Reverse Time Migration
Reverse Time Migration: In this chapter, we derive the equations for the reverse time migration (RTM) algorithm. This algorithm is used heavily by the oil industry for subsalt imaging of reflectors. It also is used to migrate residuals iteratively for both LSM and FWI. Compared to other migration methods such as diffraction-stack migration discussed in Chapter 10, RTM accounts for all the arrivals in the wavefield, including both primaries and multiples if the velocity model is suficiently accurate. This can lead to much better resolution in the image, but it is at the cost of being more sensitive to errors in the migration velocity model. For frequencies less than 20 Hz, RTM is the migration method of choice for imaging below complex geology such as salt bodies.