Evaluations of subsurface flow for reconstructions of climate change using borehole temperature and isotope data in Kamchatka     

Akinobu Miyakoshi  Makoto Taniguchi  Yasukuni Okubo  Takeshi Uemura 《Physics of the Earth and Planetary Interiors》2005,152(4):335-342

Subsurface temperature is affected by heat advection due to groundwater flow and surface temperature changes. To evaluate their effects, it was implemented the measurements of temperature-depth profile (T-D profile) and the continuous monitoring of soil temperature in the southern part of Kamchatka which has not affected by human activity. Additionally, stable isotopic compositions of surface water and groundwater were analyzed. T-D profile and stable isotopic compositions show groundwater flow system is differ from the shallow aquifer to the deep aquifer. In the shallow aquifer, T-D profile suggests the existence of upward groundwater flux. On the other hand, the annual variation of soil temperature is divided into the large variation period (VP) and the stable period (SP) by the magnitude of daily and seasonal variation. VP and SP correspond to the summer and the winter season, respectively, and it considers that the difference between VP and SP is caused by the effect of snow cover. Therefore, the T-D profile is affected by not only upward groundwater flux but also the surface warming particularly in the summer season (VP).  相似文献   

Relationship between groundwater flow estimated by soil temperature and slope failures caused by heavy rainfall, Shikoku Island, southwestern Japan   总被引：2，自引：0，他引：2  

Gen Furuya  Akira Suemine  Kyoji Sassa  Takeshi Komatsubara  Naoki Watanabe  Hideaki Marui 《Engineering Geology》2006,85(3-4):332-346

Most of the slope failure disasters in a humid area such as that of Japan are caused by heavy rain. However, even for the case of heavy rainfall that occurs once in every 10 years, total area of slope failures seldom exceeds 10% of a watershed. From this background, we focused on the vein-like groundwater flows that increase pore-water pressure, and clarified the relationship between distributions of slope failures and groundwater veins. In this study, a 1-m-depth ground temperature survey and water-chemistry analyses at springs and boreholes were conducted in Zentoku area of Shikoku Island, southwestern Japan, to grasp the distribution of groundwater veins and their sources. Subsequently, slope-stability was analyzed to investigate the relationship between groundwater veins and slope failures at study sites. These results lead to the following conclusions: The slope failures appear to concentrate around shallow groundwater veins and groundwater veins rising from deep layers. This means that slope failures caused by these groundwater veins in addition to rainfall. Two types of groundwater originate in the deep layers: one has short storage time as indicated by the fact that dissolved substances are low; the other is stored for a lengthy period as noted by a high concentration of dissolved substances. By combining the results of stability analyses and distribution of groundwater veins, it is suggested that prediction of zones with high potential for slope failure can be more accurate.  相似文献   

Accurate Isotopic and Concentration Analyses of Small Amounts of Pb Using Isotope Dilution Coupled with the Double Spike Technique   总被引：1，自引：0，他引：1  

Takeshi Kuritani  Tomohiro Usui    Tetsuya Yokoyama  Eizo Nakamura 《Geostandards and Geoanalytical Research》2006,30(3):209-220

A new method has been developed for the simultaneous determination of Pb abundance and Pb isotopic composition with high precision and accuracy for small test portion masses by thermal ionisation mass spectrometry. In this method, a ²⁰⁵pb-²⁰⁴pb double spike is added to samples prior to the chemical separation of Pb, and the isotopic composition of the spike-sample mixture is determined rigorously by the double spike technique using a ²⁰⁷Pb-²⁰⁴Pb spike. The isotopic composition and concentration of Pb in the sample are then obtained by utilising the principle of isotope dilution. Using this technique, replicate determinations of Pb from NIST SRM 981 and GSJ JP-1 (peridotite; 0.07 μg g⁻¹ Pb) were performed. The measured concentration and isotopic data were identical, within uncertainty, to published data or to data that were determined independently in this study. The application of this method to U-Pb dating and the determination of the "initial" Pb isotopic composition was also tested. Lead isotopic compositions and the concentrations of Pb, Th and U were determined for a single batch of samples, through the addition of ²⁰⁵pb-²⁰⁴pb, ²³⁰Th and ²³⁵U spikes to samples prior to chemical separation. Also in these experiments, we confirmed that this routine gives accurate data for Pb, Th and U concentrations and Pb isotopic compositions.  相似文献   

