New age constraints on counter-clockwise rotation of NE Japan     

Ayumi K. Baba  Takaaki Matsuda  Tetsumaru Itaya  Yutaka Wada  Noriyuki Hori  Masahiko Yokoyama  Nobuaki Eto  Rieko Kamei  Haider Zaman  Tesfaye Kidane  Yo-Ichiro Otofuji 《Geophysical Journal International》2007,171(3):1325-1341

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Inversion of GPS velocity and seismicity data to yield changes in stress in the Japanese Islands     

Takeshi Iinuma  Teruyuki Kato  Muneo Hori 《Geophysical Journal International》2005,160(2):417-434

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Seismic wave conversion near the upper boundary of the Pacific plate beneath the Kanto district, Japan   总被引：3，自引：0，他引：3  

Shiro Ohmi  & Sadaki Hori 《Geophysical Journal International》2000,141(1):136-148

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The detectability of shallow slow earthquakes by the Dense Oceanfloor Network system for Earthquakes and Tsunamis (DONET) in Tonankai district,Japan     

Keisuke Ariyoshi  Ryoko Nakata  Toru Matsuzawa  Ryota Hino  Takane Hori  Akira Hasegawa  Yoshiyuki Kaneda 《Marine Geophysical Researches》2014,35(3):295-310

In order to understand the characteristics of shallow very low-frequency (VLF) events as revealed by recent ocean-floor observation studies, we perform a trial simulation of earthquake cycles in the Tonankai district by taking the characteristics of the 1944 Tonankai earthquake and assuming that slow earthquakes occur on numerous small asperities. Our simulation results show that the increase of moment release rate of shallower VLF events in the pre-seismic stage of a megathrust earthquake is higher than that of deeper VLF events. This increase may make leveling change due to VLF swarms detectable at Dense Oceanfloor Network system for Earthquakes and Tsunamis (DONET). We also introduce the time series of hydraulic pressure data at DONET, comparing with the leveling change expected from our numerical simulation. Since leveling change due to shallower VLF swarms is so local as to be incoherent, removal of the moving-averaged data from the data stacked by four nearby observation points in the same node may be useful to detect the short-term local leveling change.  相似文献   

Stabilities of NAL and Ca-ferrite-type phases on the join NaAlSiO<Subscript>4</Subscript>-MgAl<Subscript>2</Subscript>O<Subscript>4</Subscript> at high pressure     

Saori Imada  Kei Hirose  Yasuo Ohishi 《Physics and Chemistry of Minerals》2011,38(7):557-560

Stabilities of hexagonal new aluminous (NAL) phase and Ca-ferrite-type (CF) phase were investigated on the join NaAlSiO₄-MgAl₂O₄ in a pressure range from 23 to 58 GPa at approximately constant temperature of 1,850 K, on the basis of in situ synchrotron X-ray diffraction measurements in a laser-heated diamond-anvil cell. The results show that NAL is formed as a single phase up to 34 GPa, NAL + CF between 34 and 43 GPa, and only CF at higher pressures in 40%NaAlSiO₄-60%MgAl₂O₄ bulk composition. On the other hand, both NAL and CF coexist below 38 and 36 GPa, and only CF was obtained at higher pressures in 60%NaAlSiO₄-40%MgAl₂O₄ and 20%NaAlSiO₄-80%MgAl₂O₄ composition, respectively. These results indicate that NAL appears only up to 46 GPa at 1,850 K, and CF forms continuous solid solution at higher pressures on the join NaAlSiO₄-MgAl₂O₄. NAL has limited stability in subducted mid-oceanic ridge basalt crust in the Earth’s lower mantle and undergoes a phase transition to CF in deeper levels.  相似文献   

Non-local memory effects of the electromotive force by fluid motion with helicity and two-dimensional periodicity     

Kumiko Hori  Shigeo Yoshida 《地球物理与天体物理流体动力学》2013,107(6):601-632

In mean-field dynamo theory, the electromotive force term 〈u′ × B′〉 due to small-scale fields connects the small-scale magnetic field with the large-scale field. This term is usually approximated as the α-effect, assumed to be instantaneous in time and local in space. However, the approximation is valid only when the magnetic Reynolds number Rm is much less than unity, and is inappropriate when Rm ? 1, which is the condition satisfied in the Earth's core or solar convection zone. We introduce a function φ _qr as a non-local and non-instantaneous generalization of the usual α-effect and examine its behaviour as a function of Rm in the range 1/64 ≤ Rm ≤ 10 for a kinematic dynamo model. We use the flow of G.O. Roberts 1972 Roberts, GO. 1972. Dynamo action of fluid motions with two-dimensional periodicity. Phil. Trans. Roy. Soc. London Ser. A, 271: 411–454. [Crossref], [Web of Science ®] , [Google Scholar] (Phil, Trans. Roy. Soc. London Ser. A, 1972, 271, 411–454), which is steady and has non-zero helicities and two-dimensional periodicity. As a result, we identify three regions in Rm space according to the behaviour of the function φ _qr : (i) Rm ? 1/4, where the function φ _qr is local and instantaneous and can be approximated by the traditional α and β effects, (ii) 1/4 ? Rm ? 4, where the deviation from the traditional α and β effects increases and non-localness and non-instantaneousness increase, and (iii) Rm ? 4, where boundary layers develop fully and non-localness and non-instantaneousness are prominent. We show that the non-local memory effect for Rm ? 4 strongly affects the dynamo action and explains an observed augmentation of the growth rate in the dispersion relation. The results imply that the non-local memory effect of the electromotive force should be important in the geodynamo or the solar dynamo.  相似文献   

