Computation of traveltimes and ray paths is important for anisotropic tomography inversions. The Eikonal-equation-based method outperforms traditional ray methods by producing more accurate results. However, most existing Eikonal solvers are formulated on structured regular meshes, which are no longer accurate for models with the presence of irregular topography and subsurface interfaces. To solve Eikonal equation in vertically transversely isotropic (VTI) or tilted transversely isotropic (TTI) models with irregular geometry, we formulate a new iterative fast sweeping method on unstructured triangular meshes. The fixed-point iteration is implemented to capture the high-order nonlinear terms therein and a fast sweeping method on unstructured triangular meshes is implemented to solve the resulting elliptically anisotropic Eikonal equation at every iteration. We test the new algorithm for direct arrivals and reflected arrivals, and then use the calculated traveltimes to track the ray path in VTI/TTI media. Numerical tests demonstrate the validity and accuracy of the new method for models with rough topography and subsurface interface.
Multi-Level Domain-Decomposition Strategy for Solving the Eikonal Equation with the Fast-Sweeping Method
