Monitoring Velocity Changes Caused By Underground Coal Mining Using Seismic Noise     

Rafał Czarny  Henryk Marcak  Nori Nakata  Zenon Pilecki  Zbigniew Isakow 《Pure and Applied Geophysics》2016,173(6):1907-1916

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Erratum to “Environmental control of short-term variation in the plankton community of inner Tokyo Bay, Japan” [Estuar., Coast. Shelf Sci. 78 (2008) 796–810]     

Toru Nakane  Kisaburo Nakata  Heather Bouman  Trevor Platt 《Estuarine, Coastal and Shelf Science》2008,80(4):598

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Multiple‐indicator study of groundwater flow and chemistry and the impacts of river and paddy water on groundwater in the alluvial fan of the Tedori River,Japan          下载免费PDF全文

Yumi Iwasaki Yoshioka  Kimihito Nakamura  Takanori Nakano  Haruhiko Horino  Ki‐Cheol Shin  Satoko Hashimoto  Shigeto Kawashima 《水文研究》2016,30(16):2804-2816

To investigate the source, flow paths, and chemistry of rich resources of high‐quality, shallow groundwater in the alluvial fan between the Tedori and Sai rivers in central Japan, we analysed stable isotope ratios of H, O, and Sr and concentrations of major dissolved ions and trace elements in groundwater, river water, and paddy water. The ⁸⁷Sr/⁸⁶Sr ratios of the groundwater are related to near‐surface geology: groundwater in sediment from the Tedori River has high ⁸⁷Sr/⁸⁶Sr ratios (>0.711), whereas that from the Sai River in the north of the fan has low ⁸⁷Sr/⁸⁶Sr ratios (<0.711). δ²H and δ¹⁸O values and ⁸⁷Sr/⁸⁶Sr ratios indicate that groundwater in the central and southern fans is recharged by the Tedori River, whereas recharge in the north is from the Sai River. Mg²⁺, Ca²⁺, Sr²⁺, HCO₃^?, and SO₄^2? concentrations and δ²H and δ¹⁸O values in the groundwater are high in the central fan and, except for the northern area, tend to increase with distance from the Tedori River. There are linear relationships between ⁸⁷Sr/⁸⁶Sr ratio and the reciprocal concentrations of Sr²⁺, Mg²⁺, and Ca²⁺. These geochemical characteristics suggest that as groundwater recharged from the Tedori River flows towards the central fan, it mixes with waters derived from precipitation and paddy water that have become enriched in these components during downward infiltration. These results are consistent with our hydrological analysis and numerical simulation of groundwater flow, thus verifying the validity of the model we used in our simulation of groundwater flow. Copyright © 2016 John Wiley & Sons, Ltd.  相似文献   

Characteristics of the response of isothermal atmospheres with nonlinear waves     

Yasuo Tanaka  Michinori Nakata  Mine Takeuti 《地球物理与天体物理流体动力学》2013,107(2):145-159

Abstract

We have studied the behavior of nonlinear waves in isothermal atmospheres using an improved beam scheme method. It is shown that although the magnitude of the mass leakage due to side beams is significant, nevertheless in a motion close to hydrostatic equilibrium it can be suppressed, if special density distributions and/or suitable mesh intervals are selected. We adopt as the parameters for our model of the atmospheres M=1 M[odot], R=50 R[odot] and T=4864 K. The time variation of the physical quantities in each cell is found for several oscillation periods. The critical frequency for the model atmosphere in the case of waves with a weak nonlinearity seems to be consistent with that in the linear theory.  相似文献   

Near Real－Time Calculation of Ionospheric Electric Fields and Currents Using GEDAS     

H.Shirai  Y.Kamide  E.A.Kihn  B.Hausman  M.Shinohara  H.Nakata  M.Isowa  T.K.Takada  Y.Watanabe  S.Masuda 《中国天文和天体物理学报》2003,3(4):375-380

This paper presents the recent progress in our project of estimating near real-time electric fields and currents in the ionosphere through our computer system called the Geospace Environment Data Analysis System (GEDAS). We show a new technique in which data from ground magnetometers are collected by the system and used as input for the KRM and AMIE programs to calculate the distribution of ionospheric electric fields and currents, as well as of other ionospheric parameters, such as electric potential patterns. One of the goals of this project is to specify ionospheric processes. Examples of the near real-time calculation and the data flow of our scheme are presented.  相似文献   

Calcium and Magnesium‐bearing Sabugalite from the Tono Uranium Deposit,Central Japan     

Masataka Nakata  Eiji Sasao  Kosei Komuro 《Resource Geology》2013,63(4):404-411

Calcium and magnesium‐bearing sabugalite occurs as aggregations of yellowish platy crystals in veinlets or druses in conglomerate from the oxidized parts of the Tono uranium deposit, Central Japan. X‐ray powder diffractometry of this mineral has reflections consistent with previous powder diffraction data of sabugalite. It is included in the monoclinic system with space group C2/m and calculated cell parameters of a = 19.68Å, b = 9.89Å, c = 9.82Å α = γ = 90°, β‐96.93° and V = 1897.83ų. Chemical analysis yields a formula of (Ca_0.10 Mg_0.09)_Σ0.19Al_0.53(UO₂)_2.04((PO₄)_1.99(AsO₄)_0.01)_Σ2.00·11.22H₂O. EMPA mapping shows that the mineral is compositionally uniform with no micron‐scale layering. Charge of cations including Ca and Mg in the cation‐H₂O layer is 1.98 being identical to that of autunite group minerals. This suggests that the charge balance in the cation‐H₂O layer of the mineral could be made by the alkaline earth or alkaline elements rather than by hydrogen ions.  相似文献   

