Surface motion of a semi-cylindrical hill for incident plane SV waves： Analytical solution     

梁建文  张彦帅Vincent W Lee 《地震学报(英文版)》2006,19(3):251-263

Introduction Scattering of incident waves by local topographies is one of the most attractive topics in the field of engineering seismology. They can be resolved by either a numerical method or an analyti-cal method. The numerical methods include finite difference method, finite element method, boundary element method, etc. The analytical method is the wave function expansion method. Al-though numerical methods can be used for arbitrary-shaped topographies, the analytical solutions are still …  相似文献   

浅圆沉积谷地对瑞雷波的散射-高频解   总被引：12，自引：3，他引：12       下载免费PDF全文

梁建文  张秋红  李方杰 《地震学报》2006,28(2):176-182

利用波函数展开法给出了浅圆沉积谷地对瑞雷波散射的一个高频解析解，并分析了入射频率、沉积谷地宽度和深度等因素对波散射的影响. 数值结果表明，由于沉积谷地的影响， 在入射波的近端，地表位移分布变得相对复杂，但位移幅值并不大；而在入射波远端，地表位移分布相对简单，但位移幅值却相对较大，多数情况下高于沉积地表位移幅值.   相似文献   

平面SV波入射下半圆凸起地形地表运动解析解   总被引：8，自引：0，他引：8       下载免费PDF全文

梁建文  张彦帅  Vincent W Lee 《地震学报》2006,28(3):238-249

采用波函数展开法，并借助辅助函数思想，给出了平面SV波入射下半圆凸起地形地表运动的一个解析解，并对解答的收敛性和截断计算精度进行了检验；最后通过若干算例分析了入射频率和入射角度以及凸起地形宽度对地表运动的影响. 数值结果表明，凸起地形对入射SV波具有显著的放大作用， 该放大作用可达自由场的4倍以上. 当入射频率较低时， 位移峰值多位于半空间地表; 而当入射频率较高时，位移峰值多位于凸起地形表面.   相似文献   

一种新的实时电磁逆散射方法   总被引：2，自引：0，他引：2       下载免费PDF全文

张清河  肖柏勋  朱国强 《地球物理学报》2006,49(5):1546-1551

为解决介质圆柱体逆散射问题，提出一种新的在线逆散射方法,通过支持向量机将逆散射问题转化成一个回归估计问题. 该方法可应用于各种逆散射方面, 尤其是目标的几何与电磁参数重构和埋地目标探测. 文中首次将支持向量机方法应用到该领域，设置多个散射场的观测点，通过提取散射场的不同信息作为样本信息训练支持向量机, 建立了介质圆柱体的逆散射模型, 利用该模型重构了介质圆柱体的电磁参数，同时探测了埋地位置. 数值结果显示了该方法的有效性和准确性,为目标的实时逆散射研究提供了一种有效方法.  相似文献   

Correlation of atmospheric visibility with chemical composition of Kaohsiung aerosols   总被引：2，自引：0，他引：2  

Chung-Shin Yuan  Chang-Gai Lee  San-Ho Liu  Jui-cheng Chang  Ching Yuan  Horng-Yu Yang   《Atmospheric Research》2006,82(3-4):663

