Rifting characteristics of eastern subbasin of South China Sea and its spreading pattern     

Li Jiabiao  Jin Xiangiong  Gaojinyao 《海洋学报(英文版)》2002,21(1):77-85

With processing and interpretation of 25 000 km full-coverage multibeam swath data fromthe eastern South China Sea, it is found that NE-trending and NW-trending linear morphological features such as scarps, horsts and grabens, govern the central part (14°- 17° N) of eastern subbasin. Compared with reflection seismic profiles, these NE-trending linear morpho-structures are considered to be the representation of basement structures on seabed and can be divided into three linear structural zones. The trend of the central zone is NE45°-50° occurring around extinct spreading center, the trend of the second zone is NE70° - 78° on both sides of the central one and the trend of the third zone is about NE60° just on the north of the second one. These three NE-trending linear zones are formed in late-stage NW - SE-trending seafloor spreading of the eastern subbasin along NW-trending linear faults, and respectively correspond to three spreading episodes: 17.0- 19.0 Ma (5d-5e), 19.0 - 21.0 Ma (5e-6a) and 21.0  相似文献   

Investigation of Π-type breakwaters performance under regular and irregular waves     

K. Günayd&#x;n  M.S. Kabdal&#x; 《Ocean Engineering》2007,34(7):1028-1043

In this paper, performance of solid and perforated Π-type breakwaters was investigated experimentally. Both regular and irregular waves were used during testing. Four depths of immersions were selected for each breakwater and wave type. Different wave groups were generated over these breakwaters, and the transmission, reflection and energy-dissipation characteristics were determined. The results of the experimental study were evaluated and some empirical expressions based on the results were suggested to define the transmission, reflection and energy-dissipation coefficients for different immersion depths of solid and perforated breakwaters under regular and irregular waves. Moreover, performance of solid and perforated Π-type breakwaters were compared with that of solid and perforated U-type breakwaters investigated by Günaydın and Kabdaşlı [2006. Performance of solid and perforated U-type breakwaters under regular and irregular waves. Ocean Engineering 31, 1377–1405]. These comparisons showed that the most reasonable model and wave type are selected to determine requiring performance parameters.  相似文献   

Feedforward and feedback optimal control for offshore structures subjected to irregular wave forces     

Hui Ma  Gong-You Tang  Yan-Dong Zhao 《Ocean Engineering》2006,33(8-9):1105-1117

This paper studies the vibration control of a jacket-type offshore platform with an active mass damper (AMD) and presents a feedforward and feedback optimal control (FFOC) law. The linearized Morison equation is employed to estimate the wave load. The offshore structure is simplified into a single degree of freedom (SDOF) system. The original vibration control is formulated as the optimal control for a linear discrete-time system affected by external disturbances with known dynamic characteristics but unknown initial conditions. We give the existence and uniqueness conditions of the FFOC law. Simulation results show that, compared with the classical state feedback optimal control (CFOC) law, the presented control scheme is more efficient in reducing the displacement and velocity of the offshore structure subjected to irregular wave forces.  相似文献   

南海的天然气水合物矿藏   总被引：61，自引：1，他引：61  

姚伯初 《热带海洋学报》2001,20(2):20-28

讨论了南海的地形地貌特征，以及中新生代的构造运动历程，认识到中中新世之前，这里经历了一系列的构造运动，但在中国新世之中，这里无构造运动，只是发生区域沉降，由此认为南海应有丰富的天然气水合物矿藏，进而估算了南海天然气水合物的总资源达643．5亿一772．2亿t油当量。  相似文献   

南黄海海底地势分区   总被引：1，自引：0，他引：1  

林美华  毛彦平 《海洋科学》1989,13(4):21-24

本文对南黄海海底地势分区进行了研究,结果表明,南黄海是半封闭的内陆浅海,为新生代沉积盆地,深受外力作用的塑造。海底由西部缓倾斜地势区、西南部辐射状地势区、东部朝鲜半岛西岸水下冲刷槽沟地势区和中部浅海平原及黄海海槽地势区组成,形成由东西两侧向中部缓倾斜的基本面貌。  相似文献   

