Rip current spacing     

Noriyuki Iwata 《Journal of Oceanography》1976,32(1):1-10

Mass, momentum and energy conservation laws, including the radiation stress, are used to derive an equation of the eigenvalues of rip current spacing.A coastal region with linear bottom slope is divided into two parts: Offshore region and surfzone separated by the breaker line. Wave set-up, wave energy and mean current are assumed to be composed of basic state, which is a function of the distance from the coast to offshore only, and of superposed two-dimensional perturbations.In the case of normal incidence of waves, basic steady current system vanishes and perturbations are found to be of cellular shape. According to the boundary conditions at the coast, stream function of perturbed motion in the surfzone can be represented by the confluent hypergeometric function, while in the offshore zone it is approximated by the modified Bessel function.Interpolation of the stream functions in the surf and offshore regions enables us to obtain a characteristic relation which gives the eigenvalues of nondimensional alongshore spacing of rip current system as a function of a parameter determined by the bottom friction coefficient, width of the surfzone and breaker height.  相似文献   

Factors regulating the distribution of elements in marine sediments predicted by a simulation model     

Noburu Takematsu  Yoshio Sato  Yoshihisa Kato  Shiro Okabe 《Journal of Oceanography》1993,49(4):425-441

The contents of oxyanionic elements (V, Se and Mo) and cationic transition metals (Mn, Fe, Co, Ni, Cu and Zn) in sediments from near-shore to deep-sea environments were measured to clarify factors regulating the distribution of these elements in marine sediments. For cationic transition metals of which contents increase from near-shore to deep-sea environments, the chemical composition of pelagic clays is modeled by a mixture of aluminosilicates having the chemical composition of average shale and Fe–Mn oxides having the chemical composition of associated manganese nodules. The content of V is fairly constant in sediments from near-shore to deep-sea areas. The mixture model of average shale and manganese nodules holds also for V, although most of the V is located in the aluminosilicate lattices. The content of Se in the near-shore sediments is higher and that in the deep-sea sediments is lower than that in average shale. The high content in the near-shore sediments is interpreted as the addition of biogenic materials to aluminosilicates with average shale composition and the low content in deep-sea sediments is explained by oxidative release of Se from aluminosilicates. The content of Mo in sediments increases from near-shore to deep-sea environments. The general distribution of Mo in marine sediments is expressed by the mixture model. An anomalously high content of Mo in a near-shore sediment is attributed to adsorption of molybdate on manganese oxides.  相似文献   

Effects of long-term sample preservation on flow cytometric analysis of natural populations of pico-and nanophytoplankton     

Mitsuhide Sato  Shigenobu Takeda  Ken Furuya 《Journal of Oceanography》2006,62(6):903-908

The effects of long-term preservation on flow cytometric parameters of natural oceanic populations of pico-and nanophytoplankton have been examined. Populations collected at oligotrophic subtropical and subarctic locations in the North Pacific were fixed with glutaraldehyde and frozen in liquid nitrogen, according to Vaulot et al. (1989). During six months’ storage, chlorophyll red fluorescence declined in all the groups examined, while forward light scatter was enhanced in Synechococcus and Prochlorococcus, and weakened in nanoeucaryotes. Cell loss was not significant except for Synechococcus. Caution is required when analyzing flow cytometric data of samples stored for more than a month.  相似文献   

The discovery of a massive supercluster at  z= 0.9  in the UKIDSS Deep eXtragalactic Survey     

A. M. Swinbank  A. C. Edge  Ian Smail  J. P. Stott  M. Bremer  Y. Sato  C. van Breukelen  M. Jarvis  I. Waddington  L. Clewley  J. Bergeron  G. Cotter  S. Dye  J. E. Geach  E. Gonzalez-Solares  P. Hirst  R. J. Ivison  S. Rawlings  C. Simpson  G. P. Smith  A. Verma  T. Yamada 《Monthly notices of the Royal Astronomical Society》2007,379(4):1343-1351

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Low-cost long-term monitoring of global climate forcings and feedbacks     

J. Hansen  W. Rossow  B. Carlson  A. Lacis  L. Travis  A. Del Genio  I. Fung  B. Cairns  M. Mishchenko  M. Sato 《Climatic change》1995,31(2-4):247-271

We describe the rationale for long-term monitoring of global climate forcings and radiative feedbacks as a contribution to interpretation of long-term global temperature change. Our discussion is based on a more detailed study and workshop report (Hansenet al., 1993b). We focus on the potential contribution of a proposed series of inexpensive small satellites, but we discuss also the need for complementary climate process studies and ground-based measurements. Some of these measurements could be made inexpensively by students, providing both valuable climate data and science educational experience.  相似文献   

Frequency-Dependent Attenuation of P and S Waves In the Kanto Area, Japan, Based On the Coda-Normalization Method   总被引：4，自引：0，他引：4  

Kazuo Yoshimoto  Haruo Sato  Masakazu Ohtake 《Geophysical Journal International》1993,114(1):165-174

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Distribution of fluorite deposits in Japanese Islands     

K. Sato 《Mineralium Deposita》1980,15(3):327-334

The occurrence of fluorite deposits in Japan is limited in the provinces characterized by tin and tungsten mineralization within Southwest Japan. The deposits were formed near acidic igneous rocks of Cretaceous to Tertiary age. The ores in limestone are generally associated with skarn and metallic ore minerals such as cassiterite, scheelite and chalcopyrite. Granitic rocks in the provinces are the ilmenite-series (Ishihara, 1977) having enhanced fluorine contents and high initial strontium ratios. A reducing condition of the ilmenite-series granitic magma may have been more favorable for the concentration of fluorine in the residual magma because of the crystallization of relatively Fe-rich mafic minerals. Presence of thick crust bearing carbonaceous matter at the site of magmatism could have involved in the enrichment of fluorine as well as the reducing condition.  相似文献   

