Investigating tomographic resolution in global crustal imaging

地壳的地震结构对于了解大陆和洋盆的形成和演化具有重要意义。 目前全球地壳模型的分辨率受到数据覆盖面高度不均匀的限制，因为海洋区域和偏远大陆内部的折射和反射实验以及接收器函数分析很少。 地震面波可以潜在地用于在全球范围内更好地约束地壳结构，因为它们在地球的外壳中传播，并且与其他地震数据集相比提供最佳的空间覆盖。 然而，了解全球地壳层析成像中面波的横向和垂直分辨率仍然是一个挑战。本研究将结合莫霍面成像的有限频率理论的发展和使用谱元法的波传播模拟，研究射线理论和有限频率理论在全球地壳结构面波层析成像中的分辨率极限。波模耦合成像的莫霍面不连续地形在各向异性介质和研究分辨率限制的非线性全球地壳层析成像的基础上相速度灵敏度核。 该团队将量化全球地壳模型中衍射效应的尺度依赖性，以及与层析理论近似和不完善的全球数据覆盖相关的分辨率限制。 在不连续地形和波速结构的联合反演中，将分析波速和莫霍面地形之间的权衡。

Seismic structure of the Earth's crust is important for the understanding of the formation and evolution of continents and ocean basins. The resolution of current global crustal models are limited by highly inhomogeneous data coverage as refraction and reflection experiments and receiver function analysis are sparse in oceanic regions and remote continent interiors. Seismic surface waves can be potentially used to better constrain crustal structure at a global scale as they propagate in the outer shell of the earth and provide best spatial coverage compared with other seismic data sets. However, understanding the lateral and vertical resolution of surface waves in global crustal tomography remains a challenge. This research will integrate development of finite-frequency theory for Moho discontinuity imaging and wave propagation simulations using the Spectral Element Method to investigate resolution limits of ray theory and finite-frequency theory in surface-wave tomography of global crustal structure.The PI will develop finite-frequency theory based on travelling-wave mode coupling for imaging the Moho discontinuity topography in anisotropic media and investigate resolution limits in non-linear global crustal tomography based on phase-velocity sensitivity kernels. The team will quantify the scale-dependence of diffractional effects in global crustal models as well as resolution limits associated with approximations in tomographic theory and imperfect global data coverage. The tradeoff between wavespeed and Moho topography will be analyzed in joint inversions of discontinuity topography and wavespeed structure.