Age and growth of John Dory, Zeus faber (Linnaeus, 1758), in the East China Sea     

Yoneda  Michio; Yamasaki  Shunji; Yamamoto  Keisuke; Horikawa  Hiroshi; Matsuyama  Michiya 《ICES Journal of Marine Science》2002,59(4):749-756

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Variation in the thermohaline front at the mouth of Tokyo Bay     

Tetsuo Yanagi  Tetsuro Sanuki 《Journal of Oceanography》1991,47(4):105-110

The generation, variation, and disappearance of the thermohaline front at the mouth of Tokyo Bay were investigated using water temperature data obtained by a commercial ferry boat in 1987. The thermohaline front was generated south of Kan-non-zaki in mid November 1987 after the beginning of sea-surface cooling. It moved northward to Kan-non-zaki until the end of the year. The thermohaline front was most intense in February and March and disappeared in late March 1987 when sea-surface warming began.  相似文献   

Mathematical Derivation of Spatially-Averaged Momentum Equations for an Urban Canopy Model Using Underlying Concepts of the Immersed Boundary Method     

Takaaki Kono  Yasunobu Ashie  Tetsuro Tamura 《Boundary-Layer Meteorology》2010,135(2):185-207

We propose a new approach to derive spatially-averaged momentum equations for an urban canopy model that resolves buildings vertically and not horizontally. First, in order to mathematically describe the actual momentum field as a completely continuous field, the underling concepts of the immersed boundary method are employed, where we assume that (i) the entire simulation space, including that occupied by buildings, is filled with a fluid, and (ii) an external body force field exists that reduces the wind speed to zero at all positions coinciding with the space occupied by the buildings. Then, in order to obtain the required spatially-averaged momentum equations in a self-consistent manner, a spatial-averaging operation is applied to the Navier–Stokes equations that include a term representing the external force field. The applied spatial-averaging operation is equivalent to the conventional spatial filtering operation used in large-eddy simulations. To examine the significance of the subgrid-scale (SGS) stresses of the spatially-averaged momentum equations, a numerical simulation is performed for a flow around a regular array of cubical blocks with a grid resolution that is sufficient to resolve the blocks. By estimating the individual terms in the spatially-averaged momentum equations using the simulation results, we show that the SGS stresses contribute significantly to the spatially-averaged momentum budget, and therefore they should not be neglected in urban canopy modelling.  相似文献   

About This Issue: Kuroko Deposits Revisited after the Discovery of Their Modern Analogues on Submarine Arc Volcanoes     

Tetsuro Urabe  Hiroshi Kubota 《Resource Geology》2004,54(4):385-386

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Landslide and debris-flow hazard analysis and prediction using GIS in Minamata–Hougawachi area, Japan     

Chunxiang Wang  Tetsuro Esaki  Mowen Xie  Cheng Qiu 《Environmental Geology》2006,51(1):91-102

On July 20, 2003, following a short duration of heavy rainfall, a debris-flow disaster occurred in the Minamata–Hougawachi area, Kumamoto Prefecture, Japan. This disaster was triggered by a landslide. In order to assess the landslide and debris-flow hazard potential of this mountainous region, the study of historic landslides is critical. The objective of the study is to couple 3D slope-stability analysis models and 2D numerical simulation of debris flow within a geographical information systems in order to identity the potential landslide-hazard area. Based on field observations, the failure mechanism of the past landslide is analyzed and the mechanical parameters for 3D slope-stability analysis are calculated from the historic landslide. Then, to locate potential new landslides, the studied area is divided into slope units. Based on 3D slope-stability analysis models and on Monte Carlo simulation, the spots of potential landslides are identified. Finally, we propose a depth-averaged 2D numerical model, in which the debris and water mixture is assumed to be a uniform continuous, incompressible, unsteady Newtonian fluid. The method accurately models the historic debris flow. According to the 2D numerical simulation, the results of the debris-flow model, including the potentially inundated areas, are analyzed, and potentially affected houses, river and road are mapped.  相似文献   

Nankai Trough and Zenisu Ridge: a deep-sea submersible survey     

Xavier Le Pichon  Toshimishi Iiyama  Jacques Boulgue  Jacques Charvet  Michel Faure  Kenichi Kano  Siegfried Lallemant  Hakuyu Okada  Claude Rangin  Asahiko Taira  Tetsuro Urabe  Seiya Uyeda 《Earth and Planetary Science Letters》1987,83(1-4)

