Horizontal electric fields in the middle latitude     

Ogawa Toshio  Tanaka Yoshikazu  Huzita Akira  Yasuhara Michihiro 《Planetary and Space Science》1975,23(5):825-830

Three dimensional electric fields were measured at the altitude of about 27 km in the stratosphere over the Pacific Ocean about 200–400 km away from the Sanriku coast of Honsyu Island (L = 1·4) on 16–17 October 1973, which was magnetically disturbed. The average horizontal electric field thus measured is about 10 mV/m, and the electric field vectors made clockwise semidiurnal rotations rather than diurnal. Daily variation of this electric field was compared with data at L = 2·7–3·5 published by Mozer (1973) and was found to be very similar. This suggests that these electric fields are of common origin in the plasmasphere. From their mean daily variation it is estimated that the plasmaspheric convection is decreased in the night side and is increased in the day side by 200–300 m/sec, and there is an outward flow in the first half of the afternoon and an inward flow in the plasma bulge region of about 500 m/sec.  相似文献   

Heat balance of the surface layer of the sea at ocean weather station T     

Yoshikazu Kurasawa  Kimio Hanawa  Yoshiaki Toba 《Journal of Oceanography》1983,39(4):192-202

Heat balance of the upper 200 m of the sea south of Japan is studied, by the use of marine meteorological and oceanographic data at Ocean Weather Station T (29°N, 135°E), intensively obtained from June 1950 to November 1953. Local time change of the heat content in the surface layer and the net heat flux through the air-sea interface are calculated directly from these data, and the heat convergence in the sea is estimated from their residuals. Regarding the relative importance of one- and three-dimensional processes, it is found that, on a time scale of a few days to one month, the variation of heat content depends on heat convergence in the sea, while on a seasonal time scale, the heat content is determined primarily by the heat flux through the sea surface in December through February, by heat convergence within the sea from March to May, and by both processes from June to November. It is inferred that the heat convergence in the sea is caused by advection of water masses which are bounded by sharp fronts. Spectral analysis of sea surface temperature indicates that they typically take 2 to 3 days to pass the station, and their typical size is estimated as around 20 km by assuming the typical advection velocity of water masses to be 10 cm s^?1.  相似文献   

Air-Sea Interactions under the Existence of Opposing Swell     

Hisashi?MitsuyasuEmail author  Yoshikazu?Yoshida 《Journal of Oceanography》2005,61(1):141-154

Data of a comprehensive laboratory study on the coexistent system of wind waves and opposing swell (Mitsuyasu and Yoshida, 1989) have been reanalyzed to clarify the air-sea interaction phenomena under the coexistence of wind waves and swell. It is shown that the magnitude of the decay rate of swell due to an opposing wind is almost the same as that of the growth rate of swell caused by a following wind, as measured by Mitsuyasu and Honda (1982). The decay rate is much smaller than that obtained recently by Peirson et al. (2003), but the reason for the disagreement is not clear at present. The effect of an opposing swell on wind waves is very different from that of a following swell; wind waves are intensified by an opposing swell while they are attenuated by a following one. The phenomenon contradicts the model of Phillips and Banner (1974), but the reason for this is not clear at this time. The high-frequency spectrum of wind waves shows a small increase of the spectral density. Wind shear stress increases a little due to the effect of opposing swell. The intensification of wind waves by opposing swell and the small increase of the spectral density in a high-frequency region can be attributed to the increase of wind shear stress. Such organized phenomena lead to the conclusion that the hypothesis of local equilibrium for pure wind waves (Toba, 1972) can also be satisfied for wind waves that coexist with opposing swell. The recent finding of Hanson and Phillips (1999) can be explained by this mechanism.  相似文献   

The chemical composition and the cadmium,chromium and vanadium contents of shall-water deposits in Tokyo Bay     

Masayoshi Ishibashi  Shunzo Ueda  Yoshikazu Yamamoto 《Journal of Oceanography》1970,26(3):189-194

