一种对二维全波形反演半积分效应的修正方法OA

Two-dimensional(2D)full waveform inversion(FWI)is often applied to inversion of 2D survey line data for preliminary geological investigation due to its relatively low computational cost.However,waveforms generated by 2D numerical simulations differ from those produced by 3D simulations by a half-order integral ef-fect.In conventional processing workflows,3D observed data are typically subjected to a half-order integral op-eration to make their waveforms consistent with those of 2D simulated data.Then,the observed and simulated data are fitted using 2D FWI to obtain the subsurface velocity model.Nevertheless,this approach only accounts for the influence of the half-order integral effect on the forward wavefield in 2D FWI,while neglecting its influ-ence on the adjoint wavefield.As a result,when the initial velocity model is underestimated,the gradient polar-ity does not reverse even if the time shift between the observed and predicted data exceeds half of the dominant period.Conversely,when the initial velocity model is overestimated,the gradient polarity reverses even though the time shift does not exceed half of the dominant period.To address this issue,this paper proposes applying a half-order derivative operation to the adjoint source in 2D FWI to eliminate the influence of the half-order inte-gral effect on 2D FWI.This correction ensures that the cycle-skipping threshold corresponds to half of the domi-nant period.Finally,numerical experiments validate the correctness of the analysis and the effectiveness of the proposed gradient correction method.