Fast static correction methods for high-frequency multichannel marine seismic reflection data: A high-resolution seismic study of channel-levee systems on the Bengal Fan     

Martin Gutowski  Monika Breitzke  Volkhard Spieß 《Marine Geophysical Researches》2002,23(1):57-75

Very high-frequency marine multichannel seismic reflection data generated by small-volume air- or waterguns allow detailed, high-resolution studies of sedimentary structures of the order of one to few metres wavelength. The high-frequency content, however, requires (1) a very exact knowledge of the source and receiver positions, and (2) the development of data processing methods which take this exact geometry into account. Static corrections are crucial for the quality of very high-frequency stacked data because static shifts caused by variations of the source and streamer depths are of the order of half to one dominant wavelength, so that they can lead to destructive interference during stacking of CDP sorted traces. As common surface-consistent residual static correction methods developed for land seismic data require fixed shot and receiver locations two simple and fast techniques have been developed for marine seismic data with moving sources and receivers to correct such static shifts. The first method – called CDP static correction method – is based on a simultaneous recording of Parasound sediment echosounder and multichannel seismic reflection data. It compares the depth information derived from the first arrivals of both data sets to calculate static correction time shifts for each seismic channel relative to the Parasound water depths. The second method – called average static correction method – utilises the fact that the streamer depth is mainly controlled by bird units, which keep the streamer in a predefined depth at certain increments but do not prevent the streamer from being slightly buoyant in-between. In case of calm weather conditions these streamer bendings mainly contribute to the overall static time shifts, whereas depth variations of the source are negligible. Hence, mean static correction time shifts are calculated for each channel by averaging the depth values determined at each geophone group position for several subsequent shots. Application of both methods to data of a high-resolution seismic survey of channel-levee systems on the Bengal Fan shows that the quality of the stacked section can be improved significantly compared to stacking results achieved without preceding static corrections. The optimised records show sedimentary features in great detail, that are not visible without static corrections. Limitations only result from the sea floor topography. The CDP static correction method generally provides more coherent reflections than the average static correction method but can only be applied in areas with rather flat sea floor, where no diffraction hyperbolae occur. In contrast, the average static correction method can also be used in regions with rough morphology, but the coherency of reflections is slightly reduced compared to the results of the CDP static correction method.  相似文献   

潜艇疲劳载荷的概率模型   总被引：1，自引：0，他引：1  

黄小平  崔维成 《海洋工程》2003,21(3):18-23

探讨了建立潜艇疲劳载荷概率模型的方法，引入了正态分布和两参数威布尔分布两种概率模型。两参数威布尔分布较适合于用来描述潜艇下潜深度分布的概率特征。可根据潜艇的设计参数、任务及航行区域等因素来选取最可能的分布形式获得潜深分布密度函数。潜艇疲劳热点部位的应力(应变)幅值分布，可由应力(应变)和潜深的关系通过相应的变换得到。  相似文献   

Rain-Flow and Reverse Rain-Flow Counting Method for the Compilation of Fatigue Load Spectrum     

宋玉普  王立成  李朝阳 《中国海洋工程》2001,(3):429-435

The rain-flow counting method is widely used to compile the fatigue load spectrum. The second stage counting of the rain-flow method is a troublesome process. In order to overcome this drawback, the rain-flow and reverse rain-flow counting method is proposed in this paper. In this counting method, the rule for counting of the rain-flow method is modified, so that the sequence of load-time need not be adjusted. This is a valid and useful method to count cycles and compile the load spectrum and it can be widely used in ocean engineering.  相似文献   

Prediction of Load Carrying Capacity of Corroded Reinforced Concrete Beam     

范颖芳  周晶冯新 《中国海洋工程》2004,18(1):107-118

A novel method for prediction of the load carrying capacity of a corroded reinforced concrete beam (CRCB) is presented in the paper. Nine reinforced concrete beams, which had been working in an aggressive environment for more than 10 years, were tested in the laboratory. Comprehensive tests, including flexural test, strength test for corroded concrete and rusty rebar, and pullout test for bond strength between concrete and rebar, were condueted. The flexural test results of CRCBs reveal that the distribution of surface cracks on the beams shows a fractal behavior. The relationship between the fractal dimensions and mechanical properties of CRCBs is then studied. A prediction model based on artificial neural network (ANN) is established by the use of the fractal dimension as the corrosion index, together with the basic intbrmation of the beam. The validity of the prediction model is demonstrated through the experimental data, and satisfactory resuits are achieved.  相似文献   

