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111.
X. Le Pichon T. Iiyama H. Chamley J. Charvet M. Faure H. Fujimoto T. Furuta Y. Ida H. Kagami S. Lallemant J. Leggett A. Murata H. Okada C. Rangin V. Renard A. Taira H. Tokuyama 《Earth and Planetary Science Letters》1987,83(1-4)
Seabeam mapping and detailed geophysical surveying have been conducted over the Nankai Trough where the fossil Shikoku Ridge is subducted below southwest Japan. The geometry of the oceanic lithosphere bending under the margin as well as the three-dimensional structure of the accretionary prism have thus been determined in detail. Three 350° trending, probably transform faults have been identified in the area of the survey. They do not extend further south and appear to be limited to the last phase of spreading within the Shikoku Basin, probably between 15 and 12 Ma; this last phase of spreading would then have been accompanied by a sharp change in spreading direction from east-west to N 350°. The two eastern transform faults limit a zone of reduced Nankai trench fill of turbidites opposite to the Tosa Bae Embayment. This observation suggests that the Tosa Bae Embayment actually results from this reduced supply of trench fill to the imbricate thrusting process. The accretionary prism can be divided into three different tectonic provinces separated by continuous mappable thrusts, the Lower and Upper Main Thrusts. Surface shortening is limited to the lower accretionary prism south of the Upper Main Thrust (UMT) whereas uplift with possible extension characterizes the prism above the UMT. Deformation, due to the relative plate motion, mostly affects the lower accretionary prism south of the UMT. 相似文献
112.
113.
The hydroxyl column abundance in the middle atmosphere is measured with ground-based uv spectroscopy using the sun as a light source. The present method is distinctive in that it utilizes the Doppler shift of the solar spectrum due to the solar rotation to discriminate the slight terrestrial hydroxyl absorption from prominent solar features. By comparing the spectra measured on the east and the west edges of the solar disk, it is possible to cancel out most of the solar structures and to make the terrestrial features much more evident. 相似文献
114.
Takashi?SasaokaEmail author Tri?Karian Akihiro?Hamanaka Hideki?Shimada Kikuo?Matsui Masatomo?Ichinose 《Geotechnical and Geological Engineering》2016,34(2):671-678
The basic objectives of mine roadways are to provide sufficient cross sections to accommodate equipment, transport, personnel travel and ventilation. However, many roadways become damaged to the extent of needing maintenance, generally dinting, and in some cases requiring re-ripping. Strata conditions play important effects on stability of roadways and other mining activities. Weak rocks cause excessive roadway closures, and water softens some rocks and worsens the closure problem. Therefore, study on effect of mine water on the stability of underground coal mine roadways is important for underground coal mine development. A scientific discussion on the effect of water on the stability of roadways is given on the basis of results obtained by means of field investigation and laboratory tests. Based on analysis, rock in saturated condition has only between 0.19 to 0.49 of its compressive strength and 0.17 to 0.59 of its tensile strength in dry condition. Among the coal measures rock in research area, water has the most obvious effect on the strength reduction of shale. The slaking behavior of shale has also been the worst among the other. Field investigation of roadway driven in shale shown vertical closure in the wet and dry condition area reached 40–60 and 5–15 cm respectively, in 30 days after the drivage. Among the measures, drainage is considered to be the most economical and simplest method to reduce the water content in the rocks or the rock masses. 相似文献
115.
1Introduction ThePacificabaloneHaliotisdiscushannaiisan importantspeciesinthecoastalfisheriesofnorthern China,andisofhighcommercialvalue.Thepro ductionofcultureseedsfortheabalonebeganin Chinaintheearly1980s.Duringthelasttwodec ades,productionofabalonehasi… 相似文献
116.
Akihiro Shiomoto Katsuyuki Sasaki Toru Shimoda Satsuki Matsumura 《Journal of Oceanography》1994,50(2):209-222
Primary productivity was measured byin situ method using13C in the offshore Oyashio region in the spring (May) and summer (September) of 1990. Most of the values were within the range of 0.1 to 4 gC 1–1 h–1 although a very large value, 7.96 gC l–1 h–1, was observed in summer. Most daily primary production fell within the range of 372 to 633 mgC m–2 d–1 although a very large value, 2,109 mgC m–2 d–1, was observed around the frontal area in summer. Chlorophylla (Chl.a) exceeded 1 g l–1 in many cases, and the maximum was 4.61 g l–1 in spring and 7.53 g l–1 in summer. Most primary productivity per unit Chl.a (photosynthetic assimilation ratio) was within the range of 0.1 to 3 gC gChl.a
–1 h–1 although higher values, 3–6 gC gChl.a
–1 h–1, were observed where small-size phytoplanktons (<2 m) were dominant. These results were compared with results obtained until now in the Oyashio region. The values beyond the range obtained so far in the offshore region were also observed in this study. Furthermore, it was pointed out that the size composition of phytoplankton community has significant influence on the results of Chl.a and photosynthetic assimilation ratio in the Oyashio region. 相似文献
117.
