3D angle domain common image gathers (ADCIGs) with reverse time migration provide a powerful tool for imaging complex geological structures. For wide azimuth (WAZ) data processing, ADCIGs retain localized information indexed by subsurface azimuth and reflection angles, which are helpful for velocity model updating and reservoir attribute interpretation. For WAZ data, the energy is well distributed in the vector (source-receiver) offset domain. However, in the subsurface angle domain, the shallow events are illuminated across a wide range of reflection angles, with a large angle sampling increment. Theoretical analysis shows that coarse shot spacing produces undersampled shallow events, especially at small reflection angles. A second problem, observed at large reflection angles when migration velocity is incorrect, is due to inadequate angular spacing for deeper events. These undersampling issues challenge our ability to produce high quality ADCIGs. We first analyze the angular sampling and noise issues with simple synthetic examples. Then we propose methods to reduce the two sources of undersampling noise for RTM 3D ADCIGs. Finally, we demonstrate the efficiency and robustness of our noise suppression algorithms using 2D and 3D examples.


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