稳恒水波的Fourier近似解研究   总被引：1，自引：0，他引：1  

ZHAO Hongjun  SONG Zhiyao  LI Ling  KONG Jun 《海洋学报(英文版)》2014,33(5):37-47

A computational method for steady water waves is presented on the basis of potential theory in the physical plane with spatial variables as independent quantities. The finite Fourier series are applied to approximating the free surface and potential function. A set of nonlinear algebraic equations for the Fourier coefficients are derived from the free surface kinetic and dynamic boundary conditions. These algebraic equations are numerically solved through Newton＇s iterative method, and the iterative stability is further improved by a relaxation technology. The integral properties of steady water waves are numerically analyzed, showing that （1） the set-up and the set-down are both non-monotonic quantities with the wave steepness, and （2） the Fourier spectrum of the free surface is broader than that of the potential function. The latter further leads us to explore a modification for the present method by approximating the free surface and potential function through different Fourier series, with the truncation of the former higher than that of the latter. Numerical tests show that this modification is effective, and can notably reduce the errors of the free surface boundary conditions.  相似文献   

黏弹性VTI介质频率空间域准P波正演模拟   总被引：7，自引：5，他引：2       下载免费PDF全文

李桂花  冯建国  朱光明 《地球物理学报》2011,54(1):200-207

有限差分方法是波场数值模拟的一个重要方法,时间域有限差分计算方法因按时间片递推计算,每个时间片的舍入误差会累积到下一片中,当时间片较多,最终会导致累积误差太大.而频率域计算是按频率片对空间网格进行整体求解方程组,其计算误差分配到了每个网格点上,并且各个频率片之间是独立计算的,因此不存在累计误差,而且在频率-空间域更易于...  相似文献   

Rapid afterslip and short-term viscoelastic relaxation following the 2008 M_W7.9 Wenchuan earthquake     

Zhigang Shao Rongjiang Wang  Yanqiang Wu  Langping Zhang Institute of Earthquake Science  China Earthquake Administration  Beijing  China GFZ German Research Center for Geosciences  D- Potsdam  Germany 《地震学报(英文版)》2011,(2):163-175

Significant postseismic deformation of the 2008 M W 7.9 Wenchuan earthquake has been observed from GPS data of the first 14 days after the earthquake. The possible mechanisms for the rapid postseismic deformation are assumed to be afterslip on the earthquake rupture plane and viscoelastic relaxation of coseismiclly stress change in the lower crust or upper mantle. We firstly use the constrained least squares method to find an afterslip model which can fit the GPS data best. The afterslip model can explain n...  相似文献   

Effective relaxation time and viscosity of the earth inferred from the postseismic vertical deformations of the 1990 MS=7.0 Gonghe earthquake   总被引：2，自引：0，他引：2  

王庆良  巩守文  张希  祝意青 《地震学报(英文版)》1997,(5)

Ｅｆｅｃｔｉｖｅｒｅｌａｘａｔｉｏｎｔｉｍｅａｎｄｖｉｓｃｏｓｉｔｙｏｆｔｈｅｅａｒｔｈｉｎｆｅｒｅｄｆｒｏｍｔｈｅｐｏｓｔｓｅｉｓｍｉｃｖｅｒｔｉｃａｌｄｅｆｏｒｍａｔｉｏｎｓｏｆｔｈｅ１９９０ＭＳ＝７．０ＧｏｎｇｈｅｅａｒｔｈｑｕａｋｅＱＩ...  相似文献   

An improved probabilistic relaxation method for matching multi-scale road networks     

Jianchen Zhang  Wenji Zhao 《International Journal of Digital Earth》2018,11(6):635-655

Matching multi-scale road networks in the same area is the first step in merging two road networks or updating one based upon the other. The quality of the merge or update depends greatly on the matching accuracy of the two road networks. We propose an improved probabilistic relaxation method, considering both local and global optimizations for matching multi-scale of road networks. The aim is to achieve local optimization, as well as to address the identification of the M:N matching pattern by means of inserting virtual nodes to achieve global optimization effects. Then, by adding two attribute-related evaluation indicators, we developed four evaluation indicators to evaluate the matching accuracy, considering both geographic and attribute information. This paper also provides instructions on how to identify the proper buffer threshold during matching procedures. Extensive experiments were conducted to compare the proposed method with the traditional approach. The results indicate that: (1) the overall matching accuracy of each evaluation indicator exceeds 90%; (2) the overall matching accuracy increases by 6–12% after an M:N matching pattern is added, and by 4–6% following the addition of topology indicators; and (3) the proper buffer threshold is about twice the average value of the closest distance from all nodes.  相似文献   

