Teleseismic waveforms contain abundant interpretable information about Earth's properties. They can be used to explore the refined structure of Earth's interior, especially in the regions with imbalanced spatial distribution of seismic activity. However, it's technically infeasible to numerically simulate high-frequency (>1 Hz) teleseismic wave propagation within a whole domain iteratively in full-waveform inversion due to its vast computational costs. We develop a 3D FK-LTSOS (Frequency-Wavenumber, Layered Time-Space Optimized Symplectic) hybrid method and then apply it to teleseismic full-waveform tomography to tackle this computational challenge. The 3D FK-LTSOS hybrid method combines the semi-analytical solution computed by the FK method rapidly in a 1D background model and the numerical solution calculated by the 3D LTSOS method accurately in 3D localized heterogeneous media with topography to simulate teleseismic wave propagation efficiently and accurately. The comparison of synthetic seismograms shows its accuracy and stability when simulating wave propagation in the topographic model. Based on this hybrid method, the teleseismic full-waveform tomographic method is developed to efficiently resolve the detailed structure of the local research domain utilizing high-frequency teleseismic data. The essential contents of full-waveform tomography are presented, including misfit function, Fréchet kernels, smoothing strategy, and nonlinear conjugate gradient method. Synthetic data application for spherical anomaly models with planer surface and Gaussian topography, and observed data application for the crust-upper mantle structure beneath eastern Tibet confirm the validity of the teleseismic full-waveform tomography and demonstrate that our tomographic method can image the localized structures speedily from full-waveform information.

中文翻译：

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基于三维 FK-LTSOS 混合方法的远震全波形层析成像局部成像


远震波形包含有关地球特性的大量可解释信息。它们可用于探索地球内部的精细结构，尤其是在地震活动空间分布不平衡的区域。然而，由于计算成本高昂，在全波形反演中迭代地对高频 （>1 Hz） 远震波在整个域内的传播进行数值模拟是不可行的。我们开发了一种 3D FK-LTSOS（频率-波数、分层时空优化对称）混合方法，然后将其应用于远震全波形断层扫描，以应对这一计算挑战。3D FK-LTSOS混合方法将FK方法在一维背景模型中快速计算的半解析解与三维LTSOS方法在具有地形的三维局部非均质介质中精确计算的数值解相结合，以高效准确地模拟远震波传播。合成地震图的比较表明了它在地形模型中模拟波传播时的准确性和稳定性。基于这种混合方法，开发了远震全波形断层扫描方法，以利用高频远震数据有效地解析局部研究域的详细结构。介绍了全波形层析成像的基本内容，包括 misfit 函数、Fréchet 核、平滑策略和非线性共轭梯度方法。 平面和高斯地形球面异常模型的合成数据应用，以及藏东地壳-上地幔结构的观测数据应用，证实了远震全波形层析成像的有效性，证明了我们的层析成像方法可以从全波形信息中快速成像局部结构。