Publication List     

Hiroshi Wakita 《Pure and Applied Geophysics》2008,165(1):173-180

  相似文献   

Cretaceous accretionary–collision complexes in central Indonesia     

K. Wakita 《Journal of Asian Earth Sciences》2000,18(6)

The geology of Cretaceous accretionary–collision complexes in central Indonesia is reviewed in this paper. The author and his colleagues have investigated the Cretaceous accretionary–collision complexes by means of radiolarian biostratigraphy and metamorphic petrology, as well as by geological mapping. The results of their work has revealed aspects of the tectonic development of the Sundaland margin in Cretaceous time. The Cretaceous accretionary–collision complexes are composed of various tectonic units formed by accretionary or collision processes, forearc sedimentation, arc volcanism and back arc spreading. The tectonic units consist of chert, limestone, basalt, siliceous shale, sandstone, shale, volcanic breccia, conglomerate, high P/T and ultra high P metamorphic rocks and ultramafic rocks (dismembered ophiolite). All these components were accreted along the Cretaceous convergent margin of the Sundaland Craton. In the Cretaceous, the southeastern margin of Sundaland was surrounded by a marginal sea. An immature volcanic arc was developed peripherally to this marginal sea. An oceanic plate was being subducted beneath the volcanic arc from the south. The oceanic plate carried microcontinents which were detached fragments of Gondwanaland. Oceanic plate subduction caused arc volcanism and formed an accretionary wedge. The accretionary wedge included fragments of oceanic crust such as chert, siliceous shale, limestone and pillow basalt. A Jurassic shallow marine allochthonous formation was emplaced by the collision of continental blocks. This collision also exhumed very high and ultra-high pressure metamorphic rocks from the deeper part of the pre-existing accretionary wedge. Cretaceous tectonic units were rearranged by thrusting and lateral faulting in the Cenozoic era when successive collision of continental blocks and rotation of continental blocks occurred in the Indonesian region.  相似文献   

Sedimentary organic matter contents and porewater chemistry at upper bathyal depths influenced by the 2011 off the Pacific coast of Tohoku Earthquake and tsunami     

Hidetaka Nomaki  Kazuno Arai  Hisami Suga  Takashi Toyofuku  Masahide Wakita  Takuro Nunoura  Kazumasa Oguri  Takafumi Kasaya  Shuichi Watanabe 《Journal of Oceanography》2016,72(1):99-111

  相似文献   

Distribution and photo-physiological condition of phytoplankton in the tropical and subtropical North Pacific     

Tetsuichi Fujiki  Kazuhiko Matsumoto  Toshiro Saino  Masahide Wakita  Shuichi Watanabe 《Journal of Oceanography》2013,69(1):35-43

To better understand the vertical distribution of phytoplankton in the tropical and subtropical North Pacific, we used fast repetition rate fluorometry to investigate the photo-physiological condition of the phytoplankton assemblage in this region between February and March 2007. Along 155°E, between the equator and 24°N, the peak of fluorescence (F _m), an indication of the deep chlorophyll maximum (DCM), was deeper than the top of the nitracline and occurred at the 2.4 ± 1.3 % (mean ± SD) light depth (relative to 0 m). The photochemical efficiency (F _v/F _m) and effective absorption cross-section of photosystem II (σ_PSII) were low at the surface but increased rapidly at depths between the top of the nitracline (40–138 m) and the DCM (70–158 m), an indication that the photo-physiological condition of the phytoplankton improved below the top of the nitracline. The depth of the maximal F _v/F _m [Z(F _v/F _{m max})] was 18–32 m deeper than the DCM and corresponded to the 0.8 ± 0.2 % light depth. The values of F _v/F _m at the Z(F _v/F _{m max}) were 20 % higher than those at the DCM and averaged 0.48 ± 0.01. These results suggest that the phytoplankton assemblage beneath the DCM had a high potential photosynthetic performance capacity and was growing by using the very low ambient light in this region.  相似文献   

Water exchange between the Bering Sea and the Pacific Ocean through the Kamchatka Strait     

I. A. Zhabin  V. B. Lobanov  S. Watanabe  M. Wakita  S. N. Taranova 《Russian Meteorology and Hydrology》2010,35(3):218-224

