了解地球内部的速度结构对地球物理研究具有极为重要的意义。各向同性速度的三维变化可以使我们知道地球内部温度或者成分上的差异，而可靠的三维各向异性模型则有助于我们认识地球内部介质的变形或者大范围的定向流动，是动力学上非常重要的参数。多年以来，速度各向异性的研究大多依赖于对剪切波分裂的观测，即通过高频射线理论，将剪切波分裂解释为来自台站下方，且各向异性对称轴在水平面内，在方向和强度上都没有空间上的变化。本项目拟利用全波形方法，建立一个对地壳与上地幔普遍（即对称轴可为倾斜）各向异性结构进行三维成像的新方法。我们将使用谱元法计算精确的理论波形来模拟剪切波分裂强度，建立应变格林张量库可以有效地提高计算剪切波分裂强度对介质各向异性参数的敏感度函数的效率，并通过线性与非线性反演相结合的方法，有效地解决大多数反演中各向异性对称轴在水平面内的限制。

Understanding the velocity structure in the Earth's interior has great importance to geophysics research. The isotropic velocity structure tells us the compositional and thermal variations in the Earth, while reliable anisotropic seismic structure reveals the deformation and/or large-scale flow patterns of the Earth materials. Therefore, anisotropy is a very important parameters for geodynamics. So far, seismic anisotropy study is largely dependent on shear-wave splitting measurements, which are interpreted through the high-frequency ray theory. As such, the anisotropy under a station is assumed to have a horizontal symmetry axis, with no spatial variation in either the strength or the symmetry axis of the anisotropy. In this study, we will develop a new approach to imaging the three-dimensional variation of general seismic anisotropy (with tilted symmetry axis) based on full-wave tomography. We use accurate synthetic seismograms computed by the spectral-element method to model the shear-wave splitting intensity measurements. The computational efficiency for calculating the sensitivity kernels of the splitting intensity to anisotropy parameters will be achieved by the establishment of strain Green tensor database. A combination of linear and non-linear inversion process will be adopted to resolve the issue of horizontal symmetry axis currently required in almost all anisotropy studies.