底部浮泥表层推移速度分布的ADCP—GPS估测方法   总被引：3，自引：0，他引：3  

吴中  陈力平等 《海洋工程》2002,20(4):85-88

ADCP对底跟踪走航观测的流速数据中包含水体底部浮泥、底沙运动信息,对比GPS定位方法算出的水体流速数据可以分离出浮泥相对于GPS定位的运动信号,从而达到对底质推移观测的目的。  相似文献   

Two-Dimensional Mathematical Model of Tidal Current and Sediment for Oujiang Estnary and Wenzhou Bay   总被引：1，自引：0，他引：1  

LU  Yongjun 《中国海洋工程》2002,16(1):107-122

A 2-D mathematical model of tidal current and sediment has been developed for the Oujiang Estuary and the WenzhouBay. This model accomodates complicated features including multiple islands, existence of turbidity, and significant differ-ence in size distribution of bed material. The governing equations for non-uniform suspended load and bed load transport arepresented in a boundary-fitted orthogonal curvilinear coordinate system. The numerical solution procedures along with theirinitial conditions, boundary conditions, and movable boundary technique are presented. Strategies for computation of thecritical condition of deposition or erosion, sediment transport capacity, non-uniform bed load discharge, etc. are suggested.The model verification computation shows that, the tidal levels computed from the model are in good agreement with the fielddata at the 18 tidal gauge stations. The computed velocities and flow directions also agree well with the values measuredalong the totally 52 synchronously observed verticals distributed over 8 cross sections. The computed tidal water throughputsthrough the Huangda‘ao cross section are close to the measured data. And the computed values of bed deformation fromYangfushan to the estuary outfall and in the outer-sea area are in good agreement with the data observed from 1986 to 1992.The changes of tidal volumes through the estuary, velocities in different channels and the bed form due to the influence of thereclamation project on the Wenzhou shoal are predicted by means of this model.  相似文献   

An Analysis on Limit Load for Corroded Submarine Pipelines     

谭开忍  肖熙 《中国海洋工程》2006,20(3):483-490

1 .Introduction Submarine pipelines are one of the safest and the least environmentally disruptive means for ma-rine gas or oil transport . With the development of exploitation of submarine oil or gas ,the safety ofsubmarine pipelines has becomethe major …  相似文献   

一种污水排海的近远区计算与控制方法──以大亚湾水容量计算及污水排海为例     

韩保新  彭海君  曾小清  胡康萍  吕先林 《热带海洋学报》1996,(4)

针对点容量计算中混合区限制的要求，采用了动量积分法、经验公式法和有限差分法，分别对污水排放后可能引起的近区、过渡区和远区的污水浓度变化进行了模拟预测，并就一定的限制性条件对容量点近区、高浓度混合区及容量点远区影响范围进行了分析。在大亚湾水容量计算及污水排海规划中的应用表明，该法具有计算机时较省、精度相对较高等优点。  相似文献   

Treatment of Hydrodynamic Loading for Random Sea State     

Anjan Sarkar  Suhail Ahmad  T. K. Datta M. Tech. Student Assistant Professor 《中国海洋工程》1996,(3)

- In order to employ cost effective frequency domain analysis for off-shore structures treatment of hydrodynamic loading is essential. Drag and inertia dominated, resonating and antiresonating cases under random sea states are analyzed to highlight the implications and relative merits of four salient linearization techniques.  相似文献   

双船中层拖网网位控制的静力学解析   总被引：1，自引：0，他引：1  

万荣  朱文斌  何鑫  崔勇  刘莉莉 《中国海洋大学学报(自然科学版)》2007,37(1):61-64,6

中层拖网是开发利用中上层鱼类资源的重要工具之一,能否有效实施对拖网作业水层的控制,是实现瞄准捕捞和提高捕捞生产效率的关键。本文提出了1种基于有限元原理的拖网曳纲形状与张力的理论计算方法,以期依据中层拖网拖曳过程中不同拖速、曳纲长度和重锤配备条件下曳纲响应的计算机模拟结果,预测拖网可能的作业水层,以实现中层拖网网位控制,为中层拖网曳纲设计和网位调整提供理论依据。  相似文献