On the Concentrations of the Dissolved Chemical Elements in the Estuary Water of the Chikugogawa River     

Iwao Hosokawa  Fumio Ohshima  Norihiko Kondo 《Journal of Oceanography》1970,26(1):1-5

When river water mixes with sea water in estuary area, the concentrations of the dissolved element in river water may be changed by either a simple physical mixing process or some complex chemical processes. It has been clarified in the Chikugogawa River estuary area that the change in concentrations of SO ₄ ²⁻ , BO ₃ ³⁻ , Mg²⁺, Ca²⁺ and F⁻ is only due to the mixing process but the change in concentrations of SiO ₃ ²⁻ and Al³⁺ is due to the chemical process in addition to the mixing process.   相似文献   

Initiation of the Mekong River delta at 8 ka: evidence from the sedimentary succession in the Cambodian lowland     

Toru Tamura  Yoshiki Saito  Sotham Sieng  Bunnarin Ben  Meng Kong  Im Sim  Sokuntheara Choup  Fumio Akiba 《Quaternary Science Reviews》2009,28(3-4):327-344

Modern deltas are understood to have initiated around 7.5–9 ka in response to the deceleration of sea-level rise. This episode of delta initiation is closely related to the last deglacial meltwater events and eustatic sea-level rises. The initial stage of the Mekong River delta, one of the world's largest deltas, is well recorded in Cambodian lowland sediments. This paper integrates analyses of sedimentary facies, diatom assemblages, and radiocarbon dates for three drill cores from the lowland to demonstrate Holocene sedimentary evolution in relation to sea-level changes. The cores are characterized by a tripartite succession: (1) aggrading flood plain to natural levee and tidal–fluvial channel during the postglacial sea-level rise (10–8.4 ka); (2) aggrading to prograding tidal flats and mangrove forests around and after the maximum flooding of the sea (8.4–6.3 ka); and (3) a prograding fluvial system on the delta plain (6.3 ka to the present). The maximum flooding of the sea occurred at 8.0 ± 0.1 ka, 2000 years before the mid-Holocene sea-level highstand, and tidal flats penetrated up to 20–50 km southeast of Phnom Penh after a period of abrupt ～5 m sea-level rise at 8.5–8.4 ka. The delta progradation then initiated as a result of the sea-level stillstand at around 8–7.5 ka. Another rapid sea-level rise at 7.5–7 ka allowed thick mangrove peat to be widely deposited in the Cambodian lowland, and the peat accumulation endured until 6.3 ka. Since 6.3 ka, a fluvial system has characterized the delta plain, and the fluvial sediment discharge has contributed to rapid delta progradation. The uppermost part of the sedimentary succession, composed of flood plain to natural-levee sediments, reveals a sudden increase in sediment accumulation over the past 600–1000 years. This increase might reflect an increase in the sediment yield due to human activities in the upper to middle reaches of the Mekong, as with other Asian rivers.  相似文献   

Center to limb variation of the intensity of the photospheric faculae     

Tadashi Hirayama  Fumio Moriyama 《Solar physics》1979,63(2):251-255

Center to limb variation of the excess brightness of photospheric facular granules was observed at 530 nm with a balloon-borne telescope of 10 cm aperture. Facular granules are found to be 9.2% and 16.2% brighter than the adjacent quiet region at cos = 0.65 and 0.50 respectively, being the angle between the Sun's normal and the line of sight. This observation, together with our earlier result (Hirayama, 1978), leads to facular models which are 600 K hotter than the photosphere if the diameter of facular granules is assumed to be 600 km, and 1000 K hotter if 150 km is assumed instead. It was also found that the soft X-ray bright points as observed with the Skylab do not correspond spatially to the photospheric facular granules near the polar region.  相似文献   

A simplified method of constructing fragility curves for highway bridges     

Kazi R. Karim  Fumio Yamazaki 《地震工程与结构动力学》2003,32(10):1603-1626

Fragility curves are found to be useful tools for predicting the extent of probable damage. They show the probability of highway structure damage as a function of strong motion parameters, and they allow the estimation of a level of damage probability for a known ground motion index. In this study, an analytical approach was adopted to develop the fragility curves for highway bridges based on numerical simulation. Four typical RC bridge piers and two RC bridge structures were considered, of which one was a non‐isolated system and the other was an isolated system, and they were designed according to the seismic design code in Japan. From a total of 250 strong motion records, selected from Japan, the United States, and Taiwan, non‐linear time history analyses were performed, and the damage indices for the bridge structures were obtained. Using the damage indices and ground motion parameters, fragility curves for the four bridge piers and the two bridge structures were constructed assuming a lognormal distribution. It was found that there was a significant effect on the fragility curves due to the variation of structural parameters. The relationship between the fragility curve parameters and the over‐strength ratio of the structures was also obtained by performing a linear regression analysis. It was observed that the fragility curve parameters showed a strong correlation with the over‐strength ratio of the structures. Based on the observed correlation between the fragility curve parameters and the over‐strength ratio of the structures, a simplified method was developed to construct the fragility curves for highway bridges using 30 non‐isolated bridge models. The simplified method may be a very useful tool to construct the fragility curves for non‐isolated highway bridges in Japan, which fall within the same group and have similar characteristics. Copyright © 2003 John Wiley & Sons, Ltd.  相似文献   

