Implementation of Improved Reverse-time Migration via Acoustic Impedance Equalization

When performing migration, reflection energy from discontinuities of velocity field may result in poor images. To suppress reflection energy, therefore, a smoothing filter is usually applied to the velocity model. But the velocity smoothing spoils the geologic plausibility of the velocity model. In this paper, we attempt to minimize migration artifacts by equalizing acoustic impedances over the entire model. To equalize acoustic impedances, we introduce fake density concept which compensate the velocity difference. If acoustic impedances are constant at every layer, reflection coefficients become zero at normal incidence and reflection energy is minimized at non-normal incidence. Then the migration result can be improved. To verify fake density concept, we implement a reverse time migration using cell-based finite-difference method. Through the numerical examples for the SEG/EAGE salt model, we show that the reverse-time migration using fake density improves the quality of migration image.