ma and 9 deg/Ma respectively (e.g., Searle et al. J. Geol. Soc. Lond. 1993). The study area also encompasses the Easter/Sala y Gomez mantle plume and the Foundation seamount chain, both of which are located close to spreading centers. We calculate mantle Bouguer anomaly (MBA) from satellite gravity measurements and shipboard soundings in order to gain a better understanding of the thermal structure of these two oceanic microplates and to quantify the effect that melting anomalies may have on their boundaries. We assume a crustal thickness of 6.0 km, a 1.7 g/cm^3 density difference at the water/crust interface, and a 0.6 g/cm^3 density difference at the crust/mantle interface. The west rift of the Easter microplate has an MBA low ranging from approximately -50 to -100 mGal, while the east rift has slightly higher MBA values ranging from roughly 10 to -50 mGal. The west rift of the Juan Fernandez microplate has a maximum MBA low of about -100 mGal with a sharp increase to -20 mGal at -35 deg S. The east rift of the Juan Fernandez microplate is characterized by more variable MBA, ranging from 0 to -140 mGal. The MBA low associated with the Easter/Sala y Gomez mantle plume has a maximum amplitude about 150 mGal. Likewise, the Foundation seamounts show a gravity low of -140 to -150 mGal. These spatial variations in gravity, as well as published isotopic data and exploratory numerical models, are used to constrain upper mantle

  7. Estimation of Non-Seasonal Oceanic Mass Redistribution and its Geodynamic Effects from the Topex/Poseidon Observation

    NASA Technical Reports Server (NTRS)

    Chao, Benjamin F.; Ray, Richard D.; Au, A. Y.

    1999-01-01

    Mass redistribution in terms of angular momentum will change the Earth's rotation under the conservation of angular momentum. It also changes the external gravitational field according to Newton's gravitational law. These small geodynamic variations can be measured very accurately by modem space geodetic techniques. We report on new estimates of the oceanic tidal angular momentum and hence the tidal variations in the Earth's rotation rate and polar motion. These are deduced from the new tidal solutions GOT99 and TPXO.3, plus M2 and Mf estimates (with error bars) from TPXO.4a. Comparisons with observed diurnal/semidiurnal tidal variations are generally similar to previous model estimates. Comparisons of models and observations of Mf polar motion are confused, with neither models nor observations agreeing among themselves or with each other. Part of this is caused by differences in Mf currents; model TPXO.4 shows current-intensive Rossby modes along western boundaries of major basins, which are indeed expected on theoretical grounds. Unfortunately, there are no reliable in situ observations of Mf currents useful for comparing models. On non-tidal oceanic mass redistribution we compute the principal components of the multi-year T/P sea surface height (SSH) field using EOF (empirical orthogonal functions) taking into consideration of the latitude-dependent area weighting. Emphasis is placed upon non-seasonal and interannual oscillations on regional scales, including ENSO and the North Atlantic Oscillation. Steric corrections to the observed SSH due to sea surface temperature changes (which has no geodynamic effects) is now under study using POCM ocean model output.

  8. Estimation of Non-Seasonal Oceanic Mass Redistribution and its Geodynamic Effects from the Topex/Poseidon Observation

    NASA Technical Reports Server (NTRS)

    Chao, Benjamin F.; Ray, Richard D.; Au, A. Y.

    1999-01-01

    Mass redistribution in terms of angular momentum will change the Earth's rotation under the conservation of angular momentum. It also changes the external gravitational field according to Newton's gravitational law. These small geodynamic variations can be measured very accurately by modem space geodetic techniques. We report on new estimates of the oceanic tidal angular momentum and hence the tidal variations in the Earth's rotation rate and polar motion. These are deduced from the new tidal solutions GOT99 and TPXO.3, plus M2 and Mf estimates (with error bars) from TPXO.4a. Comparisons with observed diurnal/semidiurnal tidal variations are generally similar to previous model estimates. Comparisons of models and observations of Mf polar motion are confused, with neither models nor observations agreeing among themselves or with each other. Part of this is caused by differences in Mf currents; model TPXO.4 shows current-intensive Rossby modes along western boundaries of major basins, which are indeed expected on theoretical grounds. Unfortunately, there are no reliable in situ observations of Mf currents useful for comparing models. On non-tidal oceanic mass redistribution we compute the principal components of the multi-year T/P sea surface height (SSH) field using EOF (empirical orthogonal functions) taking into consideration of the latitude-dependent area weighting. Emphasis is placed upon non-seasonal and interannual oscillations on regional scales, including ENSO and the North Atlantic Oscillation. Steric corrections to the observed SSH due to sea surface temperature changes (which has no geodynamic effects) is now under study using POCM ocean model output.

  9. Geodynamic investigation of the processes that control Lu-Hf isotopic differences between different mantle domains and the crust

    NASA Astrophysics Data System (ADS)

    Jones, Rosie; van Keken, Peter; Hauri, Erik; Vervoort, Jeff; Ballentine, Chris J.

    2016-04-01

    The chemical and isotopic composition of both the Earth's mantle and the continental crust are greatly influenced by subduction zone processes, such as the formation of continental crust through arc volcanism and the recycling of surface material into the deep mantle. Here we use a combined geodynamical-geochemical approach to investigate the long term role of subduction on the Lu-Hf isotopic evolution of the mantle and the continental crust. We apply the geodynamic model developed by Brandenburg et al., 2008. This model satisfies the geophysical constraints of oceanic heat flow and average plate velocities, as well as geochemical observations such as 40Ar in the atmosphere, and reproduces the geochemical distributions observed in multiple isotope systems which define the HIMU, MORB and EM1 mantle endmembers. We extend this application to investigate the detail of terrestrial Lu-Hf isotope distribution and evolution, and specifically to investigate the role of sediment recycling in the generation of EM2 mantle compositions. The model has been updated to produce higher resolution results and to include a self-consistent reorganisation of the plates with regions of up-/down-wellings. The model assumes that subduction is initiated at 4.5 Ga and that a transition from 'dry' to 'wet' subduction occurred at 2.5 Ga. The modelling suggests that the epsilon Hf evolution of the upper mantle can be generated through the extraction and recycling of the oceanic crust, and that the formation of continental crust plays a lesser role. Our future intention is to utilise the model presented here to investigate the differences observed in the noble gas compositions (e.g., 40Ar/36Ar, 3He/4He) of MORB and OIB. Brandenburg, J.P., Hauri, E.H., van Keken, P.E., Ballentine, C.J., 2008. Earth and Planetary Science Letters 276, 1-13.

  10. Geodynamics of the northern Andes: Subductions and intracontinental deformation (Colombia)

    NASA Astrophysics Data System (ADS)

    Taboada, Alfredo; Rivera, Luis A.; Fuenzalida, AndréS.; Cisternas, Armando; Philip, Hervé; Bijwaard, Harmen; Olaya, José; Rivera, Clara

    2000-10-01

    New regional seismological data acquired in Colombia during 1993 to 1996 and tectonic field data from the Eastern Cordillera (EC) permit a reexamination of the complex geodynamics of northwestern South America. The effect of the accretion of the Baudó-Panama oceanic arc, which began 12 Myr ago, is highlighted in connection with mountain building in the EC. The Istmina and Ibagué faults in the south and the Santa Marta-Bucaramanga fault to the northeast limit an E-SE moving continental wedge. Progressive indentation of the wedge is absorbed along reverse faults located in the foothills of the Cordilleras (northward of 5°N) and transpressive deformation in the Santander Massif. Crustal seismicity in Colombia is accurately correlated with active faults showing neotectonic morphological evidences. Intermediate seismicity allows to identify a N-NE trending subduction segment beneath the EC, which plunges toward the E-SE. This subduction is interpreted as a remnant of the paleo-Caribbean plateau (PCP) as suggested by geological and tomographic profiles. The PCP shows a low-angle subduction northward of 5.2°N and is limited southward by a major E-W transpressive shear zone. Normal oceanic subduction of the Nazca plate (NP) ends abruptly at the southern limit of the Baudó Range. Northward, the NP subducts beneath the Chocó block, overlapping the southern part of the PCP. Cenozoic shortening in the EC estimated from a balanced section is ˜120 km. Stress analysis of fault slip data in the EC (northward of 4°N), indicates an ˜E-SE orientation of σ1 in agreement with the PCP subduction direction. Northward, near Bucaramanga, two stress solutions were observed: (1) a late Andean N80°E compression and (2) an early Andean NW-SE compression.

  11. Dynamical approach to study and interpret geodynamical and geophysical effects

    NASA Astrophysics Data System (ADS)

    Ferronsky, V.

    2009-04-01

    It was proved by satellite and terrestrial observation that the hydrostatics, which operates by the outer forces, is not able to ensure correct description and interpretation of geodynamical and geophysical effects. In order to find solution of the problem, we applied to dynamics. For this purpose the outer force field of the Earth was replaced by its inner (volumetric) force pressure. Doing so we introduced new physical basis for study dynamics of the planet in its own force field. The analytics for that is as follows. The body is considered as a system of n elementary particles (n → ∞) of masses mi and many degrees of freedom. The volumetric moment of a particle pi is written as pi = midri/dt. Then the moment of momentum M of the system is found to be derivative from the moment of inertia I in the form: M = ∑piri = ∑miridri/dt = d/dt(∑½ miri2) = ½ dI/dt. Then derivative on time from M gives the energy of the system as second derivative from I: M' = ∑pidri/dt + ∑ridpi/dt = ½I" where ∑pidri/dt = 2T is the kinetic energy and ∑ridpi/dt = U is the potential energy of the oscillating moment of inertia (interacting particles). So, equation of dynamical equilibrium (equation of state) of a body, where the interacted particles are presented by nonlinear oscillators, is ½I" = 2T + U. We used this for study and interpretation of oscillation and rotation parameters of the Earth. Note that the center of mass of the Earth is presented here by a surface of asymmetric spheroid. For more information see our works: Ferronsky V.I. and S.V.Ferronsky (2007). Dynamics of the Earth, Scientific World, Moscow; Ferronsky V.I. (2008) Non-averaged virial theorem for natural systems: http://zhurnal.ape.relarn.ru/articles/2008/066e.pdf

  12. An Atlantic Network of Geodynamical and Space Stations

    NASA Astrophysics Data System (ADS)

    Gómez-González, Jesús; López-Fernández, José Antonio; Colomer, Francisco; Santos, Luis R.

    2014-12-01

    The National Geographic Institute (IGN) of Spain and the government of the autonomous region of Açores (Portugal) are jointly deploying an ``Atlantic Network of Geodynamical and Space Stations'' (project RAEGE). The first two radio telescopes of RAEGE were finished in Yebes (Spain) and Santa María (Açores islands, Portugal). The network will be completed with two additional stations on Tenerife (Canary Islands) and Flores (Açores). The RAEGE radio telescopes are of VGOS kind: azimuth/elevation turning head telescopes, reaching azimuth and elevation slew speeds of 12°/s and 6°/s, respectively. The optical design is based on a 13.2-m ring focus reflector. In its basic configuration, the observation frequency is in the range of 2-40 GHz. It can be enhanced up to 100 GHz by using additional options. First light at the Yebes radio telescope was achieved on February 9, 2014 on the tri-band receiver (S/X and Ka bands) developed at the laboratories at the Yebes Observatory. The RAEGE Santa María site will be in full swing in early 2015. The infrastructure project of RAEGE in Santa María includes the construction of the main control building, access roads, and a power distribution building scheduled for summer 2014. The Santa María site will include a completely isolated gravimetry pavilion, buried in a small hill, on top of which a permanent GNSS station will be installed. The Tenerife and Flores stations are scheduled for 2016. They also include new radio telescopes, permanent GNSS receivers, and gravimeter stations.

  13. Numerical Simulation of Lushan Ms7.0 earthquake geodynamic background

    NASA Astrophysics Data System (ADS)

    LIAO, L.; Yang, J.; Zhang, D.

    2013-12-01

    The Lushan Ms7.0 earthquake happened in April 20, 2013 is another strong earthquake occurred on LongMenShan Faults after Wenchuan Ms8.0 earthquake. In this paper, We have built a finite model abased on previous geology and geophysics research results, and high resolution elevation data, heat flow data. By using GPS data, stress field data as constraint condition to study the geodynamic background of this strong earthquake and to search the relationship between Lushan earthquake and Wenchuan earthquake. The result of our simulation shows that when the deep material of Tibetan plateau flowing toward east is set as our boundary condition, the elevation and different rheological strength between the Sichuan basin and Tibetan plateau, the different friction strength between Longmenshan faults south segment and north segement after Wenchuan earthquake and fault geometry all actually influent the initial rupture position and the fault dislocation form of this earthquake. The Wenchuan earthquake may influent the epicenter position of Lushan earthquake.

  14. Application of the pseudorelief method for the territory of the Bishkek geodynamic polygon

    NASA Astrophysics Data System (ADS)

    Batalev, V. Yu.

    2013-02-01

    Based on 143 magnetotelluric soundings, the Berdichevskii impedance, the Wiese—Parkinson matrix, and the phase tensor component are calculated for the Bishkek geodynamic polygon 50 × 150 km in size. The pseudoreliefs of the apparent resistance Ro brd , phase Fi brd , Wiese-Parkinson matrix norm, and apparent phase Fi k calculated from the phase tensor are constructed. An area of the crustal conductor with elevated conductivity located below the northern part of the Chui depression is distinguished during analysis of pseudoreliefs. Its characteristics will be used for solution of the 3D direct task and creation of the starting model of 2D inversion. The reliability of anomalous objects and estimation of their size during the use of real data is caused by the fact that the anomalies are displayed by different parts of the observation system for the various parameters of the MT-field: the phases vary directly over the anomalous object, and magnetovariational parameters form the rim around it. This allows us more completely and effectively to use the network of real data.

  15. High-resolution tomography of CMB and lowermost mantle coupled by geodynamics

    NASA Astrophysics Data System (ADS)

    Soldati, G.; Boschi, L.; Forte, A. M.

    2009-12-01

    Despite the fast advances of seismic tomography in the last decades provided us with very clear and reliable images of the Earth’s mantle,seismically and/or geodynamically inferred models of core-mantle boundary topography are still poorly correlated both in pattern and amplitude. A major cause for these discrepancies is the difficulty to separate, in travel-time anomalies, the contribution of CMB topography from that of lowermost-mantle and D" heterogeneities. As an attempt to reconcile the contrasting views of the Earth's CMB, we propose an innovative approach to mapping CMB topography from seismic travel-time inversions: instead of treating mantle velocity and CMB topography as independent parameters, as has been done so far (e.g., Soldati et al., 2003), we plan to account for their coupling by mantle flow, as formulated by e.g. Forte & Peltier (1991). In practice, we shall invert direct P waves, and core-sensitive phases, with coefficients of mantle (and, possibly, core) velocity structure as the only free parameters. CMB undulations will not be treated as free parameters, but accounted for via a modification of the tomographic matrix based on the estimated physical relationship between them and mantle velocities. For the first time, the resulting tomographic maps of CMB topography will be, by construction, physically sound, while explaining the inverted seismic data.

  16. Tomography of core-mantle boundary and lowermost mantle coupled by geodynamics

    NASA Astrophysics Data System (ADS)

    Soldati, Gaia; Boschi, Lapo; Forte, Alessandro M.

    2012-05-01

    We propose an innovative approach to mapping CMB topography from seismic P-wave traveltime inversions: instead of treating mantle velocity and CMB topography as independent parameters, as has been done so far, we account for their coupling by mantle flow, as formulated by Forte & Peltier. This approach rests on the assumption that P data are sufficiently sensitive to thermal heterogeneity, and that compositional heterogeneity, albeit important in localized regions of the mantle (e.g. within the D″ region), is not sufficiently strong to govern the pattern of mantle-wide convection and hence the CMB topography. The resulting tomographic maps of CMB topography are physically sound, and they resolve the known discrepancy between images obtained from classic tomography on the basis of core-reflected and core-refracted seismic phases. Since the coefficients of mantle velocity structure are the only free parameters of the inversion, this joint tomography-geodynamics approach reduces the number of parameters; nevertheless the corresponding mantle models fit the seismic data as well as the purely seismic ones.

  17. Some consequences of the geodynamics of sea level on the biosphere. The SE Asian example

    NASA Astrophysics Data System (ADS)

    Husson, Laurent; Sarr, Anta-Clarisse; Pastier, Anne-Morwenn; Sepulchre, Pierre; Pedoja, Kevin; Elliot, Mary; Hantoro, Wahyoe; Jaramillo, Carlos

    2017-04-01

    Mantle flow and subducting slabs dynamically deflect the surface of the Earth. These deflections occasionally suffice to alternatively inundate or emerge vast expanses of landmasses. This is the case in SE Asia, where geomorphological indicators attest for widespread uplift in the East, in "Wallacea" and subsidence in the West, in the very shallow Sunda platform. These movements attest for transient subduction dynamics of the Indo-Australian subduction zone. We conducted fieldwork in key areas : Sulawesi in the East, Belitung in the West. Geomorphological observations and modeling, geophysical measurements and age determinations have enable us to determine Quaternary rates of subsidence (Sunda shelf) and uplift (in Wallacea), of a few tenths of millimeters per year, faster than over longer time scales. We hypothesize that such rates of vertical ground motion triggered by the subducting slabs, though modest, are sufficient to very efficiently impact the external spheres of the Earth. More specifically, because it is associated with modifications of the relative sea level, we propose that they critically altered diverse aspects of the biosphere. We propose that such geodynamics ultimately modulate the dynamics of the biosphere in ways as diverse as boosting reef productivity by an order of magnitude, fostering the development of the "Coral Triangle" center of biodiversity and, in a rather provocative way, even helping Homo erectus reach Java and large faunas cross Sundaland even during interglacial periods.

  18. Large-scale changes of the atmosphere (climate), geodynamics and biosphere due to the galactic shocks

    NASA Astrophysics Data System (ADS)

    Khristoforova, D.

    2009-04-01

    The Solar system periodically passes through spiral arms of the Galaxy, which are stellar density waves. Processes due to the presence of galactic shocks (shock waves) may be responsible for the abrupt atmosphere changes (climate), geodynamics (supercontinental cycle, large tectonic processes, mantle convection, geomagnetic field and others) and biosphere. Galactic shocks (GS) are the narrow region of high gas compression along the inner edge of spiral wave. Shock wave leads to the interstellar dust compression and to the phase transition in the interstellar gas. GS are large-scale trigger mechanism of active star formation. GS ultimately changes temperature, pressure and the radiation balance. It is quite surprisingly that majority of the "data points" of the geochronological and stratigraphic scales are closely related to the time moments when the Solar system has passed through the galactic shocks. This extraterrestrial cause for the change of physical and chemical conditions on the Earth had profound effects on the biologic extinction and explosions. This hypothesis explains the biologic explosion in Cambrian, the Permian - Triassic and Cretaceous-Tertiary extinctions, i.e., the beginning of Paleozoic, Mesozoic and Cenozoic. It is valid in the frame of galactic shock model that any discussion time estimates of these past events and their implications for the future must be quantitative. It will permit an evaluation of age of greater catastrophes and changes in the Earth history, of the future meets with the spiral arms of the Galaxy. It predicts the existence of chronological scales of other planets.

  19. Geodetic GNSS measurements as a basis for geodynamic and glaciological research in Antarctica

    NASA Astrophysics Data System (ADS)

    Scheinert, Mirko; Dietrich, Reinhard; Knöfel, Christoph; Fritsche, Mathias; Rülke, Axel; Schröder, Ludwig; Richter, Andreas; Eberlein, Lutz

    2013-04-01

    For about twenty years our institute has been carrying out geodetic GNSS measurements and has been actively working in international collaboration for Antarctic research. Episodic GPS (and later GNSS) measurements of all contributing nations enter the "Database of the SCAR Epoch Crustal Movement Campaigns" which is being maintained at the institute in the framework of SCAR-GIANT. GNSS measurements form a basis for the realization of the International Terrestrial Reference Frame (ITRF) and its densification in Antarctica. Linked to respective products of an ongoing activity to re-process GNSS data of globally distributed stations a consistent and precise TRF realization can be reached. We will give an overview on the latest developments and the subsequent applications for geodynamic and glaciological investigations in Antarctica. Complementary to continuous GNSS observations episodic GNSS measurements have the potential to provide independent data on vertical deformations, which can be used to investigate the present-day ice-mass balance and to refine models of the glacial-isostatic adjustment. Repeated and properly referenced GNSS measurements at the ice surface yield ice-flow velocities and local ice-surface height changes. We will present latest results, e.g. for the Amundsen Sea sector, the subglacial Lake Vostok region and near-coastal regions of Dronning Maud Land or Enderby Land. Thus, it will be discussed how geodetic GNSS measurements form an important and indispensable basis for geodetic Earth system research with the focus on Antarctica.

  20. The solution of fundamental problems of geodynamics, geophysics, geology and planetology

    NASA Astrophysics Data System (ADS)

    Barkin, Yury

    2010-05-01

    On the base of geodynamic model of the forced gravitational swing and displacement of shells of a planet under action of a gravitational attraction of surrounding (external) celestial bodies [1], [2] the fundamental problems of geodynamics, geology, planetology, geophysics, etc. have been studied and solved. 1). The mechanism of cyclic variations of activity of natural processes in various time scales. 2). The nature of eccentric positions of the core and the mantle of the Earth. A role of the Moon, the Sun, Neptune and other celestial bodies in activization of the swing of core-mantle system of the Earth. 3). Power of endogenous activity of planetary natural processes on planets and satellites. 4). The nature of correlations of natural processes with features of motion of baricenter of the solar system. 5). An explanation of influence of bodies of solar system on excitation of variations of planetary processes with Milankovitch's periods (in tens and hundred thousand years). 6). A possible explanation of geological cycles as result of excitation of solar system at its motion in a gravitational field of the Galaxy. 7). The phenomenon of polar inversion of natural processes on the Earth, both other planets and satellites. 8). Spasmodic (step-by-step) and catastrophic changes of activity of natural processes. 9). Sawtooth (gear curve) variations of natural processes. 10). The phenomenon of twisting of hemispheres (latitude zones) of celestial bodies. 11). Formation of the pear-shaped form of celestial bodies and the mechanism of its change. 10). Ordered planetary structures in spatial distribution of geological formations. 12). The phenomena of bipolarity of celestial bodies and antipodality of formations. Many fundamental problems of natural sciences have been obtained an explanation on the basis of developed geodynamic model (Barkin, 2002, 2009). The fundamental problems of celestial mechanics and geodynamics, geophysics and the geology, excited of scintific

  1. Geodynamic constraints on stress and strength of the continental lithosphere during India-Asia collision.

    NASA Astrophysics Data System (ADS)

    Kaus, B. J. P.; Schmalholz, S. M.; Lebedev, S.; Deschamps, F.

    2009-04-01

    There has been quite some debate in recent years on what the long-term strength of the continental lithosphere is and how it is related to the occurrence of earthquakes. One of the best studied areas in this respect is the India-Asia collision zone, where -in some profiles- the Moho depth is known to within a few km's. A relocation of earthquake source locations revealed that in India earthquakes occur throughout the whole lithosphere whereas in Tibet, earthquakes are restricted to the upper 10-15 km of the crust with few exceptions slightly above or below the Moho. The lack of substantial earthquake activity in the sub-Moho mantle lithosphere seems puzzling since (1D) strength envelop models for the continental lithosphere predict large differential stresses (and brittle failure) in these locations. A way out of this paradox is to assume that the rheology of the mantle lithosphere (i.e. the effective viscosity) is significantly smaller than usually assumed, either because of the effects of hydration, or because of increased Moho temperatures. As a consequence, the strength of the lithosphere resides in the crust and not in the upper mantle as previously assumed. This conclusion gets some support from spectral-based inverse models of the effective elastic thickness (using topography and gravity as input data), which is typically smaller than the seismogenic thickness. Even though this explanation might appear appealing at first, there are at least two major problems with it: (1) Estimations of the effective elastic thickness (EET) of the lithosphere are non-unique and model-dependent. Others, using a direct (non-spectral) modelling approach, find significantly larger values of the EET in the same locations (again using gravity & topography as constraints). (2) Long term geodynamic models indicate that if the mantle lithosphere would indeed be as weak as suggested, it would be very difficult to generate plate-tectonics like behavior: Subducting slabs behave more

  2. Characterization of Carbopol® hydrogel rheology for experimental tectonics and geodynamics

    NASA Astrophysics Data System (ADS)

    Di Giuseppe, E.; Corbi, F.; Funiciello, F.; Massmeyer, A.; Santimano, T. N.; Rosenau, M.; Davaille, A.

    2015-02-01

    One of the long-standing challenges of modern tectonics and geodynamics is to fully understand the strong strain localization and its effects observed in the lithosphere, which presents viscous, as well as elastic and brittle properties. Recently yield stress-shear thinning hydrogels, such as Carbopol®, have been employed in analog modeling because of its great potential for mimicking the non-Newtonian behavior of rocks. Conversely its use has been limited by the difficulties in assessing its rheology and in preparing uniform samples. Ergo, it is essential to ensure a standard recipe, yielding to a reproducible behavior, no matter which rheometer model is used. We carried out, at four institutions (FAST, GFZ, IPGP and LET), a benchmark for developing a standard preparation and for testing the comparability of results. Then, we conducted a systematical rheological characterization of a wide range of Carbopol® formulas as a function of concentration, composition, pH, temperature and aging. Results show that neutral pH favors higher viscosity. The shear modulus, yield stress, viscosity, and shear thinning behavior increase with concentration. The linear viscoelastic range increases with concentration contrarily to what is observed in gelatins or colloidal suspensions. A weak inverse relationship between temperature and viscosity is found. Similarly, aging reduces both the viscosity and loss modulus, with reduction more evident for low concentration samples. Scaling analysis revealed that low concentration samples, i.e. < 0.1 wt.%, exhibiting shear thinning behavior and low yield stress, are appropriate to model the rising of thermal instabilities. Those at 0.5-1.0 wt.%, showing yield stress in the order of hundreds of Pa and n ranging between 1.6 and 3.4 are good candidates to mimic the non-linear ductile behavior of crustal rocks. We conclude that tuning the visco-elasto-plastic rheology of Carbopol® would make this material a good candidate for modeling of also

  3. Error analysis for the proposed close grid geodynamic satellite measurement system (CLOGEOS)

    NASA Technical Reports Server (NTRS)

    Mueller, I. I.; Vangelder, B. H. W.; Kumar, M.

    1975-01-01

    The close grid geodynamic measurement system experiment which envisages an active ranging satellite and a grid of retro-reflectors or transponders in the San Andreas fault area is a detailed simulated study for recovering the relative positions in the grid. The close grid geodynamic measurement system for determining the relative motion of two plates in the California region (if feasible) could be used in other areas of the world to delineate and complete the picture of crustal motions over the entire globe and serve as a geodetic survey system. In addition, with less stringent accuracy standards, the system would also find usage in allied geological and marine geodesy fields.

  4. Grain size evolution in the mantle and its effect on geodynamics and seismic observables

    NASA Astrophysics Data System (ADS)

    Myhill, R.; Dannberg, J.; Eilon, Z.; Gassmoeller, R.; Moulik, P.; Faul, U.; Asimow, P. D.

