Multi-objective Full Waveform Inversion
GIF 1: A look-ahead seismic system deployed on the cutter head of a tunnel-boring machine.
I have developed an auxiliary signal model that assists FWI to produce accurate reconstruction of the subsurface properties. The formulation of this model effectively involves simplification of the measurements by replacing the seismic arrivals by bumps. My numerical experiments have demonstrated that, during the gradient-based optimization, whenever the seismic waveforms are too complicated to be compared in the conventional least-squares sense, an objective function based on the simplified data i.e., the bump functional can be useful. In other words, the role of the bump functional is to guide the optimization towards the global minimum by pulling the trapped solution out of the local minima associated with the least-squares functional whenever necessary. The subsequent FWI algorithms that utilize the bump functional lead to an efficient multi-objective full waveform inversion.
GIF 2: Near-surface imaging using 2-D SH full waveform inversion, where the images need to be available in near real time and without human interaction.