Automatic dip-constrained reverse time migration

Reverse time migration (RTM) based on the two-way wave equation may yield high-precision images of complex subsurface structures. However, RTM is sensitive to the velocity model. This paper proposes a new dip-constrained RTM method. The forward propagating wavefield from the source and backward propagating wavefield from the receiver are decomposed into different directional components, and then an automatic dip-constrained imaging condition is utilized to improve imaging quality in the presence of velocity errors. Meanwhile, our method may mitigate the artifacts caused by non-primary reflections, even when the velocity model is correct, by using the reflection signals within the Fresnel zone. To increase efficiency, we introduce the frequency-domain snapshot to compute the incident angle for source wavefield decomposition. Numerical tests on a complex velocity model show improved imaging in the case of inaccurate velocities and mitigated artifacts caused by multiple reflection waves in the case of the accurate model.