Illuminating the heterogeneous Earth based on numerical simulations of seismic waves: from global tomography to subduction-zone imaging

了解地球的内部过程和动态演化一直是地球科学家的基本科学问题之一。过去的构造事件塑造了地表观测到的地形地质特征，而内部地球动力环流是驱动复杂板块运动的主要动力。这些板块运动和相关的构造应力通常表现为地震，其中许多地震会造成大面积的严重破坏。另一方面，这些地震发出的地震波为阐明地球内部的非均匀结构提供了重要工具，并为潜在的构造过程提供了直接证据。本提案旨在继续参与正演地震波模拟技术的发展，并进一步推进基于这些数值模拟的创新地震成像工具，以绘制全球和大陆尺度的地球内部结构。在全球范围内，我们将利用完全数值计算的有限频率灵敏度核数据库来生成整个地幔的最新剪切和体声速度模型。大量的绕射波测量将提高核幔边界（CMB）以上模型的分辨率，并有助于更好地约束大低剪切速度省（LLSVPs）和在CMB聚集的古俯冲板块。在区域尺度上，我们将应用二维和三维SEM-FK混合技术对阿拉斯加南部和中部俯冲带进行正演模拟和反演，以改善俯冲的海洋地壳和岩石圈地幔、莫霍界面和上覆板块的位置和速度变化，并为俯冲带过程的跨学科讨论做出贡献。

Understanding the internal processes and dynamic evolution of our planet Earth has been one of the fundamental scientific questions for earth scientists. The tectonic events in the past are responsible for shaping the topographic and geological features observed on the surface, while the internal geodynamic circulation is the main engine driving complex plate motions. These plate motions and associated tectonic stress are often manifested as earthquakes, many of which cause severe damage over large areas. On the other hand, seismic waves emitted from these earthquakes provide an essential tool for illuminating heterogeneous structures of the Earth’s interior and present direct evidence for the underlying tectonic processes. This proposal aims to continue our involvement in the development of forward seismic wave simulation techniques, and further advance innovative seismic imaging tools based on these numerical simulations to map internal structures of the Earth at both global and continental scales. For the whole globe, we will utilize a finite-frequency sensitivity kernel database computed fully numerically to generated updated shear and bulk-sound velocity models for the whole mantle. The large number of diffracted wave measurements will boost the resolution of the models above the core-mantle-boundary (CMB) and help provide better constraints on the Large Low Shear Velocity Provinces (LLSVPs) and ancient subducted slabs accumulating at the CMB. At regional scales, we will apply 2D and 3D SEM-FK hybrid techniques to both forward modelling and inversion of subduction zones beneath southern and central Alaska, with the goal of improving the locations and velocity variations of subducted oceanic crust and lithospheric mantle, the Moho interface and the overriding plate, and contributing to the interdisciplinary discussions on subduction zone processes.