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Linear Stability Analysis on the Influences of the Spatial Variations in Thermal Conductivity and Expansivity on the Flow Patterns of Thermal Convection with Strongly Temperature-Dependent Viscosity

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Journal of Earth Science 2014年第1期25卷 126-139页

作者： Arata Miyauchi Masanori Kameyama Hiroki Ichikawa geodynamics Research Center Ehime University

A series of linear stability analysis is carried out on the onset of thermal convection in the presence of spatial variations of viscosity, thermal conductivity and expansivity. We consider the temporal evolution of an infinitesimal perturbation superimposed to a static （motionless） and con- ductive state in a basally-heated planar layer. From the changes in flow patterns with increasing the amplitudes of temperature dependence of viscosity, we identified the transition into the ＂stagnant-lid＂（ST） regime, where the convection occurs only beneath a thick and stagnant-lid of cold fluid at the top surface. Detailed analysis showed a significant increase of the aspect ratio of convection cells in ST regime induced by the spatial variations in thermal conductivity and/or expansivity： the horizon- tal length scale of ST convection can be enlarged by up to 50% with 10 times increase of thermal conductivity with depth. We further developed an analytical model of ST convection which success- fully reproduced the mechanism of increasing horizontal length scale of ST regime convection cells for given spatial variations in physical properties. Our findings may highlight the essential roles of the spatial variation of thermal conductivity on the convection patterns in the mantle.

关键词： mantle convection stagnant-lid temperature-dependent viscosity pressure- dependent thermal conductivity pressure-dependent thermal expansivity linear stability analysis.

Geochemistry of fine-grained sediments of the upper Cretaceous to Paleogene Gosau Group(Austria,Slovakia):Implications for paleoenvironmental and provenance studies

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Geoscience Frontiers 2013年第4期4卷 449-468页

作者： Gerald Hofer Michael Wagreich Stephanie Neuhuber Department of geodynamics and Sedimentology.University of Vienna

Bulk rock geochemistry of 169 fine-grained sediment samples of the upper Cretaceous to Paleogene Gosau Group （Northern Calcareous Alps, Austria and Slovakia） fiom borehole and outcrop localities was performed to separate non-marine and marine deposits. Geochemical characteristics of different Gosau depositional systems, basins and sediment provenance using major-, trace-, and rare earth elements were also investigated. Geochemical proxies such as boron concentrations were tested for seeking the possibilities of paleosalinity indicators. Due to the [act that several pelagic sections are represented by extremely low boron contents, B/AI＊ ratios are recognized as more robust and differentiate reliably between marine （mean： 160 ± 34） and non-marine （mean： 133 ± 33） samples. Using statistical factor analysis, hemipelagic to pelagic samples flom the Gieghi_ibl Syncline and Slovakian equivalents can be differentiated from marginal-marine to non-marine samples from the Grtinbach and Glinzendorf Syncline related to terrigenous （SiO2, AI203, K20, Th, Rb, Zr and others） and pelagic indicative elements （CaO, St, TOT/C and B/AI＊）. A clear indication for ophiolitic provenance is traced by high amounts of chromium and nickel. Only non-marine successions of the Glinzendorf Syncline show higher Cr and Ni concentrations （up to 250 and 400 ppm, respectively） and enriched Cr/V and Y/Ni ratios trending to an ultramafic source.

关键词： Gosau GroupGeochemistryPre-Neogene Vienna BasinBoronFactor analysisProvenance

A review of earthquake occurrences and observations in Nigeria

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Earthquake Science 2010年第3期23卷 289-294页

作者： Ofonime Umo Akpan Tahir Abubakar Yakubu Centre for Geodesy and geodynamics

Although Nigeria is not located within the major seismic zones of the world; over the years,several minor earthquakes have been experienced in some parts of the *** first widely reported occurrence of an Earth tremor in Nigeria was in *** events were reported in 1939,1964,1984,1990,1994,1997,2000 and *** intensities of these events ranged from III to VI based on the Modified Mercalli Intensity *** these events,only the 1984,1990,1994 and 2000 events were instrumentally *** had body wave magnitudes ranging from 4.3 to 4.5,local magnitudes between 3.7 and 4.2,and surface wave magnitudes of 3.7 to *** these events occurred,there were no functional seismological observatories in ***,that has now changed with the establishment of a seismographic network managed by the Centre for Geodesy and geodynamics（CGG）,Toro,***,the network has four operational stations equipped with 24-bit 4-channel recorders and broadband 30-second *** are being made to establish more stations and migrate to real-time collection of seismic data using the general packet radio service（GPRS） technology as well as automatic location of *** sensing,geological and geophysical studies have revealed the presence of a NNE-SSW trending Ifewara-Zungeru fault zone which has been shown to be linked with the Atlantic fracture *** dynamics of the Atlantic fracture zones have been suggested to be responsible for the seismic activities experienced in the areas.

