What initial velocity model do we need for full waveform inversion?
Résumé
In the context of velocity model building, we examine if the velocity models obtained after first-arrival traveltime tomography are accurate enough for subsequent full waveform inversion of reflected energy. For that purpose, we test the quality of the velocity model obtained by first-arrival traveltime tomography on the BP salt dome model. Several 1-D inversions are conducted in two different zones. In the simplest zone corresponding to smooth velocity models, the tomographic models are good enough for waveform inversion with realistic frequency contents. In the complex part going through a salt body, one need very low frequencies (starting at around 1 Hz) or a further refinement of the tomographic model.