The major elements and the minor elements cadmium, chromium and vanadium in 12 samples of shallow-water deposits collected in Tokyo Bay were studied. Average silica content of the deposits is 53.93%, which is approximate to the average of 54.15% of red clay. Iron (av. 5.67% Fe₂O₃), titanium (av. 0.71% TiO₂), especially manganese (av. 0.87% MnO), are more abundant in the deposits than in the deposits along the entire sea-coasts of Honshu and of Nanao Bay, Japan. The deposits show higher contents of cadmium (av. 0.61 ppm), the chromium (av. 86 ppm) and vanadium (av. 79ppm). About 3 to 17 times cadmium and manganese contents compared with those in the deposits along the sea-coasts of Honshu and of Nanao Bay, Japan was found. Such accumulation, of cadmium and manganese in the deposits is probably caused by artificial contamination rather than of natural origin. No relation was found between the contents of cadmium, chromium and vanadium and those of major elements.  相似文献   

A heating process of Kuchi-erabu-jima volcano,Japan, as inferred from geomagnetic field variations and electrical structure     

Wataru Kanda  Mitsuru Utsugi  Yoshikazu Tanaka  Takeshi Hashimoto  Ikuko Fujii  Toshiaki Hasenaka  Nobuaki Shigeno 《Journal of Volcanology and Geothermal Research》2010,189(1-2):158-171

Since August 2000, we have recorded the total intensity of the geomagnetic field at the summit area of Kuchi-erabu-jima volcano, where phreatic eruptions have repeatedly occurred. A time series analysis has shown that the variations in the geomagnetic field since 2001 have a strong relationship to an increase in volcanic activity. These variations indicate thermal demagnetization of the subsurface around the presently active crater. The demagnetization source for the early variations, until summer 2002, was estimated at about 200 m below sea level. For the variations since 2003, the source was modeled on the basis of the expansion of a uniformly magnetized ellipsoid. The modeling result showed that the source is located at 300 m above sea level beneath the crater. We carried out an audio-frequency magnetotelluric survey with the aim of obtaining a relation between the demagnetization source and the shallow structure of the volcano. A two-dimensional inversion applied to the data detected two good conductors, a shallow thin one which is restricted to a region around the summit area, while the other extends over the edifice at depths between 200 and 800 m. These conductors are regarded as clay-rich layers with low permeability, which were assumed to be generated through hydrothermal alteration. The demagnetization source for the early variations was possibly located at the lower part of the deep conductor and the source after 2003 lies between the two conductors, where groundwater is considered to be abundant. Based on these results, as well as on seismological, geodetic, and geochemical information, we propose a heating process of the Kuchi-erabu-jima volcano. In the initial stage, high-temperature volcanic gases supplied from the deep-seated magma remained temporarily at the level around the lower part of the less permeable deep conductor since the ascent path had not yet been established. Then, when the pathway developed as a result of repeated earthquakes, it became possible for a massive flux of volcanic gases to ascend through the conductor. The high temperature gases reached the aquifer located above the conductor and the heat was efficiently transported to the surrounding rocks through the groundwater. As a consequence, an abrupt increase of the gas flux and diffusion of the heat through the aquifer occurred and the high-temperature zone expanded. Since the high-temperature zone is located beneath another conductor, which acts as caprock, we assume that the energy of the phreatic explosion is accumulated there.  相似文献   

Symposium: Evolution and migration of fossil marine vertebrates in the Pacific realm 29th International Geological Congress, Kyoto, Japan, August 1992     

Lawrence G.  Barnes Yoshikazu  Hasegawa 《Island Arc》1994,3(4):245-246

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Diversity of Pliocene mysticetes from eastern Japan     

Masayuki  Oishi Yoshikazu  Hasegawa 《Island Arc》1994,3(4):436-452

Abstract Assemblages of Early Pliocene Mysticeti (Cetacea) from the Sendai-Iwate and Choshi areas in eastern Japan were examined. The early Early Pliocene Tatsunokuchi and Yushima formations of the Sendai-Iwate area have yielded many cetotheres assigned to Herpetocetus (Cetotheriidae) and some extinct rorquals assigned to Burtinopsis (Balaenopteridae) and other genera. The late Early Pliocene strata of the Na-arai Formation of the Choshi area has yielded more than 300 mysticete ear bones which fall into seven morphotypes. Assemblages from the two areas differ greatly in taxonomic composition. Archaic mysticetes are dominant in the Sendai-Iwate area, while modern mysticetes are dominant and diverse in the Choshi area. Based on the results of this study we conclude that the diversity of the Early Pliocene mysticetes in the western North Pacific is comparable to that of the Recent.  相似文献   

