Investigating tomographic resolution in global crustal imaging

地壳地震结构对于认识大陆和海洋盆地的形成和演化具有重要意义。由于折射和反射实验以及接收函数分析在海洋区域和偏远大陆内部稀疏，目前全球地壳模型的分辨率受到高度不均匀数据覆盖的限制。地震表面波在地球外壳传播，与其他地震数据集相比，可以更好地用于在全球范围内更好地约束地壳结构，并提供最佳的空间覆盖。然而，了解全球地壳层析成像中表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间断成像有限频率理论的发展和波谱元法的波传播模拟，探讨射线理论和有限频率理论在全球地壳结构表面波层析成像中的分辨率极限。PI将发展基于行波模式耦合的有限频率理论，用于各向异性介质中莫霍不连续地形成像，并研究基于相速度敏感核的非线性全球地壳层析成像的分辨率限制。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。在非连续性地形和波速结构的联合反演中，将分析波速和莫霍地形之间的权衡。

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.