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31.
ACTIVE system for monitoring volcanic activity: A case study of the Izu-Oshima Volcano,Central Japan
Hisashi Utada Yuji Takahashi Yuichi Morita Takao Koyama Tsuneomi Kagiyama 《Journal of Volcanology and Geothermal Research》2007
A system is proposed for the monitoring of changes in the underground structure of an active volcano over time by applying a transient electromagnetic method. The monitoring system is named ACTIVE, which stands for Array of Controlled Transient-electromagnetics for Imaging Volcano Edifice. The system consists of a transmitter dipole used to generate a controlled transient electromagnetic (EM) field and an array of receivers used to measure the vertical component of the transient magnetic field at various distances, with automatic operation of both units. In order to verify the performance of the proposed system, numerical and field experiments were carried out by application of the system to the Izu-Oshima volcano, where a remarkable change in the apparent DC resistivity over time had been detected in association with the eruption in 1986. 相似文献
32.
1 IntroductionSalinization is one of the major problems in arid and semi-arid regions in relation to land use and in particular to agricultural production[1]. Excessive salinity leads to toxicity in crops and reduction of the availability of water to crops, by reducing the osmotic potential of the soil solution[2]. Movement of soil water induces solute transport, and solutes are transferred towards the ground surface by the upward soil-water movement caused by evaporation, resulting in an accu… 相似文献
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34.
ObservationandresearchonULFandVLFseismo-electromagneticradiationJIA-ZHIYUAN(袁家治);KozoTakahashi;SHU-QINGQIAN(钱书清),YokioFujinaw... 相似文献
35.
36.
Fog and rain water chemistry at Mt. Fuji: A case study during the September 2002 campaign 总被引:2,自引:0,他引:2
Koichi Watanabe Yusaku Takebe Nobuhiro Sode Yasuhito Igarashi Hiroshi Takahashi Yukiko Dokiya 《Atmospheric Research》2006,82(3-4):652
Measurements of fog and rain water chemistry at the summit of Mt. Fuji, the highest peak in Japan, as well as at Tarobo, the ESE slope of Mt. Fuji in September 2002. The pH of fog and rain water sampled at Mt. Fuji varied over a range of 4.0–6.8. Acidic fogs (pH < 5.0) were observed at the summit when the air mass came from the industrial regions on the Asian continent. The ratio of [SO42−]/[NO3−] in the fog water was lower at Tarobo than at the summit. High concentrations of Na+ and Cl− were determined in the rain water sampled at the summit, possibly because of the long-range transport of sea-salt particles raised by a typhoon through the middle troposphere. The vertical transport of sea-salt particles would influence the cloud microphysical properties in the middle troposphere. Significant loss of Mg2+ was seen in the rain water at the summit. The concentrations of peroxides in the fog and rain water were relatively large (10–105 μM). The potential capacity for SO2 oxidation seems to be strong from summer to early autumn at Mt. Fuji. The fog water peroxide concentrations displayed diurnal variability. The peroxide concentrations in the nighttime were significantly higher than those in the daytime. 相似文献
37.
Yoko Tsushima S. Emori T. Ogura M. Kimoto M. J. Webb K. D. Williams M. A. Ringer B. J. Soden B. Li N. Andronova 《Climate Dynamics》2006,27(2-3):113-126
We have conducted a multi-model intercomparison of cloud-water in five state-of-the-art AGCMs run for control and doubled carbon dioxide climates. The most notable feature of the differences between the control and doubled carbon dioxide climates is in the distribution of cloud-water in the mixed-phase temperature band. The difference is greatest at mid and high latitudes. We found that the amount of cloud ice in the mixed phase layer in the control climate largely determines how much the cloud-water distribution changes for the doubled carbon dioxide climate. Therefore evaluation of the cloud ice distribution by comparison with data is important for future climate sensitivity studies. Cloud ice and cloud liquid both decrease in the layer below the melting layer, but only cloud liquid increases in the mixed-phase layer. Although the decrease in cloud-water below the melting layer occurs at all latitudes, the increase in cloud liquid in the mixed-phase layer is restricted to those latitudes where there is a large amount of cloud ice in the mixed-phase layer. If the cloud ice in the mixed-phase layer is concentrated at high latitudes, doubling of carbon dioxide might shift the center of cloud water distribution poleward which could decrease solar reflection because solar insolation is less at higher latitude. The magnitude of this poleward shift of cloud water appears to be larger for the higher climate sensitivity models, and it is consistent with the associated changes in cloud albedo forcing. For the control climate there is a clear relationship between the differences in cloud-water and relative humidity between the different models, for both magnitude and distribution. On the other hand the ratio of cloud ice to cloud-water follows the threshold temperature which is determined in each model. Improved measurements of relative humidity could be used to constrain the modeled representation of cloud water. At the same time, comparative analysis in global cloud resolving model simulations is necessary for further understanding of the relationships suggested in this paper. 相似文献
38.
