Wavelet-based multiscale resolution analysis of real and simulated time-series of earthquakes   总被引：1，自引：0，他引：1  

Bogdan Enescu  Kiyoshi Ito  Zbigniew R. Struzik 《Geophysical Journal International》2006,164(1):63-74

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Electrical conductivity measurement of gneiss under mid- to lower crustal P–T conditions     

Kiyoshi Fuji-ta  Tomoo Katsura  Takuya Matsuzaki  Masahiro Ichiki  Tomoyuki Kobayashi 《Tectonophysics》2007,434(1-4):93-101

We conducted electrical conductivity measurements perpendicular and parallel to mineral foliation in dry gneiss at up to 1000 K and a constant pressure of 1 GPa. The analyzed gneisses were obtained from the Higo metamorphic belt, Kyushu, Japan. As the metamorphic conditions of these rocks have been well determined by previous studies, we were able to select samples that were representative of the middle to lower crust. Prior to the conductivity measurements, the samples were maintained at the maximum temperature for a long period, until the electrical conductivity had stabilized. Our experiment results reveal linear and reproducible conductivity data between temperatures of 600 and 1000 K. Conductivity measured perpendicular and parallel to foliation differ by an order of magnitude over the same temperature window. A plausible explanation for this discrepancy in conductivity is the contrasting configuration of minerals in the two sample orientations, as observed by backscattered electron image (BEI) and electron probe microanalysis (EPMA). We evaluated the conductivity and computed activation energy for each of the samples and compared the results with those of previous studies; our results are consistent with the conductivity values reported for other types of rocks. We also compared the experiment results with data derived from electromagnetic (EM) soundings. Electrical conductivity measurements undertaken perpendicular to foliation can account for the subsurface conductivity structure beneath central Kyushu, Japan.  相似文献   

15-digit accuracy calculations of Chandrasekhar’s H-function for isotropic scattering by means of the double exponential formula     

Kiyoshi Kawabata 《Astrophysics and Space Science》2016,361(12):373

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Propagation of Rossby Waves over Ridges Excited by Interannual Wind Forcing in a Western North Pacific Model   总被引：1，自引：4，他引：1  

Kiyoshi Tanaka  Motoyoshi Ikeda 《Journal of Oceanography》2004,60(2):329-340

Numerical experiments with a multi-level general circulation model have been performed to investigate basic processes of westward propagation of Rossby waves excited by interannual wind stress forcing in an idealized western North Pacific model with ocean ridges. When the wind forcing with an oscillation period of 3 years is imposed around 180°E and 30°N, far from Japan, barotropic waves excited by the wind can hardly cross the ridges, such as the Izu-Ogasawara Ridge. On the other hand, a large part of the first-mode baroclinic waves are transmitted across the ridges, having net mass transport. The propagation speed of the first-mode baroclinic wave is accelerated (decelerated) when an anticyclonic (cyclonic) circulation is formed at the sea surface, due to a deeper (shallower) upper layer, and to southward (slightly northward) drift of the circulation. Thus, when the anticyclonic circulation is formed on the northern side of the cyclonic one, they propagate almost together. The second-mode baroclinic waves converted from the first-mode ones on the ridges arrive south of Japan, although their effects are small. The resulting volume transport variation of the western boundary current (the Kuroshio) reaches about 60% of the Sverdrup transport variability estimated from the wind stress. These characteristics are common for the interannual forcing case with a longer oscillation period. In the intraseasonal and seasonal forcing cases, on the other hand, the transport variation is much smaller than those in the interannual forcing cases. This revised version was published online in July 2006 with corrections to the Cover Date.  相似文献   

Sensitivity of the Interannual Kuroshio Transport Variation South of Japan to Wind Dataset in OGCM Calculation   总被引：1，自引：2，他引：1  

Hiroshi Yoshinari  Motoyoshi Ikeda  Kiyoshi Tanaka  Yukio Masumoto 《Journal of Oceanography》2004,60(2):341-350