    2014-12-01

    Dynamic models of Earth's convecting mantle usually implement flow laws with constant grain size, stress-independent viscosity and a limited treatment of variations associated with changes in mineral assemblage. These simplifications greatly reduce computational requirements but preclude effects such as shear localisation and transient changes in rheology associated with phase transitions, which have the potential to fundamentally change flow patterns in the mantle. Here we use the finite-element code ASPECT (Bangerth et al., 2013) to model grain size evolution and the interplay between grain size, stress and strain rate in the convecting mantle. We include the simultaneous and competing effects of dynamic recrystallisation resulting from work done by dislocation creep, grain growth and recrystallisation at phase transitions. Further expressions account for slow growth in multiphase assemblages resulting from pinning. Grain size variations also affect seismic properties of mantle materials. We use several formulations from the literature to relate intrinsic variables (P, T, and grain size) from our numerical models to seismic velocity (Vs) and attenuation (Q). Our calculations use thermodynamically self-consistent anharmonic elastic moduli determined for the mineral assemblages in the mantle using HeFESTo (Stixrude and Lithgow-Bertelloni, 2013). We investigate the effect of realistically heterogeneous grain sizes by computing seismic observables such as body wave travel times, ray paths, and attenuation (t*) as well as mode eigenfrequencies and quality factors at different frequencies. We highlight the frequency-dependent sensitivity of seismic waves to grain size, which is important when interpreting Vs and Q observations in terms of mineral assemblage and temperature. This work is based on a project started at the CIDER 2014 summer program. References: Bangerth, W. et al., 2014, ASPECT: Advanced Solver for Problems in Earth's ConvecTion. Computational

  5. A new view for the geodynamics of Ecuador: Implication in seismogenic source definition and seismic hazard assessment

    NASA Astrophysics Data System (ADS)

    Yepes, Hugo; Audin, Laurence; Alvarado, Alexandra; Beauval, Céline; Aguilar, Jorge; Font, Yvonne; Cotton, Fabrice

    2016-05-01

    A new view of Ecuador's complex geodynamics has been developed in the course of modeling seismic source zones for probabilistic seismic hazard analysis. This study focuses on two aspects of the plates' interaction at a continental scale: (a) age-related differences in rheology between Farallon and Nazca plates—marked by the Grijalva rifted margin and its inland projection—as they subduct underneath central Ecuador, and (b) the rapidly changing convergence obliquity resulting from the convex shape of the South American northwestern continental margin. Both conditions satisfactorily explain several characteristics of the observed seismicity and of the interseismic coupling. Intermediate-depth seismicity reveals a severe flexure in the Farallon slab as it dips and contorts at depth, originating the El Puyo seismic cluster. The two slabs position and geometry below continental Ecuador also correlate with surface expressions observable in the local and regional geology and tectonics. The interseismic coupling is weak and shallow south of the Grijalva rifted margin and increases northward, with a heterogeneous pattern locally associated to the Carnegie ridge subduction. High convergence obliquity is responsible for the North Andean Block northeastward movement along localized fault systems. The Cosanga and Pallatanga fault segments of the North Andean Block-South American boundary concentrate most of the seismic moment release in continental Ecuador. Other inner block faults located along the western border of the inter-Andean Depression also show a high rate of moderate-size earthquake production. Finally, a total of 19 seismic source zones were modeled in accordance with the proposed geodynamic and neotectonic scheme.

  6. A comparison between north-central Apennines and southeastern Carpathians in terms of present-day geodynamic features

    NASA Astrophysics Data System (ADS)

    Gogus, O.; Şengül Uluocak, E.; Pysklywec, R.

    2016-12-01

    The Alpine fold & thrust belt system has been the subject of numerous studies investigating the processes ranging from the motions of plates/micro continental plates, nature of the subduction system(s), and development of post-orogenic extensions and accretion of magmatic arcs. These show at a large scale that major deformations and the structural geometries are controlled by mantle dynamics. In this study, we deal with the present-day geometric and kinematic properties related to mantle processes in the north-central Apennines (including Apennines chain and Adriatic basin) and southeast Carpathians collision regions. Seismological studies indicate the high velocity bodies beneath the eastern Carpathians (Vrancea slab) and the Italian peninsula (Adriatic slab) in the investigated area. Foredeep deposits such as the Foscani and Adriatic Basins with relatively high crustal and lithospheric thicknesses that follow the high mountain belts/fold thrust belts (i.e. eastern Carpathians and Apennines) are characterized by low structural and morphological elevation. It has been suggested that observed anomalies topography in the western Apennines ( > 1.5 km) and eastern Carpathians ( >1 km) are supported by underlying mantle; alternatively, other studies suggest subsidence in these basins is due to west, south-west directed dipping slabs based on previous geodynamic studies. Based on our new work, the structures in the mantle defined by high lateral seismic variations and potentially causing the deep and surface deformations need to be investigated with a multidimensional geodynamic modeling approach. For this purpose, we made 2 and 3D thermo-mechanical numerical models by using temperature fields derived from P-wave tomography data. Our first results were analyzed in terms of regional present-day dynamic topography by considering geological and geophysical observations such as gravity, and heat flow distributions. Further, we compared the main characteristic deformations

  7. U/Pb dating of subduction-collision in the Brooks Range: implications for Mesozoic geodynamics of Arctic Alaska

    NASA Astrophysics Data System (ADS)

    Lemonnier, Nicolas; Labrousse, Loic; Agard, Philippe; McClelland, Bill; Cobble, Mattew; Till, Alison; Roeske, Sarah

    2016-04-01

    The paleogeographic and geodynamic evolution of Northern Alaska is crucial to understand the connection between the Arctic and Pacific realms. The opening of the Canada Basin (CB) is debated both in terms of inception time (between 190 and 140 Ma) and driving mechanisms. The prevalent model assumes that CB opened in a back-arc position within the Arctic-Alaska-Chukotka (AAC) terrane following a change in subduction polarity from S- to N-dipping subduction The adjacent Brooks Range orogen (BRO) is thought to have formed when the Koyukuk volcanic arc collided with the southern extension of AAC. This collision therefore potentially provides key information for Arctic geodynamics, and for the mechanisms of CB opening, but neither the detailed timing of this collisional history nor its duration are well known. In order to constrain the timing of the collision, we performed in-situ zircon U-Pb SIMS analyses on eclogites from the BRO s.l. (BR and Seward Peninsula), which indicate that peak burial (at 510 ± 60°C, 1.6 ± 0.2 GPa) during continental subduction and subsequent collision occurred at 141 ± 6 Ma (n=10, MSWD = 1.6). Eclogite metamorphism therefore postdates the initial rifting stage of the CB but predates effective sea-floor spreading. Younger zircon domains (114 ± 13 Ma) associated with retrograde assemblages could indicate a late thermal pulse or recrystallisation during exhumation in the collisional wedge. Combined with all available information on timing, these new age constraints are used to build a tectonic model for coeval evolution of the Brooks Range and the Canada Basin. The intra-Kingak "Jurassic Unconformity" at the Jurassic Cretaceous Boundary (Houseknecht, pers. communication) could actually be considered as the signature of the AAC-Koyukuk arc collision stage in the CB.

  8. A simulation to study the feasibility of improving the temporal resolution of LAGEOS geodynamic solutions by using a sequential process noise filter

    NASA Technical Reports Server (NTRS)

    Hartman, Brian Davis

    1995-01-01

    A key drawback to estimating geodetic and geodynamic parameters over time based on satellite laser ranging (SLR) observations is the inability to accurately model all the forces acting on the satellite. Errors associated with the observations and the measurement model can detract from the estimates as well. These 'model errors' corrupt the solutions obtained from the satellite orbit determination process. Dynamical models for satellite motion utilize known geophysical parameters to mathematically detail the forces acting on the satellite. However, these parameters, while estimated as constants, vary over time. These temporal variations must be accounted for in some fashion to maintain meaningful solutions. The primary goal of this study is to analyze the feasibility of using a sequential process noise filter for estimating geodynamic parameters over time from the Laser Geodynamics Satellite (LAGEOS) SLR data. This evaluation is achieved by first simulating a sequence of realistic LAGEOS laser ranging observations. These observations are generated using models with known temporal variations in several geodynamic parameters (along track drag and the J(sub 2), J(sub 3), J(sub 4), and J(sub 5) geopotential coefficients). A standard (non-stochastic) filter and a stochastic process noise filter are then utilized to estimate the model parameters from the simulated observations. The standard non-stochastic filter estimates these parameters as constants over consecutive fixed time intervals. Thus, the resulting solutions contain constant estimates of parameters that vary in time which limits the temporal resolution and accuracy of the solution. The stochastic process noise filter estimates these parameters as correlated process noise variables. As a result, the stochastic process noise filter has the potential to estimate the temporal variations more accurately since the constraint of estimating the parameters as constants is eliminated. A comparison of the temporal

  9. New data on the Vrancea Nappe (Moldavidian Basin, Outer Carpathian Domain, Romania): paleogeographic and geodynamic reconstructions

    NASA Astrophysics Data System (ADS)

    Amadori, Maria Letizia; Belayouni, Habib; Guerrera, Francesco; Martín-Martín, Manuel; Martin-Rojas, Iván; Miclăuş, Crina; Raffaelli, Giuliana

    2012-09-01

    A study has been performed on the Cretaceous to Early Miocene succession of the Vrancea Nappe (Outer Carpathians, Romania), based on field reconstruction of the stratigraphic record, mineralogical-petrographic and geochemical analyses. Extra-basinal clastic supply and intra-basinal autochthonous deposits have been differentiated, appearing laterally inter-fingered and/or interbedded. The main clastic petrofacies consist of calcarenites, sub-litharenites, quartzarenites, sub-arkoses, and polygenic conglomerates derived from extra-basinal margins. An alternate internal and external provenance of the different supplies is the result of the paleogeographic re-organization of the basin/margins system due to tectonic activation and exhumation of rising areas. The intra-basinal deposits consist of black shales and siliceous sediments (silexites and cherty beds), evidencing major environmental changes in the Moldavidian Basin. Organic-matter-rich black shales were deposited during anoxic episodes related to sediment starvation and high nutrient influx due to paleogeographic isolation of the basin caused by plate drifting. The black shales display relatively high contents in sub-mature to mature, Type II lipidic organic matter (good oil and gas-prone source rocks) constituting a potentially active petroleum system. The intra-basinal siliceous sediments are related to oxic pelagic or hemipelagic environments under tectonic quiescence conditions although its increase in the Oligocene part of the succession can be correlated with volcanic supplies. The integration of all the data in the "progressive reorientation of convergence direction" Carpathian model, and their consideration in the framework of a foreland basin, led to propose some constrains on the paleogeographic-geodynamic evolutionary model of the Moldavidian Basin from the Late Cretaceous to the Burdigalian.

  10. The Tertiary dike magmatism in the Southern Alps: geochronological data and geodynamic significance

    NASA Astrophysics Data System (ADS)

    Bergomi, Maria Aldina; Zanchetta, Stefano; Tunesi, Annalisa

    2015-03-01

    The relationships between tectonics and magmatic activity in the Alps are still debated. Despite an active subduction since the Late Cretaceous, no arc-related magmatism is recorded prior of the Middle Eocene. The emplacement of plutons along the Insubric Fault in a short time span (~34-28 Ma) has been generally interpreted in terms of the slab break-off model. The Tertiary magmatism, however, is also characterized by the occurrence of widespread calcalkaline dikes not necessarily intruded along the Insubric Fault. The geochemical features of dikes vary along the Alps belt and are interpreted in terms of mantle source heterogeneity and degree of crustal contamination. U-Pb zircon dating of studied dikes indicates intrusion ages in the 42- to 34-Ma time interval. These data provide evidence for a pre-Oligocene magmatic activity that was not solely limited to the Adamello batholith. Moreover, it appears that dikes rejuvenate from SE to NW, in an opposite direction with respect to the Alpine subduction polarity. Thus, a more complex geodynamic scenario than the slab break-off model must be envisaged. The absence of arc magmatism prior to the Middle Eocene can be explained by the low-angle subduction of the Tethyan slab that confined the mantle partial melting zone away from the orogenic wedge. The onset of the Apennines subduction at 55-50 Ma caused the Alpine slab to retreat. The partial melting zone progressively migrated beneath the orogenic wedge and finally reached the axial belt in the Late Eocene, when the Alpine collision was completed. Only at this stage, slab break-off occurred and promoted the intrusion of the Periadriatic plutons.

  11. Bayesian geodynamic inversion to constrain the rheology of the flat subduction system in southwestern Mexico

    NASA Astrophysics Data System (ADS)

    Gérault, Mélanie; Bodin, Thomas

    2016-04-01

    The flat slab in southwestern Mexico differs from others at the present-day because (1) it is associated with abundant arc volcanism, (2) it is associated with extension in the arc and a neutral state of stress in the fore-arc, (3) it generates relatively low seismic activity, (4) the continental mantle lithosphere is very thin or nonexistent, (5) it is not directly caused by the subduction of thickened oceanic crust, and (6) there is no nearby cratonic keel. In a recent study, we showed that the topography in the area is controlled by both isostatic and dynamic contributions. The Trans-Mexican Volcanic Belt is either isostatically supported or slightly buoyed up by a low-density mantle wedge. To the contrary, the forearc is pulled downward by the flat slab, resulting in about 1 km of subsidence. Using a two-dimensional instantaneous Stokes flow finite-elements model, we found a combination of slab, mantle, and subduction interface properties that can predict the observed topography, plate velocities, and stress state in the continent. However, this solution is not unique, and there are trade-offs between these properties such that several combinations can provide a similarly good fit to the data. In this work, we present a geodynamic inversion to further investigate what viscosities and densities are required in different zones of the subduction system to explain the observations collected at the surface. The inverse problem is cast in a Bayesian framework, where model parameters (e.g. the viscosity in the mantle wedge and along the subduction interface) can be reconstructed in a probabilistic sense, and where trade-offs and uncertainties can be quantitatively constrained. We use a direct parameter search approach based on a Markov chain Monte Carlo (McMC) scheme to test a large number of potential scenarios.

  12. Detection of geodynamic activity areas based on the Earth's electromagnetic noise parameters

    NASA Astrophysics Data System (ADS)

    Gordeev, Vasily F.; Malyshkov, Sergey Yu; Shtalin, Sergey G.; Polivach, Vitaly I.; Krutikov, Vladimir A.

    2016-11-01

    In this paper, a method of using the Earth's natural pulsed electromagnetic noise for mapping of anomalies of intensely strained state of the Earth's crust is substantiated. Examples of using the method for mapping of geodynamically dangerous sites and monitoring of processes that pose threats to the operation of industrial facilities are presented.

  13. Geodetic and Geodynamic Studies at Department of Geodesy and Geodetic Astronomy Wut

    NASA Astrophysics Data System (ADS)

    Brzeziński, Aleksander; Barlik, Marcin; Andrasik, Ewa; Izdebski, Waldemar; Kruczyk, Michał; Liwosz, Tomasz; Olszak, Tomasz; Pachuta, Andrzej; Pieniak, Magdalena; Próchniewicz, Dominik; Rajner, Marcin; Szpunar, Ryszard; Tercjak, Monika; Walo, Janusz

    2016-06-01

    The article presents current issues and research work conducted in the Department of Geodesy and Geodetic Astronomy at the Faculty of Geodesy and Cartography at Warsaw University of Technology. It contains the most important directions of research in the fields of physical geodesy, satellite measurement techniques, GNSS meteorology, geodynamic studies, electronic measurement techniques and terrain information systems.

  14. Slab dragging and the recent geodynamic evolution of the western Mediterranean plate boundary region

    NASA Astrophysics Data System (ADS)

    Spakman, Wim; Chertova, Maria V.; van den Berg, Arie P.; Thieulot, Cedric; van Hinsbergen, Douwe J. J.

    2016-04-01

    The Tortonian-Present geodynamic evolution of the plate boundary between North Africa and Iberia is characterized by first-order enigmas. This concerns, e.g., the diffuse tectonic activity of the plate boundary; the crustal thickening below the Rif; the closing of the northern Moroccan marine gateways prior to the Messinian Salinity Crisis; crustal extension of the central to eastern Betics; the origin and sense of motion of the large left-lateral Trans Alboran Shear Zone (TASZ) and Eastern Betic Shear Zone (EBSZ); and lithosphere delamination of the North African continental edge. Many explanations have been given for each of these seemingly disparate tectonic features, which invariably have been addressed in the plate tectonic context of the NW-SE relative plate convergence between the major plates since the Tortonian, mostly independently from each other. Usually there is no clear role for the subducted slab underlying the region, except for presumed rollback, either to SW or to the W, depending on the type of observations that require explanation. Here we integrate the dynamic role of the slab with the NW-SE relative plate convergence by 3-D numerical modelling of the slab evolution constrained by absolute plate motions (Chertova et al., JGR,2014 & Gcubed 2014). By combining observations and predictions from seismology, geology, and geodesy, with our numerical 3-D slab-mantle dynamics modelling, we developed a new and promising geodynamic framework that provides explanations of all noted tectonic enigmas in a coherent and connected way. From the Tortonian until today, we propose that mantle-resisted slab dragging combines with the NW-SE plate convergence across the (largely) unbroken plate boundary to drive the crustal deformation of the region. Slab dragging is the lateral transport, pushing or pulling, of slab through the mantle by the absolute motion of the subducting plate (Chertova et al., Gcubed, 2014). Because the slab is connected to both the Iberian

  15. Geodynamic Evolution of Northeastern Tunisia During the Maastrichtian-Paleocene Time: Insights from Integrated Seismic Stratigraphic Analysis

    NASA Astrophysics Data System (ADS)

    Abidi, Oussama; Inoubli, Mohamed Hédi; Sebei, Kawthar; Amiri, Adnen; Boussiga, Haifa; Nasr, Imen Hamdi; Salem, Abdelhamid Ben; Elabed, Mahmoud

    2017-05-01

    The Maastrichtian-Paleocene El Haria formation was studied and defined in Tunisia on the basis of outcrops and borehole data; few studies were interested in its three-dimensional extent. In this paper, the El Haria formation is reviewed in the context of a tectono-stratigraphic interval using an integrated seismic stratigraphic analysis based on borehole lithology logs, electrical well logging, well shots, vertical seismic profiles and post-stack surface data. Seismic analysis benefits from appropriate calibration with borehole data, conventional interpretation, velocity mapping, seismic attributes and post-stack model-based inversion. The applied methodology proved to be powerful for charactering the marly Maastrichtian-Paleocene interval of the El Haria formation. Migrated seismic sections together with borehole measurements are used to detail the three-dimensional changes in thickness, facies and depositional environment in the Cap Bon and Gulf of Hammamet regions during the Maastrichtian-Paleocene time. Furthermore, dating based on their microfossil content divulges local and multiple internal hiatuses within the El Haria formation which are related to the geodynamic evolution of the depositional floor since the Campanian stage. Interpreted seismic sections display concordance, unconformities, pinchouts, sedimentary gaps, incised valleys and syn-sedimentary normal faulting. Based on the seismic reflection geometry and terminations, seven sequences are delineated. These sequences are related to base-level changes as the combination of depositional floor paleo-topography, tectonic forces, subsidence and the developed accommodation space. These factors controlled the occurrence of the various parts of the Maastrichtian-Paleocene interval. Detailed examinations of these deposits together with the analysis of the structural deformation at different time periods allowed us to obtain a better understanding of the sediment architecture in depth and the delineation of

  16. Geodynamic Evolution of Northeastern Tunisia During the Maastrichtian-Paleocene Time: Insights from Integrated Seismic Stratigraphic Analysis

    NASA Astrophysics Data System (ADS)

    Abidi, Oussama; Inoubli, Mohamed Hédi; Sebei, Kawthar; Amiri, Adnen; Boussiga, Haifa; Nasr, Imen Hamdi; Salem, Abdelhamid Ben; Elabed, Mahmoud

    2016-12-01

    The Maastrichtian-Paleocene El Haria formation was studied and defined in Tunisia on the basis of outcrops and borehole data; few studies were interested in its three-dimensional extent. In this paper, the El Haria formation is reviewed in the context of a tectono-stratigraphic interval using an integrated seismic stratigraphic analysis based on borehole lithology logs, electrical well logging, well shots, vertical seismic profiles and post-stack surface data. Seismic analysis benefits from appropriate calibration with borehole data, conventional interpretation, velocity mapping, seismic attributes and post-stack model-based inversion. The applied methodology proved to be powerful for charactering the marly Maastrichtian-Paleocene interval of the El Haria formation. Migrated seismic sections together with borehole measurements are used to detail the three-dimensional changes in thickness, facies and depositional environment in the Cap Bon and Gulf of Hammamet regions during the Maastrichtian-Paleocene time. Furthermore, dating based on their microfossil content divulges local and multiple internal hiatuses within the El Haria formation which are related to the geodynamic evolution of the depositional floor since the Campanian stage. Interpreted seismic sections display concordance, unconformities, pinchouts, sedimentary gaps, incised valleys and syn-sedimentary normal faulting. Based on the seismic reflection geometry and terminations, seven sequences are delineated. These sequences are related to base-level changes as the combination of depositional floor paleo-topography, tectonic forces, subsidence and the developed accommodation space. These factors controlled the occurrence of the various parts of the Maastrichtian-Paleocene interval. Detailed examinations of these deposits together with the analysis of the structural deformation at different time periods allowed us to obtain a better understanding of the sediment architecture in depth and the delineation of

  17. The stratigraphic record of prebreakup geodynamics: Evidence from the Barrow Delta, offshore Northwest Australia

    NASA Astrophysics Data System (ADS)

    Reeve, Matthew T.; Jackson, Christopher A.-L.; Bell, Rebecca E.; Magee, Craig; Bastow, Ian D.

    2016-08-01

    The structural and stratigraphic evolution of rift basins and passive margins has been widely studied, with many analyses demonstrating that delta systems can provide important records of postrift geodynamic processes. However, the apparent lack of ancient synbreakup delta systems and the paucity of seismic imaging across continent-ocean boundaries mean that the transition from continental rifting to oceanic spreading remains poorly understood. The Early Cretaceous Barrow Group of the North Carnarvon Basin, offshore NW Australia, was a major deltaic system that formed during the latter stages of continental rifting and represents a rich sedimentary archive, documenting uplift, subsidence, and erosion of the margin. We use a regional database of 2-D and 3-D seismic and well data to constrain the internal architecture of the Barrow Group. Our results highlight three major depocenters: the Exmouth and Barrow subbasins and southern Exmouth Plateau. Overcompaction of pre-Cretaceous sedimentary rocks in the South Carnarvon Basin, and pervasive reworking of Permian and Triassic palynomorphs in the offshore Barrow Group, suggests that the onshore South Carnarvon Basin originally contained a thicker sedimentary succession, which was uplifted and eroded prior to breakup. Backstripping of sedimentary successions encountered in wells in the Exmouth Plateau depocenter indicates that anomalously rapid tectonic subsidence (≤0.24 mm yr-1) accommodated Barrow Group deposition, despite evidence for minimal, contemporaneous upper crustal extension. Our results suggest that classic models of uniform extension cannot account for the observations of uplift and subsidence in the North Carnarvon Basin and may indicate a period of depth-dependent extension or dynamic topography preceding breakup.

  18. A scalable, parallel matrix-free Stokes solver for geodynamic applications

    NASA Astrophysics Data System (ADS)

    May, D.

    2013-12-01

    Here I describe a numerical method suitable for studying non-linear, large deformation processes in crustal and lithopspheric dynamics. The method utilizes a hybrid spatial discretisation which consists of mixed finite elements for the Stokes flow problem, coupled to a Lagrangian marker based discretisation to represent the material properties (viscosity and density). This approach is akin to the classical Marker-And-Cell (MAC) scheme of Harlow and the subsequently developed Material Point Method (MPM) of Sulsky and co-workers. The geometric flexibility and ease of modelling large deformation processes afforded by such mesh-particle methods has been exploited by the lithospheric dynamics community over the last 20 years. The strength of the Stokes preconditioner fundamentally controls the scientific throughput achievable and represents the largest bottleneck in the development of our understanding of geodynamic processes. The possibility to develop a 'cheap' and efficient preconditioning methodology which is suitable for the mixed Q2-P1 element is explored here. I describe a flexible strategy, which aims to address the Stokes preconditioning issue using an upper block triangular preconditioner, together with a geometric multi-grid preconditioner for the viscous block. The key to the approach is to utilize algorithms and data-structures that exploit current multi-core hardware and avoid the need for excessive global reductions. In order to develop a scalable method, special consideration is given to; the definition of the coarse grid operator, the smoother and the coarse grid solver. The performance characteristics of this hybrid matrix-free / partially assembled multi-level preconditioning strategy is examined. The robustness of the preconditioner with respect to the viscosity contrast and the topology of the viscosity field, together with the parallel scalability is demonstrated.

  19. Electrical structures in the northwest margin of the Junggar basin: Implications for its late Paleozoic geodynamics

    NASA Astrophysics Data System (ADS)

    Zhang, Sheng; Xu, Yixian; Jiang, Li; Yang, Bo; Liu, Ying; Griffin, W. L.; Luo, Yong; Huang, Rong; Zhou, Yong; Zhang, Liangliang

    2017-10-01

    Recent geological, geochemical and geophysical data have inclined to support the presence of a remnant Paleozoic oceanic lithosphere beneath the Western Junggar, southwestern Chinese Altaids. However, regional high-resolution geophysical data have been rarely deployed to image its geometry, making it difficult to trace its evolution and final geodynamic setting. Presently, two magnetotelluric (MT) profiles are deployed across the northwest margin of the Junggar basin and the southern Darbut belt to image the electrical structure of the crust and lithospheric mantle. High-quality data at 102 sites and the quasi-2D indications of phase tensor skew angles and impedance phase ellipses for relatively short periods (up to 500 s) allow us to invert the two profile data by a 2-D scheme. The resistivity cross-section of a NW-SE striking LINE2 sheds light on a fossil intraoceanic subduction system, and reveals the Miaoergou intrusions as a bowl-like pluton, indicating that the multi-phase intrusions primarily formed in a post-collisional setting. The resistivity cross-section of striking NE-SW LINE1 reveals a possible oceanic slab with relatively lower resistivity underlying the low-resistivity sedimentary strata and high-resistivity mélange. Given that the profile of LINE1 cuts the out-rise zone of a subducted slab developed during the late Paleozoic, the 2-D resistivity model may thus represent the zone that have experienced heterogeneous deformation, reflecting subduction with barrier variation parallel to the ancient trench. Moreover, as shown in previous results, the new MT data also illustrate that the Darbut Fault is a thin-skinned structure, which has been erased at depths during the subsequent magmatism.

  20. Densities of metapelitic rocks at high to ultrahigh pressure conditions: What are the geodynamic consequences?

    NASA Astrophysics Data System (ADS)

    Massonne, Hans-Joachim; Willner, Arne P.; Gerya, Taras

    2007-04-01

    Current geodynamic models of continental collision involving (ultra)high pressure complexes imply that even deeply subducted continental crust is significantly lighter than the ultrabasic upper mantle. To test this implication, we have investigated density changes of major components of continental crust, in particular metagreywacke and metapelite, as a function of pressure and temperature using a Gibbs free energy minimization approach. Pseudosections were calculated for fixed chemical compositions and the P- T range of 10-40 kbar, 600-1000 °C. Selected compositions were those of natural psammopelitic rocks, average crustal components, various theoretical mixtures of quartz, plagioclase, illite, chlorite and Fe,Ti-oxides, and finally mid-ocean ridge basalt and lherzolite for comparison. Calculated densities were presented as density maps (isochors in P- T diagrams). In general, observed densities of psammopelitic rocks increase with rising pressure due to the formation of advancing amounts of garnet, Na-pyroxene, and kyanite. A common assemblage, for instance, at 25 kbar/800 °C consists of phengite, quartz, jadeite, garnet, kyanite, magnetite, and rutile. After overstepping the quartz-coesite transition the density of a mean psammopelitic rock (3.35 g/cm 3) is almost as high as that of garnet lherzolite. Calculations with other pelitic compositions demonstrate that the resulting densities (up to 3.5 g/cm 3) can even exceed that of a garnet lherzolite due to high contents of garnet. Our calculations suggest that (i) even non-basic crustal material can sink into the Earth's mantle to fertilize it and (ii) the proportion of low-density granitic rocks in deeply subducted continental crust must be relatively high to claim buoyancy forces for a return of this crust to the surface.

  1. Cenozoic fluid-magmatic centers, geodynamics, seismotectonics and volcanism in Northern Caucasus

    NASA Astrophysics Data System (ADS)

    Sobissevitch, Alexei L.; Masurenkov, Yuri P.; Nechaev, Yuri V.; Pouzich, Irina N.; Laverova, Ninel I.