Hydrological and hydrochemical conditions in the Kamchatka Strait are considered, the computation of geostrophic flows is carried out, and estimations of the water exchange between the Bering Sea and the Pacific Ocean through this strait are made on the basis of the analysis of data obtained during the trip of the research vessel Miraii in August, 2004. According to the results of computations, the volume transport from the Bering Sea to the Pacific Ocean made up 10.2 Sv; mass transport, 10.4 × 10⁹ kg/s; salt transport, 0.35 × 10⁶ kg/s. The estimated value of heat transport through the strait is 11.4 × 10¹⁵ W. The Eastern Kamchatka Current carries oxygen and biogenic elements through the strait: 1222, 28, 380, and 1036 kmol/s for oxygen, phosphates, nitrates, and silicon, respectively. In total, the Bering Sea is the source of oxygen and biogenic elements for the northern part of the Pacific Ocean in the upper 500-m layer.  相似文献   

RARE EARTH AND OTHER ABUNDANCES IN THE MURCHISON CARBONACEOUS METEORITE     

D. L. Showalter  H. Wakita  R. A. Schmitt 《Meteoritics & planetary science》1972,7(3):295-301

The abundances of 27 elements are reported for the Murchison meteorite. Nine of these elements (Al, Ca, Fe, Mn, Na, K, Cr, Co, and Sc) have been determined previously for different Murchison specimens. Abundances for 18 elements (In, Cd, V, Y, and REE) are new data for this meteorite. The chemical composition is similar to the type II carbonaceous chondrites, particularly on the basis of REE, Mn, and In abundances.  相似文献   

An overview and tectonic synthesis of the pre-Tertiary very-high-pressure metamorphic and associated rocks of Java, Sulawesi and Kalimantan, Indonesia   总被引：5，自引：0，他引：5  

C. D. Parkinson  K. Miyazaki  K. Wakita  A. J. Barber  & D. A. Carswell 《Island Arc》1998,7(1-2):184-200

  相似文献   

Helium-isotope systematics at Nevado del Ruiz volcano, Colombia: implications for the volcanic hydrothermal system     

Yuji Sano  Hiroshi Wakita  Stanley N. Williams 《Journal of Volcanology and Geothermal Research》1990,42(1-2)

We have collected 14 water and gas samples from 9 thermal springs and gas vents near Nevado del Ruiz volcano, Colombia. The ³He/⁴He and ⁴He/²⁰Ne ratios vary significantly from 0.98 R_atm (where R_atm is the atmospheric ³He/⁴He ratio of 1.4 × 10⁻⁶) to 6.30 R_atm, and from 0.37 to 7.0, respectively. The ³He/⁴He ratio (corrected for air contamination) decreases with increasing distance from the central crater of the volcano to the sampling site. The trend is very similar to that observed at Ontake volcano, Japan. A hydrodynamic porous-media dispersion model can explain the ³He/⁴He trend. The temporal variations in the ³He/⁴He ratio at four sites provide useful information on the apparent velocity of the magmatic fluid flow brought on by a volcanic eruption. The estimated value of several tens m day⁻¹ agrees well with the inferred velocity of flow in Oshima volcano, Japan and is comparable to the largest rate of groundwater movement in a deep sedimentary basin.  相似文献   

Short-term and intermediate-term geochemical precursors   总被引：2，自引：0，他引：2  

Hiroshi Wakita  Yuji Nakamura  Yuji Sano 《Pure and Applied Geophysics》1988,126(2-4):267-278

Detection of precursory phenomena in observation data is essential to earthquake prediction studies. Continuous monitoring of radon concentration in groundwater in Japan in one case showed a short-term anomaly related to a nearby earthquake. With the exception of the 1978 Izu-Oshimakinkai earthquake (M7.0), however, no abnormal change has been noted. This may be due partially to difficulty in detecting insignificant precursory signals from observation data, which ordinarily contains a noise-induced fluctuations, and partially to lack of understanding of the mechanism controlling the appearance of precursory phenomena. In order to increase our knowledge of the variation pattern of precursory changes in radon concentration of groundwater, hydrologic precursors with significant features are examined in this paper. Complexity of appearance of precursory phenomena and problems in assignment of the specific earthquake are discussed.  相似文献   

Digital Terrane Map of East and Southeast Asia     

Koji Wakita  Ian Metcalfe  Shigeki Hada 《Gondwana Research》1999,2(4):613-614

  相似文献