Wave-equation traveltime and amplitude for Kirchhoff migration

Full-waveform inversion has been established as a standard tool for building high-resolution velocity models. To take full advantage of such models, the migration algorithm must be capable of handling fine-scale geo-bodies and sharp contrasts while affordably producing high-frequency migration stacks and gathers. Even though ray-based Kirchhoff migration can efficiently generate high-resolution migration stacks and gathers, the calculation of traveltimes becomes inaccurate and unstable near large velocity variations, sharp contrasts, and complex structures. Reverse[1]time migration (RTM), on the other hand, can accurately handle complex velocity models with fine details and sharp contrasts due to its deployment of full-wavefield propagation. However, the cost of RTM becomes prohibitive when high-frequency stacks and gathers are required. Following this idea of wave-equation-based traveltimes, we propose a wave-equation Kirchhoff (WEK) scheme that performs Kirchhoff migration using maximum-amplitude traveltimes and amplitudes from the wavefield. These traveltimes and amplitudes are computed through affordable low-frequency full-wavefield propagation. WEK not only partly inherits the benefit of full-wavefield propagation for high-resolution models, but it also maintains the affordability of ray-based Kirchhoff migration. We use synthetic and field data to evaluate this method and compare the WEK results with those from ray-based Kirchhoff migration and RTM.