Dintwe Tumelo K. M. Sasaoka Takashi Shimada Hideki Hamanaka Akihiro Moses Dyson N. Peng Ma Fanfei Meng Liu Seifei Ssebadduka Ronald Onyango Joan A. 《Geotechnical and Geological Engineering》2022,40(4):2213-2229
Geotechnical and Geological Engineering - Crown pillars provide regional and local support by isolating the ground surface from underground mine workings. Topography above the underground mine may... 相似文献
118.
Statistical and Parametric Studies on Natural Levees as Weak Points Against Leakages in River Levees
Geotechnical and Geological Engineering - Sandy natural levee deposits have been pointed out to provide seepage paths under river levees, which are largely related to the underseepage problems.... 相似文献
119.
Hirotoshi Sakagami Nobuo Takahashi Akihiro Hachikubo Hirotsugu Minami Satoshi Yamashita Hitoshi Shoji Oleg Khlystov Gennadiy Kalmychkov Mikhail Grachev Marc De Batist 《Geo-Marine Letters》2012,32(5-6):465-472
Assessments of the molecular and isotopic composition of hydrate-bound and dissolved gases in pore water were conducted during the multi-phase gas hydrate project (MHP-09) cruise VER09-03 to the southern basin of Lake Baikal in September 2009. To avoid changes in gas composition during core sampling and transport, various headspace methods were investigated aimed at preserving the dissolved gases in pore water. When distilled water was added to the sediment samples, the concentrations of carbon dioxide and oxygen decreased because of dissolution into the water and/or microbial consumption. When the headspace was not flushed with inert gases, trace levels of hydrogen and ethylene were detected. The findings suggest that best preparation is achieved by flushing the headspace with helium, and adding a saturated aqueous solution of sodium chloride. This improved headspace method served to examine the molecular and isotopic compositions of gas samples retrieved at several new sites in the southern basin. Methane was the major component, and the proportion of ethane ranged widely from 0.0009 to 1.67?mol% of the total hydrocarbon gases. The proportions of propane and higher hydrocarbons were small or less than their detection limits. The carbon isotope signatures suggest that microbial-sourced methane and ethane were dominant in the Peschanka study area, whereas ethane was of thermogenic origin at all other study sites in the southern basin of Lake Baikal. 相似文献
120.
Carbon isotope stratigraphy of the Late Jurassic and earliest Cretaceous was revealed from Torinosu‐type limestone, which was deposited in a shallow‐marine setting in the western Paleo‐Pacific, in Japan. Two sections were examined; the Nakanosawa section of the late Kimmeridgian to early Tithonian age (Fukushima Prefecture, Northeast Japan), and the Furuichi section of the late Kimmeridgian to early Berriasian age (Ehime Prefecture, Southwest Japan). The age‐model was established using Sr isotope ratio and fossil occurrence. The limestone samples have a low Mn/Sr ratio (mostly <0.5) and lack a distinct correlation between δ13C and δ18O, indicating a low degree of diagenetic alteration. Our composite δ13C profile from the two limestone sections shows three stratigraphic correlation points that can be correlated with the profiles of relevant ages from the Alpine Tethyan region: a large‐amplitude fluctuation (the lower upper Kimmeridgian, ~152 Ma), a positive anomaly (above the Kimmeridgian/Tithonian boundary, ~150 Ma), and a negative anomaly (the upper lower Tithonian, ~148 Ma). In addition, we found that δ13C values of the Torinosu‐type limestone are ~1‰ lower than the Tethyan values in the late Kimmeridgian. This inter‐regional difference in δ13C values is likely to have resulted from a higher productivity and/or an organic burial in the Tethyan region. The difference gradually reduces and disappears in the late Tithonian, where the Tethyan and our δ13C records show similar stable values of 1.5–2.0‰. This isotopic homogenization is probably due to changes in the continental distribution and the global ocean circulation, which propagated the 13C‐depleted signature from the larger Paleo‐Pacific to the smaller Tethys Ocean during this time. 相似文献