海底地形产生的Scholte波
Scholte waves generated by seafloor topography
摘要：
海底地形可以激发强烈的界面波，称为Scholte波，通常是色散的，其特征是传播缓慢，但振幅大。这种波可以用来反演近海底剪切波速度结构，这是多分量P-S震波成像的重要信息。三种不同的方法来理解激发Scholte波和数值方面的建模Scholte波，包括分析Cagniard-de Hoop分析，边界积分法和交错网格有限差分法。对于格林函数很容易计算的简单介质，边界元法可以得到精确的结果。有限差分法显示出强大的数值伪影和停滞的人工波可以看到在附近的地形在流体-固体界面，即使使用精细的计算网格。然而，这些人造波的振幅远离海底衰减。对于震测模型，将接收器放置在远离流体-固体界面的位置是明智的。为了研究Scholte造波，需要正确地实现流体-固体边界条件。它还显示通过数值例子，包括使用海底剖面从最近的SEG高级建模（SEAM）项目，即使是温和的地形特征可以产生Scholte波，这些波可以用来约束附近的海底S波速度的界面Scholte波的色散分析。全波形反演的含义是，尽管低频数据对于收敛至关重要，但海底地形可能对低频地震波有很大影响。
英文摘要：
Seafloor topography can excite strong interface waves called Scholte waves that are often dispersive and characterized by slow propagation but large amplitude. This type of wave can be used to invert for near seafloor shear wave velocity structure that is important information for multi-component P-S seismic imaging. Three different approaches are taken to understand excitation of Scholte waves and numerical aspects of modeling Scholte waves, including analytical Cagniard-de Hoop analysis, the boundary integral method and a staggered grid finite difference method. For simple media for which the Green's function can be easily computed, the boundary element method produces accurate results. The finite difference method shows strong numerical artifacts and stagnant artificial waves can be seen in the vicinity of topography at the fluid-solid interface even when using fine computational grids. However, the amplitude of these artificial waves decays away from the seafloor. It is sensible to place receivers away from the fluid-solid interface for seismic modeling. To investigate Scholte wave generation, one needs to correctly implement the fluid-solid boundary condition. It is also shown through numerical examples including using a seafloor profile from the recent SEG Advanced Modeling (SEAM) Project that even mild topographic features can generate Scholte waves and these waves can be used to constrain near seafloor S wave velocity by dispersion analysis of interface Scholte waves. The implication to the full waveform inversion is that, although low frequency data are crucial for convergence, seafloor topography may have a large effect on low frequency seismic waves.
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