Time-dependent receiver extension for full-waveform inversion: An alternative extension method for cycle-skipping mitigation
Mustapha Benziane, Romain Brossier, Ludovic Métivier, Serge Sambolian · Geophysics · 2025
ABSTRACT Extension strategies for full-waveform inversion (FWI) rely on introducing additional degrees of freedom to the FWI problem, which expands the search space. This search space extension helps by relaxing the nonconvexity of the problem and thereby alleviating the cycle-skipping issue. The receiver-based extension strategy introduces the receiver position as the additional degree of freedom to FWI to improve the fit between the observed and calculated data at early iterations. This helps circumvent the cycle-skipping phenomenon. In this study, we make this receiver position time dependent, meaning that the receiver positions vary as a function of the acquisition time. The resulting mathematical problem is a two-nested-loop minimization, where the outer loop is the conventional FWI loop to update the subsurface mechanical parameters and the inner loop aims at finding the optimal time-dependent virtual receiver positions. This inner-loop problem is heavily nonlinear and nonconvex. Finding the global minimum is therefore a challenging task. To do so, we use a computational intelligence technique, particle swarm optimization (PSO). PSO makes it possible to thoroughly explore the search space with few iterations. Numerical experiments using a North Sea exploration 2D synthetic model, starting from crude initial models, illustrate that the method is robust and very easy to tune.