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Influences of Lower-Mantle Properties on the Formation of Asthenosphere in Oceanic Upper Mantle

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Journal of Earth Science 2011年第2期22卷 143-154页

作者： david a yuen Nicola Tosi Ondrej adek Department of Geology and Geophysics and Minnesota Supercomputing Institute University of MinnesotaMinneapolisMN 55415USA Department of Planetary Physics Institute of Planetary ResearchGerman Aerospace Center(DLR)BerlinGermany Department of Geophysics Faculty of Mathematics and PhysicsCharles UniversityPragueCzech Republic

Asthenosphere is a venerable concept based on geological intuition of Reginald Daly nearly 100 years ago. There have been various explanations for the existence of the asthenosphere. The concept of a plume-fed asthenosphere has been around for a few years due to the ideas put forth by Yamamoto et al.. Using a two-dimensional Cartesian code based on finite-volume method, we have investigated the influences of lower-mantle physical properties on the formation of a low-viscosity zone in the oceanic upper mantle in regions close to a large mantle upwelUng. The rheological law is Newtonian and depends on both temperature and depth. An extended-Boussinesq model is assumed for the energetics and the olivine to spinel, the spinel to perovskite and perovskite to post-perovskite （ppv） phase transitions are considered. We have compared the differences in the behavior of hot upweilings passing through the transition zone in the mid-mantle for a variety of models, starting with constant physical properties in the lower-mantle and culminating with complex models which have the post-perovskite phase transition and depth-dependent coefficient of thermal expansion and thermal conductivity. We found that the formation of the asthenosphere in the upper mantle in the vicinity of large upwellings is facilitated in models where both depth-dependent thermal expansivity and conductivity are included. Models with constant thermal expansivity and thermal conductivity do not produce a hot low-viscosity zone, resembling the asthenosphere. We have also studied the influences of a cylindrical model and found similar results as the Cartesian model with the important difference that upper-mantle temperatures were much cooler than the Cartesian model by about 600 to 700 K. Our findings argue for the potentially important role played by lower-mantle material properties on the development of a plume-fed asthenosphere in the oceanic upper mantle.

关键词： oceanic asthenosphere lower mantle thermal expansivity thermal conductivity phase transition.

Submicron size-scale mapping of carbonate effective elastic properties from FIB-SEM images and finite element method

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Science China Earth Sciences 2017年第3期60卷 557-575页

作者： CHENG HuiHong ZHU BoJing david a yuen SHI YaoLin Key Laboratory of Computational Geodynamics of Chinese Academy of Sciences Beijing 100049China College of Earth Science University of Chinese Academy of SciencesBeijing 100049China Yunnan Observatories Chinese Academy of SciencesKunming 650216China Rock Mechanics and Carbon Store Lab Department of Earth SciencesDurham UniversityDurhamDH13LEUK Department of Earth Science and Minnesota Supercomputing Institute University of MinnesotaMinneapolis 55455USA

In this paper,an automatic unstructured focused ion beam(FIB) and scanning electron microscopy(SEM) images induced representative volume element(RVE) finite element(FE) method is developed to predict submicron scale carbonate rock effective Young's and bulk moduli and Poisson's ratio on parallel CPU-GPU platform.Based on high resolution-contrast surface morphology and internal fabnc-texture structure images from carbonate rock specimen(covered 0.12-64 μm^2 area and8000 μm^3 domain),the cubic RVE FE models are constructed from different sites through Avizo with user-defined parameters Matlab coding.The effective Young's and bulk moduli and Poisson's ratio of the different RVEs and porosity and pore size are computed by using periodic boundary condition in the well-known FE software Abaqus.FE mesh sensitivity analysis has been conducted where all moduli converge to a certain constant value at larger FE mesh density.The effect of fabric-texture(pore size,shape,and distribution) on the elastic properties is discussed.The correlations between the computed effective elastic properties and pore size,porosity,RVE size have been established.The simulation results show that the effective Young's and bulk moduli and Poisson's ratio have strong anisotropic behavior and depend on RVE size,porosity and pore size.The RVE size,porosity and pore size are three independent factors in affecting of the effective elastic moduli,the effect mechanism of porosity and pore size is same while the effect mechanism of RVE size is difference.

