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101.
102.
Toru Kouyama Takeshi Imamura Masato Nakamura Takehiko Satoh Yoshihumi Futaana 《Planetary and Space Science》2012,60(1):207-216
An improved cloud tracking method for deriving wind velocities from successive planetary images was developed. The new method incorporates into the traditional cross-correlation method an algorithm that corrects for erroneous cloud motion vectors by re-determining the most plausible correlation peak among all of the local maxima on the correlation surface by comparing each vector with its neighboring vectors. The newly developed method was applied to the Venusian violet images obtained by the Solid State Imaging system (SSI) onboard the Galileo spacecraft during its Venus flyby. Although the results may be biased by the choice of spatial scale of atmospheric features, the cloud tracking is the most practical mean of estimating the wind velocities with extensive spatial and temporal coverage. The two-dimensional distribution of the horizontal wind vector field over 5 days was obtained. It was found from these wind maps that the solar-fixed component in 1990 was similar to that in 1982 obtained by the Pioneer Venus orbiter. The deviation of the instantaneous zonal wind field from the solar-fixed component shows a distinct wavenumber-1 structure in the equatorial region. On the assumption that this structure is a manifestation of an equatorial Kelvin wave, the phase relationship between the zonal wind and the cloud brightness suggests a short photochemical lifetime of the violet absorber. The momentum deposition by this Kelvin wave, which is subject to radiative damping, would induce a westward mean-wind acceleration of ~0.3 m s?1 per Earth day. 相似文献
103.
Marine mammals in the past mass mortality events may have been susceptible to infection because their immune systems were suppressed through the bioaccumulation of environmental pollutants such as polychlorinated biphenyls (PCBs). We compiled mortality event data sets of 33 marine mammal species, and employed a Finely-Advanced Transboundary Environmental model (FATE) to model the exposure of the global fish community to PCB congeners, in order to define critical exposure levels (CELs) of PCBs above which mass mortality events are likely to occur. Our modelling approach enabled us to describe the mass mortality events in the context of exposure of higher-trophic consumers to PCBs and to identify marine pollution ‘hotspots’ such as the Mediterranean Sea and north-western European coasts. We demonstrated that the CELs can be applied to quantify a chemical pollution Planetary Boundary, under which a safe operating space for marine mammals and humanity can exist. 相似文献
104.
Hisafumi Asaue Taiki Kubo Toru Yoshinaga Katsuaki Koike 《Natural Resources Research》2012,21(3):383-393
Widespread definition of a groundwater system in three dimensions is necessary for the management and maintenance of groundwater resources. A magnetotelluric (MT) survey can be an effective geophysical prospecting method for imaging regional geological structures by measuring both shallow and deep resistivity. To demonstrate the capability of an MT survey to characterize a groundwater system, the Kumamoto area of central Kyushu in southwestern Japan was selected as a case study site because of its rich groundwater resources. Three-dimensional (3D) MT resistivity structure to a depth of 5?km was modeled by 1D inversion analysis of raw MT data and 3D interpolation of the resultant resistivity column data by the optimization principle method. Consequently, both deep and shallow aquifers were detected. A high-resistivity zone appears at depths between 500 and 2,000?m between the Futagawa?CHinagu faults and the Usuki?CYatsushiro tectonic line, which supports the existence of an aquiclude under the aquifer. The most important characteristic inferred from the 3D resistivity model is that the deep groundwater system below a depth of 1,000?m has two main flow paths. One path is likely to be through porous rocks because the low resistivity zone is regarded as tuff with sand and gravel, and the other flow path is interpreted to be through fractured zones along the Hinagu faults. Hence, the path and direction of the groundwater flows are probably controlled by geologic structures and the configuration of the active faults. These findings support the effectiveness of the MT method for investigating groundwater systems. 相似文献
105.
Junichi Nakajima Yusuke Tsuji Akira Hasegawa Saeko Kita Tomomi Okada Toru Matsuzawa 《Gondwana Research》2009,16(3-4):470-481
We estimate detailed three-dimensional seismic velocity structures in the subducting Pacific slab beneath Hokkaido, Japan, using a large number of arrival-time data from 6902 local earthquakes. A remarkable low-velocity layer with a thickness of ~ 10 km is imaged at the uppermost part of the slab and is interpreted as hydrated oceanic crust. The layer gradually disappears at depths of 70–80 km, suggesting the breakdown of hydrous minerals there. We find prominent low-velocity anomalies along the lower plane of the double seismic zone and above the aftershock area of the 1993 Kushiro-oki earthquake (M7.8). Since seismic velocities of unmetamorphosed peridotite are much higher than the observations, hydrous minerals are expected to exist in the lower plane as well as the hypocentral area of the 1993 earthquake. On the other hand, regions between the upper and lower planes, where seismic activity is not so high compared to the both planes, show relatively high velocities comparable to those of unmetamorphosed peridotite. Our observations suggest that intermediate-depth earthquakes occur mainly in regions with hydrous minerals, which support dehydration embrittlement hypothesis as a cause of earthquake in the subducting slab. 相似文献
106.
