Estimation of Sediment Properties during Benthic Impact Experiments     

Tetsuo Yamazaki  Rahul Sharma 《Marine Georesources & Geotechnology》2013,31(4):269-289

Sediment properties, such as water content and density, have been used to estimate the dry and wet weights, as well as the volume of sediment recovered and discharged, during benthic impact experiments conducted in the Pacific and Indian Oceans. The estimates show that the weights of dry (355-1332 t) and wet sediment (1651-4888 t) recovered during the experiments, are not only a function of the total duration and distance covered during the experiment, but also depend on water content and density of the sediment. Estimation of dry sediment and its volumetric ratio in the discharge, are key parameters for calculating the discharged volume. The estimated volume of wet sediment recovered (1427-4049 m 3 ) as well as discharged (2693-6951 m 3 ) during the experiments, provide important inputs to evaluate the sediment resettlement and migration. Using these estimates, the average depth of excavation on the seafloor, can also been calculated. However, the stages of sediment recovery and discharge are expressed differently in some of the experiments. In order to standardize these, different stages have been identified, and definitions of certain terms have been suggested, for use in the future. The methods of calculating different properties, as well as weight and volume of discharged sediment are described in the paper for use in other applications concerning deep-sea discharges.  相似文献   

Surface mass balance on Glacier No. 31 in the Suntar–Khayata Range,eastern Siberia,from 1951 to 2014     

Yong Zhang  Hiroyuki Enomoto  Tetsuo Ohata  Tsutomu Kadota  Tatsuo Shirakawa  Nozomu Takeuchi 《山地科学学报》2017,14(3):501-512

This study presents a 64-year(1951–2014) reconstruction of the surface mass balance of Glacier No. 31, located in the Suntar-Khayata Range of the eastern Siberia, where the ablation zone is characterized by the extensive dark ice surface. We use a temperature index-based glacier mass-balance model, which computes all major components of glacier mass budget and is forced by daily air temperature and precipitation from a nearby meteorological station. The glacier shows a mean annual mass balance of –0.35 m w.e.a~(–1) during the past 64 years, with an acceleration of –0.50 m w.e. a~(–1) during the recent years. A cumulative mass loss of the glacier is ~22.3 m w.e. over the study period, about 56% of which is observed during 1991–2014. In addition to the contribution of temperature rise and precipitation decrease to recent mass loss of the glacier, an experimental analysis, in which the cleanand dark ice surfaces are respectively assumed to cover the entire ablation zone, indicates that dark ice surface, caused by insoluble impurities consisting of mineral dusts, cryoconite granules, and ice algae, plays a crucial role in the changing mass balance through enhancing melt rates in the ablation zone of the glacier.  相似文献   

Dust ring formation due to ice sublimation of radially drifting dust particles under the Poynting-Robertson effect in debris disks     

Hiroshi Kobayashi  Sei-ichiro Watanabe  Tetsuo Yamamoto 《Icarus》2008,195(2):871-881

In a disk with a low optical depth, dust particles drift radially inward by the Poynting-Robertson (P-R) drag rather than are blown out by stellar radiation pressure following destructive collisions. We investigate the radial distribution of icy dust composed of pure ice and refractory materials in dust-debris disks taking into account the P-R drag and ice sublimation. We find that icy dust particles form a dust ring by their pile-ups at the edge of their sublimation zone, where they sublime substantially at the temperature 100-110 K. The distance of the dust ring is 20-35 AU from the central star with its luminosity L_??30L_⊙ and 65(L_?/100L_⊙)^1/2 AU for L_??30L_⊙, where L_⊙ is the solar luminosity. The effective optical depth is enhanced by a factor of 2 for L_??100L_⊙ and more than 10 for L_??100L_⊙. The optical depth of the outer icy dust disk exceeds that of the inner disk filled with refractory particles, namely, the residue of ice sublimation, which are further subjected to the P-R effect. As a result, an inner hole is formed inside the sublimation zone together with a dust ring along the outer edge of the hole.  相似文献   

Clockwise phase propagation of semi-diurnal tides in the Gulf of Thailand   总被引：2，自引：0，他引：2  

