Wave Propagation Operators for True-amplitude Reverse Time Migration

Amplitude behaviours of propagation operators in reverse time migration (RTM) are studied for variable density medium. Using stationary phase theory, we prove that firstly, the decay of amplitude caused by geometrical spreading in RTM will be compensated automatically; secondly, affected by transmission losses, the propagation operators of RTM contain an angle-dependent transmission coefficient item, which prevents RTM from yielding a true-amplitude output of reflection coefficient. We propose a transmission losses compensation method for true-amplitude RTM by estimation of angle-dependent reflection coefficient via the Poynting vector. Synthetic data tests demonstrate that the proposed method can provide a better amplitude performance for true-amplitude imaging.