Data-domain and image-domain wavefield tomography

Waveform inversion (FWI) requires a good starting model and/or data at very low frequency (<1 Hz) for convergence. However, this is not a necessary condition, but an artifact of the objective function defined using differences of observed and simulated data. Image-domain tomographic methods using the same wavefields and wave equations can converge to a reasonable solution from poor starting models and without long-offset and/or low-frequency data. Cascading image-domain and data-domain wavefield tomography eliminates the need for extremely low-frequency in the acquired data.