P- and S-wave angle-domain common-image gathers (ADCIGs) based on elastic-wave reverse-time migration

Elastic‐wave reverse‐time migration is an important imaging strategy because of its ability to image complex geologic structures and to efficiently extract elastic‐wave angle‐domain common‐image gathers (ADCIGs), which is an important task for amplitude‐versus‐angle (AVA) analysis and migration velocity analysis (MVA) in multicomponent exploration. Based on the characteristics of Poynting vectors in an elastic medium, we derive the wavefield‐separation imaging conditions for elastic reverse‐time migration (RTM) and establish the method of calculating the incident angle of source P‐wavefield using the propagation angle of source P‐wavefield and local dip angle of the reflector. Accurate ADCIGs can then be extracted based on the estimated incident angles with small computational cost. Two numerical examples show that the proposed method for extracting elastic‐wave ADCIGs can provide clear and accurate image and image gathers for elastic‐wave imaging tasks and therefore can provide reliable amplitude information for AVA and MVA. Copyright © 2016 John Wiley & Sons, Ltd.