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21.
Both harmonic and seismic responses of several idealized offshore oil pipelines in proximity to the sea-bed have been studied in this paper by using a digital computer algorithm. In this, spatial discretization was based on finite elements, with nodal lumped masses, while a step-by-step explicit forward integration scheme was implemented for processing in the time domain. A study of the basic system parameters shows that pipe response to a horizontal transverse ground excitation is mainly affected by the clearance between the pipe and the sea-bed, pipe geometry and its end-restraints. Results also show that the overall effect of non-linear pressure drag is not substantial. Relevant fluid dynamic aspects affecting system response as well as possible effects of marine growth on pipe surface and structural/chemical degradation of the pipe coating are also discussed. 相似文献
22.
High magnetic susceptibility produced by thermal decomposition of core samples from the Chelungpu fault in Taiwan 总被引：7，自引：0，他引：7
Wataru Tanikawa Toshiaki Mishima Tetsuro Hirono Wonn Soh Sheng-Rong Song 《Earth and Planetary Science Letters》2008,272(1-2):372-381
We carried out thermomagnetic susceptibility analyses of fault rocks from core samples from Hole B of the Taiwan Chelungpu Fault Drilling Project (TCDP) to investigate the cause of high magnetic susceptibilities in the fault core. Test samples were thermally and mechanically treated by heating to different maximum temperatures of up to 900 °C and by high-velocity frictional tests before magnetic analyses. Thermomagnetic susceptibility analyses of natural fault rocks revealed that magnetization increased at maximum heating temperatures above 400 °C in the heating cycle, and showed three step increases, at 600 to 550 °C and at 300 °C during the cooling cycle. These behaviors are consistent with the presence of pyrite, siderite and chlorite, suggesting that TCDP gouge originally included these minerals, which contributed to the generation the magnetic susceptibility by thermomechanical reactions. The change in magnetic susceptibility due to heating of siderite was 20 times that obtained by heating pyrite and chlorite, so that only a small fraction of siderite decomposition is enough to cause the slight increase of the susceptibility observed in the fault core. Color measurement results indicate that thermal decomposition by frictional heating took place under low-oxygen conditions at depth, which prevented the minerals from oxidizing to reddish hematite. This finding supports the inference that a mechanically driven chemical reaction partly accounts for the high magnetic susceptibility. A kinetic model analysis confirmed that frictional heating can cause thermal decomposition of siderite and pyrite. Our results show that decomposition of pyrite to pyrrhotite, siderite and, to some extent, chlorite to magnetite is the probable mechanism explaining the magnetic anomaly within the Chelungpu fault zone. 相似文献
23.
Euchaetid copepods (Calanoida, Clausocalanoidea) were collected from the southeastern region of Korea and the East/Japan Sea
from June 2007 to August 2008. Seven species were found and redescribed in this study: five species from the genus Euchaeta (E. concinna, E. indica, E. longicornis, E. plana and E. rimana) and two species from the genus Paraeuchaeta (P. elongata and P. russelli). Using scanning electron microscopy, we observed detailed taxonomic features with special references to their genital structure.
The euchaetid copepods show speciesspecific characteristics on their genital structures, in particular on the shapes of genital
operculum and genital flange. Their zoogeographies were also discussed. They can be regarded as an indicator species of the
Tsushima Warm Current and East Sea Intermediate Water. 相似文献
24.
Vincent Soh 《GeoJournal》2006,66(4):375-376
25.
Tetsuro Hirono Masumi Sakaguchi Kenshiro Otsuki Hiroki Sone Koichiro Fujimoto Toshiaki Mishima Weiren Lin Wataru Tanikawa Masaharu Tanimizu Wonn Soh En-Chao Yeh Sheng-Rong Song 《Tectonophysics》2008,449(1-4):63-84
To characterize the fault-related rocks within the Chelungpu fault, we performed X-ray computed tomography (CT) image analyses and microstructural observations of Hole B core samples from the Taiwan Chelungpu-fault Drilling Project. We identified the slip zone associated with the 1999 Chi-Chi earthquake, within the black gouge zone in the shallowest major fault zone, by comparison with previous reports. The slip zone was characterized by low CT number, cataclastic (or ultracataclastic) texture, and high possibility to have experienced a mechanically fluidized state. Taking these characteristics and previous reports of frictional heating in the slip zone into consideration, we suggested that thermal pressurization was the most likely dynamic weakening mechanism during the earthquake. 相似文献