    2010-05-01

    The central segment of Alpine mobile folded system of the Greater Caucasus is characterized by complex crossing of the active faults of different structural directions. On the crossings of disjunctive knots of Caucasian WNW and Trans-Caucasian NS faults the two Cenozoic fluid-magmatic centers are located featuring dormant yet not extinct volcanoes of Elbrus and Kazbek. Mentioned centers are known as the Elbrus volcano-plutonic center, the Kazbek volcano-plutonic center, they are outlined according to the results of geological, geomorphological and geophysical studies. Geodynamic position of the Elbrus volcano within the Transcaucasia uplift is considered with respect to evolution of volcanic processes and possible resumption of volcanic activity in this region. In order to carry out the multidisciplinary study of geological and geophysical processes in the vicinity of the volcanic dome it is essential to obtain reliable information about basic parameters of local magmatic structures. Results of complimentary geological and geophysical studies carried out in the Elbrus volcanic area are presented and compared to the results of theoretical approaches as well as with numerical simulations and processing of remote sensing data. In particular, the satellite imagery processing carried out according to original technology based on determination of surface lineaments and consequent transition to analysis of the field of tectonic disintegration of the lithosphere may allow one to obtain independent knowledge about deep subsurface structures for the given territory. As a result, the 3D model of tectonic disintegration field under the Elbrus volcano has been constructed. The two anomalous domains have been outlined and they were associated with local deep magmatic source and peripheral magmatic chamber of the Elbrus volcano. Comparative analysis of experimental geophysical data obtained by means of microgravity studies over the same territory, magneto-telluric profiling and

  2. Seismicity and geodynamics in the central part of the Vanuatu Arc

    NASA Astrophysics Data System (ADS)

    Baillard, C.; Crawford, W. C.; Ballu, V.; Regnier, M. M.; Pelletier, B.; Garaebiti, E.

    2013-12-01

    The Vanuatu Arc (VA) in the southwest Pacific ocean (167°E, 13-20°S), is highly seismically active, with more than 35 events of magnitude Mw ≥ 7 since 1973 (USGS catalog). The geodynamics are dominated by the east-dipping subduction of the Australian Plate under the North Fiji Basin microplate. Convergence rates are estimated to be between 130 and 170 mm/yr, except in the central part of the VA where convergence slows to 30-40 mm/yr. This slowing appears to be the result of blockage by the subducting d'Entrecastaux ridge. To quantify the tectonics of this blocked section, we deployed 30 seismometers in 2008-2009 and 8 GPS stations since 2008, in the forearc region of the central VA. The seismometers recorded more than 100 events/day. Detailed analysis of the earthquake catalog reveals: 1) a seismic gap between 40 and 60 km deep under the two largest islands of the VA (Santo and Malekula); 2) subduction plane and intraplate faulting within the down-going plate; and 3) reduced activity beneath Malekula island , perhaps indicating a locked patch on the subduction plane. We infer the geometry of the subduction interface by combining our catalog with unpublished data from the 2000 Santo Mw 6.9 earthquake and aftershocks and the USGS and Global CMT catalogs. The subduction interface appears to be composed of two different panels: a shallow one with a small dip angle and a deeper one with higher dip starting at a depth of ~50 km. We compare finite-element modeling of these panels to the geodetic data to test the connectedness of the two panels and their degree of locking.

  3. Scientific Applications in Geodesy and Geodynamics - Innovations Offered by the new GNSS Signals

    NASA Astrophysics Data System (ADS)

    Weber, R.

    2007-12-01

    Over the past 12 years the International GNSS Service (IGS) has demonstrated innovative solutions to maximize the benefits of GPS/GNSS signals in space. Today the IGS provides a large set of high quality products for a huge number of applications e.g. in geodynamics, surveying or atmosphere monitoring. A key objective of the IGS is to provide users anywhere in the world access to highest level GNSS data, products and resources for scientific applications, through an "open data policy". This is naturally dependent upon the availability and performance of the various satellite systems. Recognizing the importance of the upcoming new European satellite navigation system (GALILEO) and the modernization programs for GPS and GLONASS the IGS decided to set up a GNSS-Working Group. One of the major goals of this WG is to prepare a consolidated feedback to GNSS system engineering based on relevant IGS experience of providing highest accuracy products for the existing systems. Concerning the work of IGS Analysis Centres as well as other IGS Working Groups the opportunities offered by the various GNSS modernization programs should be reflected. The set of new signals provided by GNSS ongoing modernization programs will allow for improved ambiguity resolution techniques over longer baselines (TCAR, MCAR). Linear combinations of 3 frequencies provided by Galileo and GPS allow to mitigate second-order ionospheric effects and might subsequently improve the determination of the remaining tropospheric refraction.The optimal signal linear combination in terms of wavelength and noise level depends on the baseline length. Nevertheless in case of controlled intersystem biases the new processing models will improve the positioning accuracy of reference points and subsequently contribute to the stability of the reference frame and the determination of Earth Rotation Parameters. This presentation will give a summary of the findings of the IGS GNSS-WG concerning the determination of

  4. Origin and geodynamic significance of Tertiary postcollisional basaltic magmatism in Serbia (central Balkan Peninsula)

    NASA Astrophysics Data System (ADS)

    Cvetković, V.; Prelević, D.; Downes, H.; Jovanović, M.; Vaselli, O.; Pécskay, Z.

    2004-04-01

    ( 87Sr/ 86Sr i=0.7059-0.7115 and 143Nd/ 144Nd i=0.5122-0.5126), and that signature is typical for ultrapotassic rocks worldwide. The Paleocene/Eocene episode and formation of the ESPEMAR is referred to as asthenospheric-derived magmatism. This magmatism originated through passive riftlike structures related to possible short relaxational phases during predominantly collisional and compressional conditions. The Oligocene/Miocene episode and formation of HKCA-SHO and UP rocks were dominated by lithospheric-controlled magmatism. Its origin is connected with the activity of a wide dextral wrench corridor generated along the axis of the Dinaride orogen which collapsed in response to thickened crust caused by earlier compressional processes. To explain conditions of these two magmatic events, a three-stage geodynamic model has been proposed: (1) subduction-termination/collision stage (Paleocene/Eocene), (2) collision stage (Eocene) and (3) postcollision/collapse stage (Oligocene/early Miocene).

  5. Breaking Up is Hard to Do: On the Solvability of Incompressible Stokes with Viscoplastic Rheologies in Geodynamics

    NASA Astrophysics Data System (ADS)

    Spiegelman, M. W.; May, D.; Wilson, C. R.

    2016-12-01

    Plasticity/failure is an essential ingredient in large-scale geodynamics models as the ability to spontaneously form faults and weak plate boundaries is critical for describing crustal and lithospheric deformation. However, questions remain as to appropriate models of plasticity as well as effective solvers for these strongly non-linear systems. Here we present some simplified model problems designed to elucidate many of the issues involved in the solution of viscoplastic problems as currently used in geodynamic modeling. We first demonstrate analytically that solutions of Stokes flow for a purely plastic layer in simple shear is singular, admitting either an infinite number of solutions or no solutions depending on the structure of the yield function. We then show how an inverse viscosity mixing model regularizes these solutions. However, for a depth dependent yield envelope, the problem remains ill-posed in some parameter ranges. We then consider a more geologically relevant problem of compression and extension of a viscoplastic layer overlying an isoviscous layer. We introduce a single plastic yield criterion which includes most commonly used viscoplasticity models: von Mises, depth-dependent von Mises and Drucker-Prager. We show that for all rheologies considered, Picard iteration can stall at large values of the non-linear residual, producing spurious solutions. However, combined Picard-Newton schemes can be effective for rheologies that are independent of the dynamic pressure. Difficulties arise when solving incompressible Stokes problems for rheologies that depend on the dynamic pressure such as Drucker-Prager viscoplasticity. Analysis suggests that incompressible Stokes becomes ill-posed when the dependence of the deviatoric stress tensor on dynamic pressure (i.e. |∂ τ /∂ p'|) becomes large. We demonstrate empirically that, in these cases, Newton solvers can fail by introducing spurious shear bands and discuss the consequence of interpreting the

  6. Cenozoic geodynamic evolution of the western Mediterranean domain: A view from the Neogene peri-Tyrrhenian basins

    SciTech Connect

    Roure, F.; Montadert, L.; Mueller, C.

    1988-08-01

    Biostratigraphic and structural studies of synorogenic Neogene deposits in the southern Apennines, Calabria, and Cicily are compared to similar data from Sardinia and the Tyrrhenian Sea to trace the geodynamic evolution of the western Mediterranean domain.

  7. Abrupt plate acceleration through oblique rifting: Geodynamic aspects of Gulf of California evolution

    NASA Astrophysics Data System (ADS)

    Brune, S.

    2016-12-01

    The Gulf of California formed by oblique divergence across the Pacific-North America plate boundary. This presentation combines numerical forward modeling and plate tectonic reconstructions in order to address 2 important aspects of rift dynamics: (1) Plate motions during continental rifting are decisively controlled by the non-linear decay of rift strength. This conclusion is based on a recent plate-kinematic analysis of post-Pangea rift systems (Central Atlantic, South Atlantic, Iberia/Newfoundland, Australia/Antarctica, North Atlantic, South China Sea). In all cases, continental rifting starts with a slow phase followed by an abrupt acceleration within a few My introducing a fast rift phase. Numerical forward modeling with force boundary conditions shows that the two-phase velocity behavior and the rapid speed-up during rifting are intrinsic features of continental rupture that can be robustly inferred for different crust and mantle rheologies. (2) Rift strength depends on the obliquity of the rift system: the force required to maintain a given rift velocity can be computed from simple analytical and more realistic numerical models alike, and both modeling approaches demonstrate that less force is required to perpetuate oblique extension. The reason is that plastic yielding requires a smaller plate boundary force when extension is oblique to the rift trend. Comparing strike slip and pure extension end-member scenarios, it can be shown that about 50% less force is required to deform the lithosphere under strike-slip. This result implies that rift systems involving significant obliquity are mechanically preferred. These two aspects shed new light on the underlying geodynamic causes of Gulf of California rift history. Continental extension is thought to have started in Late Eocene/Oligocene times as part of the southern Basin and Range Province and evolved in a protracted history at low extension rate (≤15 mm/yr). However, with a direction change in Baja

  8. Seismic-geodynamic constraints on three-dimensional structure, vertical flow, and heat transfer in the mantle

    USGS Publications Warehouse

    Forte, A.M.; Woodward, R.L.

    1997-01-01

    Joint inversions of seismic and geodynamic data are carried out in which we simultaneously constrain global-scale seismic heterogeneity in the mantle as well as the amplitude of vertical mantle flow across the 670 km seismic discontinuity. These inversions reveal the existence of a family of three-dimensional (3-D) mantle models that satisfy the data while at the same time yielding predictions of layered mantle flow. The new 3-D mantle models we obtain demonstrate that the buoyancy forces due to the undulations of the 670 km phase-change boundary strongly inhibit the vertical flow between the upper and lower mantle. The strong stabilizing effect of the 670 km topography also has an important impact on the predicted dynamic topography of the Earth's solid surface and on the surface gravity anomalies. The new 3-D models that predict strongly or partially layered mantle flow provide essentially identical fits to the global seismic data as previous models that have, until now, predicted only whole-mantle flow. The convective vertical transport of heat across the mantle predicted on the basis of the new 3-D models shows that the heat flow is a minimum at 1000 km depth. This suggests the presence at this depth of a globally defined horizon across which the pattern of lateral heterogeneity changes rapidly. Copyright 1997 by the American Geophysical Union.

  9. Analysis of long-term variations in the geomagnetic poloidal field intensity and evaluation of their relationship with global geodynamics

    NASA Astrophysics Data System (ADS)

    Biggin, A. J.; Thomas, D. N.

    2003-02-01

    variation is analysed at a sufficiently high resolution to allow comparisons with the geomagnetic polarity reversal frequency (RF), it is not possible to confirm whether the two parameters are anticorrelated, decoupled or related in some more complex way. However, it is clear that GPFI and RF are definitely not positively correlated as has been previously suggested. The present database documents sharp increases in GPFI around the onset times of the two recognized superchrons, itself implying an anticorrelation. The implications, for geodynamo and mantle modelling, of both an anticorrelation and a decoupling of the geomagnetic parameters are discussed briefly. A generic geodynamic model is proposed to explain the relationship between observed long-term changes in GPFI and global geodynamic processes. The model predicts that changes in GPFI result from a chain of geodynamic processes extending from crust to core, beginning with plate reorganizations at the surface and culminating in increases in the vigour of outer core convection. Supercontinents are transient surface expressions of such geodynamic processes and provide the potential to test the generic model. Four time stages are proposed to describe the major long-term changes in GPFI since the Early Devonian: 400-350, 350-250, 250-175 and 175-10 Ma. The GPFI features within these stages are convincingly explained within the context of major events in the evolutionary cycle of Pangaea. Two major avalanching and mantle reorganization events, facilitating whole-mantle convection, are proposed; one linked with the amalgamation of Pangaea, the other (possibly less catastrophic) with the dispersal phase of the supercontinent. These events were separated by a period of mantle insulation during the time when the supercontinent was assembled and a layered mantle convection regime existed. The explanations are consistent with independent evidence from seismology, mantle modelling and mantle dynamics, though some ambiguities and

  10. Correlating basaltic composition with stages of geodynamic settings associated with breakup of supercontinent Rodinia

    NASA Astrophysics Data System (ADS)

    Sinha, A.; Hanan, B. B.

    2010-12-01

    The breakup of supercontinents is often accompanied by magmatism associated with many possible geodynamic scenarios and interactions between the mantle and the overlying continental lithosphere. We examine the geochemical and isotopic signature of late Proterozoic basalts of the Catoctin Volcanic Province (CVP) along eastern North America to identify the temporal tectono-magmatic stages associated with dispersal. We model Stage I basalt generation to be associated with incipient supercontinent extension with its chemical/isotopic signature dominated by sub-continental lithosphere mantle (SCLM). Stage II basalts mark transition to an incipient oceanic rift where Ocean island basalt (plume) or mid-ocean ridge basalt sources are diluted by SCLM. Stage III basalts are related to a mature mid-ocean ridge system where the source is dominated by the depleted asthenosphere MORB source. New isotopic and geochemical data from the Catoctin Formation (type area of CVP) in the region of the central Appalachian orogen show incompatible element ratios of Zr/Y = 4.91, La/Yb = 5.73, Th/Ta = 1.37 and Hf/Th = 2.82, as well as primitive mantle normalized trace element abundances with OIB affinity like Hawaii. These lavas have similar low Nb/La (0.63-1.04) as Hawaii but slightly higher Th/Ta (1.1-2.12). In Pb-Pb isotope space define a pseudo- binary trend between continental lithosphere-like sources and an OIB-like source similar to a C-like plume component suggestive of Stage II. Basalts of the Unicoi, Bassett and Sams Creek Formations are similar to the Catoctin Formation and are modeled as Stage II magmatism. Other basalts hosted within the Lynchburg and Ashe-Alligator Back formations are of both high (>2 wt %) and low (<2%) TiO2 types, where the low Titanium group is best modeled as stage I, while higher TiO2 samples reflect stage II OIB dominated source similar to the basalts of the Catoctin Formation. We emphasize that in order to confirm these stages additional precise

  11. Seismic imaging of the geodynamic activity at the western Eger rift in central Europe

    NASA Astrophysics Data System (ADS)

    Mullick, N.; Buske, S.; Hrubcova, P.; Ruzek, B.; Shapiro, S.; Wigger, P.; Fischer, T.

    2015-04-01

    The western Eger rift at the Czech-German border in central Europe is an important geodynamically active area within the European Cenzoic rift system (ECRS) in the forelands of the Alps. Along with two other active areas of the ECRS, the French Massif Central and the east and west Eifel volcanic fields, it is characterized by numerous CO2-rich fluid emission points and frequent micro-seismicity. Existence of a plume(s) is indicated in the upper mantle which may be responsible for these observations. Here we reprocess a pre-existing deep seismic reflection profile '9HR' and interpret the subsurface structures as mapped by seismic reflectivity with previous findings, mainly from seismological and geochemical studies, to investigate the geodynamic activity in the subsurface. We find prominent hints of pathways which may allow magmatic fluids originating in the upper mantle to rise through the crust and cause the observed fluid emanations and earthquake activity.

  12. Consortium For Central European GPS Geodynamic Reference Network (cegrn): Organization and Objectives

    NASA Astrophysics Data System (ADS)

    Fejes, I.

    After many years of informal collaboration 13 institutes from 13 Central European countries decided to formalize their organization for long term maintenance of CEGRN. The CEGRN Consortium was established on 4th of Sepember 2001 in Budapest by signing a Memorandum of Agreement. The participants recognized the importance of international collaboration in the field of Space Geodesy, Geodynamics and Earth Sciences. There is a need for a coherent, high accuracy and high quality reference network in Central Europe for geodynamic investigations. The maintenance of the network includes coordinated programme of measurements, technical developments and international access to monitoring results for a long period of time. The Consortium fosters coordinated maintenance and upgrade of existing CEGRN sites, establishment of new ones, coordinated monitoring measurements, the operation and development of CEGRN Data Centre and Processing Centres.

  13. Joint seismic and geodynamic evidence for a long-lived, stable mantle upwelling under the East Pacific Rise

    NASA Astrophysics Data System (ADS)

    Forte, A. M.; Glisovic, P.; Rowley, D. B.; Simmons, N. A.; Grand, S. P.

    2013-12-01

    Global seismic tomography has consistently imaged large-scale structures in the lower mantle under the Pacific Ocean and under Africa that are characterised by strongly reduced seismic shear velocities. These so-called "low shear-velocity provinces" (LVSP) have been variously interpreted as hot, stagnant thermochemical "piles" that are compositionally dense, or as deeply rooted expressions of positively buoyant, active upwellings. To distinguish which of these two end-member models is relevant to the actual dynamics in the deep mantle requires robust constraints on the density structure of these LVSP. Recent global tomography models reveal what appear to be three distinct 'lobes' of the Pacific LVSP: one located in the Western-Pacific mantle under the Caroline Islands, another in the South-Central-Pacific mantle under French Polynesia, and another below the East Pacific Rise (EPR), centred under Easter Island. To understand the dynamics and time-dependent evolution of these structures we employ recent tomography models derived from the joint inversion of global seismic and geodynamic data sets, which also include constraints from mineral physics (Simmons et al., GJI 2009, JGR 2010). A critically important feature of these joint tomography models is the inclusion of a laterally variable scaling between density and seismic shear velocity, thereby accounting for the spatially localized effect of compositional heterogeneity in the lower mantle. These lower-mantle compositional contributions to density are directly constrained by long-wavelength gravity anomaly data and the excess ellipticity of the CMB. We show that it is not possible to properly account for this compositional heterogeneity using a constant, or simple depth-dependent density-velocity scaling. We have carried out very-long-time mantle convection simulations employing as a starting condition the joint seismic-geodynamic inferences of mantle density structure (Glisovic et al., GJI 2012). We demonstrate

  14. Multi-disciplinary contributions of HartRAO to global geodesy and geodynamics

    NASA Astrophysics Data System (ADS)

    Combrinck, Ludwig

    2015-04-01

    The Hartebeesthoek Radio Astronomy Observatory (South Africa) supports global initiatives in both geodesy and geodynamics through an active programme of science platform provision in Africa, the Atlantic Ocean, Indian Ocean and Antarctica. Our involvement ranges from the installation of tide gauges, Global Navigation Satellite Systems stations, seismometers and accelerometers on remote islands to the installation of radar reflectors in Antarctica which enable accurate, geo-referenced maps of the Antarctic coast line to be made. Currently we also participate in the African VLBI Network (AVN), with the aim to densify not only astronomical observatories in Africa, but to improve the geometry and distribution of advanced geodetic and geophysical equipment to facilitate development of research platforms in Africa, which can be used for geodynamics and related sciences, supporting international projects such as the WEGENER initiative. We present our multi-disciplinary activities during the last decade and sketch the way forward. Participation of Africa in the global arena of astronomy, geodesy, geodynamics and related fields will receive a major boost during the next decade. This is partially due to the development of a component of the Square Kilometre Array (SKA) in Africa but also due to the Global Geodetic Observing System (GGOS) project and the international objectives of higher geodetic accuracies and more stable reference frames. Consequent spinoffs into many disciplines relying on global reference frames and sub-cm positional accuracies stand to benefit and Africa can play a major role in improving both science and network geometries.

  15. Long-term monitoring of geodynamic surface deformation using SAR interferometry

    NASA Astrophysics Data System (ADS)

    Gong, Wenyu

    Synthetic Aperture Radar Interferometry (InSAR) is a powerful tool to measure surface deformation and is well suited for surveying active volcanoes using historical and existing satellites. However, the value and applicability of InSAR for geodynamic monitoring problems is limited by the influence of temporal decorrelation and electromagnetic path delay variations in the atmosphere, both of which reduce the sensitivity and accuracy of the technique. The aim of this PhD thesis research is: how to optimize the quantity and quality of deformation signals extracted from InSAR stacks that contain only a low number of images in order to facilitate volcano monitoring and the study of their geophysical signatures. In particular, the focus is on methods of mitigating atmospheric artifacts in interferograms by combining time-series InSAR techniques and external atmospheric delay maps derived by Numerical Weather Prediction (NWP) models. In the first chapter of the thesis, the potential of the NWP Weather Research & Forecasting (WRF) model for InSAR data correction has been studied extensively. Forecasted atmospheric delays derived from operational High Resolution Rapid Refresh for the Alaska region (HRRR-AK) products have been compared to radiosonding measurements in the first chapter. The result suggests that the HRRR-AK operational products are a good data source for correcting atmospheric delays in spaceborne geodetic radar observations, if the geophysical signal to be observed is larger than 20 mm. In the second chapter, an advanced method for integrating NWP products into the time series InSAR workflow is developed. The efficiency of the algorithm is tested via simulated data experiments, which demonstrate the method outperforms other more conventional methods. In Chapter 3, a geophysical case study is performed by applying the developed algorithm to the active volcanoes of Unimak Island Alaska (Westdahl, Fisher and Shishaldin) for long term volcano deformation

  16. What can zircon ages from the Jack Hills detrital zircon suite really tell us about Hadean geodynamics?

    NASA Astrophysics Data System (ADS)

    Whitehouse, Martin; Nemchin, Alexander

    2015-04-01

    As the only direct sample of the Hadean Earth, detrital zircon grains from the Jack Hills, Western Australia, have been the subject of intense investigation over the almost three decades since their discovery. A wide variety of geochemical and isotopic analyses of these grains, as well as their mineral inclusions, have been used variously to support two fundamentally different models for Hadean geodynamics: (i) Some form of (not necessarily modern-style) plate recycling generating felsic (continental-type?) crust at the boundaries [1, 2], or conversely (ii) the persistence of a long-lived, stagnant basaltic lid within which magmatism occurred as a result of internal temperature perturbations and/or impacts [3, 4], a model also generally consistent with a wide range of observations from post-Hadean geochemical reservoirs. Despite the considerable time and resources expended, the majority of these studies uncritically accept the individual U-Pb zircon ages, even though their veracity is key to many of the interpretations [5, 6]. We report here the results of an in-depth evaluation of all published (and new) U-Pb ages from the Jack Hills zircon suite in order to define age populations that can be used with a high degree of confidence in geodynamic interpretations. A notable problem in the interpretation of U-Pb data from ancient zircon grains (including those as young as the Neoarchean) is that disturbance of the systematics even several 100 Ma after crystallization causes data to spread along the concordia curve without becoming discernably discordant within the relatively large error bounds associated with U/Pb ages from in situ dating methods (e.g. SIMS). While 207Pb/206Pb ages are typically more precise, individually they provide no means to detect Pb-loss-induced younging. However, if two or preferably more analyses have been made in the same zircon growth zone, a reasonable evaluation of the possibility of Pb-loss can be made. In the available Jack Hills zircon

  17. Geodynamics of the Carpathian-Pannonian region: Insights from low temperature thermochronology of the Polish and Ukrainian Carpathians

    NASA Astrophysics Data System (ADS)

    Andreucci, Benedetta; Zattin, Massimiliano; Castelluccio, Ada; Mazzoli, Stefano; Szaniawski, Rafal; Jankowski, Leszek

    2013-04-01

    In recent years, the geodynamic evolution of the Carpathian-Pannonian region has been the subject of a heated scientific debate. This orogenic system formed between the Late Jurassic and the Neogene by the collision of the Alcapa and Tisza-Dacia microplates with the European Platform, and assumed its present-day configuration mainly during the Miocene, when the extensional Pannonian Basin formed in a retro wedge position, while compression was still active along the Carpathian front. The most common and widely accepted interpretation for the Miocene evolution of this region is based on a classical back-arc extension model and subsequent astenospheric upwelling and slab break-off. Nonetheless several authors proposed other possible driving mechanisms for the formation of the Pannonian Basin, such as lithosphere delamination or lithospheric gravitational instability. Thermochronometry provides important constrains to the depths of burial and to the timing and rates of exhumation. Each geodynamic scenario proposed for the Carpathian-Pannonian region implies a different spatial distribution of burial and a different timing of exhumation. In this work we use a compilation of several low-temperature thermochronometric datasets, referred to the Polish and Ukrainian Carpathians, to evaluate their compatibility with the different geodynamic models proposed so far. In order to achieve this goal we examine the spatial distribution of burial depths and of ages and rates of exhumation and we put them in relation with (i) the spatial trend of the relief, (ii) heat flow, (iii) crustal and lithospheric thickness, and (iv) structural setting. We propose a subdivision of the Polish and Ukrainian Carpathians in three different tectonic domains, based on geophysical and structural parameters. Each single area is characterized also by different burial-exhumation history and requires a specific explanation in terms of driving processes. In particular, we infer that exhumation occurred

  18. New evidence of delamination in the Western Alboran Sea. Geodynamic evolution of the Alboran domain and its margins

    NASA Astrophysics Data System (ADS)

    Timoulali, Youssef; Djellit, Hamou; Hahou, Youssef; Jabour, Nacer; Merrouch, Redouane

    2014-07-01

    The presence of continuous upper crustal blocks between the Iberian Betics and Moroccan Rif in the western and middle Alboran Sea, detected with tomography, can add new information about the lithosphere structure and geodynamic evolution in this region. A large volume of seismic data (P and S wave arrival times) has been collected for the period between 1 December 1988 and 31 December 2008 by 57 stations located in northern Morocco (National Institute of Geophysics, CNRST, Rabat), southern Portugal (Instituto de Meteorologia, Lisbon) and Spain (Instituto Geografico National, Madrid) and used to investigate the lithosphere in the western Alboran Sea region. We use a linearized inversion procedure comprising two steps: (1) finding the minimal 1-D model and simultaneous relocation of hypocenters and (2) determination of local velocity structure using linearized inversion. The model parameterization in this method assumes a continuous velocity field. The resolution tests indicate that the calculated images give near true structure imaged at 5 km depth for the Tanger peninsula, the Alhoceima region and southern Spain. At 15, 30 and 45 km depth we observe a near true structure imaged in northern Morocco, and southern Spain. At 60 and 100 km, southern Spain and the SW region of the Alboran Sea give a near true structure. The resulting tomographic image shows the presence of two upper crustal bodies (velocity 6.5 km/s) at 5-10 km depth between the Betics, Rif, western and central Alboran Sea. Low velocities at the base of these two bodies favor the presence of melt. This new evidence proves that the Tethysian ocean upper crust was not totally collapsed or broken down during the late Oligocene-early Miocene. These two blocks of upper crust were initially one block. The geodynamic process in the eastern of the Mediterranean is driven by slab rollback. The delamination process of the lithospheric mantle terminates with the proposed slab rollback in the western part of the

  19. Paleoproterozoic andesitic volcanism in the southern Amazonian craton (northern Brazil); lithofacies analysis and geodynamic setting

    NASA Astrophysics Data System (ADS)

    Roverato, Matteo; Juliani, Caetano; Capra, Lucia; Dias Fernandes, Carlos Marcelo

    2016-04-01

    Precambrian volcanism played an important role in geological evolution and formation of new crust. Most of the literature on Precambrian volcanic rocks describes settings belonging to subaqueous volcanic systems. This is likely because subaerial volcanic rocks in Proterozoic and Archean volcano-sedimentary succession are poorly preserved due to erosive/weathering processes. The late Paleoproterozoic Sobreiro Formation (SF) here described, seems to be one of the rare exceptions to the rule and deserves particular attention. SF represents the subaerial expression of an andesitic magmatism that, linked with the upper felsic Santa Rosa F., composes the Uatumã Group. Uatumã Group is an extensive magmatic event located in the Xingú region, southwestern of Pará state, Amazonian Craton (northern Brazil). The Sobreiro volcanism is thought to be related to an ocean-continent convergent margin. It is characterized by ~1880 Ma well-preserved calc-alkaline basaltic/andesitic to andesitic lava flows, pyroclastic rocks and associated reworked successions. The superb preservation of its rock-textures allowed us to describe in detail a large variety of volcaniclastic deposits. We divided them into primary and secondary, depending if they result from a direct volcanic activity (pyroclastic) or reworked processes. Our study reinforces the importance of ancient volcanic arcs and rocks contribution to the terrestrial volcaniclastic sedimentation and evolution of plate tectonics. The volcanic activity that produced pyroclastic rocks influenced the amount of detritus shed into sedimentary basins and played a major role in the control of sedimentary dispersal patterns. This study aims to provide, for the first time, an analysis of the physical volcanic processes for the subaerial SF, based in field observation, lithofacies analysis, thin section petrography and less geochemical data. The modern volcanological approach here used can serve as a model about the evolution of Precambrian

  20. Cenozoic fluid-magmatic centers, geodynamics and volcanism in Northern Caucasus

    NASA Astrophysics Data System (ADS)

    Sobissevitch, A. L.; Nechaev, Yu. V.; Masurenkov, Yu. P.; Pouzich, I. N.; Pronin, A. P.; Laverova, N. I.

