Investigating tomographic resolution in global crustal imaging

地壳的地震结构对于了解大陆和海洋盆地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高度不均匀数据复盖率的限制，因为折射和反射实验和接收函数分析在海洋区域和偏远的大陆内部很稀少。与其他地震数据集相比，地震面波可以用来更好地在全球范围内约束地壳结构，因为它们在地球的外壳中传播，并提供最佳的空间复盖。然而，在全球地壳层析成像中理解面波的横向和垂直分辨率仍然是一个挑战。这项研究将把莫霍面成像的有限频率理论的发展和用谱元方法模拟波的传播结合起来，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。PI将发展基于行波模式耦合的有限频率理论来成像各向异性介质中的莫霍面地形，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极限。该小组将量化全球地壳模型中绕射效应的尺度依赖性，以及与层析成像理论中的近似和不完善的全球数据复盖率相关的分辨率限制。波速和莫霍面地形的权衡将在不连续地形和波速结构的联合反演中进行分析。

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.