关键词：焦化有效有弹性的性质有限元素分析集中的离子横梁 Nano 孔 Nano 毛孔尺寸

Parallel Numerical Analysis on the Rheology of the Martian Ice-Rock Mixture

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Journal of Earth Science 2011年第2期22卷 176-181页

作者：景惠敏张怀李菡 david a yuen 石耀霖 Laboratory of Computational Geodynamics Graduate University of Chinese Academy of Sciences Department of Geology and Geophysics and Minnesota Supercomputing Institute University of MinnesotaMinneapolisMN 55415USA

The distribution and amount of ground ice on Mars is an important issue to be addressed for the future exploration of the planet.The occurrence of interstitial ice in Martian frozen ground is indicated by landforms,such as fluidized ejecta craters,softened terrain,and fretted channels.How-ever,experimental data on the rheology of ice-rock mixture under Martian physical conditions are sparse,and the amount of ground ice that is required to produce the viscous deformation observed in Martian ice-related landforms is still unknown.In our study,we put forward a three-dimensional non-Newtonian viscous finite element model to investigate the behavior of ice-rock mixtures numeri-cally.The randomly distributed tetrahedral elements are generated in regular domain to represent the natural distribution of ice-rock materials.Numerical simulation results show that when the volume of rock is less than 40%,the rheology of the mixture is dominated by ice,and there is occurrence of a brittle-ductile transition when ice fraction reaches a certain value.Our preliminary results contribute to the knowledge of the determination of the rheology and ice content in Martian ice-rock mixture.The presented model can also be utilized to evaluate the amount of ground ice on Mars.

关键词： parallel simulation rheology,ice-rock mixture Mars.

Regional Stress Fields under Tibet from 3D Global Flow Simulation

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Journal of Earth Science 2011年第2期22卷 155-159页

作者：张斯奇 david a yuen 张怀石耀霖 Laboratory of Computational Geodynamics Graduate University of Chinese Academy of Sciences Earth System Sciences Computational Center The University of QueenslandSt LuciaQLD 4072Australia Department of Geology and Geophysics and Minnesota Supercomputing Institute University of MinnesotaMinneapolisMN 55415USA

Tibetan area is the most active continental collision zone on earth. Several major earthquakes occurred around the boundaries of Tibetan plateau and caused massive damages and casualties. The dynamics of this area is not well understood due to the complex structure of Tibet and its surrounding area. In this study, a 3D global flow simulation with only viscous rheology is applied to studying the stress distribution in this area, and the interaction between Tibet and its surrounding areas is investigated. Finally, the possibility of combining regional modeling with global models is also discussed.

关键词： Tibet global flow stress simulation.

SEPRAN: A Versatile Finite-Element Package for a Wide Variety of Problems in Geosciences

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Journal of Earth Science 2015年第1期26卷 89-95页

作者： Arie van den Berg Guus Segal david A.yuen Department of Theoretical Geophysics Institute of Earth SciencesUtrecht University3508 TC UtrechtThe Netherlands Faculty of Electrical Engineering Mathematics and Computer ScienceTU DelftThe Netherlands Department of Earth Sciences and Minnesota Supercomputing Institute University of MinnesotaMinneapolis MN 55455USA School of Environmental Studies China University of Geosciences

Numerical modelling of geological processes, such as mantle convection, flow in porous media, and geothermal heat transfer, has become quite common with the increase in computing and the availability of usable software. Today modelling these dynamical processes entails the solving of the governing equations involving the mass, momentum, energy and chemical transport. These equations represent partial differential equations and must be solved on powerful enough computers because they require sufficient spatial and temporal resolution to be useful. We describe here the salient and outstanding features of the SEPRAN software package, developed in the Netherlands, as a case study for a robust and user-friendly soft- ware, which the geological community can utilize in handling many thermal-mechanical-chemical problems found in geology, which will include geothermal situations, where many types of partial differential equations must be solved at the same time with thermodynamical input parameters.

关键词： SEPRAN finite element package geodynamic and planetary modelling geothermal groundwater flow.