    2009-04-01

    The central segment of Alpine mobile folded system of the Greater Caucasus is characterized by complex crossing of the active faults of different structural directions. On the crossings of disjunctive knots of Caucasian WNW and Trans-Caucasian NS faults the two Cenozoic fluid-magmatic centers are located featuring dormant yet not extinct volcanoes of Elbrus and Kazbek. Mentioned centers are known as the Elbrus volcano-plutonic center, the Kazbek volcano-plutonic center, they are outlined according to the results of geological, geomorphological and geophysical studies. Geodynamic position of the Elbrus volcano within the Transcaucasia uplift is considered with respect to evolution of volcanic processes and possible resumption of volcanic activity in this region. In order to carry out the multidisciplinary study of geological and geophysical processes in the vicinity of the volcanic dome it is essential to obtain reliable information about basic parameters of local magmatic structures. The satellite imagery processing carried out according to original technology based on determination of surface lineaments and consequent transition to analysis of the field of tectonic disintegration of the lithosphere may allow one to obtain independent knowledge about deep subsurface structures for the given territory. As a result, the 3D model of tectonic disintegration field under the Elbrus volcano has been constructed. The two anomalous domains have been outlined and they were associated with local deep magmatic source and peripheral magmatic chamber of the Elbrus volcano. Comparative analysis of experimental geophysical data obtained by means of microgravity studies over the same territory, magneto-telluric profiling and search for thermal anomalies has shown appropriate correlation in terms of shape, size and position of magmatic structures in the vicinity if the Elbrus volcanic center. Thus, the position and size of the magmatic chamber and the deep magmatic source of the

  1. Red Sea Rift-Related Quseir Basalts, Central Eastern Desert, Egypt: Petrogenetic and Geodynamic Evolution

    NASA Astrophysics Data System (ADS)

    Farahat, Esam; Ali, Shehata; Hauzenberger, Christoph

    2015-04-01

    Mineral and whole rock chemistry of Tertiary Red Sea rift-related basalts occurred in south Quseir city, Central Eastern Desert, Egypt has been presented to investigate their petrogenetic and geodynamic evolution. The South Quseir basalts (SQB) have been classified as high-Ti tholeiitic lava (TiO2 >2 wt. %) emplaced in anorogenic tectonic setting. Their Mg# varies from 48 to 53. Pearce element ratios (PER) suggest that the SQB magmas have evolved through fractional crystallization of olivine + clinopyroxene ± plagioclase assemblages, however, the absence of Eu-anomaly argues against plagioclase fractionation. The clinopyroxene compositions provide evidence for polybaric fractionation of the parental mafic magma. Estimated temperatures of crystallization range from 1143 to 1323 oC for olivines, 1031 to 1207 oC for clinopyroxenes, 600 to 900 oC for feldspars, and 638 to 787 oC for Fe-Ti oxides. Oxygen fugacity (ƒO2) values range from -15.16 to -19.5. The incompatible trace element signatures of the SQB (La/Ba = 0.08-0.10 and La/Nb = 0.89-1.04) are similar to those of ocean island basalts (OIB) generated from asthenospheric mantle source unaffected by subduction components. Modelling calculations indicate that the SQB primary magmas were derived from 4-5% partial melting of a garnet-bearing lherzolite mantle source which had a potential temperature (Tp= 1334-1432 °C; based on olivine liquid equilibria) corresponding to ambient temperature of MORB (i.e. passive rifting). This ambient mantle would have to rise to shallower depths (< 100 km) in the upper mantle to cross the dry mantle solidus and stimulate adiabatic partial melting. These estimates along with absence of HIMU (high μ refers to high 238U/204Pb) components (based on trace element data) show that the SQB volcanism isn't associated with thermally driven mantle plumes. Thus, the SQB magma generation is related to extensional regime through passive upwelling and adiabatic decompression melting of an

  2. Geodynamic evolution and the history of the atmospheres of Mars and Venus

    NASA Astrophysics Data System (ADS)

    Gillmann, C.; Tackley, P. J.; Lognonne, P.

    2011-12-01

    To investigate in what measure the interactions between the mantle and the atmosphere would have caused the divergent evolutions of the terrestrial planets in our solar system, we propose to model the effects of mantle dynamics on the evolution of CO2, H2O and other species like Argon or Nitrogen in the atmosphere, but also of the surface temperature. We consider several processes that are considered to have a strong influence on the atmosphere of terrestrial planets. First, the main source of volatiles in our model is the degassing from the mantle. We use and adapt the StagYY code developed by Tackley (Tackley, 2008) for the geodynamic part of the study. This modeling gives a realistic and advanced account of the mantle convection processes. When possible, we compare those results to published modeling (Breuer and Spohn, 2006; Grott et al., 2011) and observation. Atmospheric escape is considered as the main volatile loss flux. Early escape is thermal, caused by hydrodynamic escape. Its effects can be modeled, as we did for Venus. After the first few hundred of million years, the main atmospheric escape flux becomes non-thermal. We model the evolution of the present escape flux by comparing recent study on these processes and ASPERA (Analyzer of Space Plasma and EneRgetic Atoms) measurements. Differences in present-day escape depending on solar activity are used to extrapolate early escape. We combine these models to calculate the state of the atmosphere of Venus and Mars. This lets us estimate the surface temperature of those planets either from a Mars Global Circulation Model (e.g. Forget at al., 1999), or with a gray radiative-convective atmosphere model, for Venus. In the case of Mars, Ar appears to be a tracer of volcanic degassing. We also show that the present-day atmosphere of Mars is likely to be constituted by a large part of volcanic gases. Even with a low CO2 concentration in the magma (150 ppm), present-day atmosphere is constructed of 50% of volcanic

  3. Comparative analysis of geodynamic activity of the Caucasian and Eastern Mediterranean segments of the Alpine-Himalayan convergence zone

    NASA Astrophysics Data System (ADS)

    Chelidze, Tamaz; Eppelbaum, Lev

    2013-04-01

    activity in this region highlights the need for combined analysis of seismo-neotectonic signatures. For this purpose, this article presents the key features of the tectonic zonation of the Eastern Mediterranean. Map of derivatives of the gravity field retracked from the Geosat satellite and novel map of the Moho discontinuity illustrate the most important tectonic features of the region. The Post-Jurassic map of the deformation of surface leveling reflects the modern tectonic stage of Eastern Mediterranean evolution. The developed tectono-geophysical zonation map integrates the potential geophysical field analysis and seismic section utilization, as well as tectonic-structural, paleogeographical and facial analyses. Tectonically the map agrees with the earlier model of continental accretion (Ben-Avraham and Ginzburg, 1990). Overlaying the seismicity map of the Eastern Mediterranean tectonic region (for the period between 1900 and 2012) on the tectonic zonation chart reveals the key features of the seismo-neotectonic pattern of the Eastern Mediterranean. The results have important implications for tectonic-seismological analysis in this region (Eppelbaum and Katz, 2012). A difference in the geotectonic patterns makes interesting comparison of geodynamic activity and seismic hazard of the Caucasian and Eastern Mediterranean segments of the AHCZ.

  4. Geodynamic inversion to constrain the nonlinear rheology of the lithosphere

    NASA Astrophysics Data System (ADS)

    Baumann, Tobias; Kaus, Boris

    2015-04-01

    A common method to determine the strength of the lithosphere is through estimating its effective elastic thickness from the coherence between gravity and topography. This method assumes a priori that the lithosphere is a thin elastic plate floating on a viscous mantle. Whereas this seems to work well with oceanic plates, it has given controversial results in continental collision zones. Usually, continental collisions zones are well-studied areas for which additional geophysical datasets such as receiver functions and seismic tomography exist that constrain the geometry of the lithosphere and often show that it is rather complex. Yet, lithospheric geometry by itself is insufficient to understand the dynamics of the lithosphere, as this also requires knowledge of the rheology of the lithosphere. Experimental results show significant variability between various rock types and there are large uncertainties in extrapolating laboratory values to nature, which leaves room for speculation. An independent approach is thus required to better understand the rheology and dynamics of the lithosphere in collision zones. Our method combines numerical thermo-mechanical forward models of the present-day lithosphere with a massively parallel Bayesian inversion approach. The geometry of the forward models is part of the a priori knowledge and is constructed from seismological data. We jointly invert topography, gravity, horizontal and vertical surface velocities to constrain the unknown rheological material parameters of the forward models in a probabilistic sense. The model rheology is described with experimentally determined viscous creep laws and other parameters describing the plastic behaviour. As viscosity is temperature dependent, the temperature structure of the forward models is parameterised as well. We apply the method to cross-sections of the India-Asia collision system. In this case, we deal with 17 to 20 model parameters, which requires solving up to 2 × 106 forward

  5. Geodynamic investigation of a Cretaceous superplume in the Pacific ocean

    NASA Astrophysics Data System (ADS)

    Xue, Jing; King, Scott D.

    2016-08-01

    The similarity in both age and geochemistry of the Ontong-Java, Hikurangi, and Manihiki plateaus suggests that they formed as a single superplateau from a unique mantle source. We investigate the necessity of a thermal superplume to form the Great Ontong-Java plateau at about 120 Ma using 3D spherical models of convection with imposed plate reconstruction models. The numerical simulations show that the giant plateau which formed as a result of melting due to the interaction of a plume head and the lithosphere would have been divided into smaller plateaus by spreading ridges, and end up at the present locations of Ontong-Java, Manihiki, and Hikurangi plateaus as well as a fragment in the western Caribbean. By comparing temperature and melt fraction between models with and without an initial thermal superplume, we propose that a Cretaceous superplume in Pacific at 120 Ma is required to form large igneous plateaus.

  6. Integration of permanent and periodic GPS/GNSS measurements for local and regional geodynamic research in the area of the Polish-Czech Network SUDETEN

    NASA Astrophysics Data System (ADS)

    Kontny, Bernard; Kaplon, Jan; Schenk, Vladimir; Schenkova, Zdenka; Badura, Janusz

    2014-05-01

    Since 1997 all current local geodynamic studies in the area of the Polish and Czech parts of the Sudeten and the Sudetic Foreland have been associated with annual periodic GPS campaigns, epoch measurements. The most epochs consisted of more than twelve observation hours and some of them kept on two or three 24-hour observations. Experience collected by international research teams carrying out geodynamic researches with the GPS technique in seismically active areas (USA, Japan) proved that more information can give permanent measurements. However, the Sudeten area, regarded as an area of the weak tectonic activity, can be hardly covered with the dense network of GNSS stations from economic reasons. Hence rational using of existing permanent GPS stations located in studied area and in its vicinity detects the coordinate changes that cannot be appointed from periodic campaign data and that, on the other hand, have rather regional than local character. Creating the spatial models of irregularities of the continuous signals should improve results of the epoch measurements. From this viewpoint, in this project authors used measurement data of chosen permanent GPS stations located in the area: the EPN stations, ASG-EUPOS stations, GEONAS stations and all epoch observations. These data were gained as part of research projects carried out within 1997-2009 period, as well as during new supplementing campaigns realized in the frame of the project N526278940 in the 2011 and 2012 years. Reprocessing of all the permanent and epoch data performed by the latest version of Bernese GNSS Software (V5.2) was performed using EPN guidelines for the processing, reference frame realization and the usage of physical models (atmosphere, Earth rotation, etc.). Standardized results of processing the aggregated GPS network, including permanent stations and all local networks on the area of research, serve for conducting new geodynamic interpretation. Further parameters that estimate the

  7. Reconstructing Pliocene coastlines, topography and bathymetry: A geodynamic perspective

    NASA Astrophysics Data System (ADS)

    Chandan, D.; Peltier, W. R.

    2014-12-01

    The middle Pliocene period (~3.3-3.0 Mya) was characterized by warm temperatures (2-3℃ higher) and high carbon-dioxide (~400 ppmv) concentrations which has led to its recognition as a possible analogue for the future climate. Under the auspices of the Pliocene Modeling and Intercomparison Project (PlioMIP), general circulation models (GCM's) are being employed to simulate mid-Pliocene climate to better understand the biases in these models, which are presently used to make future climate predictions. Necessary boundary conditions for these simulations — land mask, topography, surface albedo and vegetation cover are being provided by the Pliocene Research, Interpretation and Synoptic Mapping (PRISM) project. Bathymetry, which is not part of the PRISM supplied dataset has been adjusted by raising the sea-level by an assumed constant eustatic amount. At present the PRISM land mask, topography and bathymetry reconstructions do not incorporate the gravitationally self consistent changes that would be required to account for the mass loss from the Greenland and Antarctic ice-sheets that produced the assumed rise in eustatic sea level. The effects of dynamic topography induced corrections, due to the action of the mantle convection process, have also been neglected.The influence of these corrections on the predictions of Pliocene climate using modern GCM's remains unexplored. The continuing failure of these models to simulate proxy inferred levels of warming in high-latitude [Dowsett et al., 2013, Sci. Rep.] regions where the magnitude of the required corrections are expected to be largest make it especially important that their impact be assessed. Here, we present the results from a preliminary of the required modifications to the boundary condition data sets.We compute the gravitationally self consistent corrections using the viscoelastic theory of global, glacial isostatic adjustment and relative sea level history for a spherically symmetric Earth model. Dynamic

  8. Geodynamic inversion to constrain the non-linear rheology of the lithosphere

    NASA Astrophysics Data System (ADS)

    Baumann, T. S.; Kaus, Boris J. P.

    2015-08-01

    , we first perform a geodynamic inversion of a synthetic forward model of intraoceanic subduction with known parameters. This requires solving an inverse problem with 14-16 parameters, depending on whether temperature is assumed to be known or not. With the help of a massively parallel direct-search combined with a Markov Chain Monte Carlo method, solving the inverse problem becomes feasible. Results show that the rheological parameters and particularly the effective viscosity structure of the lithosphere can be reconstructed in a probabilistic sense. This also holds, with somewhat larger uncertainties, for the case where the temperature distribution is parametrized. Finally, we apply the method to a cross-section of the India-Asia collision system. In this case, the number of parameters is larger, which requires solving around 1.9 × 106 forward models. The resulting models fit the data within their respective uncertainty bounds, and show that the Indian mantle lithosphere must have a high viscosity. Results for the Tibetan plateau are less clear, and both models with a weak Asian mantle lithosphere and with a weak Asian lower crust fit the data nearly equally well.

  9. Geodynamics of the Yellowstone hotspot and mantle plume: Seismic and GPS imaging, kinematics, and mantle flow

    NASA Astrophysics Data System (ADS)

    Smith, Robert B.; Jordan, Michael; Steinberger, Bernhard; Puskas, Christine M.; Farrell, Jamie; Waite, Gregory P.; Husen, Stephan; Chang, Wu-Lung; O'Connell, Richard

    2009-11-01

    Integration of geophysical and geological data show that the Yellowstone hotspot resulted from a mantle plume interacting with the overriding North America plate, a process that has highly modified continental lithosphere by magmatic and tectonic processes and produced the 16-17 Ma, 700-km-long Yellowstone-Snake River Plain (YSRP) silicic volcanic system. Accessibility of the YSRP allowed large-scale geophysical projects to seismically image the hotspot and evaluate its kinematic properties using geodetic measurements. Seismic tomography reveals a crustal magma reservoir of 8% to 15% melt, 6 km to 16 km deep, beneath the Yellowstone caldera. An upper-mantle low-P-wave-velocity body extends vertically from 80 km to 250 km beneath Yellowstone, but the anomalous body tilts 60 °WNW and extends to 660 km depth into the mantle transition zone. We interpret this conduit-shaped low-velocity body as a plume of up to - 3.5% Vp and - 5.5% Vs perturbation that corresponds to a 1-2% partial melt. Models of whole mantle convection reveal eastward upper-mantle flow beneath Yellowstone at relatively high rates of 5 cm/yr that deflects the ascending plume into its west-tilted geometry. A geodynamic model of the Yellowstone plume constrained by Vp and Vs velocities and attenuation parameters suggests low excess temperatures of up to 120 K, corresponding to a maximum 2.5% melt, and a small buoyancy flux of 0.25 Mg/s, i.e., properties of a cool, weak plume. The buoyancy flux is many times smaller than for oceanic plumes, nonetheless, plume buoyancy has produced a ~ 400-km-wide, ~ 500-m-high topographic swell centered on the Yellowstone Plateau. Contemporary deformation derived from GPS measurements reveals SW extension of 2-3 mm/yr across the Yellowstone Plateau, one-fourth of the total Basin-Range opening rate, which we consider to be part of Basin-Range intraplate extension. Locally, decadal episodes of subsidence and uplift, averaging ~ 2 cm/yr, characterize the 80-year

  10. Newly developed paleomagnetic map of the Easternmost Mediterranean joined with tectono-structural analysis unmask geodynamic history of this region

    NASA Astrophysics Data System (ADS)

    Eppelbaum, Lev; Katz, Youri

    2015-02-01

    Comprehensive magnetic-paleomagnetic analysis of physical-geological models developed for the Easternmost Mediterranean (northern part of the Sinai plate) accompanied by gravity and seismic data examination enabled the detection of a zone of inverse magnetization of submeridional strike with a total volume exceeding 120,000 km3. Such a large zone must correspond to the prolonged period of inverse polarity in the Earth's magnetic field history. We suggest that this inversely magnetized thick block of the Earth's crust corresponds to the known Kiama hyperzone. A paleomagnetic map constructed on the basis of abovementioned geophysical data analysis combined with detailed examination of structural, radiometric, petrological, facial, paleogeographical and some other data indicates that to the west of the Kiama zone is situated the Jalal zone, and to the east - Illawarra, Omolon and Gissar zones. Discovery of the Kiama paleomagnetic zone combined with tectonogeodynamical analysis and paleobiographical data examination indicates that the Earth's oceanic crust blocks may have been shifted by transform faults from the eastern part of the Tethys Ocean to their modern position in the Easternmost Mediterranean. Analysis of potential geophysical fields and seismological maps integrated with tectonostructural examination show the isolation of the northern part of Sinai plate from other terranes. For the first time formation-paleogeographical maps of Triassic and Jurassic for the Easternmost Mediterranean have been compiled and their tectono-geodynamical explanation has been given. The obtained data create a basis for reconsidering tectonic zonation, paleogeodynamical reconstructions and searching for economic deposits in this region.

  11. Upper crust response to geodynamic processes beneath Isparta Angle, SW Turkey: Revealed by CMT solutions of earthquakes

    NASA Astrophysics Data System (ADS)

    Över, Semir; Özden, Süha; Kamacı, Züheyr; Yılmaz, Hüseyin; Ünlügenç, Ulvi Can; Pınar, Ali

    2016-09-01

    The Isparta Angle is an important area of SW Anatolia where extensions in all directions (N-S, NE-SW, NW-SE and E-W) meet. These extensions were determined by normal faulting structures as well as by shallow earthquakes. All extensions, except the E-W one, were attributed to the deviatoric stresses in relation to slab forces and/or extrusion of Anatolia. The moment tensor inversion of 40 shallow earthquakes which occurred in the inner part of the Isparta Angle give focal mechanisms mostly indicating normal faulting. Inversion of all focal mechanisms of the earthquakes obtained from the moment tensor inversion yields normal faulting characterized by an approximately E-W (N268°E) σ3 axis. The calculated stress ratio R is 0.6944 indicating a triaxial stress state. Commonly accepted geodynamic models for the eastern Mediterranean region do not include plate boundary forces acting in the east or west direction. Our hypothesis is that the cause of the E-W extension is the combined forces of Gravitational Potential Energy and the hot asthenosphere upwelling through a tear fault in the subducted African plate between the Hellenic and Cyprus arcs beneath the Isparta Angle.

  12. Paleogeographic and geodynamic Miocene evolution of the Tunisian Tell (Numidian and Post-Numidian Successions): bearing with the Maghrebian Chain

    NASA Astrophysics Data System (ADS)

    Belayouni, Habib; Guerrera, Francesco; Martín-Martín, Manuel; Serrano, Francisco

    2013-04-01

    The Numidian and Post-Numidian stratigraphy of the Tunisian Tell has been updated based on 16 stratigraphic sections belonging to the Massylian sub-domain of the Maghrebian Flysch Basin and to the External Domain. The new data concern detailed litho- and biostratigraphy, gaps, synchronous marker levels, lateral correlations, tectonic contacts, etc. The successions studied show many diachronous and unconformity boundaries delimiting sedimentary depositional sequences related to some tectonic/sedimentary processes. Two main Miocene sedimentary successions (Numidian and Post-Numidian) are recognized overlying the Sub-Numidian Succession (pre-Early Aquitanian) by new integrated (planktonic foraminifera and calcareous nannoplankton) chronostratigraphic analyses, allowing an update of the formations studied. The Miocene tectonic/sedimentary relationships and the timing of the deformation are summarized as follows: (1) the activation of a foredeep stage and a tectogenesis phase gives rise to an accretionary orogenic wedge during mainly the Early Miocene; (2) a late-orogenic phase is checked in the Late Burdigalian-Early Langhian characterized by a marine glauconitic terrigenous sedimentation; (3) a post-orogenic generalized phase is confirmed from the Middle Miocene on in shallow marine or continental sedimentation. These results show good correlation along the Maghrebian Chain and Betic Cordillera. Finally, a paleogeographic and geodynamic evolutionary model concerning the Miocene African Tunisian Margin is postulated.

  13. Thermal rocketing and the Laser Geodynamic Satellite (LAGEOS-1)

    SciTech Connect

    Miller, W.A.

    1997-08-01

    This is the final report of a one-year, Laboratory Directed Research and Development (LDRD) project at the Los Alamos National Laboratory. LAGEOS is the most accurately tracked satellite in orbit. It is a totally passive, dense spherical satellite covered with 426 cube corner reflectors. Besides its great utility in measuring the Earth`s length of day and polar wobble, this satellite can be used to measure, for the first time, the general relativistic frame-dragging effect. Of the five dominant error sources in such an experiment, the largest one involves surface interaction of thermal forces (thermal rocketing) and its influence on the orbital nodal precession. The project objective was to enhance an already available theoretical model (computer code) developed at Los Alamos based on new optical-spin data obtained at the University of Maryland. The project objective was met and the enhanced code will serve as the new spin-dynamics model for future LAGEOS satellite missions.

  14. The Data Base of the International Geodynamics and Earth Tide Service (IGETS)

    NASA Astrophysics Data System (ADS)

    Voigt, Christian; Förste, Christoph; Wziontek, Hartmut; Crossley, David; Meurers, Bruno; Pálinkáš, Vojtech; Hinderer, Jacques; Boy, Jean-Paul; Barriot, Jean-Pierre; Sun, Heping

    2017-04-01

    The International Geodynamics and Earth Tide Service (IGETS) was established in 2015 by the International Association of Geodesy (IAG). IGETS continues the activities of the Global Geodynamics Project (GGP, 1997-2015) to provide support to geodetic and geophysical research activities using superconducting gravimeter data within the context of an international network. The primary objective of IGETS is to provide a service for continuous ground based measurements to monitor temporal variations of the Earth's gravity field and deformation of the Earth's surface by long term records from ground gravimeters, tiltmeters, strainmeters and other geodynamic sensors. IGETS also continues the activities of the International Center for Earth Tides (ICET), in particular, in collecting, archiving and distributing Earth tide records from long series of the various geodynamic sensors. This presentation introduces the IGETS data base hosted by GFZ and accessible via http://igets.gfz-potsdam.de to the geodetic and geodynamics community as well as to all other interested data producers and users. At present, records from superconducting gravimeters at 34 stations worldwide are available. Level 1 products are raw gravity and local pressure records decimated at 1 minute samples. As a new feature, records with 1 or 2 seconds samples are already provided for a few stations. Level 2 products consist of gravity and pressure data corrected for instrumental perturbations and ready for tidal analysis, which are derived from Level 1 datasets and computed by the University of French Polynesia (Tahiti, French Polynesia). Gravity residuals after particular geophysical corrections (including solid Earth tides, polar motion, tidal and non-tidal loading effects) considered as Level 3 products are derived from Level 2 datasets and computed by EOST (Ecole et Observatoire des Sciences de la Terre, Strasbourg, France). The IGETS data sets are stored by GFZ on a FTP server and are freely available after

  15. Crustal structure and geodynamic of the Middle and Lower reaches of Yangtze metallogenic belt and neighboring areas: insights from deep seismic reflection profiling

    NASA Astrophysics Data System (ADS)

    Lu, Q.; Shi, D.; Liu, Z.; Zhang, Y.; Zhao, J.

    2014-12-01

    A 300 km deep seismic reflection profile across the middle and lower Yangtze River metallogenic belt (YRMB) and its adjacent areas established the architecture and geodynamic framework of the region. Results based on the interpretation of the deep seismic data include the deep complicated geometry of the Tan-Lu fault and Zhangbaling uplift, appears as a subvertical thrust fault with its deep portion dip toward the southeast, and along which the Zhangbaling uplift is squeezed out; complex upper crust deformation structure beneath Chuquan depression, within which there are both kink bands, thrusts, imbrication and fold structures reflecting contraction deformation, and detachment fault and normal-fault structures reflecting extensional deformation; the "crocodile" reflection structure emerging beneath the Tan-Lu fault and Ningwu-Lishui volcanic basin, i.e., the upper crust reflection thrust upward, and the lower crust reflection thrust downward and offsetting the Moho discontinuity, which reflects the decoupled deformation process of the upper and lower crust, and is interpreted as an intracontinental subduction. Further to the southeast, the upper crust deformation shows a large-scale "wave-form" pattern, making crustal scale syncline and anticline. The entire section of the reflection Moho is clearly discernible at depth of 30.0-34.5 km, and the Moho beneath the YRMB is shallowest, while the Moho beneath the North China block is deeper than that beneath the Yangtze block. Moho offsets could be seen beneath the Ningwu volcanic basin. Overall, the seismic data show evidence for an intracontinental orogeny and imposes constraints on the deep geodynamic model applied to study region. Our interpretation of seismic profile supports the view that the Yanshanian orogeny, due to the northwest subduction of the paleo-Pacific plate during the Middle-Late Jurassic, is the major event that shaped the tectonic framework of the region. A geodynamic model is proposed for the

  16. Using garnet peridotites as tools to reconstruct paleo-geodynamic settings of fossil continental collision zones

    NASA Astrophysics Data System (ADS)

    Zhang, Cong; van Roermund, Herman; Zhang, Lifei

    2010-05-01

    recognition of a complete new, deep-seated, subcratonic, lithospheric mantle setting. In addition better characterization of SCLM processes in mantle wedge garnet peridotite will also allow for further subdivision of SCLM wedges into different subtypes that all may be present during collision in the hanging wall of a fossil collision/subduction system. In the following we will present the basic outlines of such a mantle wedge classification system. A simple "conceptual" model will be presented that will allow orogenic mantle wedge garnet peridotite to be used as a tool to reconstruct the former paleo-geodynamic setting of the collision/subduction system. Using field, petrological, geochemical, geochronological and geothermobarometric criteria, all of which can be analysed directly in the mantle wedge garnet peridotite body itself, the model allows for discrimination between four different end-member types within the SCLM (equivalent to young/hot/dynamic- versus cold/old/static mantle in thick or thin garnet-olivine bearing mantle wedges). In addition our conceptual model is based on the fundamental assumption that all SCLM was once formed by rising, accretion and cooling of hot asthenospheric mantle. Note also that all mantle wedge end member types may become overprinted by the subduction zone type. The latter, when complete, may evidently erase all former mantle wedge evidences. To test the applicability of our model we have applied the proposed mantle wedge classification system to well studied orogenic garnet peridotites of the Caledonian Orogeny in Scandinavia and the Triassic Sulu-Dabie Orogeny in China. Results will be presented. References: Brueckner (1998). Geology 26, 631-634; Vrijmoed et al. (2010). Eur. J. Mineralogy.