Eight submersible dives between 3000 and 4200 m water depth were made off southern Japan in the eastern Nankai subduction zone. Benthic communities associated with chemosynthetic processes were discovered along the 800 m wide active tectonic zone, at the toe of the accretionary prism. A benthic community was also discovered along a zone of active compression, at the foot of Zenisu Ridge, 30 km south of Nankai Trough. Temperature measurements within the sediments below the benthic communities confirm that upward motion of interstitial water occurs there. Studies of water samples indicate advection of methane and light hydrocarbons. Specimens of the benthic community have been shown to have included in their shells carbonate resulting from methane consumption. Thus the benthic communities are related to overpressure-driven fluid advection along tectonic zones with active surface deformation. A 300 m high active scarp at the toe of the accretionary prism is related to relative motion in a 280° direction which is close to the 305° average direction of subduction in this area. The dives establish further that compressive deformation is presently occurring at the foot of Zenisu Ridge. The previous interpretation of the Zenisu Ridge as a zone of recent north-south intraplate shortening, 40 km south of the Nankai Trench, is confirmed. We conclude that tectonic evolution might well lead to future detachment of the Zenisu Ridge and overthrusting of this large piece of oceanic crust over the continental margin. Such a process might be an efficient one to emplace ophiolites over continents.  相似文献   

Slake durability and mineralogical properties of some pyroclastic and sedimentary rocks   总被引：1，自引：0，他引：1  

Ganesh Dhakal  Tetsuro YonedaMasaji Kato  Katsuhiko Kaneko 《Engineering Geology》2002,65(1):31-45

Slake durability of rocks is an important property of rock-mass and rock-materials in geotechnical practice. The slake durability of rocks is closely related to their mineralogical composition. In this paper, mineralogical examinations and slake durability tests for argillaceous clastic rocks, especially pyroclastic rocks, sandstones and mudstones of Neogene Tertiary age from Japan, were performed in order to assess the slake durability and rock alteration process of these rocks as well as to understand the relationship between mineralogy and durability.The mineral composition and textural features of the rocks were studied by means of optical microscopy (OM), X-ray diffractometry (XRD), electron microprobe analysis (EPMA), and scanning electron microscopy (SEM). In addition, the slake durability test was carried out by using the standard testing method of ISRM [Int. J. Rock Mech. Min. Sci. 16 (1979) 148] in distilled water and in the aqueous solutions with dissolved electrolytes of NaCl and CaCl₂.The pyroclastic rocks and tuffaceous sandstone, rich in di-octahedral and tri-octahedral Fe smectite, respectively, show distinctively different slaking behaviors. The pyroclastic rocks show relatively high slaking (Id₂=55.5% and Id₁₀=10.5%) than the tuffaceous sandstone (Id₂=94.1% and Id₁₀=87.8%, refer to text for Id₂ and Id₁₀). This difference in the slake durability observed in these rocks is due to the microscopic occurrences of smectite present in the interspaces between the particles (pyroclastic rocks) and zeolite cementing the interspaces (tuffaceous sandstone) as alteration minerals. In addition, the durability results of tuffaceous sandstone show that the slake durability decreases as the degree of weathering increases (weathered material Id₂=88.7% and Id₁₀=65.3%). Furthermore, two mudstones of Miocene and Pliocene ages, having different clay mineral compositions (smectite vs. illite+chlorite), show the lowest and the highest slake durability among the tested clastic rocks. Hard mudstone shows the highest (Id₂=98.1% and Id₁₀=95.5%) while the soft mudstone shows the lowest (Id₂=33.9% and Id₆=0.4%.) slake durability. Thus, the slake durability of pyroclastic and sedimentary rocks is greatly affected by their mineral composition and texture, and is closely related to their alteration history. Slake durability is also affected by the kind of dissolved electrolyte and its concentration in the aqueous solution, providing some useful information for geotechnical practice.  相似文献   

Fault configuration produced by initial arc rifting in the Parece Vela Basin as deduced from seismic reflection data   总被引：1，自引：0，他引：1  

Mikiya  Yamashita  Tetsuro  Tsuru  Narumi  Takahashi  Kaoru  Takizawa  Yoshiyuki  Kaneda  Kantaro  Fujioka  Keita  Koda 《Island Arc》2007,16(3):338-347

