We propose to attenuate diffracted multiples with an apex-shifted tangent-squared Radon transform in angle domain common image gathers (ADCIG). Usually, where diffracted multiples are a problem, the wavefield propagation is complex and the moveout of primaries and multiples in data space is irregular. In our method, the complexity of the wavefield is handled by the migration provided reasonably accurate migration velocities are used. As a result, the moveout of the multiples is well behaved in the ADCIGs.
For 2D data, our apex-shifted tangent-squared Radon transform maps the 2D image space into a 3D model space cube whose dimensions are depth, curvature and apex-shift distance. Well-corrected primaries map to or near the zero curvature plane and specularly-reflected multiples map to or near the zero apex-shift plane. Diffracted multiples map elsewhere in the cube according to their curvature and apex-shift distance. Thus, specularly reflected as well as diffracted multiples can be attenuated simultaneously. We illustrate our approach with a segment of a 2D seismic line over a large salt body in the Gulf of Mexico. We show that ignoring the apex shift compromises the attenuation of the diffracted multiples, whereas our approach attenuates both the specularly-reflected and the diffracted multiples without compromising the primaries.