Characterization of Magnetically Zoned Pluton, Tsushima, Japan     

Nobutaka SHIMADA  Youichi OHYAMA  Hiroaki IKEMI 《Resource Geology》2000,50(1):65-73

Abstract: Systematic measurements of magnetic susceptibility were carried out at the outcrops of the Uchiyama granitic pluton, Tsushima Islands. The pluton consists of hornblende-biotite granodiorite and biotite granite. It intrudes concordantly along an anticline axis of the Taishu Group in middle Miocene (16. 10. 5 Ma), and crops out in five areas. The results show that the low magnetic susceptibility facies (LM–facies, <100A-10^-6 emu/g) always occurs in the peripheral part of the pluton, while the high magnetic susceptibility facies (HM–facies, > 250 A 10^-6 emu/g) occupies the core through the medium magnetic susceptibility zone (MM–facies). It is pointed out that the pluton forms a magnetic zoning within a single plutonic body.
Chemical compositions of the granitoids show no conspicuous differences in major elements among the LM–, MM–, and HM–facies. Biotites from the LM–, MM–, and HM-facies also indicate uniform compositions with Fe/(Fe+Mg)=0. 6.
The pluton is principally surrounded by black mudstones of the Lower Formation of the Taishu Group, which is deltaic to shallow sea sediments of the Eocene to early Miocene age, and the carbon contents in them were analyzed. The analyses show that carbon was mostly decomposed and lost in the hornfels zone, while mudstones in the non-hornfels zone usually contain 0. 5 to 0. 7 % C.
From these facts, it is concluded that the magnetically zoned pluton at Tsushima was formed by an external volatile buffer system such as CH₄–CO₂ during the solidifying magma process.  相似文献   

Forces acting on bridge abutments over liquefied ground     

Akihiro Takahashi  Hideki Sugita  Shunsuke Tanimoto 《Soil Dynamics and Earthquake Engineering》2010

Large earthquake-induced displacements of a bridge abutment can occur, when the bridge is built on a floodplain or reclaimed area, i.e., liquefiable ground, and crosses a water channel. Seismic responses of a bridge abutment on liquefiable ground are the consequence of complex interactions between the abutment and surrounding soils. Therefore identification of the factors dominating the abutment response is important for the development of simplified seismic design methods. This paper presents the results of dynamic three-dimensional finite element analyses of bridge abutments adjacent to a river dike, including the effect of liquefaction of the underlying ground using earthquake motions widely used in Japan. The analysis shows that conventional design methods may underestimate the permanent abutment displacements unless the following two items are considered: (1) softening of the soil beneath the liquefiable layer, due to cyclic shearing of the soil surrounding the piles, and (2) the forces acting on the side faces of the abutment.  相似文献   

Intercomparisons of Experimental Convective Heat Transfer Coefficients and Mass Transfer Coefficients of Urban Surfaces     

Aya?HagishimaEmail author  Jun?Tanimoto  Ken-ich?Narita 《Boundary-Layer Meteorology》2005,117(3):551-576

The convective heat transfer coefficient (CHTC) of an urban canopy is a crucial parameter for estimating the turbulent heat flux in an urban area. We compared recent experimental research on the CHTC and the mass transfer coefficient (MTC) of urban surfaces in the field and in wind tunnels. Our findings are summarised as follows.

(1)	In full-scale measurements on horizontal building roofs, the CHTC is sensitive to the height of the reference wind speed for heights below 1.5 m but is relatively independent of roof size.
(2)	In full-scale measurements of vertical building walls, the dependence of the CHTC on wind speed is significantly influenced by the choice of the measurement position and wall size. The CHTC of the edge of the building wall is much higher than that near the centre.
(3)	In spite of differences of the measurement methods, wind-tunnel experiments of the MTC give similar relations between the ratio of street width to canopy height in the urban canopy. Moreover, this relationship is consistent with known properties of the flow regime of an urban canopy.
(4)	Full-scale measurements on roofs result in a non-dimensional CHTC several tens of times greater than that in scale-model experiments with the same Reynolds number.

Although there is some agreement in the measured values, our overall understanding of the CHTC remains too low for accurate modelling of urban climate.  相似文献   

Inversion of the HZ ratio of microseisms for S-wave velocity in the crust   总被引：1，自引：1，他引：1  

T. Tanimoto  C. Alvizuri 《Geophysical Journal International》2006,165(1):323-335

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Seasonality in particle motion of microseisms   总被引：5，自引：0，他引：5  

T. Tanimoto  S. Ishimaru  C. Alvizuri 《Geophysical Journal International》2006,166(1):253-266

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Teleseismic surface wave study for S-wave velocity structure under an array: Southern California   总被引：2，自引：0，他引：2  

K. Prindle  T. Tanimoto 《Geophysical Journal International》2006,166(2):601-621

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