Joint inversion of velocity and density in preserved amplitude full waveform inversion

The importance of inverting jointly velocity and density parameters in full waveform inversion (FWI) is well established. In a former work we had proposed an innovative preserved amplitude FWI allowing improving the convergence rate of FWI. It was derived from preserved amplitude reverse time migration (RTM), involved a deconvolution imaging condition and was limited to the estimation of velocity perturbation from reflection data. We extend here the approach to a joint velocity and density preserved amplitude FWI. We present the theoretical derivation of the improved common shot FWI gradients and show how we can decouple the two parameters. We validate our approach on the Marmousi II synthetic model which shows that we can efficiently reconstruct the two parameters, and on a real data showing that we significantly reduce the data residual with the joint inversion.