Tetsuo Yanagi  Toshiyuki Takao 《Journal of Oceanography》1998,54(2):143-150

The phase of semi-diurnal tides (M₂ and S₂) propagates clockwise in the central part of the Gulf of Thailand, although that of the diurnal tides (K₁, O₁ and P₁) is counterclock-wise. The mechanism of clockwise phase propagation of semi-diurnal tides at the Gulf of Thailand in the northern hemisphere is examined using a simple numerical model. The natural oscillation period of the whole Gulf of Thailand is near the semi-diurnal period and the direction of its phase propagation is clockwise, mainly due to the propagation direction of the large amplitude part of the incoming semi-diurnal tidal wave from the South China Sea. A simplified basin model with bottom slope and Coriolis force well reproduces the co-tidal and co-range charts of M₂ tide in the Gulf of Thailand.  相似文献   

A Challenge of Water Purification in Dokai Bay, Japan     

Tetsuo Yanagi  Machiko Yamada  Manabu Suzuki 《Marine pollution bulletin》1999,38(12):10-1069

A history of water pollution and countermeasures for water purification in Dokai Bay, Japan are reviewed. Now, Dokai Bay suffers from the occurrences of red tides and oxygen-deficiency in summer. In order to prevent the occurrences of red tides and oxygen-deficiency, an ecological numerical model has been developed. The model experiments forecast that when the phosphorus or nitrogen load from land will be cut by 90% or 95%, respectively, red tides and oxygen-deficiency will not occur in Dokai Bay. If the industrial and sewage facilities are not sufficient to cut the nutrients load to the necessary degree, we have to consider other countermeasures such as cultivating bivalves and algae in order to decrease the nutrients concentration in the bay. International co-operation related to coastal zone management is also discussed.  相似文献   

河西绿洲区春小麦蒸腾蒸散的变化研究   总被引：4，自引：0，他引：4  

王亚军  谢忠奎  小林哲夫  兰念军 《中国沙漠》1999,19(3):272-275

在甘肃张掖绿洲区利用浮力称重式蒸散仪对春小麦蒸散量进行了测定,对蒸散量的日变化和季节变化特征进行了论述。研究结果表明:小麦田的日蒸散量在白天12:00~16:00达到最大,夜间20:00~08:00最小甚至呈负值。灌溉前后蒸腾强度出现峰值的时间有所变化。但灌溉以后,蒸腾与蒸散量均呈增大趋势。日蒸散量随着净辐射的增加而加大。在小麦不同的生育阶段,蒸散量有所不同,小麦拔节以前较小,拔节以后开始增大,灌浆期达到最大,接近成熟时逐渐降低。  相似文献   

Characteristics of crustal structures in the Yamato Basin,sea of Japan,deduced from seismic explorations     

Takeshi Sato  Tetsuo No  Shuichi Kodaira 《Island Arc》2023,32(1):e12474

Crustal structures around the Yamato Basin in the southeastern Sea of Japan, inferred from recent ocean bottom seismography (OBS) and active-source seismological studies, are reviewed to elucidate various stages of crustal modification involved from rifting in the crust of the surrounding continental arc to the production of oceanic crust in the Yamato Basin of the back-arc basin. The northern, central, and southern areas of the Yamato Basin have crustal thicknesses of approximately 12–16 km, and lowermost crusts with P-wave velocities greater than 7.2 km/s. Very few units have P-wave velocities in the range 5.4–6.0 km/s, which corresponds to the continental upper crust. These findings, combined with previous geochemical analysis of basalt samples, are interpreted to indicate that a thick oceanic crust has been formed in these areas of the basin, and that this oceanic crust has been underplated by mantle-derived magma. In the central Yamato Basin, the original continental crust has been fully breached and oceanic crust has been formed. Conversely, the presence of a unit corresponding to the continental upper crust and the absence of a high-velocity part in the lower crust implies that the southwestern edge of the Yamato Basin has a rifted crust without significant intrusion. The Oki Trough has a crust that is 17–19 km thick with a high-velocity lower crust and a unit corresponding to the continental upper crust. The formation of the Oki Trough resulted from rifting with magmatic intrusion and/or underplating. We interpret these variations in the crustal characteristics of the Yamato Basin area as reflecting various instances of crustal modification by thinning and magmatic intrusion due to back-arc extension, resulting in the production of a thick oceanic crust in the basin.  相似文献   