关键词： Nigeria seismic activity seismological observatories Ifewara-Zungeru fault zone

Deep geodynamics of far field interconti- nental back-arc extension: Formation of Cenozoic volcanoes in northeastern China

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Acta Seismologica Sinica(English Edition) 2004年第z1期17卷 1-8页

作者： SHI Yao-lin(石耀霖) ZHANG Jian(张健) Laboratory of Computational geodynamics Graduate School of Chinese Academy of Sciences Beijing 100039China

There are three cases of variation of trench location possible to occur during subduction: trench fixed, trench ad- vancing, and trench retreating. Retreat of trench may lead to back-arc extension. The Pacific plate subducts at low angle beneath the Eurasia plate, tomographic results indicate that the subducted Pacific slab does not penetrate the 670 km discontinuity, instead, it is lying flat above the interface. The flattening occurred about 28 Ma ago. Geo- dynamic computation suggests: when the frontier of the subducted slab reaches the phase boundary of lower and upper mantle, it may be hindered and turn flat lying above the boundary, facilitates the retreat of trench and back-arc extension. Volcanism in northeastern China is likely a product of such retreat of subduction, far field back-arc extension, and melting due to reduce of pressure while mantle upwelling.

关键词： back-arc basin Cenozoic volcano geodynamics northeastem China

Finite element simulation of deformation and stress changes of Kalpin-Kemin fault system in the Southwest Tianshan Orogenic Belt

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Science China Earth Sciences 2022年第5期65卷 863-873页

作者： Zitao WANG Huai ZHANG Qiu MENG Yaolin SHI Key Laboratory of Computational geodynamics University of Chinese Academy of SciencesBeijing 100049China

Under the shadow of the far-field effect of the India-Eurasia collision,the Tianshan orogenic belt underwent tectonic re-activation in the Cenozoic,accompanied by strong tectonic deformation and frequent large *** by two rigid cratonic blocks located in its north and south,a series of marginal foreland fold-and-thrust belts are developed within the Tianshan orogenic belt and continue to develop to the bilateral pull-apart ***,the faults in the orogenic belt are *** deformation caused by thrust-related structure accounts for larger than 50%of the total convergence of the Tianshan Mountains,which results in the most active structure with large earthquakes in the Tianshan ***,it is of great significance to study the dynamic process of the newly generated and reactivated thrust-nappe structures in Tianshan orogen via numerical *** paper selects a classical cross-section profile in the western segment of the Southwest Tianshan Mountains,which contains the Kalpin-Maidan-Nalati-Kemin fault system from the south to the *** attempt to establish a two-dimensional plane strain,viscoelastic finite element model,by treating the regional faults as a whole fault system and considering the topography,fault geometry,and GPS *** displacement and stress fields of the model are retrieved,the short-term cumulative deformation field of the overall fault system is analyzed,and the rate of Coulomb failure stress change of each fault is also *** results show that the deformation is concentrated in the middle and southern parts of the Southwest Tianshan *** contrast,the deformation of the Kemin fault in the north is relatively *** to the Coulomb failure stress changes of these four faults and the historical earthquake catalog,the potential seismicity of each fault is qualitatively *** preliminary results suggest that the possibility of large earthquake occurrence is higher in the

关键词： Tianshan orogenic belt Viscoelastic finite element Coulomb failure stress change Seismicity

Numerical simulation of Martian historical dynamo:Impact of the Rayleigh number on the dynamo state

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Science China Earth Sciences 2009年第3期52卷 402-410页

作者： WANG TianYuan KUANG WeiJia MA ShiZhuang Laboratory for Computational geodynamics Graduate University of Chinese Academy of SciencesBeijing 100049China Planetary geodynamics Laboratory NASA Goddard Space Flight CenterGreenbeltMD 20771USA

The observed Mars remnant magnetism suggests that there was an active dynamo in the Martian core. We use the MoSST core dynamics model to simulate the Martian historical dynamo, focusing on the variation of the dynamo states with the Rayleigh number Ra (a non-dimensional parameter describing the buoyancy force in the core). Our numerical results show that the mean field length scale does not vary monotonically with the Rayleigh number, and the field morphology at the core mantle boundary changes with Rayleigh number. In particular, it drifts westward with a speed decreasing with Rayleigh number.

