About ADCIG Residual Moveout

The increasing usage of wave equation and reverse time migration has motivated investigations about new types of common images gathers. Several types of angle domain common image gathers have then been proposed. While they should have the same aspect (up to specific artefacts) when the exact velocity model is used it appears that they exhibit significant differences in curvature when the velocity model is erroneous. This observation is analysed here by a theoretical analysis in the frame of high frequency asymptotics. This analysis is performed for several types of angle domain common image gathers revealing much more complexity than expected. It demonstrates that some well admitted statements such as the validity of Snell Descartes law for tomographic rays or the idea that the tomographic ray tracing could be limited to lower layers may not be satisfied for all type of angle gathers.