Distribution of ductile deformation around the Main Central Thrust zone at the frontal part of nappe in southeastern Nepal Himalaya     

Katsushi Sato  Harutaka Sakai  Tetsuo Kawakami 《Island Arc》2020,29(1)

A geological survey and morphological analysis of quartz grains were performed to investigate the distribution of ductile deformation caused by the Himalayan Main Central Thrust (MCT) around Dhankuta, southeastern Nepal. The MCT was mapped as the lithological boundary between the gneiss of the Higher Himalayan Crystalline (HHC) as the hanging wall and the inverted metamorphic sequence of the Lesser Himalayan Sediments (LHS) as the footwall. The MCT was found to truncate various stratigraphic levels of LHS and cuts a map‐scale gentle fold developed in the LHS. Ductile deformation was quantified by fractal dimension between size and perimeter of dynamically recrystallized quartz grains in bedded metaquartzite intercalated in both HHC and LHS. Serrate and polygonal shapes of quartz indicate large and small strain rates, respectively, when the temperature during ductile deformation was assumed to be uniform. A peak of strain rate was found at the lithological boundary with the peak width of ca. 500 m. Such a thin shear zone is favorable for producing frictional heat to promote the inverted metamorphism in LHS.  相似文献   

Evolution of induced fabric in a strain space multiple mechanism model for granular materials     

Susumu Iai  Tetsuo Tobita  Osamu Ozutsumi 《国际地质力学数值与分析法杂志》2013,37(10):1326-1336

The strain space multiple mechanism model idealizes the behavior of granular materials based on a multitude of virtual simple shear mechanisms oriented in arbitrary directions. Within this modeling framework, the virtual simple shear stress is defined as a quantity that depends on the contact distribution function as well as the normal and tangential components of inter‐particle contact forces, which evolve independently during the loading process. In other terms, the virtual simple shear stress is an intermediate quantity in the upscaling process from the microscopic level (characterized by the contact distribution and inter‐particle contact forces). The stress space fabric (i.e. the orientation distribution of the virtual simple shear stress) produces macroscopic stress through the tensorial average. Thus, the stress space fabric characterizes the fundamental and higher modes of anisotropy induced in granular materials. Comparing an induced fabric associated with the biaxial shear of plane granular assemblies obtained via a simulation using Discrete Element Method to the strain space multiple mechanism model suggests that the strain space multiple mechanism model has the capability to capture the essential features in the evolution of an induced fabric in granular materials. Copyright © 2012 John Wiley & Sons, Ltd.  相似文献   

Reaction of forsterite with hydrogen molecules at high pressure and temperature     

Ayako?ShinozakiEmail author  Hisako?Hirai  Hiroyuki?Kagi  Tadashi?Kondo  Taku?Okada  Daisuke?Nishio-Hamane  Shin-ichi?Machida  Tetsuo?Irifune  Takumi?Kikegawa  Takehiko?Yagi 《Physics and Chemistry of Minerals》2012,39(2):123-129

High pressure and temperature reactions of a mixture of forsterite and hydrogen molecules have been carried out using a laser heated diamond anvil cell at 9.8–13.2 GPa and ~1,000 K. In situ X-ray diffraction measurements showed no sign of decomposition or phase transitions of the forsterite under these experimental conditions, indicating that the olivine structure was maintained throughout all runs. However, a substantial expansion of the unit cell volume of the forsterite was observed for samples down to ~3 GPa upon quenching to ambient pressure at room temperature. The Raman spectroscopy measurements under pressure showed significant shifts of the Raman peaks of the Si–O vibration modes for forsterite and of the intramolecular vibration mode for H₂ molecules toward a lower frequency after heating. Additionally, no OH vibration modes were observed by Raman and FT-IR spectroscopic measurements. These lines of evidence show that the observed volume expansion in forsterite is not explained by the incorporation of hydrogen atoms as hydroxyl, but suggest the presence of hydrogen as molecules in the forsterite structure under these high pressure and temperature conditions.  相似文献