Studies on multi-scale full waveform inversion for time-domain acoustic wave equation based on virtual-source precondition

Time-domain multi-scale full waveform inversion (FWI) is an important method for seismic imaging. Using different frequency contents of seismic data, this method mitigates the effect of the local-minima problem by sequential inversion. One of the important factors determining the convergence rate of the nonlinear inversion is the precondition of the gradient. Virtual-source precondition has been successfully applied to Laplace-domain and Laplace-Fourier-domain FWI. In this paper, we will examine the application of the virtual-source precondition to time-domain multi-scale FWI. The research results reveal that, compared to the gradient method without precondition, the virtual-source-based gradient method achieves much greater convergence rate while its additional computational cost is very low. Therefore, virtual-source precondition is very effective for time-domain multi-scale FWI.