ABSTRACT To improve the computational accuracy of seismic traveltime for complex structures in inhomogeneous media, a mesh generation method that is adaptive to a rugged seafloor or interface is presented. A hybrid mesh discrete velocity model consisting of conventional rectangular mesh and irregular quadrilateral mesh is also proposed. The local traveltime equations for the hybrid mesh are derived from the linear traveltime interpolation (LTI) method and are shown to be stable. The relationship between the group velocity and group angle is converted into that between group velocity and interpolated point coordinates, extending the LTI ray tracing algorithm to multiwave simulation in vertical transversely isotropic (VTI) medium by multi-stage partitioning. Computations of the first arrival, reflection, multiple reflection, multiple transmission conversion, and multiple reflection conversion seismic waves in the VTI medium with rugged seafloor and complex structural interfaces are realised. The results show that the proposed method can adapt to the rugged seafloor and velocity interfaces of complex structures, resulting in higher computational accuracy of the traveltime and ray paths for ocean bottom node (OBN) seismic wave simulation. The accuracy of the proposed method is verified by comparison with the finite-difference method. This method will be useful for modelling of seismic waves, wavefield identification, and study of seismic wave propagation in OBN seismic observations.

中文翻译：

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VTI介质中崎岖海底的走时计算和OBN地震记录模拟

摘要 为了提高非均匀介质中复杂结构地震走时的计算精度，提出了一种适应崎岖海底或界面的网格生成方法。还提出了一种由常规矩形网格和不规则四边形网格组成的混合网格离散速度模型。混合网格的局部走时方程是从线性走时插值 (LTI) 方法推导出来的，并且表明是稳定的。将群速度与群角的关系转化为群速度与插值点坐标之间的关系，通过多级分割将LTI射线追踪算法扩展到垂直横向各向同性(VTI)介质中的多波模拟中。初到、反射、多次反射的计算，在具有崎岖海底和复杂结构界面的VTI介质中实现了多次传输转换和多次反射转换地震波。结果表明，该方法能够适应复杂结构的崎岖海底和速度界面，从而提高了海底节点（OBN）地震波模拟的走时和射线路径的计算精度。通过与有限差分法的对比验证了所提方法的准确性。该方法将有助于地震波建模、波场识别以及 OBN 地震观测中地震波传播的研究。结果表明，该方法能够适应复杂结构的崎岖海底和速度界面，从而提高了海底节点（OBN）地震波模拟的走时和射线路径的计算精度。通过与有限差分法的对比验证了所提方法的准确性。该方法将有助于地震波建模、波场识别以及 OBN 地震观测中地震波传播的研究。结果表明，该方法能够适应复杂结构的崎岖海底和速度界面，从而提高了海底节点（OBN）地震波模拟的走时和射线路径的计算精度。通过与有限差分法的对比验证了所提方法的准确性。该方法将有助于地震波建模、波场识别以及 OBN 地震观测中地震波传播的研究。