多尺度重力分析伊朗莫霍面及其构造意义     

张弛  张双喜  汪海洪 《大地测量与地球动力学》2020,40(2):182-186

利用多尺度重力分析方法提取源自莫霍面起伏的重力异常信号,并确定整个伊朗的莫霍面,反演的伊朗莫霍面与前人研究结果相一致。另外,伊朗西部的莫霍面深度比东部深,表明西部的阿拉伯地块与欧亚板块相对于东部具有更早期的碰撞。  相似文献   

Large-scale Circulation Control of the Occurrence of Low-level Turbulence at Hong Kong International Airport     

Marco Y.T.LEUNG  Wen ZHOU  Chi-Ming SHUN  Pak-Wai CHAN 《大气科学进展》2018,35(4):435-444

This study identifies the atmospheric circulation features that are favorable for the occurrence of low-level turbulence at Hong Kong International Airport [below 1600 feet(around 500 m)]. By using LIDAR data at the airport, turbulence and nonturbulence cases are selected. It is found that the occurrence of turbulence is significantly related to the strength of the southerly wind at 850 h Pa over the South China coast. On the other hand, the east–west wind at this height demonstrates a weak relation to the occurrence. This suggests that turbulence is generated by flow passing Lantau Island from the south. The southerly wind also transports moisture from the South China Sea to Hong Kong, reducing local stability. This is favorable for the development of strong turbulence. It is also noted that the strong southerly wind during the occurrence of low-level turbulence is contributed by an anomalous zonal gradient of geopotential in the lower troposphere over the South China Sea. This gradient is caused by the combination of variations at different timescales. These are the passage of synoptic extratropical cyclones and anticyclones and the intraseasonal variation in the western North Pacific subtropical high. The seasonal variation in geopotential east of the Tibetan Plateau leads to a seasonal change in meridional wind, by which the frequency of low-level turbulence is maximized in spring and minimized in autumn.  相似文献   

用T／P测高数据确定中国海域及其邻海的海面高及海面地形     

陈俊勇  李建成  晁定波 《武汉大学学报(信息科学版)》1995,(4)

描述了利用Ｔ／Ｐ卫星测高数据确定中国海域及其邻海的海面地形。处理了Ｔ／Ｐ５９～８２周（Ｃｙｃｌｅ）１９９４年第８３ｄ～３１１ｄ的数据，将５９～８２周数据分成两部分分别估计海面高，并分析了海面高变化。结果与Ｂａｓｉｃ和Ｒａｐｐ１９９２年确定的海面高作了比较。利用Ｓｈｅｐａｒｄ曲面拟合方法给出了３０′×３０′平均海面高结果，分别以ＯＳＵ９１和ＷＤＭ９４地球重力场模型作为参考重力场，计算了相应的３０′×３０′平均海面地形。  相似文献   

Modelling gravel-bed topography from sediment transport     

Pamela Naden 《地球表面变化过程与地形》1987,12(4):353-367

A simple queueing model which generates bed topography consistent with the mechanics of gravel motion is presented. The equations on which it is based are derived from the application of simple theoretical ideas and an analysis of published flume data (Meland and Norrman, 1966; Francis, 1973; Abbott and Francis, 1977). The simulation produces an extremely variable bed topography in which at least two scales of bedform may be identified. Features of 5–10 grain wavelengths, similar to pebble clusters, are superimposed on other forms whose wavelength is up to 30–40 grains and which resemble step-pools systems and antidunes. Sediment transport shows many of the characteristics found in the field and the model is, therefore, thought to provide a useful starting point from which to examine the interaction between flow, sediment transport, and bedforms in gravel-bed and cobble streams.  相似文献   

Flow,bed topography,grain size and sedimentary structure in open channel bends: A three-dimensional model: A reply     

John S. Bridge 《地球表面变化过程与地形》1978,3(4):423-424

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