Least-squares Reverse Time Migration with Variable Density

Least-squares reverse time migration (LSRTM) aims to match the amplitudes of the simulated data with the observed data. The amplitude of reflected seismic wave is dominantly affected by contrasts in acoustic impedance, which is a product of velocity and density. Therefore, if the P-wave velocity is the only variable parameter in LSRTM, the seismic amplitudes will not be correctly modelled. In this study, we present a LSRTM scheme applicable in the presence of density variations. Reflectivity models associated with velocity and density perturbations are simultaneously retrieved to generate simulated data better matches the recorded data in amplitudes. Numerical examples based on a two-layer model verified the effectiveness of the proposed method.