Research on domain visco-acoustic multiparameter full waveform inversion based on modified FR conjugate gradient method

The real earth media is characterized by the visco-elasticity, and it is of practical importance to study the full waveform inversion method in visco-elastic media. The full waveform inversion (FWI) is used to estimate the subsurface parameters by matching the simulated data obtained by the forward simulation with the actual recorded seismic data, and the optimization algorithm is generally used to solve the problem. To address the problems of complicated Hessian matrix calculation and slow convergence speed of conjugate gradient method in full waveform inversion, the modified FR conjugate gradient method is applied to the full waveform inversion. The modified FR conjugate gradient method uses more gradient information and has similar structure and properties as the quasi-newton algorithm, which makes the convergence more stable while speeding up the convergence speed and needs little more calculation. This paper use this method conduct a study of the time-domain visco-acoustic multiparameter full waveform inversion under the SLS model. The model test show that the modified method can obtain more accurate inversion results than the conventional FR conjugate gradient method, accelerate the convergence and resolution of deep layer. And the two-step inversion strategy is used to further improve the inversion effect of Q.