A list of fossil cetaceans in Japan     

Masayuki  Oishi Yoshikazu  Hasegawa 《Island Arc》1994,3(4):493-505

Abstract Fossil cetacea of Japan are abundant and diverse. Despite several summary articles, all the known taxa have not previously been compiled in one place. Here we present a list of the published fossil cetacean records from the Japanese archipelago. The record extends from Middle or Late Oligocene to the Holocene, and includes representatives of both the suborders Odontoceti and Mysticeti. No Eocene Cetacea or Archaeoceti are recorded from Japan. As is typical of the eastern North Pacific and the South Pacific, the Oligocene and Early Miocene assemblages are comprised of archaic and usually extinct families, and the younger assemblages are represented by modern groups comprised of extant genera and families.  相似文献   

Oxygen and strontium isotopic characteristics of calc-alkalic volcanic rocks from the central and western Japan arcs: Evaluation of contribution of crustal components to the magmas     

Yukihiro Matsuhisa  Hajime Kurasawa 《Journal of Volcanology and Geothermal Research》1983,18(1-4)

¹⁸O/¹⁶O and ⁸⁷Sr/⁸⁶Sr ratios were determined for Quaternary calc-alkalic volcanic rocks from six volcanic rock suites in the central and western Japan arcs. The δ¹⁸O values relative to SMOW and ⁸⁷Sr/⁸⁶Sr ratios range from +6.3 to +9.9⁰/₀₀ and 0.70357 to 0.70684, respectively. Both the O- and Sr-isotopic compositions are higher than those for island-arc primitive magmas and their differentiates. The isotopic compositions of the calc-alkalic rocks cannot be derived by a simple fractional crystallization of the primitive magmas. On the other hand, the ¹⁸O- and ⁸⁷Sr-enrichment is confined to the rock suites located in well-developed island arcs having thick continental-type crust with low or negative Bouguer anomalies. Involvement of ¹⁸O- and ⁸⁷Sr-rich crustal material in the magma formation is suggested.The isotopic compositions vary remarkably within individual rock suites as well as from volcano to volcano. The data points in δ¹⁸O vs. ⁸⁷Sr/⁸⁶Sr plot accord with a mixing model between primitive magmas and crustal material of dioritic composition on an average, assuming their comparative Sr contents. The primitive magmas involved could not be low-Sr tholeiites, but magmas more or less enriched in incompatible elements including Sr, which correspond to high-alkali tholeiites or alkali basalts and their evolved magmas. The nature of the primitive magmas seems to change from tholeiitic to more alkalic with progressing island-arc evolution.Mixing of crust-derived melts is more plausible than assimilation of solid-rocks for involving 20 to 30% crustal material in the magmas along simple mixing curves. Isotopic variations between the rock suites are ascribed to variable Sr concentration radio of the end-members, variable isotopic compositions of crustal material or variable mixing ratio of the end-members. Extremely high-δ ¹⁸O rocks with moderate increase in ⁸⁷Sr/⁸⁶Sr ratio suggest another mixing process in shallower magma chambers between andesite magmas and metasedimentary rocks having high δ ¹⁸O and ⁸⁷Sr/⁸⁶Sr values but low Sr content. Subsequent fractional crystallization of once-derived magmas would be the prominent process for the rock suites showing gradual increase in ¹⁸O up to 1⁰/₀₀ with uniform ⁸⁷Sr/⁸⁶Sr ratios.  相似文献   

Cloning and sequencing of the allophycocyanin genes fromSpirulina maxima (Cyanophyta)     

Song  Qin  Kojima  Hiroyuki  Kawata  Yoshikazu  Yano  Shin-ichi  Cheng-kui  Zeng 《中国海洋湖沼学报》1998,16(1):6-11

The genes coding for the α-and β-subunit of allophycocyanin (apcA andapcB) from the cyanophyteSpirulina maxima were cloned and sequenced. The results revealed 44.4% of nucleotide sequence similarity and 30.4% of similarity of deduced amino acid sequence between them. The amino acid sequence identities betweenS. maxima andS. platensis are 99.4% for α subunit and 100% for β subunit.

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