Quadrangular adaptive mesh for elastic wave simulation in smooth anisotropic media
Résumé
Despite continuous improvements in computational methods and facilities, numerical simulation of elastic waves still remains a challenge when taking into account fine geological features or quantifying uncertainties in full waveform inversion (FWI). In the first context, smooth effective media can be computed thanks to the non-periodic homogenization method, which considerably reduces the computation cost of wave simulations. When considering these media or performing FWI, a way to further lighten the computational requirement consists in optimizing the mesh which supports the simulation. In this work, we present an algorithm to mesh 2D smooth media for quadrangular spectral element methods (SEM). Our meshing strategy first relies on the quadtree-based method introduced by Mare´chal (2009) to adapt the size of the elements to the local minimum wavelength. During this process, we properly handle anisotropy by considering directional wavelength. Then, a Laplacian smoothing is applied to further optimize the size of the elements, which increases the global time-step and, consequently, makes SEM simulations faster. To test our method, we consider a 2D section of the homogenized Groningen gas filed.