Submicron Volume Roughness & Asperity Contact Friction Model for Principle Slip Surface in Flash Heating Process

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Journal of Earth Science 2015年第1期26卷 96-107页

作者： Bojing Zhu david A.yuen Yaolin Shi Huihong Cheng Carbon Capture & Store & Rock Mechanics & Fluid Dynamic Laboratory Department of Earth SciencesDurham UniversityDH1 3LEUK Department of Earth Sciences and Minnesota Supercomputing Institute University of MinnesotaMinneapolis MN 55455USA School of Environmental Studies China University of Geosciences Key Laboratory of Computational Geodynamics of Chinese Academy of Sciences College of Earth ScienceUniversity of Chinese Academy of Sciences

Based on focused ion beam and shear friction apparatus data, the multi-resolutions （0.2 nm-5μm） volume roughness ＆ asperity contact （VR ＆ AC） three-dimensional structure on principle slip surface interface-surface （PSS-IS） is measured on high performance computational platform; and physical plastic-creep friction model is established by using hybrid hyper-singular integral equation ＆ lattice Boltzmann ＆ lattice Green function （BE-LB-LG）. The correlation of rheological property and VR ＆ AC evolution under transient （10 μs） macro-normal stress （18-300 MPa） and slip rate （0.25-7.5 m/s） are obtained; and the PSS-IS friction in co-seismic flash heating is quantitative analyzed for the first time.

关键词： VR ＆ AC BE-LB-LC submicron-scale structure measurement plastic-creep model,friction model.

Electron acceleration in interaction of magnetic islands in large temporal-spatial turbulent magnetic reconnection

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Earth and Planetary Physics 2019年第1期3卷 17-25页

作者： BoJing Zhu Hui Yan david a yuen YaoLin Shi Yunnan Observatories Chinese Academy of Sciences Center for Astronomical Mega-Science Chinese Academy of Sciences National Supercomputer Center in Guangzhou Sun Yat-sen University Department of Earth Science and Minnesota Supercomputing Institute University of Minnesota Applied Physics and Applied Mathematics Department Columbia University Key Laboratory of Computing Geodynamics Chinese Academy of Sciences College of Earth and Planetary Sciences University of Chinese Academy of Sciences

A new combined Fermi, betatron, and turbulent electron acceleration mechanism is proposed in interaction of magnetic islands during turbulent magnetic reconnection evolution in explosive astrophysical phenomena at large temporal-spatial scale(LTSTMR), the ratio of observed current sheets thickness to electron characteristic length, electron Larmor radius for low-β and electron inertial length for high-β, is on the order of 10^(10)–10^(11); the ratio of observed evolution time to electron gyroperiod is on the order of 10~7–10~9).The original combined acceleration model is known to be one of greatest importance in the interaction of magnetic islands; it assumes that the continuous kinetic-dynamic temporal-spatial scale evolution occurs as two separate independent processes.In this paper, we reconsider the combined acceleration mechanism by introducing a kinetic-dynamic-hydro full-coupled model instead of the original micro-kinetic or macro-dynamic model.We investigate different acceleration mechanisms in the vicinity of neutral points in magnetic islands evolution, from the stage of shrink and breakup into smaller islands(kinetic scale), to the stage of coalescence and growth into larger islands(dynamic scale), to the stages of constant and quasi-constant(contracting-expanding) islands(hydro scale).As a result, we give for the first time the acceleration efficiencies of different types of acceleration mechanisms in magnetic islands' interactions in solar atmosphere LTSTMR activities(pico-, 10^(–2)–10~5 m; nano-, 10~5–10~6 m; micro-, 10~6–10~7 m; macro-, 10~7–10~8 m; large-,10~8–10~9 m).

关键词： hybrid particle acceleration mechanism large temporal-spatial turbulent magnetic reconnection Hydro-Dynamic-Kinetic model

Electro-Pulse-Boring(EPB): Novel Super-Deep Drilling Technology for Low Cost Electricity

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Journal of Earth Science 2015年第1期26卷 37-46页

作者： Hans O.Schiegg Arild Rdland Guizhi Zhu david A.yuen SwissG eo Power AG Stadtturmstrasse 19 CH-5401Switzerland Department of Petroleum Engineering and Applied Geophysics Norwegian University of Science and Technology7491 TrondheimNorway Department of Earth Sciences ETH-Zurich CH-8092Switzerland Department of Earth Sciences and Minnesota Supercomputing Institute University of MinnesotaMinneapolis MN 55455USA School of Environmental Studies China University of Geosciences

