Discussion and Conclusion

We propose plane-wave LSRTM as an efficient alternative to RTM and, unlike random phase-encoded LSRTM, a viable method for marine data. To reduce the computational cost, the original shot-domain data are transformed into dozens of plane-wave gathers. The advantages include (1) stable convergence even with velocity errors up to 5% in my example and (2) the common image gathers are available for quality control and migration velocity analysis. The drawback is that extra memory is needed to store all the prestack LSRTM images at any one iteration. Numerical tests on the Marmousi2 model and a 2D marine dataset show that plane-wave prestack LSRTM can produce images with fewer migration artifacts, and higher resolution compared to a corresponding RTM image. The method shows good convergence even when the velocity model is not accurate. I conclude that the least-squares reverse time migration in the plane-wave domain can be an efficient method to improve the quality of RTM images and produce common image gathers for MVA.