Land seismic multi-parameter full waveform inversion in elastic VTI media by simultaneously interpreting body waves and surface waves with optimal transport based objective function
IPGP - Îlot Cuvier
Séminaire de sismologie, de géosciences marines et de géophysique d'exploration
Université Grenoble Alpes
Land seismic multi-parameter full waveform inversion in anisotropic media is challenging because of high medium contrasts and because of surface waves. With a data-residual leastsquares misfit function, the surface wave energy usually masks the body waves and the gradient of the misfit function exhibits high values in the very shallow depths preventing from recovering the deeper part of the earth model parameters. The optimal transport objective function, coupled with a Gaussian time-windowing strategy, allows to overcome this issue by more focusing on phase shifts and by balancing the contributions of the different events in the adjoint source and the gradients. We first illustrate the advantages of the optimal transport function with respect to the least-squares one, with two realistic examples. We then discuss a vertical transverse isotropic (VTI) example starting from a quasi 1D isotropic initial model. Despite some cycle-skipping issues in the initial model, the inversion based on the windowed optimal transport approach converges. Both the near-surface complexities and the variations at depth are recovered.