Aaron J. Beck Yoko Tsukamoto Antonio Tovar-Sanchez Miguel Huerta-Diaz Henry J. Bokuniewicz Sergio A. Sañudo-Wilhelmy 《Applied Geochemistry》2007
Seasonal (Spring and Summer 2002) concentrations of dissolved (<0.22 μm) trace metals (Ag, Al, Co, Cu, Mn, Ni, Pb), inorganic nutrients (NO3, PO4, Si), and DOC were determined in groundwater samples from 5 wells aligned along a 30 m shore-normal transect in West Neck Bay, Long Island, NY. Results show that significant, systematic changes in groundwater trace metal and nutrient composition occur along the flowpath from land to sea. While conservative mixing between West Neck Bay water and the groundwaters explains the behavior of Si and DOC, non-conservative inputs for Co and Ni were observed (concentration increases of 10- and 2-fold, respectively) and removal of PO4 and NO3 (decreases to about half) along the transport pathway. Groundwater-associated chemical fluxes from the aquifer to the embayment calculated for constituents not exhibiting conservative behavior can vary by orders of magnitude depending on sampling location and season (e.g. Co, 3.4 × 102– 8.2 × 103 μmol d−1). Using measured values from different wells as being representative of the true groundwater endmember chemical composition also results in calculation of very different fluxes (e.g., Cu, 6.3 × 103 μmol d−1 (inland, freshwater well) vs. 2.1 × 105 μmol d−1(seaward well, S = 17 ppt)). This study suggests that seasonal variability and chemical changes occurring within the subterranean estuary must be taken into account when determining the groundwater flux of dissolved trace metals and nutrients to the coastal ocean. 相似文献
39.
Poisson's ratios of the upper and lower crust and the sub-Moho mantle beneath central Honshu, Japan, are investigated using three independent methods that are based on S to P ratios of apparent velocities, the Wadati diagrams and an inversion of P and S arrivals. Shallow earthquakes at distances of 200—500 km from the Nagoya University Telemeter Network are used for the apparent velocity ratio method. Crustal and subcrustal earth-quakes under the network are used for the other two methods. The network consists of wide-band seismometers with three components which are particularly suitable for detecting S waves. The three different methods give a consistent result for Poisson's ratio σ, that is, (1) σ = 0.23 ± 0.01 in the upper crust, (2) σ = 0.26−0.28 in both the lower crust and in the sub-Moho mantle. The result indicates a sharp contrast in σ between the upper and the lower crust rather than at the Moho. The low σ in the upper crust can only be explained by the presence of a substantial amount of free quartz, indicating granitic rocks. A higher σ in the lower crust suggests that this portion is presumably less saturated in silica and may be even undersaturated, pointing to intermediate to mafic rocks. The sub-Moho σ is almost equal to the σ averaged over the entire upper mantle that has been estimated from the Wadati diagrams of deep shocks beneath Japan but is higher than those calculated from Pn and Sn velocities in oceanic and stable continental regions. 相似文献
40.
Partitioning of Ni2+, Co2+, Fe2+, Mn2+ and Mg2+ between olivine and silicate melts: compositional dependence of partition coefficient 总被引:1,自引:0,他引:1
Eiichi Takahashi 《Geochimica et cosmochimica acta》1978,42(12):1829-1844
Partitioning of Ni2+, Co2+, Fe2+, Mn2+ and Mg2+ between olivine and silicate melts has been determined near the join (Mg0.5·-Fe0.5)2SiO4-K2O 4SiO2 and for seven different basaltic compositions. The experiments were made at 1 atm total pressure, 1500-1100°C, and under moderate to reducing oxygen fugacities. The concentration factor, defined as KMO = (MO)ol/(MO)liq (molar ratio), increases markedly for all the cations studied as the olivine component of the liquid decreases. Much of the increase in KMO is considered as due to the compositional effect of the coexisting liquid: the temperature effect on KMO is probably opposite to the compositional effect (KMO decreases as temperature decreases).The partition coefficient KMO-MgO = (MO/MgO)ol/(MO/MgO)liq for the reaction, Mol2+ + Mgliq2+ = Mliq2+ + Mgol2+. is relatively constant over a wide range of SiO2 content of the liquid, except in the case of Ni2+. The partition coefficients have similar ranges both in synthetic and natural rock systems: KNiO-MgO = 1.8–3.0, KCoO-MgO = 0.6–0.8, KFeO-MgO = 0.27–0.38, and KMnO-MgO = 0.23–0.32. There is a systematic variation in the partition coefficient KMO-MgO with the composition of liquid; KMO-MgO increases with increasing SiO2 content of melt. The partition coefficients for Co2+, Fe2+ and Mn2+ are useful to test the equilibration of olivine with magma of a wide compositional range. 相似文献