Imaging condition for reverse time migration

Abstract

In reverse time migration the imaging condition is estimated by cross‐correlating the source wave‐field with the receiver wave‐field under the basic assumption that the source wave‐field represents the down‐going wave‐field and the receiver wave‐field the up‐going wave‐field. However, for large impedance contrasts and complex geological structures the wave‐fields cannot be separated efficiently. In these cases the cross‐correlation leads to low frequency artifacts. The imaging condition can be improved by dividing the cross‐correlated image of each shot by the receiver illumination. This method is simple, it does not introduce phase shifts and it requires little additional computation, because the receiver illumination can be directly computed from the receiver wave‐field.