  17. Gravimetry and Space Techniques Applied to Geodynamics and Ocean Dynamics

    NASA Astrophysics Data System (ADS)

    Schutz, Bob E.; Anderson, Allen; Froidevaux, Claude; Parke, Michael

    The variety of disciplines represented in this volume (including space geodesy, oceanography, geophysics, and celestial mechanics) attest to the interdisciplinary applications of gravimetry and space techniques. The relation to sea level is addressed within some of the papers and the contributions of the techniques to development of global gravity models are discussed. The space technique of satellite altimetry has become a prominent contributor to sea surface topography as well as ocean tide models and determination of gravity, especially in ocean areas. Ocean tides influence the motion of near-Earth satellites and the rotation of the Earth. Modern space geodesy is increasingly relying on the Global Positioning System for measuring geophysical phenomena manifested at the surface through crustal deformations. Furthermore, the geophysical interpretation of gravity anomalies has been facilitated by the introduction of modern techniques. This volume represents only a small "snapshot" of the interdisciplinary research being conducted. Modem space geodesy is one of the common links between the disciplines reflected in this volume. New developments in gravimetry and space techniques will further enhance and foster interdisciplinary work in coming years.

  18. Geodynamic simulations using the fast multipole boundary element method

    NASA Astrophysics Data System (ADS)

    Drombosky, Tyler W.

    Interaction between viscous fluids models two important phenomena in geophysics: (i) the evolution of partially molten rocks, and (ii) the dynamics of Ultralow-Velocity Zones. Previous attempts to numerically model these behaviors have been plagued either by poor resolution at the fluid interfaces or high computational costs. We employ the Fast Multipole Boundary Element Method, which tracks the evolution of the fluid interfaces explicitly and is scalable to large problems, to model these systems. The microstructure of partially molten rocks strongly influences the macroscopic physical properties. The fractional area of intergranular contact, contiguity, is a key parameter that controls the elastic strength of the grain network in the partially molten aggregate. We study the influence of matrix deformation on the contiguity of an aggregate by carrying out pure shear and simple shear deformations of an aggregate. We observe that the differential shortening, the normalized difference between the major and minor axes of grains is inversely related to the ratio between the principal components of the contiguity tensor. From the numerical results, we calculate the seismic anisotropy resulting from melt redistribution during pure and simple shear deformation. During deformation, the melt is expelled from tubules along three grain corners to films along grain edges. The initially isotropic fractional area of intergranular contact, contiguity, becomes anisotropic due to deformation. Consequently, the component of contiguity evaluated on the plane parallel to the axis of maximum compressive stress decreases. We demonstrate that the observed global shear wave anisotropy and shear wave speed reduction of the Lithosphere-Asthenosphere Boundary are best explained by 0.1 vol% partial melt distributed in horizontal films created by deformation. We use our microsimulation in conjunction with a large scale mantle deep Earth simulation to gain insight into the formation of

  19. Active geodynamics of the Caucasus/Caspian region educed from GPS, and seismic Observations

    NASA Astrophysics Data System (ADS)

    Gadirov (Kadirov), Fakhraddin; Floyd, Michael; Reilinger, Robert; Alizadeh, Akif; Guliyev, Ibrahim; Mammadov, Samir; Safarov, Rafig

    2017-04-01

    The geodynamic and earthquake activity in the Caucasus/Caspian region is due to the ongoing collision of the Arabian plate with Eurasia. The Caucasus and Caspian Sea are historically among the most seismically active regions on earth. These earthquakes have caused thousands of deaths and great economic distress. Future earthquakes in the Caucasus and Caspian Sea must be considered and planned for in order to limit their impact on the people, ecology, and infrastructure of the region. Within this plate tectonics context, we examine deformation of the Caucasus region and show that most crustal shortening in the collision zone is accommodated by the Greater Caucasus Fold-and-Thrust Belt (GCFTB) along the southern edge of the Greater Caucasus Mountains. The eastern GCFTB appears to bifurcate west of Baku, with one branch following the accurate geometry of the Greater Caucasus, turning towards the south and traversing the Neftchala Peninsula. A second branch may extend directly into the Caspian Sea south of Baku, likely connecting to the Central Caspian Seismic Zone. We model deformation in terms of a locked thrust fault that coincides in general with the main surface trace of the GCFTB. We consider two end-member models, each of which tests the likelihood of one or other of the branches being the dominant cause of observed deformation. Our models indicate that strain is actively accumulating on the fault along the 200 km segment of the fault west of Baku (approximately between longitudes 47-49°E). Parts of this segment of the fault broke in major earthquakes historically (1191, 1859, 1902) suggesting that significant future earthquakes (M 6-7) are likely on the central and western segment of the fault. We observe a similar deformation pattern across the eastern end of the GCFTB along a profile crossing the Kura Depression and Greater Caucasus Mountains in the vicinity of Baku. Along this eastern segment, a branch of the fault changes from a NW-SE striking thrust to an

  20. Meteorites, Continents, Heat, and Non-Steady State Geodynamics

    NASA Astrophysics Data System (ADS)

    White, W. M.; Morgan, J. P.

    2011-12-01

    Previous geochemical estimates of terrestrial radiogenic heat production were based on the assumption that refractory lithophile elements, such as the REE, U, and Th, are present in the Earth in chondritic relative proportions (the 'modified chondritic Earth' model, e.g., McDonough & Sun, Chem. Geol., 120: 223, 1995). However, 142Nd/144Nd ratios in modern terrestrial materials are 10 and 18 ppm higher than in enstatite and ordinary chondrites, respectively. One explanation is that the Sm/Nd ratio in the Earth, or at least the observable part of it, is 3 to 6% higher than chondritic, implying the Earth is non-chondritic, even for refractory lithophile elements. The most likely explanation is that a low Sm/Nd igneous protocrust formed as the Earth accreted and was lost through collisional erosion. A protocrust 3 to 6% enriched in Nd relative to Sm would have been even more strongly enriched in the more highly incompatible elements K, U, and Th. Calculations based on a model of protocrust formation and collisional erosion (O'Neill, & Palme, Phil. Trans. R. Soc. A366: 4205, 2008) that satisfy both Sm-Nd and Lu-Hf isotopic constraints imply U and Th concentrations in the bulk silicate Earth (BSE) that are 20 to 40% lower than in the 'modified chondritic Earth' model. Assuming a K/U = 13800 for the BSE, the K concentration is 10 to 30% lower than previously believed. This corresponds to a terrestrial heat production of 3.0 to 3.9 pW/kg or 11.9 to 15.8 TW. At the high end, these estimates are in excellent agreement with those of Lyubetskaya & Korenaga (JGR, 112: B03211, 2007), but are much lower than the 20 TW value derived from the 'modified chondritic Earth' model. Of this, some 5 to 10 TW of heat production is in the continental crust, leaving ≤10 TW of heat production in the mantle. For comparison, recent estimates of U, Th, and K in the depleted mantle imply heat production in the range of 0.7-1.0 pW/kg; if the depleted mantle occupies the entire mantle, this

  1. Plume capture by a migrating ridge: Analog geodynamic experiments

    NASA Astrophysics Data System (ADS)

    Mendez, J. S.; Hall, P.

    2010-12-01

    Paleomagnetic data from the Hawaii-Emperor Seamount Chain (HESC) suggests that the Hawaiian hotspot moved rapidly (~40 mm/yr) between 81 - 47 Ma but has remained relatively stationary since that time. This implies that the iconic bend in the HESC may in fact reflect the transition from a period of rapid hotspot motion to a stationary state, rather than a change in motion of the Pacific plate. Tarduno et al. (2009) have suggested that this period of rapid hotspot motion might be the surface expression of a plume conduit returning to a largely vertical orientation after having been “captured” and tilted by a migrating mid-ocean ridge. We report on a series of analog fluid dynamic experiments designed to characterize the interaction between a migrating spreading center and a thermally buoyant mantle plume. Experiments were conducted in a clear acrylic tank (100 cm x 70 cm x 50 cm) filled with commercial grade high-fructose corn syrup. Plate-driven flow is modeled by dragging two sheets of Mylar film (driven by independent DC motors) in opposite directions over the surface of the fluid. Ridge migration is achieved by moving the point at which the mylar sheets diverge using a separate motor drive. Buoyant plume flow is modeled using corn syrup introduced into the bottom of the tank from an external, heated, pressurized reservoir. Small (~2 mm diameter), neutrally buoyant Delrin spheres are mixed into reservoir of plume material to aid in visualization. Plate velocities and ridge migration rate are controlled and plume temperature monitored using LabView software. Experiments are recorded using digital video which is then analyzed using digital image analysis software to track the position and shape of the plume conduit throughout the course of the experiment. The intersection of the plume conduit with the surface of the fluid is taken as an analog for the locus of hotspot volcanism and tracked as a function of time to obtain a hotspot migration rate. Experiments are

  2. Parallelization of the Legendre Transform for a Geodynamics Code

    NASA Astrophysics Data System (ADS)

    Lokavarapu, H. V.; Matsui, H.; Heien, E. M.

    2014-12-01

    Calypso is a geodynamo code designed to model magnetohydrodynamics of a Boussinesq fluid in a rotating spherical shell, such as the outer core of Earth. The code has been shown to scale well on computer clusters capable of computing at the order of millions of core hours. Depending on the resolution and time requirements, simulations may require weeks to years of clock time for specific target problems. A significant portion of the code execution time is spent transforming computed quantities between physical values and spherical harmonic coefficients, equivalent to a series of linear algebra operations. Intermixing C and Fortran code has opened the door to the parallel computing platform, Cuda and its associated libraries. We successfully implemented the parallelization of the scaling of the Legendre polynomials by both Schmidt Normalization coefficients, and a set of weighting coefficients; however, the expected speedup was not realized. Specifically, the original version of Calypso 1.1 computes the Legendre transform approximately four seconds faster than the Cuda-enabled modified version. By profiling the code, we determined that the time taken to transfer the data from host memory to GPU memory does not compare to the number of computations happening within the GPU. Nevertheless, by utilizing techniques such as memory coalescing, cached memory, pinned memory, dynamic parallelism, asynchronous calls, and overlapped memory transfers with computations, the likelihood of a speedup increases. Moreover, ideally the generation of the Legendre polynomial coefficients, Schmidt Normalization Coefficients, and the set of weights should not only be parallelized but be computed on-the-fly within the GPU. The end result is that we reduce the number of memory transfers from host to GPU, increase the number of parallelized computations on the GPU, and decrease the number of serial computations on the CPU. Also, the time taken to transform physical values to spherical

  3. The role of carbon in extrasolar planetary geodynamics and habitability

    SciTech Connect

    Unterborn, Cayman T.; Kabbes, Jason E.; Pigott, Jeffrey S.; Panero, Wendy R.; Reaman, Daniel M.

    2014-10-01

    The proportions of oxygen, carbon, and major rock-forming elements (e.g., Mg, Fe, Si) determine a planet's dominant mineralogy. Variation in a planet's mineralogy subsequently affects planetary mantle dynamics as well as any deep water or carbon cycle. Through thermodynamic models and high pressure diamond anvil cell experiments, we demonstrate that the oxidation potential of C is above that of Fe at all pressures and temperatures, indicative of 0.1-2 Earth-mass planets. This means that for a planet with (Mg+2Si+Fe+2C)/O > 1, excess C in the mantle will be in the form of diamond. We find that an increase in C, and thus diamond, concentration slows convection relative to a silicate-dominated planet, due to diamond's ∼3 order of magnitude increase in both viscosity and thermal conductivity. We assert then that in the C-(Mg+2Si+Fe)-O system, there is a compositional range in which a planet can be habitable. Planets outside of this range will be dynamically sluggish or stagnant, thus having limited carbon or water cycles leading to surface conditions inhospitable to life as we know it.

  4. Water in the Martian interior—The geodynamical perspective

    NASA Astrophysics Data System (ADS)

    Breuer, Doris; Plesa, Ana-Catalina; Tosi, Nicola; Grott, Matthias

    2016-11-01

    Petrological analysis of the Martian meteorites suggests that rheologically significant amounts of water are present in the Martian mantle. A bulk mantle water content of at least a few tens of ppm is thus expected to be present despite the potentially efficient degassing during accretion, magma ocean solidification, and subsequent volcanism. We examine the dynamical consequences of different thermochemical evolution scenarios testing whether they can lead to the formation and preservation of mantle reservoirs, and compare model predictions with available data. First, the simplest scenario of a homogenous mantle that emerges when ignoring density changes caused by the extraction of partial melt is found to be inconsistent with the isotopic evidence for distinct reservoirs provided by the analysis of the Martian meteorites. In a second scenario, reservoirs can form as a result of partial melting that induces a density change in the depleted mantle with respect to its primordial composition. However, efficient mantle mixing prevents these reservoirs from being preserved until present unless they are located in the stagnant lid. Finally, reservoirs could be formed during fractional crystallization of a magma ocean. In this case, however, the mantle would likely end up being stably stratified as a result of the global overturn expected to accompany the fractional crystallization. Depending on the assumed density contrast, little secondary crust would be produced and the lithosphere would be extremely cool and dry, in contrast to observations. In summary, it is very challenging to obtain a self-consistent evolution scenario that satisfies all available constraints.

  5. The Role of Carbon in Extrasolar Planetary Geodynamics and Habitability

    NASA Astrophysics Data System (ADS)

    Unterborn, Cayman T.; Kabbes, Jason E.; Pigott, Jeffrey S.; Reaman, Daniel M.; Panero, Wendy R.

    2014-10-01

    The proportions of oxygen, carbon, and major rock-forming elements (e.g., Mg, Fe, Si) determine a planet's dominant mineralogy. Variation in a planet's mineralogy subsequently affects planetary mantle dynamics as well as any deep water or carbon cycle. Through thermodynamic models and high pressure diamond anvil cell experiments, we demonstrate that the oxidation potential of C is above that of Fe at all pressures and temperatures, indicative of 0.1-2 Earth-mass planets. This means that for a planet with (Mg+2Si+Fe+2C)/O > 1, excess C in the mantle will be in the form of diamond. We find that an increase in C, and thus diamond, concentration slows convection relative to a silicate-dominated planet, due to diamond's ~3 order of magnitude increase in both viscosity and thermal conductivity. We assert then that in the C-(Mg+2Si+Fe)-O system, there is a compositional range in which a planet can be habitable. Planets outside of this range will be dynamically sluggish or stagnant, thus having limited carbon or water cycles leading to surface conditions inhospitable to life as we know it.

  6. Geodynamic simulation of ore-bearing geological structural units by the example of the Strel'tsovka uranium ore field

    NASA Astrophysics Data System (ADS)

    Petrov, V. A.; Leksin, A. B.; Pogorelov, V. V.; Rebetsky, Yu. L.; San'kov, V. A.; Ashurkov, S. V.; Rasskazov, I. Yu.

    2017-05-01

    Information on designing a 3D integrated model of the deflected mode (DM) of rock massif near the Strel'tsovka uranium ore field (SUOF) in the southeastern Transbaikal region is presented in the paper. This information is based on the contemporary stresses estimated by geostructural and tectonophysical techniques and by studying the seismotectonic deformation of the Earth's surface using the data on earthquake source mechanisms and GPS geodesy focused on the recognition of active faults. A combination of the results of geostructural, geophysical, geotectonic, and petrophysical research, as well as original maps of faulting and the arrangement of seismic dislocations and seismotectonic regimes (stress tensors), allowed us to design models of the structure, properties, and rheological links of the medium and to determine the boundary conditions for numerical tectonophysical simulation using the method of terminal elements. The computed 2D and 3D models of the state of the rock massif have been integrated into 3D GIS created on the basis of the ArcGIS 10 platform with an ArcGIS 3D-Analyst module. The simulation results have been corroborated by in situ observations on a regional scale (the Klichka seismodislocation, active from the middle Pliocene to date) and on a local scale (heterogeneously strained rock massif at the Antei uranium deposit). The development of a regional geodynamic model of geological structural units makes it possible to carry out procedures to ensure the safety of mining operations under complex geomechanical conditions that can expose the operating mines and mines under construction, by the Argun Mining and Chemical Production Association (PAO PPGKhO) on a common methodical and geoinformational platform, to the hazards of explosions, as well as to use the simulation results aimed at finding new orebodies to assess the flanks and deep levels of the ore field.

  7. Tracing lithosphere amalgamation through time: chemical geodynamics of sub-continental lithospheric mantle

    NASA Astrophysics Data System (ADS)

    Wittig, Nadine

    2014-05-01

    The theory of plate tectonics is a relatively young concept in the Earth Sciences and describes the surface expression of planetary cooling via magmatism and reconciles mantle convection and plate movement with orogenesis, earthquakes and volcanism. Detailed observation of current tectonic plate movement has purported a relatively clear picture of the planet's geodynamics. Modern oceanic basins are the predominant sites of thermal equilibration of Earth interior resulting from decompressional, convective melting of peridotites. This magmatism generates mid-ocean ridge mafic crust and depleted upper mantle and in this model, oceanic crust becomes associated with buoyant mantle to form oceanic lithosphere. Subduction zones return this material together with sediments into the deeper mantle and presumably aid the formation of continental crust via arc magmatism. The mechanisms of continental crust amalgamation with buoyant mantle are less clear, and distinctly more difficult to trace back in time because metamorphism and metasomatism render the processes associating convecting mantle with continental crust elusive. Paramount in assessing these mechanisms is understanding the timing of crust and mantle formation so that the onset of plate tectonics and potential changes in modi operandi with respect to convection, mantle composition and melting pressure and temperature may be traced from the early Hadean to the present day. Typically the formation age of continental crust is more easily determined from felsic samples that contain accessory and relatively robust phases such as zircon and monazite that render a geochronological approach feasible. The lack of equally robust minerals and pervasive and ubiquitous metasomatism afflicting obducted orogenic peridotites and mantle xenoliths obliterates primary mineralogical and geochemical information. Hence it has proven difficult to acquire mantle depletion ages from continental lithospheric mantle, perhaps with the exception

  8. International Tectonic Map of the Circumpolar Arctic and its Significance for Geodynamic Interpretations

    NASA Astrophysics Data System (ADS)

    Petrov, O. V.; Morozov, A.; Shokalsky, S.; Leonov, Y.; Grikurov, G.; Poselov, V.; Pospelov, I.; Kashubin, S.

    2011-12-01

    In 2003 geological surveys of circum-arctic states initiated the international project "Atlas of Geological Maps of Circumpolar Arctic at 1:5 000000 scale". The project received active support of the UNESCO Commission for the Geological Map of the World (CGMW) and engaged a number of scientists from national academies of sciences and universities. Magnetic and gravity maps were prepared and printed by the Norwegian Geological Survey, and geological map was produced by the Geological Survey of Canada. Completion of these maps made possible compilation of a new Tectonic Map of the Arctic (TeMAr), and this work is now in progress with Russian Geological Research Institute (VSEGEI) in the lead of joint international activities. The map area (north of 60o N) includes three distinct roughly concentric zones. The outer onshore rim is composed of predominantly mature continental crust whose structure and history are illustrated on the map by the age of consolidation of craton basements and orogenic belts. The zone of offshore shelf basins is unique in dimensions with respect to other continental margins of the world. Its deep structure can in most cases be positively related to thinning and rifting of consolidated crust, sometimes to the extent of disruption of its upper layer, whereas the pre-rift evolution can be inferred from geophysical data and extrapolation of geological evidence from the mainland and island archipelagoes. The central Arctic core is occupied by abyssal deeps and intervening bathymetric highs. The Eurasia basin is commonly recognized as a typical oceanic opening separating the Barents-Kara and Lomonosov Ridge passive margins, but geodynamic evolution of Amerasia basin are subject to much controversy, despite significant intensification of earth science researchin the recent years. A growing support to the concept of predominance in the Amerasia basin of continental crust, particularly in the area concealed under High Arctic Large Igneous Province, is

  9. Aegean crustal thickness inferred from gravity inversion. Geodynamical implications

    NASA Astrophysics Data System (ADS)

    Tirel, Céline; Gueydan, Frédéric; Tiberi, Christel; Brun, Jean-Pierre

    2004-12-01

    Since Oligo-Miocene times, the Aegean domain has undergone regional extension due to the southward retreat of the Hellenic subduction zone. Boundary conditions have been more recently modified by the westward extrusion of Anatolia. A new map of the Aegean crustal thickness inferred from gravity inversion is proposed here to better constrain the variations in space and time of crustal thinning that has accumulated since Oligo-Miocene times. Moho topography is obtained by inversion of satellite marine gravity data. Data are first corrected for terrain anomalies and deep mantle effects (African subducting slab). They are then filtered between 50 and 300 km to avoid short wavelength intracrustal effects. Results are consistent with previous 2D geophysical studies (seismic refraction, receiver functions) and show that an overall regional isostatic compensation of the crust holds for the Aegean area, with a mean crustal thickness of 25 km. Three different provinces (North Aegean, Cyclades and Cretan Sea) can be identified. Thinner crust is observed both in the North Aegean region (NE-SW trending of thinning, with crustal thickness lower than 24 km) and in the Cretan Sea (crustal thickness of 22-23 km). Between these two regions, the Cyclades are marked by a rather flat Moho at 25 km. A two-stage model of the Aegean extension could well explain the observed crustal thickness variation. From Oligocene to middle Miocene, gravitational collapse of the Hellenides, due to the southward retreat of the African slab, reduced the Aegean continental crust from 50 km (by reference to continental Greece and Anatolia) to a mean value of 25 km at the scale of the whole Aegean. From upper Miocene to present, the westward extrusion of Anatolia modified the extension and the associated crustal thinning in the North Aegean domain. During this second episode, crustal thinning related to the southward retreat of the African slab tends to localize in the Cretan Sea. The Cyclades likely behave

  10. Geodynamic and Magmatic Evolution of the Eastern Anatolian-Arabian Collision Zone, Turkey

    NASA Astrophysics Data System (ADS)

    Keskin, Mehmet

    2014-05-01

    The Eastern Anatolian-Arabian Collision Zone represents a crucial site within the Tethyan domain where a subduction system involving a volcanic arc (i.e. Cretaceous to Oligocene Pontide volcanic arc in the north) associated with a large subduction-accretion complex (i.e. Cretaceous to Oligocene Eastern Anatolian Accretionary Complex i.e. "EAAC" in the south) turned later into a major continental collision zone that experienced a series of geodynamic events including lithospheric delamination, slab-steepening & breakoff, regional domal uplift, widespread volcanism and tectonic escape via strike slip fault systems. The region includes some of the largest volcanic centers (e.g. Karacadaǧ, Aǧırkaya caldera, Ararat, Nemrut, Tendürek and Süphan volcanoes) and plateaus (e.g. The Erzurum-Kars Plateau) as well as the largest transform fault zones in the Mediterranean region. A recent geodynamic modeling study (Faccenna et al., 2013) has suggested that both the closure of the Tethys Ocean and the resultant collision were driven by a large scale and northerly directed asthenospheric mantle flow named the "Tethyan convection cell". This convection cell initiated around 25 Ma by combined effects of mantle upwelling of the Afar super plume located in the south, around 3,000 km away from the collision zone and the slab-pull of the Tethyan oceanic lithosphere beneath Anatolia in the north. The aforementioned mantle flow dragged Arabia to the north towards Eastern Anatolia with an average velocity of 2 cm/y for the last 20 My, twice as fast as the convergence of the African continent (i.e. 1 cm/y) with western and Central Turkey. This 1 cm/y difference resulted in the formation of the left lateral Dead Sea Strike Slip Fault between the African and Arabian plates. Not only did this mantle flow result in the formation of a positive dynamic topography in the west of Arabian block, but also created a dynamic tilting toward the Persian Gulf (Faccenna et al., 2013). Another

  11. Reply to: Comment by Aftabi and Atapour on « Arc magmatism and subduction history beneath the Zagros Mountains, Iran: A new report of adakites and geodynamic consequences »

    NASA Astrophysics Data System (ADS)

    Omrani, Jafar; Agard, Philippe; Whitechurch, Hubert; Benoit, Mathieu; Prouteau, Gaëlle; Jolivet, Laurent

    2009-12-01

    We herein answer the comments by Aftabi and Atapour to our paper entitled "Arc magmatism and subduction history beneath the Zagros Mountains, Iran: A new report of adakites and geodynamic consequences". We show that their criticism rests on rather weak grounds and numerous contradictions. We reassess the validity of our analytical results and stress the lack of alteration in our adakitic samples. We further discuss the interpretation of our findings, in particular the fact that the distribution of these adakites is not random in the Urumieh-Dokhtar magmatic arc, neither in space nor time (being restricted to the central part and to Upper Miocene to younger rocks). Finally, we point out that Aftabi and Atapour even somewhat support our model when they suggest "slab break-off (as a cause) for the Miocene-Pliocene adakitic rocks" .

  12. On information-provided monitoring of geodynamic processes in the Kuznetsk Coal Basin in the conditions of highly intensive sub-soil usage

    SciTech Connect

    Oparin, V.N.; Potapov, V.P.; Tanaino, A.S.

    2006-09-15

    It is shown that formation of underground hollows of the Kuznetsk Coal Basin (Kuzbass), induced by opencut and underground mining has reached an intensity of 1.3-1.5 million m{sup 3}/day. In the conditions of high concentration of mines and open-cuts in small areas, a regional monitoring network is required in view of a generated geomechanical space, hazardous in geodynamic manifestations. A developed information support of this network is presented, including information models of a geological environment and database obtained from instrumental observations on geomechanical processes. The equations of connection between structural and strength characteristics of rocks, their metamorphization grade and occurrence depth are given for five geological-tectonic zones of the Kuzbass as a way of prediction of their properties.

  13. Geodynamics of the Barents-Kara margin in the Mesozoic inferred from paleomagnetic data on rocks from the Franz Josef Land Archipelago

    NASA Astrophysics Data System (ADS)

    Mikhaltsov, N. E.; Karyakin, Yu. V.; Abashev, V. V.; Bragin, V. Yu.; Vernikovsky, V. A.; Travin, A. V.

    2016-12-01

    New data on paleomagnetism and isotope geochronology of Jurassic and Early Cretaceous basic igneous rocks on Franz Josef Land Archipelago (FJL) represented by flows and dikes are discussed. The first paleomagnetic data obtained for these rocks offer the opportunity to suggest a model of spatial changes in the FJL block position during the Jurassic‒Cretaceous. In the Early Jurassic, the block occupied a different position relative to Europe from the modern one. It was displaced in the northeasterly direction by a distance of approximately 500 km and rotated clockwise by about 40° relative to its modern position. By the Early Cretaceous, the FJL block occupied a position close to the present-day one avoiding subsequent substantial relative displacements. The data obtained are of principal significance for reconstructing the geodynamic evolution of Arctic structures in the Mesozoic and contribute greatly to the base of paleomagnetic data for the Arctic region, development of which is now in progress.

  14. Detrital provenance of Early Mesozoic basins in the Jiangnan domain, South China: Paleogeographic and geodynamic implications

    NASA Astrophysics Data System (ADS)

    Xu, Xianbing; Tang, Shuai; Lin, Shoufa

    2016-04-01

    Detrital provenance analysis is an effective way to understand paleogeographic change and geodynamics. In this paper, we present petrological, whole-rock geochemical and detrital zircon U-Pb geochronological analysis of Early and Middle Jurassic terrestrial clastic rocks in the Jingdezhen Basin and the Huangshan Basin in the Jiangnan domain, South China. Petrology and whole-rock geochemistry show that the source rocks are dominated by intermediate to acid component. The Chemical Index of Alteration ranges from 69 to 86, suggesting a moderate weathering history for the source rocks. The Early-Middle Jurassic sediments in the Jingdezhen and Huangshan basins were mostly sourced from magmatogenic greywackes and felsic magmatic rocks, respectively. Detrital zircons have seven age peaks at 240 Ma, 430 Ma, 1390 Ma, 1880 Ma, 2500 Ma, -3200 Ma and 788-999 Ma (a wide peak). Provenance analysis indicates that the source rocks are in the Jiangnan domain, the Northwest Zhejiang Basin and the Wuyishan domain. Combining these with previous results and paleocurrent directions, we infer that the NE-trending Wuyishan and Xuefengshan domains and the nearly E-W-Jiangnan domain and Nanling tectonic belt were orogenic uplifts and watersheds during the Late Triassic to Middle Jurassic. The Early Mesozoic geodynamics in the South China Block was related to the westward subduction of the Paleo-Pacific Plate and the northward continent-continent collision following the closure of the Paleo-Tethys Ocean.