Naoki Uchida Satoshi Yui Satoshi Miura Toru Matsuzawa Akira Hasegawa Yoshinobu Motoya Minoru Kasahara 《Gondwana Research》2009,16(3-4):527-533
We analyzed small repeating earthquakes recorded over a 13-year period and GPS data recorded over an 8-month period to estimate interplate quasi-static slip associated with the 2003 Tokachi-oki earthquake (M8.0) and the 2004 off-Kushiro earthquake (M7.1). The repeating-earthquake analysis revealed that the slip rate near the source region of the Tokachi-oki earthquake was relatively low (< 5 cm/year) prior to the earthquake; however, in the last 3 years leading up to the event, a minor acceleration in slip occurred upon the deeper extension of the coseismic slip area of the earthquake. Repeating-earthquake and GPS data indicate that large amounts of afterslip occurred around the rupture area following the earthquake; the afterslip mainly propagated to the east of the coseismic slip area. We also infer that the occurrence of the 2004 off-Kushiro earthquake, located about 100 km northeast of the epicenter of the Tokachi-oki earthquake, was advanced by the afterslip associated with the Tokachi-oki earthquake. 相似文献
107.
Calorimetric measurements of fusion enthalpies for Ni2SiO4 and Co2SiO4 olivines were carried out using a high-temperature calorimeter, and Ni and Co partitioning between olivine and silicate liquid was analyzed using the measured heats of fusion. The fusion enthalpy of Co2SiO4 olivine measured by transposed-temperature drop calorimetry was 103 ± 15 kJ/mol at melting point (1688 K). The fusion enthalpy of Ni2SiO4 olivine was calculated based on the enthalpies of liquids in the system An50Di50-Ni2SiO4 measured by transposed-temperature drop calorimetry at 1773 K, and was 221 ± 26 kJ/mol at its metastable melting point (1923 K). The fusion enthalpy of Ni2SiO4 is the largest among those of olivine group, this is caused by the large crystal field stabilization energy of six-coordinated Ni2+ in olivine. The larger fusion enthalpy of Ni2SiO4 can account for the large and variable partition coefficient of Ni between olivine and silicate liquid. Based on the comparison between partition coefficients calculated from thermodynamic data and those observed in partition experiments, it is considered that the magnitude of partition coefficients is primarily dependent on the heats of fusion of the components. Furthermore, the activity coefficients for Ni-, Co- and Mn-bearing components in magmatic liquid are nearly of the same magnitude. 相似文献
108.
Hiroshi Tateyama Susumu Shimoda Toshio Sudo 《Contributions to Mineralogy and Petrology》1978,66(2):149-156
In the system Na2CO3-MgO-SiO2-H2O a new sodium magnesium silicate was synthesized under hydrothermal conditions; 450–600 ° C and 300–1000 Kg/cm2. The structure of the specimen was determined by X-ray powder methods, and its properties were studied by chemical, infrared and TG analyses. The specimen has a triple chain structure (space group, C2/c) with the ideal chemical composition, 4 (Na2Mg4Si6O16(OH)2) and lattice parameters, a= 10.152(2), b=27.137(4), c=5.276(1) Å, and = 106.97(3) °.The essential feature of the structure is shown by the presence of SiO4 tetrahedra linked to form chains which have three times the width of those in pyroxene. These triple chains have a periodicity, 5.27 Å, along their lengths, and are bonded to each other laterally by the brucite layer made up by eight Mg cations and sandwiched between two inward pointing bands of tetrahedra. These units are linked back to back by cations (Mg or Na) in the Na(2) site and by a large cation (Na) at the Na(1) site. 相似文献
109.
The interaction between an isotropic protostellar wind and an ambient molecular cloud is investigated by two-dimensional hydrodynamic computations. The wind-cloud interaction model is promising for explanation of the observed properties of the Orion-KL Nebula.Paper presented at the IAU Third Asian-Pacific Regional Meeting, held in Kyoto, Japan, between 30 September–6 October, 1984. 相似文献
110.