Near‐fault spatial variation in strong ground motion due to rupture directivity and hanging wall effects from the Chi‐Chi,Taiwan earthquake     

Khosrow T. Shabestari  Fumio Yamazaki 《地震工程与结构动力学》2003,32(14):2197-2219

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U–Pb zircon geochronology of the North Pole Dome adamellite in the eastern Pilbara Craton          下载免费PDF全文

Hisashi Asanuma  Yusuke Sawaki  Shuhei Sakata  Hideyuki Obayashi  Kazue Suzuki  Kouki Kitajima  Takafumi Hirata  Shigenori Maruyama 《Island Arc》2018,27(4)

Supracrustal rocks around the North Pole Dome area, Western Australia, provide valuable information regarding early records of the evolution of crustal processes, surface environments, and biosphere. Owing to the occurrence of the oldest known microfossils, the successions at the North Pole Dome area have attracted interest from many researchers. The Paleoarchean successions (Warrawoona Group) mainly comprise mafic‐ultramafic greenstones with intercalated cherts and felsic lavas. Age constraints on the sediments have been mainly based on zircon U–Pb geochronology. However, many zircon grains have suffered from metamictization and contain anomalously high contents of common Pb, which makes interpretation of the U–Pb data complicated. In order to provide more convincing chronological constraints, an U–Pb Concordia age is widely accepted as the best estimate. Most zircons separated from two adamellites also suffered from severe metamictization. In our analyses, less metamictized domains were selected using a pre‐ablation technique in conjunction with elemental mapping, and then their U–Pb isotopic compositions were determined with a laser ablation inductively coupled plasma mass spectrometry. Most analyzed domains contained certain amounts of common Pb (²⁰⁴Pb/²⁰⁶Pb > 0.000 1), whereas three and five U–Pb data points with less common Pb (²⁰⁴Pb/²⁰⁶Pb < 0.000 1) were obtained. These U–Pb datasets yielded U–Pb Concordia ages of ca 3 445 Ma and 3 454 Ma, respectively. These ages represent the timing of the adamellite intrusion, and constrain the minimum depositional age of the Warrawoona Group. In addition, a single xenocrystic zircon grain showed a ²⁰⁷Pb/²⁰⁶Pb age of ca 3 545 Ma, supporting the idea that the sialic basement of the Pilbara Craton existed prior to 3 500 Ma. The in situ U–Pb zircon dating combined with the pre‐ablation technique has the potentials to identify non‐metamictized parts and to yield precise and accurate geochronological data even from partially metamictized zircons.  相似文献   

Multi-scale solution for building extraction from LiDAR and image data     

T. Thuy Vu  Fumio Yamazaki  Masashi Matsuoka 《International Journal of Applied Earth Observation and Geoinformation》2009

This paper presents a multi-scale solution based on mathematical morphology for extracting the building features from remotely sensed elevation and spectral data. Elevation data are used as the primary data to delineate the structural information and are firstly represented on a morphological scale-space. The behaviors of elevation clusters across the scale-space are the cues for feature extraction. As a result, a complex structure can be extracted as a multi-part object in which each part is represented on a scale depending on its size. The building footprint is represented by the boundary of the largest part. Other object attributes include the area, height or number of stories. The spectral data is used as an additional source to remove vegetation and possibly classify the building roof material. Finally, the results can be stored in a multi-scale database introduced in this paper. The proposed solution is demonstrated using the data derived from a Light Detection And Ranging (LiDAR) surveying flight over Tokyo, Japan. The results show a reasonable match with reference data and prove the capability of the proposed approach in accommodation of diverse building shapes. Higher density LiDAR is expected to produce better accuracy in extraction, and more spectral sources are necessary for further classification of building roof material. It is also recommended that parallel processing should be implemented to reduce the computation time.  相似文献   

Probabilistic description of the first-order Fermi acceleration in shock waves: time-dependent solution by the single-particle approach     

Tsunehiko N. Kato †  Fumio Takahara 《Monthly notices of the Royal Astronomical Society》2003,342(2):639-650