  15. Early signs of geodynamic activity before the 2011-2012 El Hierro eruption

    NASA Astrophysics Data System (ADS)

    López, Carmen; García-Cañada, Laura; Martí, Joan; Domínguez Cerdeña, Itahiza

    2017-02-01

    The potential relation between mantle plume dynamics, regional tectonics and eruptive activity in the Canary Islands has not been studied yet through the analysis of long-time series of geophysical observational data. The existence of highly reliable seismic and geodetic data has enabled us to study from 1996 to 2014 the geodynamic evolution of the North Atlantic Azores-Gibraltar region (including the NW African margin) and its relationship with recent volcanic activity in El Hierro (Canary Islands). We compiled a new and unified regional seismic catalog and used long time-series of digital 3D surface displacements recorded by permanent GPS stations in the region. A joint regional- and local-scale analysis based on these data enabled us to identify signs of anomalous tectonic activity from 2003 onwards, whose intensity increased in 2007 and finally accelerated three months before the onset of the volcanic eruption on El Hierro in October 2011. Activity included the occurrence of regional extension and an uplift process affecting the southern Iberian Peninsula, NW Africa, and the Canary Islands. We interpret these observations as early signs of the geodynamic activity, which led to El Hierro eruption and the subsequent episodes of magma intrusion. Results point to the significant contribution of the mantle plume dynamics (i.e. external forces) in this renewed volcanic activity in the Canary Islands and emphasize the role of mantle dynamics in controlling regional tectonics.

  16. Geodetic implications on block formation and geodynamic domains in the South Shetland Islands, Antarctic Peninsula

    NASA Astrophysics Data System (ADS)

    Berrocoso, M.; Fernández-Ros, A.; Prates, G.; García, A.; Kraus, S.

    2016-01-01

    The South Shetland Islands archipelago is dynamically complex due to its tectonic surroundings. Most islands are part of a formerly active volcanic arc, although Deception, Penguin and Bridgeman Islands, as well as several submarine volcanoes, are characterized by active back-arc volcanism. Geodetic benchmarks were deployed and the movement of the lithosphere to which they were fixed measured to provide geodynamic insight for the South Shetland Islands, Bransfield Basin and Antarctic Peninsula area based on surface deformation. These benchmarks' data add spatial and temporal coverage to previous results. The results reveal two different geodynamic patterns, each confined to a distinct part of the South Shetland Islands archipelago. The inferred absolute horizontal velocity vectors for the benchmarks in the northeastern part of the archipelago are consistent with the opening of the Bransfield Basin, while benchmark vectors in the southwestern part of the archipelago are similar to those of the benchmarks on the Antarctic Peninsula. In between, Snow, Deception and Livingston Islands represent a transition zone. In this area, the horizontal velocity vectors relative to the Antarctic plate shift northeastwards from N to NW. Furthermore, the South Shetland Islands benchmarks, except for that at Gibbs (Elephant) Islands, indicate subsidence, which might be a consequence of the slab roll-back at the South Shetland Trench. In contrast, the uplift revealed by the Antarctic Peninsula benchmarks suggests glacial isostatic adjustment after the Larson B ice-shelf breakup.

  17. Superkimberlites: A geodynamic diamond window to the Earth's core

    NASA Astrophysics Data System (ADS)

    Haggerty, Stephen E.

    1994-03-01

    Carbon is the fourth most abundant element in the solar system. In the Earth carbon is in atmospheric CO2, limestone, other organic products, graphite and trace diamond; interstellar diamond, however, is ubiquitous. Diamond is well known for some unique physical and chemical properties, but it is perhaps less well known that the mineral is geologically ancient (3.3 Ga), that its origins are deep in the mantle (greater than 180 km), and that diamonds are among the deepest solid objects to reach the surface of the Earth; rare diamonds are from the transition zone (400-670 km), and other diamonds possibly nucleated in the lower mantle (greater than 670 km). Transport to the surface is in volatile (C-O-H-N-S)-charged highly explosive kimberlite and lamproite volcanoes. These volcanoes are sited exclusively in the oldest (greater than 1.7 Ga), tectonically most stable, and thickest (approximately 200 km) regions of crust and upper mantle lithosphere. The energetics required for volcanism are so exceptional and the sources so deep that possible connections between and among the core, geomagnetism, plumes and diamonds are explored. Some correlations are established and others are implied. The results are sufficiently enticing to propose that kimberlites and geographically and temporally associated carbonatites are continental recorders of plumes dating back to at least 2.8 Ga, and that some diamonds may have recorded core events dating back to 3.3 Ga, or possibly earlier. Peaks in kimberlite magmatic activity correlate , on average, with normal and reverse superchron and subchron behavior of the geomagnetic field. The time lag between magnetohydrodynamic activity in the core and kimberlite eruptive cycles at the Earth's surface is of the order of 25-50 Ma, consistent with the travel times modeled for the passage of plumes from the D'' layer to the subcontinental lithosphere. Although the existence of plumes and the nature of D'' are debated, the correlations established

  18. Neoproterozoic geodynamic evolution of SW-Gondwana: a southern African perspective

    NASA Astrophysics Data System (ADS)

    Frimmel, H. E.; Basei, M. S.; Gaucher, C.

    2011-04-01

    Our current understanding of the tectonic history of the principal Pan-African orogenic belts in southwestern Africa, reaching from the West Congo Belt in the north to the Lufilian/Zambezi, Kaoko, Damara, Gariep and finally the Saldania Belt in the south, is briefly summarized. On that basis, possible links with tectono-stratigraphic units and major structures on the eastern side of the Río de la Plata Craton are suggested, and a revised geodynamic model for the amalgamation of SW-Gondwana is proposed. The Río de la Plata and Kalahari Cratons are considered to have become juxtaposed already by the end of the Mesoproterozoic. Early Neoproterozoic rifting led to the fragmentation of the northwestern (in today's coordinates) Kalahari Craton and the splitting off of several small cratonic blocks. The largest of these ex-Kalahari cratonic fragments is probably the Angola Block. Smaller fragments include the Luis Alves and Curitiba microplates in eastern Brazil, several basement inliers within the Damara Belt, and an elongate fragment off the western margin, named Arachania. The main suture between the Kalahari and the Congo-São Francisco Cratons is suspected to be hidden beneath younger cover between the West Congo Belt and the Lufilian/Zambezi Belts and probably continues westwards via the Cabo Frío Terrane into the Goiás magmatic arc along the Brasilia Belt. Many of the rift grabens that separated the various former Kalahari cratonic fragments did not evolve into oceanic basins, such as the Northern Nosib Rift in the Damara Belt and the Gariep rift basin. Following latest Cryogenian/early Ediacaran closure of the Brazilides Ocean between the Río de la Plata Craton and the westernmost fragment of the Kalahari Craton, the latter, Arachania, became the locus of a more than 1,000-km-long continental magmatic arc, the Cuchilla Dionisio-Pelotas Arc. A correspondingly long back-arc basin (Marmora Basin) on the eastern flank of that arc is recognized, remnants of which

  19. Sedimentary Markers : a window into deep geodynamic processes Examples from the Western Mediterranean Sea

    NASA Astrophysics Data System (ADS)

    Rabineau, Marina; Aslanian, Daniel; Leroux, Estelle; Pellen, Romain; Gorini, Christian; Moulin, Maryline; Droz, Laurence; Bache, Francois; Molliex, Stephane; Silenzario, Carmine; Rubino, Jean-Loup

    2017-04-01

    Deep Earth dynamics impact so strongly on surface geological processes that we can use sediment palaeo-markers as a window into the deeper Earth. Derived from climatic and tectonic erosive actions on the continents, and related to eustasy, subsidence and isostasy, the sediment in a deep basin is the main recorder of these processes. Nevertheless, defining and quantifying the relative roles of parameters that interact to give the final sedimentary architecture is not a simple task. Using a 3D-grid of seismic and wide-angle data, boreholes and numerical stratigraphic modelling, we propose here a quantification of post-rift vertical movements in the Provençal Basin (Western Mediterranean) involving three domains of subsidence: seaward tilting on the platform and the slope and purely vertical subsidence in the deep basin (Rabineau et al., 2014 ; Leroux et al., 2015). These domains fit the deeper crustal domains highlighted by previous geophysical data (Moulin et al., 2015 ; Afilhado et al., 2015). Post-break-up sedimentary markers may therefore be used to identify the initial hinge lines of the rifting phase, to quantify sedimentation rates and isostatic rebound (Rabineau et al., 2014) and redefine the subsidence laws. Similar work and results are obtained in the Valencia Basin (Pellen et al., 2016). This Western Mediterranean Sea is a natural laboratory with very high total subsidence rates that enable high sedimentation rates along the margin with sediments provided by the Rhône and Ebro rivers flowing from the Alps, the Pyrennees and Catalan chains, which in turn archives the detailed record of climate/tectonic evolution during the Neogene. The Western Mediterranean Sea could therefore further probe deep-earth and surface connections using deep drillings of this land-locked ocean basin transformed into a giant saline basin (Rabineau et al., 2015). Leroux, E., Aslanian, D., Rabineau, M., M. Moulin, D. Granjeon, C. Gorini, L. Droz, 2015. Sedimentary markers: a

  20. Geodynamic problems

    NASA Technical Reports Server (NTRS)

    Kaula, W. M.

    1978-01-01

    The understanding of the solid earth and suggestions of what measurements should be undertaken based on estimates of instrumental feasibilities were reviewed. The observations include: (1) earth evolution and mantle convection; (2) lithosphere-asthenosphere-surface load interaction; (3) glacier-ocean-solid earth interaction; (4) solid earth interactions with the sun, moon, core, oceans, and atmosphere; (5) zones of strain accumulation; and (6) earthquakes.

  1. Geodynamical Nature of the Formation of Large Plates of Platforms, Jointed in North Caspian Oil and Gas Basin

    ERIC Educational Resources Information Center

    Seitov, Nassipkali; Tulegenova, Gulmira P.

    2016-01-01

    This article addresses the problems of tectonic zoning and determination of geodynamical nature of the formation of jointed tectonic structures within the North Caspian oil and gas basin, represented by Caspian Depression of Russian platform of East European Pre-Cambrian Craton and plate ancient Precambrian Platform stabilization and Turan…

  2. Simple Lu-Hf isotope patterns resulting from complex Archean geodynamics: example of the Pietersburg block (South Africa)

    NASA Astrophysics Data System (ADS)

    Laurent, Oscar; Zeh, Armin

    2015-04-01

    The combined use of U-Pb and Lu-Hf isotope data from Hadean and Archean zircons is widely used to constrain the mechanisms of continental crust formation and evolution in the early Earth. Such data generally define ɛHf-time arrays, interpreted as reflecting the closed-system, protracted reworking of single crustal reservoirs episodically extracted from depleted mantle (DM) sources. Many models about early Earth evolution and continental growth rely on this interpretation and its consequences (i.e. determination of Hf model ages and crustal residence times). However, this straightforward interpretation is difficult to reconcile with the complex evolution of Archean terranes, involving progressive crustal maturation and a range of crustal and mantle sources to granitoid magmas. Here we present a database of U-Pb and Lu-Hf isotopes measured in situ by LA-(MC-)ICPMS in zircons from >30 samples, representative of the temporal and spatial record of a single segment of Archean crust, the Pietersburg block (Kaapvaal Craton, South Africa). Coupling of age-Hf data with petrological and geochemical constraints shows that >1 Ga-long crustal evolution in the PB is characterized by (i) crustal nucleation in an intra-oceanic setting between 3.4 and 3.1 Ga; (ii) rapid formation of large volumes of juvenile TTG crust in an accretionary orogen at the northern edge of the proto-Kaapvaal craton between 3.1 and 2.9 Ga; (iii) intracrustal reworking and subduction of TTG-derived sediments along an Andean-type continental margin between 2.9 and 2.75 Ga; (iv) continental collision with the Central Zone of the Limpopo Belt at 2.75-2.69 Ga, resulting in magmatism derived from local crust and metasomatized mantle; (v) a discrete anorogenic event at ~2.05 Ga with the emplacement of SCLM-derived alkaline magmas. Despite the diversity of magmas and geodynamic settings depicted by this evolution, all samples emplaced between 3.0 and 2.0 Ga plot along a single, robust array of decreasing

  3. The Early Miocene "Bisciaro volcaniclastic event" (northern Apennines, Italy): a key study for the geodynamic evolution of the central-western Mediterranean

    NASA Astrophysics Data System (ADS)

    Guerrera, Francesco; Martín-Martín, Manuel; Raffaelli, Giuliana; Tramontana, Mario

    2015-06-01

    The Early Miocene Bisciaro Fm., a marly limestone succession cropping out widely in the Umbria-Romagna-Marche Apennines, is characterized by a high amount of volcaniclastic content, characterizing this unit as a peculiar event of the Adria Plate margin. Because of this volcaniclastic event, also recognizable in different sectors of the central-western Mediterranean chains, this formation is proposed as a "marker" for the geodynamic evolution of the area. In the Bisciaro Fm., the volcaniclastic supply starts with the "Raffaello" bed (Earliest Aquitanian) that marks the base of the formation and ends in the lower portion of the Schlier Fm. (Late Burdigalian-Langhian p.p.). Forty-one studied successions allowed the recognition of three main petrofacies: (1) Pyroclastic Deposits (volcanic materials more than 90 %) including the sub-petrofacies 1A, Vitroclastic/crystallo- vitroclastic tuffs; 1B, Bentonitic deposits; and 1C, Ocraceous and blackish layers; (2) Resedimented Syn-Eruptive Volcanogenic Deposits (volcanic material 30-90 %) including the sub-petrofacies 2A, High- density volcanogenic turbidites; 2B, Low- density volcanogenic turbidites; 2C, Crystal- rich volcanogenic deposits; and 2D, Glauconitic- rich volcaniclastites; (3) Mixing of Volcaniclastic Sediments with Marine Deposits (volcanic material 5-30 %, mixed with marine sediments: marls, calcareous marls, and marly limestones). Coeval volcaniclastic deposits recognizable in different tectonic units of the Apennines, Maghrebian, and Betic Chains show petrofacies and chemical-geochemical features related to a similar calc-alkaline magmatism. The characterization of this event led to the hypothesis of a co-genetic relationship between volcanic activity centres (primary volcanic systems) and depositional basins (depositional processes) in the Early Miocene palaeogeographic and palaeotectonic evolution of the central-western Mediterranean region. The results support the proposal of a geodynamic model of this area

  4. The Lanzarote Geodynamic Laboratory: new capabilities for monitoring of volcanic activity at Canary Islands

    NASA Astrophysics Data System (ADS)

    Arnoso, J.; Vélez, E. J.; Soler, V.; Montesinos, F. G.; Benavent, M.

    2012-04-01

    The volcanic island of Lanzarote is located at the northeastern end of the Canary Islands. Together with Fuerteventura Island, Lanzarote constitutes the emergent part of the East Canary Ridge, which presents a NNE-SSW volcanic alignment. Last eruptive events took place in 1824 and during the period 1730-1736, which is the largest to occur in the archipelago and throw out about 1.3 km3 of volcanic materials. The Lanzarote Geodynamic Laboratory (LGL) was created in 1986 with the idea of making Lanzarote as a natural laboratory to carry out studies in order to acquire more knowledge about its origin, present status and evolution (Vieira et al., 1991; 2006). The LGL has a multidisciplinary scientific purpose and, among others, various objectives are devoted to investigate mass distribution in the Earth system and surface displacements associated to volcanic and/or seismic activity in the island. The influence of LGL is extended throughout the whole geographical area of Lanzarote, including small islands located at the north. The laboratory has 3 observing modules distributed along the island according to its infrastructure and scientific objectives, where more than 70 sensors are recording continuously gravity variations, ground deformations, sea level, seismic activity, meteorological parameters, etc. All these observations are supplemented by periodic measurement of geodetic and geophysical networks that allow us to make studies at local, insular and regional scales. The application of geodetic and geophysical techniques to identify geodynamic signals related to volcanic processes is then a permanent research activity of the laboratory. Nowadays, this fact becomes more interesting due to the ongoing volcanic eruption that is taking place in other island of the Canary Archipelago, El Hierro, since past July 2011. That is, the multidisciplinary research carry on up to now at the LGL allow us to apply multiparameter observations of different kinds of volcanic

  5. Gnss Geodetic Monitoring as Support of Geodynamics Research in Colombia, South America

    NASA Astrophysics Data System (ADS)

    Mora-Paez, H.; Acero-Patino, N.; Rodriguez-Zuluaga, J. S.; Diederix, H.; Bohorquez-Orozco, O. P.; Martinez-Diaz, G. P.; Diaz-Mila, F.; Giraldo-Londono, L. S.; Cardozo-Giraldo, S.; Vasquez-Ospina, A. F.; Lizarazo, S. C.

    2013-05-01

    To support the geodynamics research at the northwestern corner of South America, GEORED, the acronym for "Geodesia: Red de Estudios de Deformación" has been adopted for the Project "Implementation of the National GNSS Network for Geodynamics" carried out by the Colombian Geological Survey, (SGC), formerly INGEOMINAS. Beginning in 2007, discussions within the GEORED group led to a master plan for the distribution of the base permanent GPS/GNSS station array and specific areas of interest for campaign site construction. The use of previously identified active faults as preferred structures along which stresses are transferred through the deformational area led to the idea of segmentation of the North Andes within Colombia into 20 tectonic sub-blocks. Each of the 20 sub-blocks is expected to have, at least, three-four permanent GPS/GNSS stations within the block along with construction of campaign sites along the boundaries. Currently, the GEORED Network is managing 46 continuously including: 40 GEORED GPS/GNSS continuously operating stations; 4 GNSS continuously operating stations provided by the COCONet (Continuously Operating Caribbean GPS Observational Network) Project; the Bogotá IGS GPS station (BOGT), installed in 1994 under the agreement between JPL-NASA and the SGC; and the San Andres Island station, installed in 2007 under the MOU between UCAR and the SGC. In addition to the permanent installations, more than 230 GPS campaign sites have been constructed and are being occupied one time per year. The Authority of the Panama Canal and the Escuela Politecnica de Quito have also provided data of 4 and 5 GPS/GNSS stations respectively. The GPS data are processed using the GIPSY-OASIS II software, and the GPS time series of daily station positions give fundamental information for both regional and local geodynamics studies. Until now, we have obtained 100 quality vector velocities for Colombia, 23 of them as part of the permanent network. The GPS/GNSS stations

  6. Geoelectrical, strain and tilt investigations of hydrological processes at the broadband Geodynamical Observatory Moxa, Germany

    NASA Astrophysics Data System (ADS)

    Hermann, Tobias; Kroner, Corinna; Jahr, Thomas

    2013-11-01

    The Geodynamic Observatory Moxa, located in Thuringia/Germany, is dedicated to studies of temporal deformations of the earth's crust and of variations of the gravity field. One of the essential issues with respect to these investigations is the reduction of the hydrological impact on the data of the gravimeters, strainmeters and tiltmeters. In order to optimise the reductions, we investigated the changes in the hydrological conditions in the woody mountain slope above the observatory with time-lapse electrical resistivity tomography (ERT), and analysed the strain and tilt measurements for prominent signatures of pore pressure induced subsurface deformations. Here we present the results for two profiles - parallel and perpendicular to the slope - measured with ERT during 33 campaigns between June 2007 and April 2010. Resistivity changes and variations of apparent soil moisture, inferred from ERT sections, were found to primarily occur in the first two metres of the subsurface. These variations can be related to subsurface flow in the upper two metres induced by precipitation events and snowmelts. Trees close to the profiles only show a minimum impact on the resistivity and soil moisture changes. Furthermore, systematic hydrologically induced deformations can be observed in hodographs of strain and tilt measurements for large precipitation events (> 80 mm) and snowmelts. In the strain data a short-term (< 3 days) dilatational signal is found with an amplitude of 20 nstrain to 60 nstrain and a long-term (> 7 days) compressional signal between 40 nstrain and 180 nstrain. The preferential N-S direction of long-term deformational signals (> 1 week) is also observed in the tilt data. The direction of tilt changes (25 nrad-120 nrad) is nearly parallel to the drainage direction of the nearby Silberleite creek indicating variations of pore pressure gradients during hydrological events. The results of these hydrological studies at the Geodynamic Observatory Moxa can be used

  7. Understanding the geodynamic setting of São Miguel, Azores: A peculiar bit of mantle in the Central Atlantic

    NASA Astrophysics Data System (ADS)

    Wilson, M.; Houlie, N.; Khan, A.; Lithgow-Bertelloni, C. R.

    2012-12-01

    The Azores Plateau and Archipelago in the Central Atlantic Ocean has traditionally been considered as the surface expression of a deep mantle plume or hotspot that has interacted with a mid-ocean ridge. It is geodynamically associated with the triple junction between the North American, African and Eurasian plates. (Yang et al., 2006) used finite frequency seismic tomography to demonstrate the presence of a zone of low P-wave velocities (peak magnitude -1.5%) in the uppermost 200km of the mantle beneath the plateau. The tomographic model is consistent with SW deflection of a mantle plume by regional upper mantle shear flow driven by absolute plate motions. The volcanic island of Sao Miguel is located within the Terceira Rift, believed to represent the boundary between the African and Eurasian plates; magmatic activity has been characterised by abundant basaltic eruptions in the past 30,000 years. The basalts are distinctive within the spectrum of global ocean island basalts for their wide range in isotopic composition, particularly in 87Sr/86Sr. Their Sr-Nd-Pb isotopic compositions show systematic variations from west to east across the island which can be interpreted in terms of melting of a two-component mantle source. The low melting point (enriched) component in the source has been attributed to recycled ancient (~3 Ga) oceanic crust(Elliott et al., 2007). Using the thermo-barometry approach of (Lee et al., 2009) we demonstrate that the pressure and temperature of magma generation below Sao Miguel increase from west (2 GPa, 1425 °C) to east (3.8 GPa, 1575 °C), consistent with partial melting along a mantle geotherm with a potential temperature of ~ 1500 °C. This is consistent with the magnitude of the thermal anomaly beneath the Azores Plateau (ΔT ~ 150-200 °C) inferred on the basis of the seismic tomography study. The site of primary magma generation extends from the base of the local lithosphere (~ 50 km) to ~ 125 km depth. To understand the geodynamic

  8. Study of the geodynamic evolution of the Chinese Tianshan metamorphic belt to unravel deep processes occurring at the plate interface.

    NASA Astrophysics Data System (ADS)

    Bayet, L.; John, T.; Agard, P.; Becker, H.; Gao, J.

    2016-12-01

    Field-based studies of fossil plate interfaces can be used to provide constraints on the mechanical behaviour of subduction channel processes at depth. The Chinese Tianshan metamorphic belt (TMB) represents a suitable test area to study such processes since it contains fresh high-pressure rocks and well exposed structures in its central part. Lithologies composed of intercalated metasediments and volcanoclastics are likely derived from the trench during subduction with incorporation of first metapelitic-rich components and then increasing amounts of psammitic- and mafic-rich components and few carbonates. During burial, this material as well as pieces of the upper oceanic crust (pillow basalts) were scrapped off the slab and stacked to the upper plate and/or to the subduction channel at depth. During exhumation most of the deformation was accommodated by shearing and schistosity developed at blueschist-facies conditions (glaucophane lineations). A systematic sampling survey was carried out in the area through two N-S transects in order to reconstruct the P-T-t history of the central part of the TMB. Peak pressures and temperatures were estimated independently using Raman spectroscopy (quartz inclusions in garnet (P) and carbonaceous material (T)) and electron microprobe analysis (Zr-in rutile) on metasediments and metabasites. These yield coherent peak conditions of 530±30°C and 2.3±3 GPa. We combined these results with new geochronological Rb-Sr data to constrain the age of underplating and exhumation. We finally propose a tentative model for the geodynamic evolution of the TMB, based on field observations and P-T-t conditions. The TMB is interpreted to represent an erosive margin with accretion and stacking of tectonic slices at depths of 70 km, implying strong coupling/decoupling processes around this depth. During later exhumation this stack of detached material was brought back to the surface as a single unit undergoing shearing with minor internal

  9. Soil gas radon measurements around Mt. Etna volcano in terms of evaluation of geodynamic events

    NASA Astrophysics Data System (ADS)

    Immè, Giuseppina; Catalano, Roberto; Giammanco, Salvatore; Ichedef, Mutlu; Neri, Marco; Morelli, Daniela; Murè, Filippo; Giudice, Nunzio

    2017-04-01

    Soil gas radon measurements were performed continuously in the east flank of Mt. Etna since July 2015 volcano in order to correlate soil gas radon anomalies with local geodynamic processes. Both volcanic activity and seismic monitoring have been carried out by means of seismic stations and video-cameras located around the volcano, while the evaluation of radon data has been done using basic statistics and signal processing methods. Preliminary analysis of data seems to indicate a clear correlation between soil gas radon variations and volcanic activity of Mt. Etna, being the November 2015 and May 2016 eruptions preceded by marked anomalous variations (mainly decreases) of radon levels in all monitoring stations. Further anomalies have been recognized since November 2016, which may suggest new arrival of fresh magma into the volcano, possibly leading to future eruptions.

  10. Spatial and temporal patterns of exhumation across the Venezuelan Andes: Implications for Cenozoic Caribbean geodynamics

    NASA Astrophysics Data System (ADS)

    Bermúdez, Mauricio A.; Kohn, Barry P.; van der Beek, Peter A.; Bernet, Matthias; O'Sullivan, Paul B.; Shagam, Reginald

    2010-10-01

    The Venezuelan Andes formed by complex geodynamic interaction between the Caribbean Plate, the Panamá Arc, the South American Plate and the continental Maracaibo block. We study the spatial and temporal patterns of exhumation across the Venezuelan Andes using 47 new apatite fission track (AFT) ages as well as topographic analyses. This approach permits the identification of at least seven tectonic blocks (Escalante, Cerro Azul, Trujillo, Caparo, Sierra Nevada, Sierra La Culata and El Carmen blocks) with contrasting exhumation and cooling histories. The Sierra Nevada, Sierra La Culata and El Carmen blocks, located in the central part of the Venezuelan Andes and separated by the Boconó fault system, cooled rapidly but diachronously during the late Miocene-Pliocene. Major surface uplift and exhumation occurred in the Sierra Nevada block since before 8 Ma. A second phase of uplift and exhumation affected the El Carmen and Sierra La Culata blocks to the north of the Boconó fault during the late Miocene-Pliocene. The highest topography and steepest relief of the belt coincides with these blocks. The Caparo and Trujillo blocks, located at the northeastern and southwestern ends of the orogen, cooled more slowly from the Oligocene to the late Miocene. These blocks are characterized by significantly lower mean elevations and slightly lower mean slopes than the central blocks. Unraveling the cooling history of the individual blocks is important to better understand the control of preexisting faults and regional Caribbean geodynamics on the evolution of the Venezuelan Andes. Our data indicate a strong control of major preexisting fault zones on exhumation patterns and temporal correlation between phases of rapid exhumation in different blocks with major tectonic events (e.g., collision of the Panamá arc; rotation of the Maracaibo block).