Open Fissure Folds record coseismic loading and postseismic stress relaxation     

《Journal of Structural Geology》2015

Open Fissure Folds hosted by high pressure/low temperature metamorphic rocks of south Evia (Greece) are introduced, their structural and microstructural record is analysed, and a mechanical model is proposed. Open Fissure Folds are preserved as at least two parallel folded quartz–feldspar veins separated by narrow buckled rock columns. The veins originated as tensile cracks that propagated in the middle crust driven by high differential stress. Features diagnostic for Open Fissure Folds indicate that the rock columns represented the layers of high viscosity, and not the veins as consistently reported in many previous studies on folded veins. This record is taken to indicate that buckling of the rock columns initiated after arrest of the fractures and terminated prior to complete vein sealing. Accordingly, mechanical decoupling by open fissures allowed for buckling of the rock columns in response to episodic creep of the host rocks according to stress relaxation, as expected for postseismic deformation in the earthquake cycle. I propose that the parental fractures propagated in response to quasi-instantaneous coseismic loading of the middle crust. Buckling was attributed to transient postseismic creep and stress relaxation. Complete sealing of the veins occurred when stresses were largely relaxed. Each Open Fissure Fold records the stress and strain history of a single earthquake.  相似文献   

鲜水河断裂带库仑应力演化与强震间关系   总被引：14，自引：5，他引：9       下载免费PDF全文

徐晶  邵志刚  马宏生  张浪平 《地球物理学报》2013,56(4):1146-1158

以鲜水河断裂带为研究区,首先验证了该断裂带上1893年以来M6.7以上地震的相互触发作用,然后采用更符合实际的分层黏弹介质模型研究强震震后黏滞松弛引起的库仑应力变化对后续地震的影响,并基于负位错理论计算鲜水河断裂带10个断层段的震间长期构造加载作用引起的断层上的应力积累.在此基础上,讨论同震、震后、震间效应引起的累积库仑应力变化与区域强震活动的关系,给出断层上库仑应力随时间的演化.结果表明,鲜水河断裂带上1893年以来发生的7次强震均在其前面一系列强震及构造应力加载的驱使下发生,同震、震后、震间三方面效应均引起了鲜水河断裂带不可忽略的库仑应力变化.对断层上的库仑应力状态的研究,可进一步为揭示地震的发生规律、找寻危险断层段提供线索.  相似文献   

塔里木盆地晚志留世-石炭纪伸展构造的发现及其地质意义   总被引：1，自引：0，他引：1       下载免费PDF全文

李日俊  孙龙德  杨海军  张光亚  曾昌民  冯晓军  文磊  张强  贾铁干 《地质科学》2014,(1):30-48

通过精细的地震资料解释,在塔里木盆地中部的满西地区发现晚志留世-石炭纪伸展构造。伸展构造由一系列规模不大的正断层组成,平面上组成两条北东-南西向的左行雁列状正断层带,剖面上构成负花状构造和堑垒构造。根据生长系数计算结果,正断层形成于晚志留世,在泥盆纪和石炭纪持续活动,于石炭纪末停止活动。正断层活动的高峰期为晚志留世。该期伸展构造在塔中和塔北地区也有发育,反映当时塔里木盆地处于区域性伸展构造背景。塔里木盆地晚志留世-石炭纪的伸展构造,是昆仑早古生代晚期（晚奥陶世-中志留世）碰撞造山后构造应力松弛作用的产物。  相似文献   

On the use of discrete element modelling to simulate the viscoelastic deformation behaviour of an idealized asphalt mixture     

《Geomechanics and Geoengineering》2013,8(2):77-86

The use of discrete-element modelling (DEM) to simulate the behaviour of a highly idealized bituminous mixture under uniaxial and triaxial compressive creep tests is investigated in this paper. The idealized mixture comprises single-sized spherical particles (sand) mixed with bitumen and was chosen so that the packing characteristics are known and the behaviour of the mixture is dominated by the bitumen. The bitumen is represented as shear and normal (tensile and compressive) contact stiffnesses. Numerical sample preparation procedures for specimens containing spherical particles or clumps have been developed to ensure that the final specimen is isotropic and has the correct volumetric proportions. An elastic contact was used for the compressive normal contact stiffness and a viscoelastic contact was used for shear and tensile normal contact stiffness. Simulation results show that the idealized mixture is found to dilate when the ratio of compressive to tensile contact stiffness increases as a function of loading time. Uniaxial and triaxial viscoelastic simulations have been performed to investigate the effect of stress ratio on dilation and the numerical results have been verified with experimental data. The effects of introducing a proportion of frictional contacts and a more complex particle shape (clump) on dilation have been examined.  相似文献   

引入松弛因子的高分辨率遥感影像自动多层次分割     

邓富亮  唐娉  刘源  杨崇俊 《遥感学报》2013,17(6):1492-1507

针对当前高分辨率遥感影像多层次分割尺度参数设置缺少理论框架支持、人为因素影响较多等缺点,提出一种引入松弛因子的高分辨率遥感影像自动多层次分割方法。该方法利用1个松弛因子调节引导区域对象合并的异质性值大小,通过控制每次递归合并区域的对象个数,提高了整体分割的速度;以区域对象间异质性平均值作为基数,引入另一个松弛因子控制分割过程中层次输出的尺度参数,使整个分割过程自动得到不同尺度的多层次分割结果。实验结果表明,该方法具有较高的分割质量,能够满足遥感影像分析及地物提取的精度要求,并且减少了人为因素影响,提高了自动化程度。但是,对于复杂图像内容的地物目标边界处理和减少狭长区域对象的出现还需要进一步深入研究和实践。  相似文献