A lower trophic ecosystem model including iron effects in the Okhotsk Sea     

Takeshi Okunishi  Michio J. Kishi  Yukiko Ono  Toshihiko Yamashita 《Continental Shelf Research》2007

We applied a three-dimensional ecosystem-physical coupled model including iron the effect to the Okhotsk Sea. In order to clarify the sources of iron, four dissolved iron compartments, based on the sources of supply, were added to Kawamiya et al.'s [1995, An ecological-physical coupled model applied to Station Papa. Journal of Oceanography, 51, 635-664] model (KKYS) to create our ecosystem model (KKYS-Fe). We hypothesized that four processes supply iron to sea water: atmospheric loadings from Northeastern Asia, input from the Amur River, dissolution from sediments and regeneration by zooplankton and bacteria. We simulated one year, from 1 January 2001 to 31 December 2001, using both KKYS-Fe and KKYS. KKYS could not reproduce the surface nitrate distribution after the spring bloom, whereas KKYS-Fe agreed well with observations in the northwestern Pacific because it includes iron limitation of phytoplankton growth. During the spring bloom, the main source of iron at the sea surface is from the atmosphere. The contribution of riverine iron to the total iron utilized for primary production is small in the Okhotsk Sea. Atmospheric deposition, the iron flux from sediment and regeneration of iron in the water column play important roles in maintaining high primary production in the Okhotsk Sea.  相似文献   

Discrete‐like crack simulation by smeared crack‐based FEM for reinforced concrete     

Yuichi Sato  Kazuhiro Naganuma 《地震工程与结构动力学》2007,36(14):2137-2152

A numerical process that simulates crack propagation in reinforced concrete through post‐crack stress redistribution is presented. This process is developed within the context of the smeared crack approach. Continuity and orientation of the reinforcing bar components are automatically recognized in the pre‐processing stage. The process explicitly outputs crack widths by computing the bond slips along reinforcement, without imposing any additional nodes between the reinforcement and concrete. The process is incorporated with a finite element algorithm, and the validation is investigated through sample 3D static analyses of nine concrete specimens subjected to monotonic shear and flexure loads. These specimens contain relatively well‐distributed steel bars and fiber reinforced polymer (FRP) sheets of reinforcement ratio from 0.11 to 0.57%. The analyses predict the crack patterns and crack widths well, although some disagreements are found between the test and the analysis results. The proposed process outputs discrete, continuous in crack directions, and element boundary‐free crack patterns. Copyright © 2007 John Wiley & Sons, Ltd.  相似文献   

Geochemistry of Sulfide Chimneys and Basement Pillow Lavas at the Southern Mariana Trough (12.55°N–12.58°N)     

Takeshi Kakegawa    Motoo Utsumi  Katsumi Marumo 《Resource Geology》2008,58(3):249-266

Three submarine hydrothermal sites (Snail, Y and Pika sites) in the southern Mariana area were investigated to clarify the geochemical difference between off-axis and on-axis submarine hydrothermal activities and volcanic rocks. The Snail and Y sites are located on the axis of the spreading ridge, and the Pika site is located on the off-axis region. Low-temperature venting of submarine hydrothermal fluids was observed at the Snail and Y sites. High-temperature black smoker activities were found at the Pika site. For further geochemical study, sulfide chimneys and mounds were collected from each site by manned submersible Shinkai 6500 . Basement short drill cores of volcanic rocks and sulfides were also obtained from the Snail and Pika sites using a multi-coring system. All drilled pillow lavas were tholeiitic andesite with a narrow range of chemical variation. Significant enrichments of Rb, Ba and Th were absent in both on-axis (Y and Snail sites) and off-axis (Pika site) samples, suggesting the least incorporation of subducting sediments to the magmatic system. Concentrations of Au and Ag in the sulfide chimney were within the range of massive sulfides at the mid-ocean ridge rather than typical arc-type massive sulfides. It is found that sulfur isotope compositions of sulfides were different between the on-axis and off-axis samples: on-axis samples had heavy δ³⁴S (+2.9–+8.7‰) and off-axis samples (–0.3 to +3.8‰) were similar to the local magmatic value. Such a regional difference probably results from changes of deep hydrothermal processes during the water–rock interaction rather than differences in tectonic settings.  相似文献   

Petrology of peridotite and garnet clinopyroxenite of the Mt. Higasi-Akaisi mass,central Sikoku,Japan — Subsolidus relation of anhydrous phases     

Takeshi Mori  Shohei Banno 《Contributions to Mineralogy and Petrology》1973,41(4):301-323