Abstract   The Parece Vela Basin (PVB), which is a currently inactive back-arc basin of the Philippine Sea Plate, was formed by separation between the Izu-Ogasawara Arc (IOA) and the Kyushu-Palau Ridge (KPR). Elucidating the marks of the past back-arc opening and rifting is important for investigation of its crustal structure. To image its fault configurations and crustal deformation, pre-stack depth migration to multichannel seismic reflection was applied and data obtained by the Japan Agency for Marine-Earth Science and Technology and Metal Mining Agency of Japan and Japan National Oil Corporation (Japan Oil, Gas and Metals National Corporation). Salient results for the pre-stack depth-migrated sections are: (i) deep reflectors exist around the eastern margin of KPR and at the western margin of IOA down to 8 km depth; and (ii) normal fault zones distributed at the eastern margin of the KPR (Fault zone A) and the western margin of the IOA (Fault zone B) have a total displacement of greater than 500 m associated with synrift sediments. Additional normal faults (Fault zone C) exist 20 km east of the Fault zone B. They are covered with sediment, which indicates deposition of recent volcanic products in the IOA. According to those results: (i) the fault displacement of more than 500 m with respect to initial rifting was approximately asymmetric at 25 Ma based on PSDM profiles; and (ii) the faults had reactivated after 23 Ma, based on the age of deformed sediments obtained from past ocean drillings. The age of the base sediments corresponds to those of spreading and rotation after rifting in the PVB. Fault zone C is covered with thick and not deformed volcanogenic sediments from the IOA, which suggests that the fault is inactive.  相似文献   

Concentrations of trace elements in marine fish and its risk assessment in Malaysia   总被引：1，自引：0，他引：1  

Agusa T  Kunito T  Yasunaga G  Iwata H  Subramanian A  Ismail A  Tanabe S 《Marine pollution bulletin》2005,51(8-12):896-911

Concentrations of trace elements (V, Cr, Mn, Co, Cu, Zn, Ga, Se, Rb, Sr, Mo, Ag, Cd, Sn, Sb, Cs, Ba, Hg, Tl, Pb and Bi) were determined in muscle and liver of 12 species of marine fish collected from coastal areas in Malaysia. Levels of V, Cr, Mn, Co, Cu, Zn, Ga, Sr, Mo, Ag, Cd, Sn, Ba and Pb in liver were higher than those in muscle, whereas Rb and Cs concentrations showed the opposite trend. Positive correlations between concentrations in liver and muscle were observed for all the trace elements except Cu and Sn. Copper, Zn, Se, Ag, Cd, Cs and Hg concentrations in bigeye scads from the east coast of the Peninsular Malaysia were higher than those from the west, whereas V showed the opposite trend. The high concentration of V in the west coast might indicate oil contamination in the Strait of Malacca. To evaluate the health risk to Malaysian population through consumption of fish, intake rates of trace elements were estimated on the basis of the concentrations of trace elements in muscle of fish and daily fish consumption. Some specimens of the marine fish had Hg levels higher than the guideline value by US Environmental Protection Agency (EPA), indicating that consumption of these fish at the present rate may be hazardous to Malaysian people. To our knowledge, this is the first study on multielemental accumulation in marine fish from the Malaysian coast.  相似文献   

公路沿线花岗岩风化区滑坡危险度评价--以日本49号国道合户地区为例   总被引：2，自引：1，他引：2  

邱骋  谢谟文  江崎哲郎 《中国地质灾害与防治学报》2005,16(1):23-28

对公路沿线边坡进行稳定性评价及滑坡灾害分析，对于由滑坡、泥石流等引起的公路灾害的防治具有重要指导意义。为了评价处于花岗岩风化区的日本福岛县合户地区49号国道沿线边坡的滑坡危险程度，在调查和分析了该地区的表层破坏模式、并通过简易探测方法摸清了风化土层的厚度分布后，将研究区域划分为边坡单元(Slopeunit)，使用椭球体下半部模拟滑动面的形状，通过随机试算法确定各边坡单元危险滑动面的位置及空间形状；采用一种基于GIS的边坡稳定性三维分析模型计算各边坡单元最小安全系数以及滑坡发生概率，定量评价滑坡灾害危险程度。所有的计算过程及结果显示均在一个基于GIS平台的系统中完成，为如何利用GIS技术更好地为滑坡灾害防治工作服务拓宽了思路。  相似文献