关键词： Mars magnetic field Rayleigh number dynamo

Tensile-strain induced phonon splitting in diamond

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Chinese Physics B 2019年第5期28卷 71-74页

作者： Meifang Pu Feng Zhang Shan Liu Tetsuo Irifune Li Lei Institute of Atomic and Molecular Physics Sichuan University geodynamics Research Center Ehime University

The first-order Raman spectroscopy of diamond exhibits splitting and redshift after the burst of high-pressure(160–200 GPa) and high-temperature(～2000 K). The observed longitudinal optical(LO) and the transverse optical(TO) splitting of Raman phonon is related to the tensile-strain induced activation of the forbidden or silent Raman modes that arise in the proximity of the Brillouin zone center.

关键词： diamond tensile-strain phonon splitting Brillouin zone

Three-dimensional numerical simulation of glacial trough forming process

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Science China Earth Sciences 2015年第9期58卷 1656-1668页

作者： YANG ShaoHua SHI YaoLin Key Laboratory of Computational geodynamics of Chinese Academy of Sciences University of Chinese Academy of Sciences

The glacial trough is a common glacier erosion landscape, which plays an important role in the study of glacier erosion processes. In a sharp contrast with the developing river, which is generally meandering, the developing glacial trough is usually wide and straight. Is the straightness of the glacial trough just the special phenomenon of some areas or a universal feature? What controls the straightness of the glacial trough? Until now, these issues have not been studied yet. In this paper, we conduct systematic numerical models of the glacier erosion and simulate the erosion evolution process of the glacial trough. Numerical simulations show that:(1) while the meandering glacier is eroding deeper to form the U-shaped cross section, the glacier is eroding laterally. The erosion rate of the ice-facing slope is bigger than that of the back-slope.(2) The smaller(bigger) the slope is, the smaller(bigger) the glacier erosion intensity is.(3) The smaller(bigger) the ice discharge is, the smaller(bigger) the glacier erosion intensity is. In the glacier erosion process, the erosion rate of the ice-facing slope is always greater than that of the back-slope. Therefore, the glacial trough always develops into more straight form. This paper comes to the conclusion that the shape evolution of the glacial trough is controlled mainly by the erosion mechanism of the glacier. Thereby, the glacial trough prefers straight geometry.

关键词： glacial trough erosion action numerical simulation finite element method

Preliminary Deformation Experiment of Ringwoodite at 20 GPa and 1 700 K Using a D-DIA Apparatus

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Journal of Earth Science 2010年第5期21卷 517-522页

作者： Takaaki Kawazoe Tomohiro Ohuchi Norimasa Nishiyama Yu Nishihara Tetsuo Irifune geodynamics Research Center Ehime University Senior Research Fellow Center Ehime University

A deformation experiment of ringwoodite with a strain of 9% was achieved at 20 GPa and 1 700 K and at a strain rate of 3×10^-5 s^-1 using a deformation-DIA （D-DIA） apparatus and a multi-anvil 6-6 （MA 6-6） assembly. The crystallographic orientations of the deformed sample were successfully analyzed by the electron backscatter diffraction （EBSD） method, although any notable latticepreferred orientation （LPO） was not observed presumably due to the insufficient strain in the present experiment. In this study, the deformation experiment on ringwoodite succeeded at P-T conditions consistent with the lower part of the mantle transition zone and at a controlled strain rate for the first time. The present study extended the pressure range of deformation experiments in the D-DIA apparatus from 16 GPa in our earlier study to 20 GPa at 1 700 K. The successful extension of the pressure range demonstrates potential importance of the D-DIA apparatus in studying rheological properties of minerals under the P-T conditions of the whole mantle transition zone.

关键词： ringwoodite mantle transition zone rheology viscosity mantle dynamics.