  11. Basin geodynamics and sequence stratigraphy of Upper Triassic to Lower Jurassic deposits of Southern Tunisia

    NASA Astrophysics Data System (ADS)

    Carpentier, Cédric; Hadouth, Suhail; Bouaziz, Samir; Lathuilière, Bernard; Rubino, Jean-Loup

    2016-05-01

    Aims of this paper are to propose a geodynamic and sequential framework for the late Triassic and early Jurassic of and south Tunisia and to evidence the impact of local tectonics on the stratigraphic architecture. Facies of the Upper Triassic to Lower Jurassic of Southern Tunisia have been interpreted in terms of depositional environments. A sequential framework and correlation schemes are proposed for outcrops and subsurface transects. Nineteen middle frequency sequences inserted in three and a half low frequency transgression/regression cycles were evidenced. Despite some datation uncertainties and the unknown durations of Lower Jurassic cycles, middle frequency sequences appear to be controlled by eustasy. In contrast the tectonics acted as an important control on low frequency cycles. The Carnian flooding was certainly favored by the last stages of a rifting episode which started during the Permian. The regression accompanied by the formation of stacked angular unconformities and the deposition of lowstand deposits during the late Carnian and Norian occured during the uplift and tilting of the northern basin margins. The transpressional activity of the Jeffara fault system generated the uplift of the Tebaga of Medenine high from the late Carnian and led to the Rhaetian regional angular Sidi Stout Unconformity. Facies analysis and well-log correlations permitted to evidence that Rhaetian to Lower Jurassic Messaoudi dolomites correspond to brecciated dolomites present on the Sidi Stout unconformity in the North Dahar area. The Early-cimmerian compressional event is a possible origin for the global uplift of the northern African margin and Western Europe during the late Carnian and the Norian. During the Rhaetian and the early Jurassic a new episode of normal faulting occured during the third low frequency flooding. This tectonosedimentary evolution ranges within the general geodynamic framework of the north Gondwana margin controlled by the opening of both

  12. Large-scale Geodynamics Controls Secular Trend of the Total Ozone

    NASA Astrophysics Data System (ADS)

    Steblova, R. S.

    2014-12-01

    A steady tendency towards decrease in the observed total ozone cannot be attributed to space sources of energy such as the sun and cosmic galactic rays because the energy of these sources is stable for several decades. The north-south asymmetry of ozone in the global structure of ozonosphere rules out man-made sources as a significant factor of the ozone decrease. Most of the pollutants come to the northern hemisphere; however, there is about 30% more ozone in it than in the southern hemisphere. We jointly analyzed the global distribution of ozone from TOMS satellite data, the surface of the earth's core from seismic tomography, and lithospheric plate movements from GPS and concluded the following: (1) There are sources of energy in the solid earth which contribute to the atmospheric ozone; (2) The large-scale geodynamics should be considered among the mechanisms responsible for the global structure of ozonosphere and its evolution with time. We also note similarities in the pattern of ozone caused by sources in the solid earth ("terrestrial ozone") and the patterns of geomagnetic and gravity fields. The global morphology of terrestrial ozone suggests a "breakup" in the initial ozone distribution at about the same time as a breakup of Pangea and subsequent spreading of the area of higher ozone content. A restored initial breakup is located in the oceanic region and runs northwest to southeast across Africa. We propose a large-scale geodynamic process: a convective flow in the mantle from the earth's core surface provokes the breakup of Pangea and the breakup of ozone distribution

  13. Geodynamic settings of microcontinents, non-volcanic islands and submerged continental marginal plateau formation

    NASA Astrophysics Data System (ADS)

    Dubinin, Evgeny; Grokholsky, Andrey; Makushkina, Anna

    2016-04-01

    Complex process of continental lithosphere breakup is often accompanied by full or semi isolation of small continental blocks from the parent continent such as microcontinents or submerged marginal plateaus. We present different types of continental blocks formed in various geodynamic settings. The process depends on thermo-mechanical properties of rifting. 1) The continental blocks fully isolated from the parent continent. This kind of blocks exist in submerged form (Elan Bank, the Jan-Mayen Ridge, Zenith Plateau, Gulden Draak Knoll, Batavia Knoll) and in non-submerged form in case of large block size. Most of listed submerged blocks are formed in proximity of hot-spot or plume. 2) The continental blocks semi-isolated from the parent continent. Exmouth Plateau, Vøring, Agulhas, Naturaliste are submerged continental plateaus of the indicated category; Sri Lanka, Tasmania, Socotra are islands adjacent to continent here. Nowadays illustration of this setting is the Sinai block located between the two continental rifts. 3) The submerged linear continental blocks formed by the continental rifting along margin (the Lomonosov Ridge). Suggested evolution of this paragraph is the rift propagation along existing transtensional (or another type) transform fault. Future example of this type might be the California Peninsula block, detached from the North American plate by the rifting within San-Andreas fault. 4) The submerged continental blocks formed by extensional processes as the result of asthenosphere flow and shear deformations. Examples are submerged blocks in the central and southern Scotia Sea (Terror Bank, Protector Basin, Discovery Bank, Bruce Bank etc.). 5) The continental blocks formed in the transform fault systems originated in setting of contradict rifts propagation in presence of structure barriers, rifts are shifted by several hundreds kilometers from each other. Examples of this geodynamic setting are Equatorial Atlantic at the initial development stage

  14. Estimates of geodynamic state and structure of the local crust on the base of microseismic noise analysis

    NASA Astrophysics Data System (ADS)

    Loktev, D.; Spivak, A.

    2013-05-01

    A method for obtaining estimates of geodynamic state of the local crust and rock masses on the base of microseismic noise analysis is discussed. Microseismic noise is considered as a superposition of background microvibrations and a discrete component in the form of weak microseismic pulses generated by relaxational processes in the medium [1]. Currently active tectonic faults can be identified as zones with clustered sources of microseismic pulses and more intense amplitude variations of background microvibrations in tidal waves and baric variations in the atmosphere [2,3]. The presence of underground nonheterogeneities (i.e. contrasts in mechanic properties) and their scales are obtained from analysis of spectral characteristics of microseismic noise [4]. In the epicentral zone of an underground inhomogeneity we evidence characteristic quasi-chromatic pulses, stronger spectral density of local noise at high frequencies (more than 10 Hz) as well as maximum of spatial distribution of horizontal to vertical component spectral noise ratio (Nakamura parameter). The size of structural elements (blocks) of the Earth's crust is estimated by peak frequencies of momochromatic components of the spectrum on the base of the elaborated analytical model [1]. Parameters of weak pulses generated by relaxation (such as max velocity of oscillations, dominating (observed) period, etc.) yield estimates of differential movements of structural blocks in the medium as well as max stresses in the latter [5,6]. Examples are given to illustrate application of the proposed method to locating and mapping fault zones and underground nonheterogeneities in the Earth's crust, as well as to estimating scales of active structural blocks and their mobility potential when assessing places for nuclear atomic plants and underground nuclear waste storages. The method has also been successfully used for ranging hillsides of South Alps in terms of their liability to landslides. [1]. A.A. Spivak, S

  15. Uzon-Geysernaya volcano-tectonic depression: geodynamics phenomena last years

    NASA Astrophysics Data System (ADS)

    Kugaenko, Yulia

    2010-05-01

    (swarm) type. - The majority of earthquakes are connected with areas of hydrothermal activity in western slop of Kikhpinych volcanic massif. - Seismicity is located in part of caldera displacement, discovered by INSAR data. - By our mind, the seismicity and Uzon caldera inflation (as a result of activation of magma chamber or hydrothermal system) effected and destructed the caldera slop by activation of fissures and by change of pore-fracture configuration. Summarizing data about the tectonics, the raising of east slope of depression, the landsliding and local seismicity, we can suppose that all these phenomena are connected with the deep processes under Uzon-Geysernaya depression and Kikhpinuch volcano are the reason of all these events. It is the indication of the renewal of the dynamics within eastern part of the calderas. References: Belousov, V. I., E. N. Grib, and V. L. Leonov (1984), The geological setting of the hydrothermal systems in the Geysers Valley and Uzon caldera, Volcanol. Seismol., 5, 67-81. Kugaenko, Yu. (2008), Geodynamic processes as the risk factor of June 3, 2007 landslide in the Valley of the Geysers (Kamchatka, Russia), Proceedings of the First World Landslide Forum. 18-21 November 2008, Tokio, Japan, 333-336. Leonov, V. L., E. N. Grib, G. A. Karpov, V. M. Sugrobov, N. G. Sugrobova, and Z. I. Zubin (1991). Uzon caldera and Valley of Geysers, in Active Volcanoes of Kamchatka, edited by S. A. Fedotov and Y. P. Masurenkov, Nauka, Moscow, 92- 141. Leonov, V.L. (2007) Valley of the Geysers struck by large destructive landslide and related flood. Bulletin of the Global Volcanism Network (BGVN 32:07). 07/2007. Lundgren, P., Lu, Zh. (2006) Inflation model of Uzon caldera, Kamchatka, constrained by satellite radar interferometry observations. Geophysical Research Letters. 33, L06301, doi:10.1029/2005GL025181

  16. Magmatic evolution of Sulawesi (Indonesia): constraints on the Cenozoic geodynamic history of the Sundaland active margin

    NASA Astrophysics Data System (ADS)

    Polvé, M.; Maury, R. C.; Bellon, H.; Rangin, C.; Priadi, B.; Yuwono, S.; Joron, J. L.; Atmadja, R. Soeria

    1997-04-01

    Tertiary and Quaternary magmatic rocks from West Sulawesi record the complex history of part of the Sundaland margin where subduction and collision have been and are still active. The present study, based on petrographic data, major- and trace-element chemistry and 40K 40Ar dating aims to document the age and chemical characteristics of the magmatic formations from West Sulawesi and to determine the corresponding constraints on the geodynamic evolution of the Sundaland border. The West Sulawesi magmatic province includes the South Arm of Sulawesi (Ujung Pandang area), the western part of Central Sulawesi with the Toraja and Palu areas, and finally, the North Arm, extending from Palu to Manado, which includes the Tolitoli and Manado areas. Paleocene magmatic activity seems to be restricted to an episode of calc-alkaline magmatism in the Ujung Pandang area (61-59 Ma). The major Eocene (50-40 Ma) magmatic event is tholeiitic and is documented in all areas except in Ujung Pandang. It led to the emplacement of tholeiitic pillow-lavas and basaltic dykes of back-arc basin (BAB) affinity. These rocks are potential equivalents to the Celebes Sea basaltic basement. From Oligocene to Miocene, magmatic eruptions produced successively island-arc tholeiitic (IAT) and calc-alkaline (CA) rock series. The youngest IAT activity occurred around 18 Ma in the central part (Palu area) and around 14 Ma in the North Arm (Tolitoli area) while CA magmas were emplaced in the North Arm at ca. 18 Ma (Tolitoli and Manado areas). Typical calc-alkaline activity resumed only in the North Arm (Tolitoli and Manado areas) during the Late Miocene (9 Ma) and is still active in the Manado region. In other areas (Palu, Toraja and Ujung Pandang areas) an important and widespread magmatic event occurred between 13 and 10 Ma and emplaced K-rich magmas, either silica-undersaturated alkali-potassic basalts (AK), ultrapotassic basanites (UK) or shoshonites (SH). K-rich activity continued in the south until

  17. Miocene Onset of Extension in the Turkana Depression, Kenya: Implications for the Geodynamic Evolution of the East African Rift System

    NASA Astrophysics Data System (ADS)

    Boone, S.; Gleadow, A. J. W.; Kohn, B. P.; Seiler, C.

    2015-12-01

    The Paleogene-Recent East African Rift System (EARS) is the foremost modern example of continental rifting, providing much of our understanding of the early stages of continental breakup. The EARS traverses two regions of crustal uplift, the Ethiopian and East African Domes, separated by the Turkana Depression. This wide region of subdued topography coincides with the NW-SE trend of the Jurassic-Paleogene Anza Rift. Opinions on the fundamental geodynamic driver for EARS rifting are divided, however, principally between models involving migrating plume(s) and a single elongated 'superplume'. While competing models have similar topographic outcomes, they predict different morphotectonic evolutions for the Turkana Depression. Models inferring southward plume-migration imply that the plume must have passed below the Turkana Depression during the Paleogene, in order to have migrated to the East African Dome by the Miocene. The possible temporal denudational response to such plume activity is testable using low temperature thermochronology. We present apatite fission track (AFT) and (U-Th)/He (AHe), and zircon (U-Th)/He (ZHe) data from the Lapurr Range, an uplifted Precambrian basement block in northern Turkana. Low radiation damage ZHe results displaying an age range of ~70-210 Ma, and combined with stratigraphic evidence, suggest ~4-6 km of Jurassic-Early Cretaceous denudation, probably associated with early Anza Rift tectonism. AFT ages of ~9-15 Ma imply subsequent burial beneath no more than ~4 km of overburden, thus preserving the Jurassic-Cretaceous ZHe ages. Together with AFT results, AHe data (~3-19 Ma) support ~2-4 km of Miocene-Pliocene uplift of the Lapurr Range in the footwall of the E-dipping Lapurr normal fault. Miocene AFT and AHe ages are interpreted to reflect the initiation of the EARS in the Turkana Depression. If extension is associated with plume activity, then upwelling in the Turkana region is unlikely to have started prior to the Miocene, much

  18. Geological and geodynamic investigations of Alaskan tectonics: Responses in the ancient and modern geologic records to oblique plate convergence

    NASA Astrophysics Data System (ADS)

    Kalbas, James L.

    Stratigraphic, structural, and geophysical modeling studies focusing on both the Mesozoic and modern development of southern Alaska aid in understanding the nature of tectonic responses to oblique plate convergence. Analyses of the Lower to Upper (?) Cretaceous Kahiltna assemblage of the western Alaska Range and the Upper Cretaceous Kuskokwim Group of the northern Kuskokwim Mountains provide a stratigraphic record of orogenic growth in southwestern Alaska. The Kahiltna assemblage records dominantly west-directed gravity-flow transport of sediment to the axis of an obliquely closing basin that made up the suture zone between the allochthonous Wrangellia composite terrane and the North American pericratonic margin. Stratigraphic, compositional, and geochronologic analyses suggest that submarine-fan systems of the Kahiltna basin were fed from the subearial suture zone and contain detrital grains derived from both allochthonous and pericratonic sources, thereby implying a relatively close proximity of the island-arc terrane to the North American margin by late Early Cretaceous time. In contrast, Upper Cretaceous strata exposed immediately west of the Kahiltna assemblage record marine deposition during a period of transition from island arc accretion to strike-slip tectonics. The new stratigraphic model presented here recognizes diverse bathyal- to shelfal-marine depositional systems within the Kuskokwim Group that represent distinctive regional sediment entry points to the basin. Collectively, these strata suggest that the Kuskokwim Group represents the waning stages of marine deposition in a long-lived intra-oceanic and continental margin basin. Geodynamic studies focus on the mechanics of contemporary fault systems in southern Alaska inboard of the collisional Yakutat microplate. Finite-element analyses predict that a poorly understood Holocene strike-slip fault in the St. Elias Mountains transfers shear from the Queen Charlotte fault northward to the Denali fault

  19. A late Tortonian paleotectonic restoration of the Gibraltar Arc System (GAS) based on the restoration of block rotations. Consequences on the GAS geodynamic evolution

    NASA Astrophysics Data System (ADS)

    Crespo-Blanc, Ana; Comas, Menchu; Balanyá, Juan Carlos

    2014-05-01

    The Gibraltar Arc System (GAS) closes the Alpine-Mediterranean orogenic system to the west and includes the Betic-Rif orogenic belt, the Alboran and Argelian-Balearic basins and the accretionary prism present in the Cadiz Gulf. Previous investigations on this orogenic system, both onshore and offshore have permit to establish the first order milestones of its Miocene to Recent geodynamic evolution. In most of the models of the geodynamic evolution of the GAS, the external boundary of the Betic-Rif orogenic wedge, initially N-S directed, sweeps from east to west the Gibraltar Arc area, acquiring his arcuate geometry during this westward movement. Nevertheless, most of these models are generally at scale equivalent to 1:10.000.000 or even smaller, and frequently based on 2D schematic cross-sections from which a model for the whole arc is deduced. This fact under evaluates not only the mass movements oblique to the selected cross-section plane, but also the diachronism of the deformation, in turn expected in a so closed arc. In this communication, we want to zoom on the Gibraltar Arc area, to draw a detailed Late Tortonian paleotectonic restoration and to highlight the consequence of this reconstruction on the final evolution of the westernmost Mediterranean. Our approach is based on: 1) the identification and characterization of structural domains of the Gibraltar Arc orogenic system and the transfer fault zones that separate them, 2) an accurate dating of the superposed events of deformations for each one of these domains, 3) the restoration of vertical axis-rotations of some of these structural domains (evidenced by paleomagnetic data previously published), and 4) the quantification of Miocene shortening in the External zones. This exercise makes us to put all together the results of twenty years of research of our teams on this natural case-study, mainly with field and marine geology techniques, and to test it through the revision of an extensive bibliography. It

  20. Venus Geological History: Current Perspectives, Unknowns, and Opportunities for the Modeling Community.

    NASA Astrophysics Data System (ADS)

    Head, J. W.

    2017-05-01

    The geological record yields multiple major modeling challenges: internal structure-evolution, mantle convection, thermal evolution, geodynamic, geochemical, petrogenetic, atmospheric origin-evolution, ionosphere, solar system formation-evolution.

  1. On the use of the stabilised Q1P0 element for geodynamical simulations and why this is a bad choice for buyoancy-driven flows.

    NASA Astrophysics Data System (ADS)

    Thieulot, Cedric

    2016-04-01

    Many Finite Element geodynamical codes (Fullsack,1995; Zhong et al., 2000; Thieulot, 2011) are based on bi/tri­-linear velocity constant pressure element (commonly called Q1P0), because of its ease of programming and rather low memory footprint, despite the presence of (pressure) checker­board modes. However, it is long known that the Q1P0 is not inf­-sup stable and does not lend itself to the use of iterative solvers, which makes it a less­ than­ ideal candidate for high resolution 3D models. Other attempts were made more recently (Burstedde et al., 2013; Le Pourhiet et al., 2012) with the use of the stabilised Q1Q1 element (bi/tri­-linear velocity and pressure). This element, while also attractive from an implementation and memory standpoint, suffers a major drawback due to the artificial compressibility introduced by the polynomial projection stabilization. These observations have shifted part of the community towards the Finite Difference Method while the remaining part is now embracing inf­sup stable second­ order elements [May et al., 2015; Kronbichler,2012). Rather surprinsingly, a third option exists when it comes to first ­order elements in the form of the stabilised Q1P0 element, but virtually no literature exists concerning its use for geodynamical applications. I will then recall the specificity of the stabilisation and will carry out a series of benchmark experiments and geodynamical tests to assess its performance. While being shown to work as expected in benchmark experiments, the stabilised Q1P0 element turns out to introduce first-order numerical artefacts in the velocity and pressure solutions in the case of buoyancy-driven flows. Burstedde, C., Stadler, G., Alisic, L., Wilcox, L. C., Tan, E., Gurnis, M., & Ghattas, O. (2013). Large­scale adaptive mantle convection simulation. Geophysical Journal International, 192(3), 889­906. Fullsack, P. (1995). An arbitrary Lagrangian­Eulerian formulation for creeping flows and its application in

  2. Impact of geodynamic development of the Barents Sea deep rift on evolving petroleum systems

    NASA Astrophysics Data System (ADS)

    Balanyuk, I.; Dmitrievsky, A.

    2009-04-01

    All the Barents Sea deposits are situated in the epicenter on active geodynamic development of the Barents Sea rift and, most important, over the zone of listric faults intersection, which consist a knot system over the mantle diapir. This is confirmed by prospecting seismology. Intrusion of hot mantle matter with further cooling down of abnormal lense might be a possible cause of appearance and evolution of ultradeep depressions. A high "seismic stratification" of the lower crust (nearly reaching the basement surface) at time scale about 8 sec. is typical for the inner, the deepest part of the depression. Supposing the "seismic stratified" lower crust correspond to "basalt" layer, this area is nearly upper crust ("granitic-gneiss") free. This fact confurmes conception on development of "granite free gaps" in the depression basement. Thick blocks of "seismically transparent" upper crust corresponding to the "granitic-gneiss" layer are marked out within Kolsk-Kanin monocline. An abrupt thickness decrease and appearance of "stratified" areas takes place at the southern edge of the depression. A filling of the over-rift sag with sediments, revival of the faults and their effect on the filtration processes and gas hydrates formation took place in the South Barents Sea depression. Repeating activation of the fault blocks in the basement, especially during late Jurassic - early Cretaceous period contributed to formation of the structures related to the greatest deposits of the South Barents Sea depression. An extended field acoustic data collected in the Barents Sea led to understanding of general fundamental problems for all Arctic Seas and, first of all, the problem of Quaternary glaciations. An analysis of Eurasian-Arctic continental margin shows correspondence between the rift systems of the shelf with those of the ocean. This relation can be observed by an example of the central Arctic region. All the rift systems underlying the sediment basin are expressed in the

  3. Parallel implementation of the particle simulation method with dynamic load balancing: Toward realistic geodynamical simulation

    NASA Astrophysics Data System (ADS)

    Furuichi, M.; Nishiura, D.

    2015-12-01

    Fully Lagrangian methods such as Smoothed Particle Hydrodynamics (SPH) and Discrete Element Method (DEM) have been widely used to solve the continuum and particles motions in the computational geodynamics field. These mesh-free methods are suitable for the problems with the complex geometry and boundary. In addition, their Lagrangian nature allows non-diffusive advection useful for tracking history dependent properties (e.g. rheology) of the material. These potential advantages over the mesh-based methods offer effective numerical applications to the geophysical flow and tectonic processes, which are for example, tsunami with free surface and floating body, magma intrusion with fracture of rock, and shear zone pattern generation of granular deformation. In order to investigate such geodynamical problems with the particle based methods, over millions to billion particles are required for the realistic simulation. Parallel computing is therefore important for handling such huge computational cost. An efficient parallel implementation of SPH and DEM methods is however known to be difficult especially for the distributed-memory architecture. Lagrangian methods inherently show workload imbalance problem for parallelization with the fixed domain in space, because particles move around and workloads change during the simulation. Therefore dynamic load balance is key technique to perform the large scale SPH and DEM simulation. In this work, we present the parallel implementation technique of SPH and DEM method utilizing dynamic load balancing algorithms toward the high resolution simulation over large domain using the massively parallel super computer system. Our method utilizes the imbalances of the executed time of each MPI process as the nonlinear term of parallel domain decomposition and minimizes them with the Newton like iteration method. In order to perform flexible domain decomposition in space, the slice-grid algorithm is used. Numerical tests show that our

  4. AlpArray Austria - Illuminating the subsurface of Austria and understanding of Alpine geodynamics

    NASA Astrophysics Data System (ADS)

    Fuchs, Florian; Bokelmann, Götz; Bianchi, Irene; Apoloner, Maria-Theresia; AlpArray Working Group

    2015-04-01

    AlpArray Austria is a research project to study the geodynamics of the Eastern Alps and the subsurface of Austria with a large-scale mobile broadband seismological network. AlpArray Austria is part of the AlpArray project - a unique European transnational research initiative in which 64 research institutes from 17 countries join their expertise to advance our knowledge about the structure and evolution of the lithosphere beneath the entire Alpine area. AlpArray Austria is coordinated by the Department of Meteorology and Geophysics (IMGW) at the University of Vienna and funded by the Austrian Science Fund (FWF). During spring 2015 the deployment of 42 mobile broadband seismometers (and two permanent stations) will commence and by autumn 2015 Austria will be completely covered by a dense seismological network with an average station spacing of about 40 kilometers. The mobile network consisting of 27 Reftek 151 60s sensors (provided by IMGW) and 15 Trillium 120s instruments (provided by the Dublin Institute for Advanced Studies, DIAS, Ireland) will complement the permanent Austrian seismic network operated by the Austrian Zentralanstalt für Meteorologie und Geodynamik (ZAMG) that will also install the two permanent stations. AlpArray Austria will be continuously recording high-quality ground motion data for three years. Seismic data will be distributed through the European Integrated Data Archive (EIDA) and shared with the collaborating AlpArray institutes. AlpArray Austria will shed light on the detailed geological structure and geodynamical evolution of the Eastern Alps and the subsurface of Austria. Utilizing seismic analysis methods such as shear wave splitting, receiver functions and body wave dispersion the AlpArray Austria working group at IMGW will, together with the international partners, focus on seismic anisotropy in the upper mantle, the location of interfaces and tomography, to answer outstanding questions on slab geometry and subduction polarity under

  5. Restoration of the evolution of a plume, Numerical assessment of the compressible adjoint equations in geodynamics

    NASA Astrophysics Data System (ADS)

    Ghelichkhan, S.; Bunge, H. P.

    2016-12-01

    Seismic tomography has seen continuous improvements over the last decades, to the point that some recent studies have reached the resolution necessary to image mantle plumes. Seismic tomography, however, can only give us a snapshot of mantle convection. In order to understand the dynamics of mantle plumes and their role in global mantle convection, one needs to study their evolution in time.Unfortunately, there is a fundamental lack of knowledge about the past history of mantle convection in general. It is possible, however, to restore past mantle states by recasting mantle convection as an inverse problem. An elegant and efficient method to solve this geodynamic inverse problem is given by the adjoint method, which allows to restore the mantle state at some arbitrary time in the past. This result is achieved through the solution of the equations that govern mantle convection, together with an auxiliary set of equations, called adjoint equations.The adjoint equations in geodynamics have already been derived under the assumption of incompressible (Boussinesq) flow, but the applicability to the real Earth of this approximation is limited, as density increases by almost a factor of two from the surface to the core-mantle boundary. Here we introduce the compressible adjoint equations for the conservation equations in the anelastic-liquid approximation and use them in a synthetic test based on the twin experiment method, reconstructing the past evolution of a plume rising from the lower boundary layer.We focus on three simulations. A first, termed Compressible, assumes the compressible forward and adjoint equations, and represents the consistent means of including compressibility effects. A second, termed Mixed, applies the compressible forward equation, but ignores compressibility effects in the adjoint equations. A third simulation, termed Incompressible, neglects compressibility effects entirely in the forward and adjoint equations relative to the reference twin. The

  6. Plio-Quaternary coastal sequences, sea-level changes and coastal geodynamics :

    NASA Astrophysics Data System (ADS)

    Pedoja, Kevin; Husson, Laurent; Nexer, Maëlle; Regard, Vincent; Delcaillau, Bernard

    2013-04-01

    Sequences of Plio-Quaternary shorelines generated by sea-level cyclicity and tectonics massively shape the coasts worldwide. Here, we compile a worldwide synthesis of sea-level changes for the following highstands : MIS 1, MIS 3, MIS5e, and MIS 11 and explore the relationships to regional geodynamics. We identified 896 sequences including the MIS 5e benchmark, out of which 177 also feature the highest Holocene shorelines, 6 where the elevation of the MIS 3 shorelines are known, and 40 including that of MIS 11 shorelines. We considered 8 main geodynamical contexts for a statistical analysis: passive margin (337 sites, 14 domains, U=0.06 ± 0.01 mm/a), hot spot chains (45 sites, 14 domains, U=0.02 ± 0.02 mm/a), rifts (45 sites, 2 domains, U=0.12 ± 0.02 mm/a), ridges (3 sites, 1 domain, U=0.14 ± 0.02 mm/a), transform plate boundaries (119 sites, 7 domains, U=0.25 ± 0.03 mm/a), intra-oceanic subductions (131 sites, 4 domains, U=0.43 ± 0.04 mm/a), continental subductions underneath oceanic plates (12 sites, 1 domain, U=0.54+/- 0.04 mm/a), oceanic subductions underneath continental plates (166 sites, 7 domains, U=0.06 ± 0.01 mm/a), intra-continental convergence (10 sites, 2 domains, U=1.47 ± 0.08 mm/a). Counter-intuitive is the fact that passive margin are ubiquitously uplifting, while tectonic segmentation is more important on active margins. Additionally, 511 sites document the elevation of the highest shoreline of the sequence, from which we extrapolate a minimum age of onset for the sequence (based on MIS 5e uplift rates). 99% (511 sites) were formed at least during Pliocene and/or Quaternary, showing that potentially more ancient records are either eroded or non-existent.

