Robust FWI Updates in the Presence of Cycle Skipping

Full Waveform Inversion (FWI) success depends on producing seamless short- and long-wavelength model updates while avoiding cycle skipping. In its traditional implementation, FWI risks converging to an inaccurate result if the data lacks sufficient low frequencies or the starting model is far from the true one. Additionally, the model updates may display a reflectivity imprint before the long-wavelength features are fully recovered. A solution to these fundamental challenges combines the quadratic form of the Wasserstein distance (W2-norm) for measuring the data misfit with a robust implementation of a velocity gradient. The W2-norm reduces the risk of cycle skipping whereas the velocity gradient effectively eliminates the reflectivity imprint and emphasizes the long-wavelength model updates. We illustrate the performance of the new solution on a field survey acquired offshore Brazil. There, we demonstrate how FWI successfully updates the earth model and resolves a high-velocity carbonate layer that was missing from the starting model.