The inexhaustible heat deposit in great depths （5-10 km） is a scientific fact. Such deposit occurs around the globe. Thereby, everybody is enabled to generate autonomously clean and renewable energy, ample electricity and heat. The economical exploration and exploitation of this superdeep geothermal heat deposit requires a novel drilling technique, because the currently only deep drilling method （Rotary） is limited to about 5 km, due to the rising costs, depending exponentially on depth. Electro-pulse-boring （EPB） is a valuable option to Rotary drilling. EPB, originally investigated in Russia, is ready to be developed for industrialization. The feasibility of EPB is proven by many boreholes drilled up to 200 m in granite （crystalline）. Estimates show outstanding low costs for drilling by EPB： 100 E/m for a borehole with a large diameter （φ） such as 20 （50 cm）, independent on depth and applicable likewise for sediments and crystalline rocks, such as granite. The current rate of penetration （ROP） of 3 m per hour is planned to be augmented up to 35 m per hour, and again, irrespective whether in sedimentary or crystalline formations. Consequently, a 10 km deep borehole with φ 50 cm will ultimately be drilled within 12 days. EPB will create new markets, such as：（i） EPB shallow drilling for geotechnics, energy piles, measures in order to mitigate natural hazards, etc., （ii） EPB deep drilling （3-5 km） for hydro-geothermics, exploration campaigns etc. and （iii） EPB super-deep drilling （5-10 km） for petro-geothermies, enabling the economic generation of electricity. The autonomous and unlimited supply with cost efficient electricity, besides ample heat, ensures reliably clean and renew- able energy, thus, high supply security. Such development will provide a substantial relief to cope with the global challenge to limit the climate change below 2 ℃. The diminution of fossil fuels, due to the energy transition in order to mitigate the climate change, implies likewise the decrease of air pollution.

关键词： drilling technology electro pulse petro-geothermics geoenergy geothermal electricity climate change air pollution.

Small-Scale Mineralogical Heterogeneity from Variations in Phase Assemblages in the Transition Zone and D" Layer Predicted by Convection Modelling

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Journal of Earth Science 2011年第2期22卷 160-168页

作者： Arie P van den Berg david a yuen Michael H G Jacobs Maarten V de Hoop Earth Sciences Department Utrecht University Department of Geology and Geophysics and Minnesota Supercomputing Institute University of MinnesotaMinneapolisMN 55415USA Institut für Metallurgie TU ClausthalClausthal-ZellerfeldGermany Department of Mathematics and Center of Applied and Computational Mathematics Purdue UniversityWest LafayetteINUSA

Small-scale heterogeneity in the deep mantle is concentrated in the upper-mantle transition zone （TZ）, in the depth range 410-660 km and also at the bottom 250 km D＂ region. This encourages a more detailed investigation of the potential for seismic reflectivity imaging by modelling heterogeneous structures in mantle convection models including phase transitions of the TZ and D＂ regions. We applied finite elements with variable spacing near the boundary layers in 2-D cylindrical geometry that allow for sufficient spatial resolution. We investigated several models including an extended Boussinesq （EBA） model, focused on the D＂ region, and a compressible （ALA） model for the TZ region. The results for the D＂ region show typical lens-shaped structures of post-perovskite （PPV） embedded in the perovskite （PV） background mantle, where the thickness of the lenses, at 200-400 km, strongly depends on the Clapeyron slope of the PV-PPV transition. A second phase transition （double crossing） occurs in case the core temperature is higher than the intercept temperature Ti. Our phase-dependent rheology results in contrasting effective viscosity between PV and PPV. Our model results reveal a distinctly clear mechanical weakening of the PPV lenses with about an order of magnitude lower viscosity. The shear wave-speed distributions computed from our convection results are strongly correlated with the heterogeneous distribution of the mineral phase. Gradients in the seismic wave-speed that are the target of seismological reflectivity imaging are clearly revealed. The wave-speed results show a clear resolution of the top and bottom interfaces of the PPV lenses. Our ALA model for the TZ is based on a thermodynamical model for the magnesium end- member of an olivine-pyroxene mantle. The model predicts a much more complex distribution of mineral phases, compared to our D＂ results, in agreement with the greater number of mineral phases involved in the olivine-pyroxene phase diagram for the P, T conditions of the transition zone. Near cold

关键词： mantle convection phase transition post-perovskite mineralogical heterogeneity.