S-wave velocity structures of sediments estimated from array microtremor records and site responses in the near-fault region of the 1999 Chi-Chi,Taiwan earthquake     

Satoh?ToshimiEmail author  Hiroshi?Kawase  Tomotaka?Iwata  Sadanori?Higashi  Sato?Toshiaki  Huey-Chu?Huang 《Journal of Seismology》2004,8(4):545-558

The 1999 Chi-Chi, Taiwan earthquake, M_W = 7.6, caused severe damage in the near-fault region of the earthquake. In order to evaluate site effects in the near-field strong motions we estimate S-wave velocity structures of sediments at four sites using array records of microtremors. We also recalculated S-wave velocity structures at other four sites previously reported. To show the validity of the estimated S-wave velocity structures we separate empirical site responses from aftershock records using the generalized inversion method and show the agreement between empirical and theoretical site responses. We also show an observed fact that suggests soil nonlinearity during the Chi-Chi earthquake by comparing horizontal-to-vertical spectral ratios (HVRs) for main shock records with HVRs for aftershock records. Then we calculate one-dimensional equivalent-linear site responses using the estimated S-wave velocity structures and the main shock records observed on the surface. It is found that site amplification due to thick (about 6 km) sediments is one of the important factors for explaining the long-period velocity pulses of about 5 to 10 sec observed at sites in the footwall during the Chi-Chi earthquake. It is also found that the theoretical site responses of shallow soft sediments at sites that sustained severe damage in the hanging wall shows significant amplification around 1 sec. As the amplitude of velocity pulses with period around 1 sec is most critical in causing damage to ordinary buildings of moderate heights, our results suggest that the 1-sec period velocity pulses, amplified by the site response of shallow sediments should contribute to the severe damage during the Chi-Chi earthquake.  相似文献   

Trace Fossils and Sulfur Isotopes in Mudstones around the Kuroko Deposits in the Hokuroku Basin, Northeast Japan: An Attempt to Delineate the Depositional Environment     

Kosei Komuro    Hiroshi Kubota  Tokiyuki Sato    Yoshimichi Kajiwara  Shojiro Tanimura 《Resource Geology》2004,54(4):425-436

Abstract. A comprehensive investigation was carried out on the distribution of both trace fossils and sulfur isotopes in mud-stones in the Hokuroku district, northeast Japan, in the hope of delineating the depositional environment of the mudstones in which the Kuroko deposits are embedded. The mudstones are generally massive in structure and usually contain large trace fossils, being indicative of an aerobic biofacies. On the other hand, some mudstones in and above the Kuroko ore horizon are partly laminated and usually contain smaller trace fossils, being assignable to an anaerobic or dysaerobic biofacies. The δ³⁴S values of sulfides in the mudstones above and below the ore horizon range from -40 to -12 %o, indicating mostly oxic depositional conditions in equilibrium with the inferred aerobic biofacies. In the mudstones in the ore horizon, the δ³⁴S values exhibit regionally discriminated variations: -44 to -12 %o in areas far (>1 km) from the known Kuroko deposits and -24 to +6 %o in areas closer to them. The latter high δ³⁴S group implies the temporal occurrence of local anoxic basins in the vicinity of the known Kuroko deposits. At the time of late Nishikurosawa Stage (i.e. the currently assumed Kuroko metallogenic epoch), an intense oceanic stagnation is suggested to have taken place to form the local anoxic basins responsible for the formation and preservation of Kuroko deposits. This oceanic environmental event is considered to be most likely due to increasing biological productivity primarily triggered and enhanced by upwelling of NADW in the paleo-Sea of Japan at that time.  相似文献   

Principal fault zone width and permeability of the active Neodani fault, Nobi fault system, Southwest Japan   总被引：2，自引：0，他引：2  

A. Tsutsumi  S. Nishino  K. Mizoguchi  T. Hirose  S. Uehara  K. Sato  W. Tanikawa  T. Shimamoto 《Tectonophysics》2004,379(1-4):93-108

The internal structure and permeability of the Neodani fault, which was last activated at the time of the 1891 Nobi earthquake (M8.0), were examined through field survey and experiments. A new exposure of the fault at a road construction site reveals a highly localized feature of the past fault deformation within a narrow fault core zone. The fault of the area consists of three zone units towards the fault core: (a) protolith rocks; (b) 15 to 30 m of fault breccia, and (c) 200 mm green to black fault gouge. Within the fault breccia zone, cataclastic foliation oblique to the fault has developed in a fine-grained 2-m-wide zone adjacent to the fault. Foliation is defined by subparallel alignment of intact lozenge shaped clasts, or by elongated aggregates of fine-grained chert fragments. The mean angle of 20°, between the foliation and the fault plane suggests that the foliated breccia accommodated a shear strain of γ<5 assuming simple shear for the rotation of the cataclastic foliation. Previous trench surveys have revealed that the fault has undergone at least 70 m of fault displacement within the last 20,000 years in this locality. The observed fault geometry suggests that past fault displacements have been localized into the 200-mm-wide gouge zone. Gas permeability analysis of the gouges gives low values of the order of 10⁻²⁰ m². Water permeability as low as 10⁻²⁰ m² is therefore expected for the fault gouge zone, which is two orders of magnitude lower than the critical permeability suggested for a fault to cause thermal pressurization during a fault slip.  相似文献