Numerical experiments were carried out using OGCM (Ocean General Circulation Model), MOM2.2 (Modular Ocean Model Ver. 2.2), over realistic topography data, ETOPO5 (Earth Topography - 5 Minute), to investigate the interannual variability of the Kuroshio transport in 1960–2000 south of Japan; 1) the PN line located off the East China Sea, and 2) the ASUKA (Affiliated Surveys of the Kuroshio off Cape Ashizuri) line located off Cape Ashizuri. We adopted two wind datasets as driving forces of the OGCM: 1) the NCEP/NCAR (National Centers for Environmental Prediction/National Center for Atmospheric Research) reanalysis monthly mean wind stress data, and 2) the ECMWF (European Centre for Medium-range Weather Forecasts) daily wind data. In the ECMWF experiments we replaced the NCEP/NCAR data only in 1979–1993 because of the availability of the data. The OGCMs and observation basically agree on the temporal variation patterns of the transports until 1986 on the PN line with correlation coefficients of about 0.6. During the 1990s, when data were collected on the ASUKA line, the NCEP/NCAR experiments give lower correlation coefficients (less than 0.3), on both PN and ASUKA lines, while the ECMWF experiments have a higher value on the ASUKA line (0.5). One of the reasons for the disagreement between the observations and OGCMs during the 1990s might arise from the NCEP/NCAR data. An additional analysis of a wind-driven circulation was performed to examine the sensitivity of integrated Sverdrup transport along the western boundary to the propagation speed of a baroclinic Rossby wave, which is varied by stratification. A variation of the stratification, which might be induced by variability of air-sea heat and freshwater fluxes, cannot be a main cause of the disagreement. This revised version was published online in July 2006 with corrections to the Cover Date.  相似文献   

90Sr and137Cs contents in the surface waters of the adjacent seas of Japan and the North Pacific during 1969 to 1973     

Yutaka Nagaya  Kiyoshi Nakamura 《Journal of Oceanography》1976,32(5):228-234

The concentrations of⁹⁰Sr and¹³⁷Cs, derived from the radioactive fallout, in the surface layers of the adjacent seas of Japan and the North Pacific were determined radiochemically during 1969 to 1973. The⁹⁰Sr and¹³⁷Cs concentrations in sea water decreased markedly with increase of the depth and below the depth of 1,000 m, the concentrations were approximately uniform. The distribution of⁹⁰Sr in the surface water of the North Pacific in spring of 1970 was approximately uniform, except two regions; rather large low-concentration region between 160°E and 170°W and relatively higher contamination area around 32°N and 146°W.  相似文献   

Fine-scale structure and mixing across the front between the Tsugaru Warm and Oyashio Currents in summer along the Sanriku Coast,east of Japan     

Sachihiko Itoh  Hitoshi Kaneko  Miho Ishizu  Daigo Yanagimoto  Takeshi Okunishi  Hajime Nishigaki  Kiyoshi Tanaka 《Journal of Oceanography》2016,72(1):23-37

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Spreading of river water in Suruga Bay     

Kiyoshi Tanaka  Yutaka Michida  Teruhisa Komatsu  Kenji Ishigami 《Journal of Oceanography》2009,65(2):165-177

We have investigated the spreading of river water in Suruga Bay by performing numerical experiments and conducting field surveys with drifting buoys. There are clear seasonal variations in the large river discharges into the bay: increased discharge in the rainy summer season and decreased discharge in the dry winter season. The numerical model reproduces the main feature that has been observed in the actual sea: the river water extends gradually from the northwestern to the southeastern regions in the bay, especially in summer. The river water spreading is greatly influenced by the bottom topography of the bay: the Fuji River water spreads over a deep continental slope as a surface-advected plume and extends well offshore, since a large bulge (anticyclonic eddy at the river mouth) extends well offshore and effectively transports the river water offshore. On the other hand, the Oi River water tends to flow parallel to isobaths (along a coastline) on a shallow continental shelf as a bottomadvected plume. Moreover, the influences of seasonal variations in the stratification and a bay-scale, wind-driven circulation are also investigated. Trajectories of the drifting buoys, which were released around the Fuji River mouth, certainly suggest that the bulge exists there.  相似文献   

Numerical experiments on wind-driven circulations and associated transport processes in Suruga Bay     

Kiyoshi Tanaka  Yutaka Michida  Teruhisa Komatsu 《Journal of Oceanography》2008,64(1):93-102

The dynamics of the wind-driven circulations and surface transport processes in Suruga Bay have been examined by performing numerical experiments. While strong winds exist outside the bay, the winds inside the bays are greatly reduced, which generates a strong wind stress curl in winter and autumn. In particular, in winter, a strong positive curl region is located across the bay mouth, and a strong surface circulation with counterclockwise rotation is generated beneath it. The circulation is nearly geostrophic, but is not affected by the bottom topography in the deep bay. It is suggested that intense surface water exchange through the bay mouth occurs in winter, whereas it is not active in the other seasons when no significant vorticity is supplied on the bay mouth from the atmosphere. Moreover, we propose a hypothesis that the atmospheric wind stress curl will cause the frequent appearance of the counterclockwise circulation in winter in the real ocean.  相似文献   

Superior solid solubility of MnSiO3 in CaSiO3 perovskite     

Lin Li  Takaya Nagai  Yusuke Seto  Kiyoshi Fujino  Jun Kawano  Shoich Itoh 《Physics and Chemistry of Minerals》2015,42(2):123-129

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