Improved AVA imaging for vector-based elastic reverse time migration using angle-domain dot-product imaging condition

This paper proposes modified angle-domain dot-product imaging conditions for vector-based elastic reverse time migration, which yields PP and PS angle gathers that capture improved amplitude-versus-angle (AVA) information. The vector P-wavefields and converted S-wavefields can be constructed by separating the coupled elastic wavefields. A simple and stable dot-product imaging condition can be employed to generate scalar PP and PS angle gathers. However, estimating amplitudes via migrated angle gathers using the conventional angle-domain dot-product imaging conditions leads to inaccurate AVA information. The inaccuracy arises because the dot-product imaging condition does not correctly represent seismic PP and PS reflectivity. Hence, the relationship between the dot-product imaging conditions and the reflection coefficients is explicitly derived in this paper. Then, the modified angle-domain dot-product imaging conditions for calculating PP and PS angle gathers are presented based on the kinematic characteristics of the vector P- and S-wavefields, along with an explanation of their amplitude correction mechanism. Finally, simple layer models with positive and negative reflection polarities are used to compute angle gathers to demonstrate the accuracy of the proposed imaging conditions in calculating AVA imaging. Numerical results from the Marmousi2 model validate the effectiveness and correctness of the proposed imaging conditions in complex media.