Moving beyond the Born approximation involves one of the two solutions: we can either artificially create image perturbations that are compliant with this approximation (), or we can improve the WEMVA operator to better handle the non-linearity in the image perturbations, as presented in this paper.
We propose two improved versions of the WEMVA operator which are more appropriate for the case of large/strong slowness anomalies. Our new operators involve linearizations using bilinear and implicit approximations to the exponential function. With the new operators, we not only improve accuracy but we also maintain stability of the inversion scheme at much higher values of the slowness anomalies, even in the order of 221#221 of the background.
Finally, we note that our new operators come at a cost which is practically no different than the cost of the Born-linearized operator, while improving its accuracy and stability.