Reproducibility of spatial and temporal distribution of aseismic slips in Hyuga-nada of southwest Japan     

Ryoko Nakata  Shin’ichi Miyazaki  Mamoru Hyodo  Takane Hori 《Marine Geophysical Researches》2014,35(3):311-317

The Hyuga-nada region of southwest Japan, which is located off the east coast of Kyushu Island, may have the potential to generate great interplate earthquakes along the Nankai trough in the future. In this area, thrust earthquakes of M = 6.7–7.2 have occurred with recurrence intervals of approximately 30 years. In association with these earthquakes, possible local heterogeneities of plate coupling may be expected within 100 km from the coast in the Hyuga-nada region. We investigate numerical experiments to determine the spatial and temporal resolution of slip on the plate interface beneath the Hyuga-nada offshore region. For this purpose, we calculated synthetic displacement data from the result of numerical simulation conducted for the afterslip following an M_w 6.8 earthquake, for existing global positioning system stations on land and planned ocean floor seismic network stations. The spatial and temporal distribution of fault slip is then estimated using a Kalman filter-based inversion. The slip distribution estimated by using ocean floor stations demonstrates that the heterogeneity of plate coupling is resolved approximately within 50 km from the coastal area. This heterogeneity corresponds to the coseismic area of an M_w 6.8 earthquake with a radius of 10 km. Our study quantitatively evaluates the spatial resolution of aseismic slip in the Hyuga-nada region. Analysis based on continuous ocean floor data is useful for resolving the spatial variations of heterogeneities in plate couplings.  相似文献   

Microbial community respiration and structure of dead zone sediments of Omura Bay, Japan   总被引：1，自引：0，他引：1  

Minoru Wada  Shotaro Suzuki  Tadashi Nara  Yu Umezawa  Motohiro Shimanaga  Kazumi Matsuoka  Hideaki Nakata 《Journal of Oceanography》2012,68(6):857-867

Monitoring sediment microbial community metabolism and structure is instrumental to understanding biogeochemical processes in and ecological impacts on bottom environments. The aim of this study was to determine potential community respiration and to reveal community dynamics of the microorganisms in the dead zone sediments of Omura Bay, Japan. The bay is highly enclosed and develops severe hypoxia in the central regions every summer. We collected sediment core samples from the center of the bay during hypoxia, estimated sediment oxygen consumption by using an adapted in vivo electron transport system activity (in vivo ETSA) assay, enumerated abundance of bacteria, and analyzed bacterial community structure by automated ribosomal intergenic spacer analysis. Higher ETSA and bacterial diversity were found in upper sediments (within 3?cm depth) from the center than the fringe of the bay. Sediment bacterial community structure of the bay center was distinct from that of the fringe. From these results, upper sediment in the dead zone of Omura Bay was characterized by (1) greater community respiration and (2) greater diversity of bacterial components compared with the non-hypoxic sediment of the bay fringe. These characteristics have important implications for understanding the interaction between microbial communities and the development of hypoxia in Omura Bay.  相似文献   

A Numerical Simulation of the Seasonal Cycle of Temperature, Salinity and Velocity Fields in Tokyo Bay     

Fumio Horiguchi  Joji Yamamoto  Kisaburo Nakata 《Marine pollution bulletin》2001,43(7-12):145-153

To understand when oxygen-depleted waters occur, how they develop and when they dissipate in inner Tokyo Bay, realistic simulations were attempted with fine spatial and temporal resolution by applying realistic time dependent external forcing. A 3D hydrodynamic model was driven by time-dependent external forcing factors/parameters such as solar radiation, air temperature, relative humidity, wind velocity, and fluvial discharge, under the open boundary conditions of 1995. A simulated time series of salinity and temperature agreed fairly well with observed data, except in summer. The model failed to reproduce the development of the surface mixed layer in summer. Several sensitivity analyses on the external forcing parameters such as wind velocity and vertical diffusivity were conducted to reproduce the mixed layer. However, changing these parameter values did not improve the model results.  相似文献   

Interannual Changes of the Winter to Early Spring Biomass and Composition of Mesozooplankton in the Kuroshio Region in Relation to Climatic Factors     

Kaoru Nakata  Sachiko Koyama 《Journal of Oceanography》2003,59(2):225-234

Interannual variations of biomass of major mesozooplankton groups (Cnidaria, Chaetognatha, Copepoda, Crustacea other than copepods, Tunicata) in the January to March period were examined in the slope, Kuroshio and offshore waters off the Pacific coast of western Japan (western region) from 1971 to 1988 and off central Japan (central region) from 1971 to 1989. The mean biomass for each year of most of the mesozooplankton groups was high in the early 1970s and tended to decrease (in the western region) or to have dropped to a lower level (in the central region) after the mid-1970s. Stepwise multiple linear regression analyses of the mean biomass for each year of each mesozooplankton group in the Kuroshio in both regions against climatic factors revealed that the biomass was related positively to wind speed. It is therefore considered that the nutrient supply to the upper layers limits the production of many of the mesozooplankton groups examined in the Kuroshio, even in winter. Similar relationships were also found for the biomass of Copepoda, non-copepod Crustacea and Tunicata in the offshore water in the western region. The percentage of copepods in the biomass in the central region seemed to decrease under high water temperature conditions, while that of Chaetgnatha tended to increase. Climatic factors thus largely influenced the interannual variations of biomass and composition of mesozooplankton in and near the Kuroshio during the winter to early spring period. This revised version was published online in July 2006 with corrections to the Cover Date.  相似文献