Compression of Na0.4Mg0.6Al1.6Si0.4O4 NAL and Ca-ferrite-type phases     

Saori Imada  Kei Hirose  Tetsuya Komabayashi  Toshihiro Suzuki  Yasuo Ohishi 《Physics and Chemistry of Minerals》2012,39(7):525-530

Compression behaviors of two Al-rich phases in the lower mantle, hexagonal new aluminum-rich (NAL) phase and its high-pressure polymorph Ca-ferrite-type (CF) phase, were examined for identical Na_0.4Mg_0.6Al_1.6Si_0.4O₄ (40?% NaAlSiO₄–60?% MgAl₂O₄) composition. The volumes of the NAL and CF phases were obtained at room temperature up to 31 and 134?GPa, respectively, by a combination of laser-annealed diamond-anvil cell techniques and synchrotron X-ray diffraction measurements. Fitting of the third-order Birch–Murnaghan equation of state to such pressure–volume data yields bulk modulus K ₀?=?199(6) GPa at 1?bar and its pressure derivative K ₀′?=?5.0(6) for the NAL phase and K ₀?=?169(5) GPa and K ₀′?=?6.3(3) for the CF phase. These results indicate that the bulk modulus increases from 397 to 407 GPa across the phase transition from the NAL to CF phase at 43 GPa, where the NAL phase completely transforms into the CF phase on Na_0.4Mg_0.6Al_1.6Si_0.4O₄. Density also increases by 2.1?% across the phase transition.  相似文献   

An integrated analysis platform merging SuperDARN data within the THEMIS tool developed by ERG-Science Center (ERG-SC)     

Tomoaki Hori  Nozomu Nishitani  Yoshizumi Miyoshi  Yukinaga Miyashita  Kanako Seki  Tomonori Segawa  Keisuke Hosokawa 《极地研究(英文版)》2013,24(1)

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Comprehensive numerical analysis of fault‐structure systems – Computation of the large‐scale seismic structural response to a given earthquake scenario –     

T. Ichimura  M. Hori  P. E. Quinay  M. L. L. Wijerathne  T. Suzuki  S. Noguchi 《地震工程与结构动力学》2012,41(4):795-811

The seismic structural response is affected by temporal and spatial variations in strong ground motion. It can be evaluated through the fault‐structure system: the fault mechanism, wave propagation through the crust, amplification near the surface, and soil‐structure interaction. To analyze this system at high resolution and accuracy, we previously proposed a new multiscale analysis method and numerically verified its validity. However, the problem of the extremely large computation cost of constructing a three‐dimensional numerical model and solving the discretized governing equations still remains. Here, we introduce a new method to resolve these difficulties. By combining this new method with our multiscale analysis, we developed a tool for fault‐structure system analysis. The accuracy of this tool is verified by comparing it to a Green's function solution. Finally, we demonstrate the potential utility of the method by estimating the seismic response of a large and complex underground highway junction in a given earthquake scenario. Copyright © 2011 John Wiley & Sons, Ltd.  相似文献   

Geochemical and hydrological controls on biannual lamination of tufa deposits     

Tatsuya Kawai  Akihiro Kano  Masako Hori 《Sedimentary Geology》2009,213(1-2):41-50

Fluvial tufa deposits in southwest Japan commonly develop biannual lamination consisting of dense summer layers and porous winter layers, and the clearness of the laminae varies among the sites. The laminae have been largely attributed to a seasonally variable inorganic precipitation rate of calcite. This rate-controlled hypothesis was examined by using quantitative data for calcite packing-density (CPD) and the precipitation rate of calcite (PWP rate) calculated from water chemistry. The results for four tufa-depositing sites in SW Japan show that a positive correlation between CPD and PWP rate becomes less certain with increasing PWP rate. In the temperature realm of SW Japan, tufas develop regular distinct seasonal change in CPD when deposited in water containing Ca values less than 65 mg/l, which results in a relatively low precipitation rate. The CPD of tufa deposits rarely exceeds 65%, owing to pore space between fine-grained calcite crystals and to porosity derived from decomposed cyanobacteria and other microorganisms. By increasing the Ca content to more than 65 mg/l, the CPD often attains an upper limit and becomes insensitive to seasonal changes in the PWP rate. Therefore, seasonal variations in CPD at sites with a higher Ca content are unclear, as seen in two examples from tropical islands in southern Japan and in one locality in a temperate climate. The flow rate and microbial density on the tufa surface are subordinate factors with respect to the CPD. Seasonal changes in these two factors often enhance the porous/dense contrast of biannual lamination in SW Japan.  相似文献