The mineralogy of anhydrous minerals of peridotite and garnet clinopyroxenite of the Mt. Higasi-Akaisi peridotite mass, Japan, is described. The subsolidus equilibria among garnet, clinopyroxene, orthopyroxene and olivine are discussed in terms of composition range of solid solutions and of Fe-Mg partition. It is concluded that the anydrous minerals of this mass equilibrated at lower temperatures than any of well studied peridotite-garnet clinopyroxenite association. The tentative estimation gives 5–600° C and 7–13 Kb as the physical conditions of equilibration. Comparison with similar associations from other occurrences and geological implications are briefly discussed.  相似文献   

A Study on Confined Flow of Ground Water Through a Tunnel     

Takeshi Chisyaki 《Ground water》1984,22(2):162-167

Confined flow of ground water through a tunnel, which might be encountered in tunneling under the bottom of a sea or river, is numerically analyzed by a reductive finite element method formulated in our research. That is, the rate and potential distribution of the confined flow of ground water through an opening are obtained in connection with the permeability of rock masses, the thickness of covered ground, the location of impermeable bedrock, and other variables. In addition, flow through an opening in the ground with highly permeable masses and discharge of ground water through a tunnel in grouted masses are illustrated, and some useful results for the practical application of tunneling work are obtained.  相似文献   

Influence of Indian Ocean Dipole and Pacific recharge on following year’s El Niño: interdecadal robustness   总被引：1，自引：1，他引：0  

Takeshi Izumo  Matthieu Lengaigne  Jérôme Vialard  Jing-Jia Luo  Toshio Yamagata  Gurvan Madec 《Climate Dynamics》2014,42(1-2):291-310

The Indian Ocean Dipole (IOD) can affect the El Niño–Southern Oscillation (ENSO) state of the following year, in addition to the well-known preconditioning by equatorial Pacific Warm Water Volume (WWV), as suggested by a study based on observations over the recent satellite era (1981–2009). The present paper explores the interdecadal robustness of this result over the 1872–2008 period. To this end, we develop a robust IOD index, which well exploits sparse historical observations in the tropical Indian Ocean, and an efficient proxy of WWV interannual variations based on the temporal integral of Pacific zonal wind stress (of a historical atmospheric reanalysis). A linear regression hindcast model based on these two indices in boreal fall explains 50 % of ENSO peak variance 14 months later, with significant contributions from both the IOD and WWV over most of the historical period and a similar skill for El Niño and La Niña events. Our results further reveal that, when combined with WWV, the IOD index provides a larger ENSO hindcast skill improvement than the Indian Ocean basin-wide mode, the Indian Monsoon or ENSO itself. Based on these results, we propose a revised scheme of Indo-Pacific interactions. In this scheme, the IOD–ENSO interactions favour a biennial timescale and interact with the slower recharge-discharge cycle intrinsic to the Pacific Ocean.  相似文献   

Anomalously large seismic amplifications in the seafloor area off the Kii peninsula     

Takeshi Nakamura  Masaru Nakano  Naoki Hayashimoto  Narumi Takahashi  Hiroshi Takenaka  Taro Okamoto  Eiichiro Araki  Yoshiyuki Kaneda 《Marine Geophysical Researches》2014,35(3):255-270

Seismic wave amplifications were investigated using strong-motion data obtained from the ground’s surface (K-net) on the Kii peninsula (southwestern Japan) and from the network of twenty seismic stations on the seafloor (DONET) located off the peninsula near the Nankai trough. Observed seismograms show that seismic signals at DONET stations are significantly larger than those at K-net stations, independent of epicentral distances. In order to investigate the cause of such amplifications, seismic wavefields for local events were simulated using the finite-difference method, in which a realistic 3D velocity structure in and around the peninsula was incorporated. Our simulation results demonstrate that seismic waves are significantly amplified at DONET stations in relation to the presence of underlying low-velocity sediment layers with a total thickness of up to 10 km. Our simulations also show considerable variations in the degree of amplification among DONET stations, which is attributed to differences in the thickness of the sediment layers. The degree of amplification is relatively low at stations above thin sediment layers near the trough axis, but seismic signals are much more amplified at stations closer to the Kii peninsula, where sediment layers are thicker than those at the trough axis. Simulation results are consistent with observations. This study, based on seafloor observations and simulations, indicates that because seismic signals are amplified due to the ocean-specific structures, the magnitude of earthquakes would be overestimated if procedures applied to data observed at land stations are used without corrections.  相似文献