  7. Tectonics, recent geodynamics and seismicity of Azerbaijan part of the Greater Caucasus

    NASA Astrophysics Data System (ADS)

    Aliyev, Fuad; Kangarli, Talat; Rahimov, Fuad; Murtuzov, Zaur; Aliyev, Ziya

    2016-04-01

    Transition area of the Eastern Caucasus - Caspian Megadepression corresponds to a periclinal submergence zone of the mountain folded structure of the Greater Caucasus under Pliocene-Holocenic sedimentary complex of Caspian megabasin. Being a part of Alpine-Himalayan folded belt, Greater Caucasus has formed during alpine stage of tectogenesis under geodynamic conditions of convergent interactions between Northern and Southern Caucasus continental microplates. This process has been accompanied by pseudosubduction of the first plate under the second with formation of allochtonous accretion prism above underthrust zone. Modern folding and napping structure of the orogeny has formed as a result of the horizontal movements of different phases and subphases of alpine tectogenesis, that are presented represented by Late Cimmerian - Wallachian tectonic phases within Azerbaijan territory. Limited by meridional fault-slip zones, Caspian megadepression present itself as a young structure that layered on sublatitudinal convergent zone and developed during Late Miocene (10 million years ago) as a flexure zone between two indenters which actively move northward provoking their separation from the African continent and Arabian plate in the west and secession from Central Iranian plate of the Lut block in the east. The acting movement of Arabian plate to the north results in accumulation of the horizontal stress at the current stage of tectogenesis. Current process reveals itself both in the fragmentation of Southern and Northern Caucasus continental microplates into various-size blocks along the general and anti-Caucasus trended faults, and in consideration horizontal and vertical movements within the convergence zone. All these factors define the complexity of geodynamic condition revealed here, in which seismic activity of a transition zone become apparent. There exist the seismic zones here that are confined both to a convergence line and to the fault zones that confine Caspian

  8. Nature and distribution of geological domains at the Africa-Eurasia plate boundary off SW Iberia and regional geodynamic implications

    NASA Astrophysics Data System (ADS)

    Martínez-Loriente, Sara; Sallarès, Valentí; Gràcia, Eulàlia; Bartolome, Rafael

    2014-05-01

    We present a new classification of geological domains at the Africa-Eurasia plate boundary off SW Iberia, together with a regional geodynamic reconstruction spanning from the Mesozoic extension to the Neogene-to-present-day convergence. It is based on seismic velocity and density models along two regional wide-angle seismic transects, one running NW-SE from the Horseshoe to the Seine abyssal plains, and the other running N-S from S Portugal to the Seine Abyssal Plain, combined with previously available information. The seismic velocity and density structure at the Seine Abyssal Plain and the internal Gulf of Cadiz indicates the presence of a highly heterogeneous oceanic crust, similar to that described in ultra-slow spreading centers, whereas in the Horseshoe and Tagus abyssal plains, the basement structure resembles that of exhumed mantle sections identified in the Northern Atlantic margin. The integration of all this new information allows defining the presence of three oceanic domains offshore SW Iberia: (1) the Seine Abyssal Plain domain, generated during the first stages of slow seafloor spreading in the NE Central Atlantic (Early Jurassic); (2) the Gulf of Cadiz domain, made of oceanic crust generated in the Alpine-Tethys spreading system between Iberia and Africa, which was coeval with the formation of the Seine Abyssal Plain domain and lasted up to the North Atlantic continental break-up (Late Jurassic); and (3) the Gorringe Bank domain, mainly made of rocks exhumed from the mantle with little synchronous magmatism, which formed during the first stages of North Atlantic opening. Our models suggest that the Seine Abyssal Plain and Gulf of Cadiz domains are separated by the Lineament South strike-slip fault, whereas the Gulf of Cadiz and Gorringe Bank domains appear to be limited by a deep thrust fault located at the center of the Horseshoe Abyssal Plain. The formation and evolution of these three domains during the Mesozoic is key to understand the sequence

  9. Geodynamics of flat-slab subduction, sedimentary basin development, and hydrocarbon systems along the southern Alaska convergent plate margin

    NASA Astrophysics Data System (ADS)

    Finzel, Emily S.

    Combining field-based geologic studies and numerical modeling provides a robust tool for evaluating the geodynamics of convergent margins. Southern Alaska is arguably the most tectonically active part of the convergent margin of western North America. This conceptual approach has been used to interpret the modern basin dynamics, as well as key stages in the Cenozoic development of this region, including spreading-ridge and flat-slab subduction. New macrofossil, palynological, and lithostratigraphic data for the Bear Lake Formation in the Bristol Bay retroarc basin allow us to construct the first chronostratigraphic framework for this formation, and indicate deposition during Middle and Late Miocene time in a regional transgressive estuarine depositional system. In the Cook Inlet forearc basin, new detrital zircon U-Pb geochronology, rare earth element geochemistry, and clast compositional data from middle Eocene-Pliocene strata demonstrate the importance of sediment sources located in the retroarc region and along strike within the basin. The Yakutat microplate has recently been reinterpreted to represent buoyant crust that is presently subducting at a shallow angle beneath southern Alaska. Integration of stratigraphic, geochronologic, and thermochronologic data indicate that in the flat-slab region, exhumation initiated ca. 43 Ma and migrated inboard, magmatism ceased at ca. 32 Ma, and deposition in sedimentary basins ended by ca. 23 Ma. Sedimentary basins positioned along the western and northern perimeter of the flat-slab region record enhanced subsidence and sediment delivery from the flat-slab region beginning in late Oligocene and middle Miocene time respectively. The discrete contributions of unique driving forces for lithospheric deformation in western Canada and Alaska have not been quantified in detail, so their relative role in influencing deformation has remained unresolved. Using finite element models, we calculate a continuous strain rate and velocity

  10. Probing the deep structure and geodynamics of the Gibraltar Arc System by integrating new data sets from the IberArray platform (Invited)

    NASA Astrophysics Data System (ADS)

    Gallart, J.

    2010-12-01

    The Gibraltar Arc system is a complex interaction zone between the Eurasia and African plates. This tectonically thickened arc with extended basins result from the interaction of slab roll back processes with upper plate deformation. Many different, often controversial evolutionary models have been proposed, from continental-scale thermal mantle source processes to regional-scale recycling of the lithosphere by either delamination, slab break-off, convective removal or the presence of active eastward subduction of oceanic crust. Structural features that could deserve prioritization between such models could not be properly constrained from geophysical results existing till now. However, the Topo-Iberia project currently on-going in Spain should provide such constraints. Topo-Iberia is a large-scale integrative research effort to achieve new, high resolution results on structure and geodynamics of the Iberian plate. It is based on the implementation of an IberArray platform, formed by GPS, MT and Broad-Band Seismic networks, similar to the Earthscope in US. Major features of the project and achieved results concerning the Gibraltar Arc System will be presented. Particularly, the seismic network, composed by more than 130 permanent and portable BB instruments, samples the Iberian-African domains of plate interaction in a 60km x 60km homogeneous grid and provides deep structural results from either tomographical methods (ambient noise, travel-time local + teleseismic events, or surface waves), Moho depths from receiver functions or mantle anisotropy from SKS splittings. As examples of results, significant variations on crustal thicknesses have been inferred within rather short distances, from more than 40 km Moho depths beneath the axes of the Betic and Rif chains to around 20 km towards the easternmost part of the study area, and the fast polarization directions (FPD) from SKS splitting measurements clearly show a spectacular rotation along the arc following the

  11. A new numerical method to calculate inhomogeneous and time-dependent large deformation of two-dimensional geodynamic flows with application to diapirism

    NASA Astrophysics Data System (ADS)

    Fuchs, L.; Schmeling, H.

    2013-08-01

    A key to understand many geodynamic processes is studying the associated large deformation fields. Finite deformation can be measured in the field by using geological strain markers giving the logarithmic strain f = log 10(R), where R is the ellipticity of the strain ellipse. It has been challenging to accurately quantify finite deformation of geodynamic models for inhomogeneous and time-dependent large deformation cases. We present a new formulation invoking a 2-D marker-in-cell approach. Mathematically, one can describe finite deformation by a coordinate transformation to a Lagrangian reference frame. For a known velocity field the deformation gradient tensor, F, can be calculated by integrating the differential equation DtFij = LikFkj, where L is the velocity gradient tensor and Dt the Lagrangian derivative. The tensor F contains all information about the minor and major semi-half axes and orientation of the strain ellipse and the rotation. To integrate the equation centrally in time and space along a particle's path, we use the numerical 2-D finite difference code FDCON in combination with a marker-in-cell approach. For a sufficiently high marker density we can accurately calculate F for any 2-D inhomogeneous and time-dependent creeping flow at any point for a deformation f up to 4. Comparison between the analytical and numerical solution for the finite deformation within a Poiseuille-Couette flow shows an error of less than 2 per cent for a deformation up to f = 1.7. Moreover, we determine the finite deformation and strain partitioning within Rayleigh-Taylor instabilities (RTIs) of different viscosity and layer thickness ratios. These models provide a finite strain complement to the RTI benchmark of van Keken et al. Large finite deformation of up to f = 4 accumulates in RTIs within the stem and near the compositional boundaries. Distinction between different stages of diapirism shows a strong correlation between a maximum occurring deformation of f = 1, 3 and

  12. Intracontinental Deformation and Surface Uplift - Geodynamic Evolution of the Hangay Dome, Mongolia Central Asia

    NASA Astrophysics Data System (ADS)

    Meltzer, A.; Ancuta, L. D.; Carlson, R. W.; Caves, J. K.; Chamberlain, P.; Gosse, J. C.; Idleman, B. D.; Ionov, D. A.; Mcdannell, K. T.; Mendelson, T.; Mix, H. T.; Munkhuu, U.; Proussevitch, A. A.; Russo, R. M.; Sabaj-Perez, M.; Sahagian, D. L.; Sjostrom, D. J.; Stachnik, J. C.; Tsagaan, B.; Wegmann, K. W.; Winnick, M. J.; Zeitler, P. K.

    2012-12-01

    The origin of high topography in continental interiors is a first-order question in continental dynamics. Standing significantly above the median continental freeboard, higher-elevation surfaces having relatively low relief and wavelengths of hundreds to thousands of kilometers are common on the continents and are excellent sites to investigate the interplay of solid-earth and surface processes. Continental plateaus occur in a number of tectonic settings and explanations for their origin such as asthenospheric upwelling, magmatic underplating, and delamination, are as diverse as their tectonic settings. The Hangay in Mongolia occupy a broad domal upland (~200,000 km2) embedded in the greater Mongolian Plateau (~425,000 km2) of Central Asia. The high interior of the dome sits at elevations ~1.5 km above the regional trend, locally reaches elevations over 4000 m, contains a high-elevation low-relief surface cut into crystalline basement and a 30 my record of basalt magmatism including mantle and crustal xenoliths. Global seismic tomography indicates a poorly resolved low-velocity zone in the upper mantle. Uplift, faulting, and volcanism are active. We present results from initial fieldwork in the Hangay in geomorphology, geochronology, paleoaltimetry, biogeography, petrology, geochemistry, and seismology designed to document the geodynamics, timing, rate, and pattern of surface uplift in the Hangay located deep in the Asian continental interior.

  13. Tracing the origin of Geodynamics: The Alfred Wegener Memorial Expedition 2014

    NASA Astrophysics Data System (ADS)

    Stüwe, Kurt

    2015-04-01

    2012 marked the 100st anniversary of the seminal publications on Continental Drift Theory by Alfred Wegener. These publications (and Wegener's book "On the origin of the continents", published three years later) are widely accepted to be the fundamental breakthrough that opened the path to the Theory of Plate Tectoncis and ultimately the path to modern Geodynamics some 50 years later. In the same historic year of the 1912 publications, Alfred Wegener set off for what was to become the most dramatic of his three Greenland expeditions. On this expedition Wegener and Koch crossed the entire northern icecap of Greenland. In honour of the hundreds anniversary of Wegener's publications, the Austrian Academy of Sciences funded an expedition to trace the footsteps of the 1912 expedition in the spirit of Alfred Wegener, while also conducting modern Earth Science. This expedition that was conducted in summer 2014. For the expedition, a 1952 Cessna180 was acquired in Alaska, adapted with bush wheels, wing extensions and extra tanks and was flown by the author and one of the worlds most renown bush pilots from Alaska in a 10 day effort to Greenland. There, the entire NE Greenland Caledonides were covered and photographed. Field work for a masters projects was conducted and samples were collected from a series of some of the most remote locations in the Caledonides ever visited. Most spectacularly, the original sled of Wegeners 1912 expedition was found some 30 kilometers from its expected location in the Dove Bugt Region of northeastern Greenland.

  14. Solution of geodynamical Problems from the Point of View of Synergeric

    NASA Astrophysics Data System (ADS)

    Hachay, Olga

    2015-04-01

    It is considered the relation of solution geodynamic problems by geosynergetical approach. A new algorithm of seismological information processing of detailed mines catalogue with use kinematic and dynamical characteristics of deformation waves, which propagate with different velocities in the rock massif under heavy influence of single blasts and technological explosions had been developed. It is estimated that the waves, which propagate with the velocities from 10 to 1 m/hour are primary carrier of the energy in the massif and promote its releasing. Events, which occur in the massive with these waves with releasing energy less than 104 joules promote to the creep rebuilding of the massif. Events, which occur in the massive with these waves with releasing energy more, than 105 joules, can be used as rock burst precursory and it is recommend taking into account by changing of explosions in the indicated part of the massif. The whole absence of such events indicates the growing of the stress massif state in the mine as a whole. The received joined information from the seismic catalogue is very significant for forecasting of dangerous events in the rock mines. It is developed an algorithm for scenario of rock shocks treatment in the rock massif. It can be used for analyze massif natural state on seismological polygons. References 1. Hachay O.A. Geosynergetic: theory, method, experiment. Complex analyze of electromagnetic and other geophysical data. M.: KRASAND, 2011.

  15. Preliminary results of systematic sampling of gas manifestations in geodynamically active areas of Greece

    NASA Astrophysics Data System (ADS)

    Daskalopoulou, Kyriaki; D'Alessandro, Walter; Calabrese, Sergio; Kyriakopoulos, Konstantinos

    2016-04-01

    Greece is located on a convergent plate boundary comprising the subduction of the African Plate beneath the Eurasian, while the Arabian plate approaches the Eurasian in a northwestward motion. It is considered to be one of the most tectonically active regions of Earth with a complex geodynamic setting, deriving from a long and complicated geological history. Due to this specific geological background, conditions for the formation of many thermal springs are favoured. In the past years, almost all the already known sites of degassing (fumaroles, soil gases, mofettes, gas bubbling in cold and thermal waters) located in the Hellenic area were sampled at least one time. Collected samples were analysed for their chemical (He, Ne, Ar, O2, N2, H2, H2S, CO, CH4 and CO2) and isotopic composition (He, C and N). Some of these sites have been selected for systematic sampling. Four of them have records longer than 10 years with tens of samplings also considering some literature data. Two of the sites are located in active volcanic areas (Santorini and Nisyros) while the other two are close to actively spreading graben structures with intense seismic activity (Gulf of Korinth and Sperchios basin). Results allowed to define long term background values and also some interesting variation related to seismic or volcanic activity.

  16. GPS net­work operations for the International GPS Geodynamics Service

    USGS Publications Warehouse

    Neilan, Ruth E.

    1993-01-01

    As GPS technology comes of age in the 1990’s, it is evident that an internationally sponsored GPS tracking system is called for to provide consistent, timely ground tracking data and data products to the geophysical community. The planning group for the International GPS Geodynamics Service (IGS), sponsored by the International Association of Geodesy (IAG), is addressing all elements of the end-to-end tracking system, ranging from data collection to data analysis and distribution of products (Mueller, 1992). Part of the planning process is to formulate how these various elements work together to create the common infrastructure needed to support a wide variety of GPS investigations. A key element for any permanent satellite tracking system is certainly the acquisition segment; the reliability and robustness of the ground network operations directly determine the fates and limitations of final products. The IGS planning group therefore included a committee tasked to develop and establish standards governing data acquisition and site-specific characteristics deemed necessary to ensure the collection of a high quality, continuous data set.

  17. Thermal regime, hydrocarbon maturation and geodynamic events along the western margin of India since late Cretaceous

    NASA Astrophysics Data System (ADS)

    Pandey, O. P.; Agrawal, P. K.

    2000-11-01

    The passive continental margin of western India and the adjacent offshore region are associated with a transitional type thinned crust. It contains several sedimentary basins where substantial recoverable oil/gas reserves exist. The northern Cambay graben, northern and eastern parts of the Bombay offshore and the Konkan coast region that are situated close to western margin exhibit reasonably high heat flow and geothermal gradients beneath which the asthenosphere is upwarped to a depth of 30-70 km. Temperatures at the depth of 3 km are estimated to be in the range of 105-260°C. Curie depth analysis from MAGSAT studies in an area between latitudes 11°N and 19°N and longitudes 65°E and 73°E also indicates a high geothermal gradient of about 30°C/km within the upper crustal column. We suggest that the occurrence of oil and gas in these areas may be due to catastrophic and geodynamic events which took place in the last 130 Ma. India's super-mobility, continental breakups, possible bolide impact and Deccan volcanic episode at the western margin resulted in substantial lithospheric heating, accompanied by subcrustal melting and rise of isotherms, to eventually enhance the hydrocarbon maturation process. The study indicates that all other sedimentary basins situated on the western margin are also thermally mature and may have high potential for the occurrence of hydrocarbons.

  18. Geodynamic Inferences from Integrated Ocean Drilling Program Expedition 330 to the Louisville Seamount Trail

    NASA Astrophysics Data System (ADS)

    Koppers, A. A.; Yamazaki, T.; Geldmacher, J.; Scientific Party, E. 3; IODP Expedition 330 Scientific Party

    2011-12-01

    Integrated Ocean Drilling Program (IODP) Expedition 330 drilled five different guyots in the Louisville Seamount Trail ranging in age between 80 and 50 Ma. The primary goals of this expedition were to drill a sufficiently large number of in situ lava flows at each seamount for high-quality estimates of their paleolatitudes using paleomagnetic measurements, for improving the overall age progression using high-precision 40Ar/39Ar geochronology, and for detailed geochemical studies of the volcanic evolution of these seamounts. With these data we can provide the unique record of the paleolatitude shift (or lack thereof) of the Louisville mantle plume and compare it with the ~15° paleolatitude shift observed for seamounts in the Hawaiian-Emperor Seamount Trail over the same time period. These comparisons are of fundamental importance to determine whether these two primary hotspots have moved coherently or not, to understand the nature of hotspots and convection in the Earth's mantle, and to evaluate the possibility of true polar wander. We will present new 40Ar/39Ar age data for Sites U1372, U1373, U1374 and U1376 in conjunction with Expedition 330 shipboard paleomagnetic inclination data to discuss the geodynamic inferences from the resulting paleolatitude history of the Louisville hotspot between 80 and 65 Ma.

  19. The Central Atlantic Magmatic Province (CAMP) in Brazil: Petrology, geochemistry, 40Ar/39Ar ages, paleomagnetism and geodynamic implications

    NASA Astrophysics Data System (ADS)

    De Min, Angelo; Piccirillo, Enzo M.; Marzoli, Andrea; Bellieni, Giuliano; Renne, Paul R.; Ernesto, Marcia; Marques, Leila S.

    The CAMP tholeiitic magmatism in Brazil (mean 40Ar/39Ar age of 199.0+2.4 Ma) occurs on the continental margin to ca. 2,000 km into the South American platform, near the boundary between the ancient terrains of the Amazonia craton and Proterozoic/Brazilian-cycle related mobile belts. Geological evidence indicates that this magmatism was preceded, in Permo-Triassic times, by continental sedimentation, indicating a possible regional uplift. The Brazilian CAMP tholeiites are generally evolved and characterized by a low TiO2 concentration (less than 2 wt%). The Cassiporé dykes, which are usually high in TiO2 (more than 2wt%) are an exception. The Cassiporé low- and high-TiO2 basalts are characterized by a positive Nb anomaly and Sr-Nd isotopes that are parallel to "typical" mantle array. Except for one sample, all the other Brazilian CAMP tholeiites that are low in TiO2, show Sr-Nd isotopes trending towards crustal components. The latter isotopic characteristics could be related to "crustal recycling" ancient (Middle-Late Proterozoic) subductions, and/or low-pressure crustal interaction. All the Brazilian CAMP tholeiites show a decoupling between their Sr-Nd isotopic composition and Rb/Sr and Sm/Nd values, suggesting "mantle metasomatism", and/or subduction-related crustal interaction before mantle melting. Notably, the chemical data show that tholeiites from specific Brazilian regions are related to mantle sources that reflect compositional mantle heterogeneity, including the lower mantle of the lithospheric thermal boundary layer. In general, paleomagnetic poles for CAMP rocks from South America, Africa and North America match an age of ca. 200 Ma, but also show a distribution pattern trending to younger ages (e.g. 190 Ma), especially for the South American poles relative to the CAMP magmatism of the continental edge. The Brazilian CAMP magmatism cannot be easily explained through "plume head" (active) models, being instead consistent with mantle geodynamic

  20. Geodynamic Implications of Himu Mantle In The Source of Tertiary Volcanics From The Veneto Region (south Eastern Alps)

    NASA Astrophysics Data System (ADS)

    Macera, P.; Gasperini, D.; Blichert-Toft; Bosch, D.; del Moro, A.; Dini, G.; Martin, S.; Piromallo, C.

    DuringTertiary times extensive mafic volcanism took place in the South-Eastern Alps, along a half-graben structure bounded by the Schio-Vicenza main fault. This mag- matism gave rise to four main volcanic centers: Lessini, Berici, Euganei, and Maros- tica. The dominating rock types are alkali basalts, basanites and transitional basalts, with hawaiites, trachybasalts, tephrites, basaltic andesites, and differentiated rocks be- ing less common. Major and trace element and Sr-Nd-Hf-Pb isotopic data for the most primitive lavas from each volcanic center show the typical features of HIMU hotspot volcanism, variably diluted by a depleted asthenospheric mantle component (87Sr/86Sr48Ma = 0.70314-0.70321; eNd48Ma = +6.4 to +6.5; eHf48Ma = +6.4 to +8.1, 206Pb/204Pb48Ma = 18.786-19.574). Since the HIMU component is consid- ered to be of deep mantle origin, its presence in a tectonic environment dominated by subduction (the Alpine subduction of the European plate below the Adria plate) has significant geodynamic implications. Slab detachment and ensuing rise of deep man- tle material into the lithospheric gap is proposed to be a viable mechanism of hotspot magmatism in a subduction zone setting. Interaction between deep-seated plume ma- terial and shallow depleted asthenospheric mantle may account for the geochemical features of the Veneto volcanics, as well as those of the so-called enriched astheno- spheric reservoir (EAR) component. Ascending counterflow of deep mantle material through the lithospheric gap to the top of the subducting slab further may induce heat- ing of the overriding plate and trigger it to partially melt. Upwelling of the resulting mafic magmas and their subsequent underplating at the mantle-lower crust bound- ary would favor partial melting of the lower crust, thereby giving rise to the bimodal mafic-felsic magmatism that characterizes the whole Periadriatic province. According to this model, the HIMU-like magmatism of the Alpine foreland is therefore

  1. Performance of Basic Geodynamic Solvers on BG/p and on Modern Mid-sized CPU Clusters

    NASA Astrophysics Data System (ADS)

    Omlin, S.; Keller, V.; Podladchikov, Y.

    2012-04-01

    Nowadays, most researchers have access to computer clusters. For the community developing numerical applications in geodynamics, this constitutes a very important potential: besides that current applications can be speeded up, much bigger problems can be solved. This is particularly relevant in 3D applications. However, current practical experiments in geodynamic high-performance applications normally end with the successful demonstration of the potential by exploring the performance of the simplest example (typically the Poisson solver); more advanced practical examples are rare. For this reason, we optimize algorithms for 3D scalar problems and 3D mechanics and design concise, educational Fortran 90 templates that allow other researchers to easily plug in their own geodynamic computations: in these templates, the geodynamic computations are entirely separated from the technical programming needed for the parallelized running on a computer cluster; additionally, we develop our code with minimal syntactical differences from the MATLAB language, such that prototypes of the desired geodynamic computations can be programmed in MATLAB and then copied into the template with only minimal syntactical changes. High-performance programming requires to a big extent taking into account the specificities of the available hardware. The hardware of the world's largest CPU clusters is very different from the one of a modern mid-sized CPU cluster. In this context, we investigate the performance of basic memory-bounded geodynamic solvers on the large-sized BlueGene/P cluster, having 13 Gb/s peak memory bandwidth, and compare it with the performance of a typical modern mid-sized CPU cluster, having 100 Gb/s peak memory bandwidth. A memory-bounded solver's performance depends only on the amount of data required for its computations and on the speed this data can be read from memory (or from the CPUs' cache). In consequence, we speed up the solvers by optimizing memory access and CPU

  2. Geodynamic model for the Palaeozoic crustal consolidation of Western and Central Europe

    NASA Astrophysics Data System (ADS)

    Ziegler, P. A.

    1986-06-01

    The crystalline basement of Western and Central Europe consists of a mosaic of crustal elements which were consolidated during pre-Grenvillian, the Grenvillian-Dalslandian, Morarian, Cadomian, Caledonian and Hercynian orogenic cycles. Contemporaneous with the Caledonian suturing of the Precambrian Laurentia-Greenland and Fennosarmatian shields a number of Gondwana-derived Cadomian micro-cratons were accreted to the southern margin of Laurasia. Following the Late Caledonian paroxysm, the Devonian and Early Carboniferous evolution of Europe was dominated by continued northward subduction of the Proto Tethys plate at an arc-trench system parallelling the southern margin of Laurasia, the accretion of additional Gondwana-derived continental fragments, back-arc rifting and a sinistral translation of major proportions between the Laurentia-Greenland and the Fennosarmatian sub-plates. The Acadian and Bretonian orogenies were of the Pacific type. The Visean collision of Gondwana with Laurasia marked the onset of the Himalayan-type Variscan orogeny, during which collision-related compressive stresses overpowered the Devonian-Early Carboniferous back-arc rift systems and caused the development/reactivation of A-subduction zones. The Central Armorican and Saxothuringian successor basins became folded and destroyed during the latest Visean, whilst the Variscan foredeep became scooped out, in part by nappes involving the basement, during the Late Westphalian. Major crustal shortening during the Variscan diastrophism was accompanied by the anatectic remobilisation of subducted crustal and upper mantle material and a widespread syn- and late-orogenic magmatism. The latest Carboniferous-Early Permian reorientation of the convergence direction between Gondwana and Laurasia induced the development of a complex wrench-fault system transecting the Variscan fold belt and an extensive post-orogenic volcanism. The hypotheses summarised here require confirmation by further palaeomagnetic and radiometric data and faunal analyses.

  3. Geodynamic models of the Wilson Cycle: From rifts to mountains to rifts

    NASA Astrophysics Data System (ADS)

    Buiter, Susanne; Tetreault, Joya; Torsvik, Trond

    2015-04-01

    The Wilson Cycle theory that oceans close and reopen along the former suture is a fundamental concept in plate tectonics. The theory suggests that subduction initiates at a passive margin, closing the ocean, and that future continental extension localises at the ensuing collision zone. Each stage of the Wilson Cycle will therefore be characterised by inherited structural and thermal heterogeneities. Here we investigate the role of Wilson Cycle inheritance by considering the influence of (1) passive margin structure on continental collision and (2) collision zones on passive margin formation. Passive margins may be preferred locations for subduction initiation because inherited faults and areas of exhumed serpentinized mantle may weaken a margin enough to localise shortening. If subduction initiates at a passive margin, the shape and structure of the passive margins will affect future continental collision. Our review of present-day passive margins along the Atlantic and Indian Oceans reveals that most passive margins are located on former collision zones. Continental break-up occurs on relatively young sutures, such as Morocco-Nova Scotia, and on very old sutures, such as the Greenland-Labrador and East Antarctica-Australia systems. This implies that it is not always post-collisional collapse that initiates the extensional phase of a Wilson Cycle. We highlight the impact of collision zone inheritance on continental extension and rifted margin architecture. We show numerical experiments of one Wilson Cycle of subduction, collision, and extension. Subduction initiates at a tapered passive margin. Closure of a 60 Ma ocean leads to continental collision and slab break-off, followed by some tens of kilometres of slab eduction. Mantle flow above the sinking detached slab enhances deformation in the rift area. The resulting rift exposes not only continental crust, but also subduction-related sediments and oceanic crust remnants. Renewed subduction in the post-collision phase is enabled by lithosphere delamination and slab rollback, leading to back-arc extension in a style similar to the Tyrrhenian Sea.

  4. The Dynamics of Oceanic Transform Faults: Constraints from Geophysical, Geochemical and Geodynamic