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Geology of the Gorny Altai subduction–accretion complex, southern Siberia: Tectonic evolution of an Ediacaran–Cambrian intra-oceanic arc-trench system   总被引：1，自引：0，他引：1  

Tsutomu Ota  Atsushi Utsunomiya  Yuko Uchio  Yukio Isozaki  Mikhail M. Buslov  Akira Ishikawa  Shigenori Maruyama  Koki Kitajima  Yoshiyuki Kaneko  Hiroshi Yamamoto  Ikuo Katayama   《Journal of Asian Earth Sciences》2007,30(5-6):666-695

The Gorny Altai region in southern Siberia is one of the key areas in reconstructing the tectonic evolution of the western segment of the Central Asian Orogenic Belt (CAOB). This region features various orogenic elements of Late Neoproterozoic–Early Paleozoic age, such as an accretionary complex (AC), high-P/T metamorphic (HP) rocks, and ophiolite (OP), all formed by ancient subduction–accretion processes. This study investigated the detailed geology of the Upper Neoproterozoic to Lower Paleozoic rocks in a traverse between Gorno-Altaisk city and Lake Teletskoy in the northern part of the region, and in the Kurai to Chagan-Uzun area in the southern part. The tectonic units of the studied areas consist of (1) the Ediacaran (=Vendian)–Early Cambrian AC, (2) ca. 630 Ma HP complex, (3) the Ediacaran–Early Cambrian OP complex, (4) the Cryogenian–Cambrian island arc complex, and (5) the Middle Paleozoic fore-arc sedimentary rocks. The AC consists mostly of paleo-atoll limestone and underlying oceanic island basalt with minor amount of chert and serpentinite. The basaltic lavas show petrochemistry similar to modern oceanic plateau basalt. The 630 Ma HP complex records a maximum peak metamorphism at 660 °C and 2.0 GPa that corresponds to 60 km-deep burial in a subduction zone, and exhumation at ca. 570 Ma. The Cryogenian island arc complex includes boninitic rocks that suggest an incipient stage of arc development. The Upper Neoproterozoic–Lower Paleozoic complexes in the Gorno-Altaisk city to Lake Teletskoy and the Kurai to Chagan-Uzun areas are totally involved in a subhorizontal piled-nappe structure, and overprinted by Late Paleozoic strike-slip faulting. The HP complex occurs as a nappe tectonically sandwiched between the non- to weakly metamorphosed AC and the OP complex. These lithologic assemblages and geologic structure newly documented in the Gorny Altai region are essentially similar to those of the circum-Pacific (Miyashiro-type) orogenic belts, such as the Japan Islands in East Asia and the Cordillera in western North America. The Cryogenian boninite-bearing arc volcanism indicates that the initial stage of arc development occurred in a transient setting from a transform zone to an incipient subduction zone. The less abundant of terrigenous clastics from mature continental crust and thick deep-sea chert in the Ediacaran–Early Cambrian AC may suggest that the southern Gorny Altai region evolved in an intra-oceanic arc-trench setting like the modern Mariana arc, rather than along the continental arc of a major continental margin. Based on geological, petrochemical, and geochronological data, we synthesize the Late Neoproterozoic to Early Paleozoic tectonic history of the Gorny Altai region in the western CAOB.  相似文献   

Effect of isolation on fragility curves of highway bridges based on simplified approach   总被引：1，自引：0，他引：1  

Kazi Rezaul Karim  Fumio Yamazaki 《Soil Dynamics and Earthquake Engineering》2007,27(5):414-426

The trend of isolating highway bridges is on the rise after the recent large earthquakes in Japan, the United States, and other countries. Recent investigation shows that isolated systems perform well against seismic forces as the substructures of such systems experience less lateral forces due to energy dissipation of the isolation device. Hence, it is anticipated that there might be an effect on fragility curves of highway bridges due to isolation. In this study, 30 isolated bridge models were considered (and they were designed according to the seismic design code of highway bridges in Japan) to have a wider range of the variation of structural parameters, e.g. pier heights, weights, and over-strength ratio of structures. Then, fragility curves were developed by following a simplified procedure using 250 strong motion records, which were selected from 5 earthquake events that occurred in Japan, the USA, and Taiwan. It is observed that the level of damage probability for the isolated system is less than that of the non-isolated one for a lower level of pier height. However, having the same over-strength ratio of the structures, the level of damage probability for the isolated system is found to be higher for a higher level of pier height compared to the one of the non-isolated system. The proposed simple approach may conveniently be used in constructing fragility curves for a class of isolated bridge structures in Japan that have similar characteristics.  相似文献