The objective of this study was to investigate the correlation of visibility with chemical composition of Kaohsiung aerosols. Daytime visibility was observed around noon at two observation sites in metropolitan Kaohsiung, Taiwan in the years of 1999 and 2000. Both seasonal and diurnal variation patterns of visibility were observed in the region. Ambient aerosols were sampled and analyzed for 11 constituents, including water-soluble ionic species (Cl⁻, NO₃⁻, SO₄⁻², NH₄⁺, K⁺, Na⁺, Ca⁺², and Mg⁺²) and carbonaceous contents (OC, EC, and TC), to characterize the chemical composition of Kaohsiung aerosols. Furthermore, a stepwise multiple linear regression model was developed to elucidate the influence of aerosol species on visibility impairments. The results showed that sulfate was the dominant species that affected both light scattering coefficient and visibility. On average, the percentage contributions of visibility degrading species to light scattering coefficient were 29% for sulfate, 28% for nitrate, 22% for total carbon, and 21% for PM_2.5-remainder. An empirical regression model of visibility based on sulfate, nitrate, and relative humidity was also developed. The model showed that sulfate in PM_2.5 was the most sensitive species to visibility variation, suggesting that the reduction of sulfate in PM_2.5 could effectively improve the visibility of metropolitan Kaohsiung. During the investigation period, an event of Asian dusts intruded metropolitan Kaohsiung and dramatically increased the aerosol loadings, especially in the coarse particles. However, local visual air quality did not degrade accordingly during the Asian dust event because both visibility and light scattering coefficient are affected mainly by the fine particles. The results are discussed in detail in the paper.  相似文献   

Time domain method for calculating free field motion of a layered half-space subjected to obliquely incident body waves     

李山有  朱海燕  高淑芳 《地震工程与工程振动(英文版)》2007,6(2):191-196

In numerical simulation of wave scattering under oblique incident body waves using the finite element method, the free field motion at the incident lateral boundary induced by the background layered half-space complicates the computational area. In order to replace the complex frequency domain method, a time-domain method to calculate the free field motion of a layered half-space subjected to oblique incident body waves is developed in this paper. The new method decouples the equations of motion used in the finite element method and offers an interpolation formula of the free field motion. This formula is based on the fact that the apparent horizontal velocity of the free field motion is constant and can be calculated exactly. Both the theoretical analysis and numerical results demonstrate that the proposed method offers a high degree of accuracy.  相似文献   

半球形沉积谷场地对入射平面Rayleigh波的三维散射解析解   总被引：2，自引：0，他引：2  

韩铮  赵成刚 《岩土力学》2007,28(12):2607-2613

把半球形沉积谷和周围半空间场地分别用具有不同弹性模量和不同半径的球坐标描述。利用Fourier-Bessel级数展开法,在频域内给出了半空间中半球形沉积谷场地在平面Rayleigh波入射下三维散射问题的解析解。利用这一解析解计算分析了入射波频率、场地软硬对场地内地表位移幅值的影响。  相似文献   

起伏地表条件下的声波散射数值模拟的积分方程法   总被引：2，自引：1，他引：2  

刘宁  孙建国 《吉林大学学报(地球科学版)》2007,(Z1)

从散射理论的角度来看,起伏地表可以看作是一种特殊的扰动介质,因此应用散射积分方程求解起伏地表条件下的散射场在理论上是可行的。从三维频率域声波方程出发,由格林函数定理,得出起伏地表条件下的散射积分方程。散射积分方程为关于起伏地表的面积分和与速度扰动体有关的体积分之和,同时给出了格林函数在奇异点的积分方法。由于数值离散求解积分方程存在着计算时间太长和存储内存不足的问题,采用电磁散射积分方程的拟解析近似的方法。在假设反射函数为缓变函数的基础上,最终得到其近似表达式,因此散射场的数值求解不必再借助于代数方程组,只要进行数值积分即可。这种方法避开了传统数值计算方法存在的问题,为地震散射波场快速正演模拟打下了基础。理论分析表明,这种方法适用于小扰动的问题。当扰动较大时,拟解析近似会产生较大的误差。  相似文献   

Three-dimensional waveform sensitivity kernels   总被引：2，自引：0，他引：2  

Henk Marquering  Guust Nolet  & F.A. Dahlen 《Geophysical Journal International》1998,132(3):521-534

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scattering and refracting of plane strain wave by a cylindrical inclusion in fluidsaturated soils   总被引：1，自引：0，他引：1  

胡亚元  王立忠  陈云敏  吴世明  张忠苗 《地震学报(英文版)》1998,(3)

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