Mapping 2D multiples to image space Gabriel Alvarez Mapping 2D multiples to image space Good evening: My name is Gabriel Alvarez. My main research interest is the attenuation of multiples in the image space. This summer I was working on understanding the mapping of 2D specularly-reflected and diffracted multiples. I gave a presentation about that yesterday afternoon.

Specularly-reflected multiple Half-subsurface offset (m) -200 -400 400 200 1000 1200 1400 Depth (m) Half-aperture angle (degrees) 20 10 40 30 Depth (m) 1200 1400 1600 SODCIG Let me show you here a subsurface-offset-domain common image gather and the corresponding angle domain common image gather for a specularly-reflected multiple from a flat water-bottom. The red lines represent the analytical solutions that I computed and that you read on my paper in the current report. Two things to take away from these figure are that the specularly-reflected multiples migrate as primaries and that, when migrated with velocity faster than water velocity they map to the negative subsurface offsets. ADCIG Flat water-bottom

Diffracted Multiple Raypath hD mD hD V1 Zdiff V2 Xdiff Finally, here is the case of the diffractor sitting on top of the dipping reflector. Again, the image space coordinates can be computed from the data space coordinates and the position of the diffractor. φ

SODCIGs Diffracted multiple. Dipping water-bottom Half-subsurface offset (m) -800 800 Depth (m) 1000 1600 1400 1200 1800 Half-subsurface offset (m) -800 800 Depth (m) 1000 1600 1400 1200 1800 Half-subsurface offset (m) -800 800 Depth (m) 1000 1800 1400 1200 1600 Here again are three common image gathers again showing that the diffracted multiple can map to positive or negative subsurface offsets depending on the relative position of the gather location with respect to the diffractor. Diffracted multiple. Dipping water-bottom

ADCIGs Diffracted multiple. Dipping water-bottom Half-aperture angle (degrees) -40 40 Depth (m) 1400 2000 1600 Half-aperture angle (degrees) -40 40 Depth (m) 1400 2000 1600 -40 40 Depth (m) 1400 2000 1600 Half-aperture angle (degrees) Finally, here are three angle gathers at different locations with respect to the diffractor. Diffracted multiple. Dipping water-bottom