基于传播矩阵法改进的SS及其前驱波合成算法

410 km和660 km地幔间断面在地球内部动力学研究中具有重要意义. 在研究地幔间断面的方法中, SS前驱波由于具有全球采样优势得以广泛应用. SS及其前驱波模拟可利用有限差分和谱元法等数值模拟方法, 它们在模拟全球尺度地震波传播时具有高精度的特点, 但往往计算量很大. 因此, 该类方法难以应用于反射点广泛分布的情形. 而基于传播矩阵发展的SS及其前驱波模拟方法在保持高精度计算的同时, 可大幅提高计算效率.
本文针对SS及其前驱波的传播特征, 改进了基于传播矩阵方法的波形合成算法FASHSHWF. 通过简单层状模型对该算法进行了测试, 验证了算法及相应程序的正确性. 计算效率测试表明改进算法相较常规传播矩阵算法可节约50%以上的计算时间. 通过与AxiSEM计算的波形对比, 验证了FASHSHWF用于SS及其前驱波模拟的有效性. 在上述工作的基础上, 本文进一步探讨了新算法在研究全球近地表结构对地幔间断面复杂性探测影响中的应用.

An improved algorithm for simulating waveforms of SS and its precursors based on propagation matrix method

The 410 km and 660 km mantle discontinuities are vital for studying the dynamics of the earth's interior. Among numerous research methods of mantle discontinuity, SS precursors have been widely used due to its advantage of global sampling. SS and its precursors can be simulated by numerical methods such as the finite-difference and spectral-element methods featuring high precision in simulating worldwide seismic wave propagation. However, massive computations are necessary for these simulating methods when bounce points are widely distributed. The simulation method for SS and its precursors based on propagation matrix can significantly improve the calculation efficiency while maintaining high accuracy.
According to propagation characteristics of SS and its precursors, this work improves the waveform synthesis algorithm FASHSHWF based on the propagation matrix method. The algorithm is verified through a simple layered model. The calculation efficiency saves more than 50% of time compared with conventional algorithm. Furthermore, the effectiveness of FASHSHWF in SS and its precursors' simulation is verified comparing with the waveforms calculated by AxiSEM. Based on the above work, application of the new algorithm in detection of mantle discontinuities affected by the near-surface complex structure is discussed.