Field data

Figure 4a displays a shot gather recorded in a marine survey in the Arctic. A strong water bottom reflection and its multiples are visible. After the processing, these low-velocity events are eliminated, as shown in Figure 4b. At far offsets we see some events with linear moveout. These are either refracted waves propagating along the water bottom with an apparent velocity equal to the velocity of the first layer of sediments, or truncation artifacts. Because the structures of the area are simply horizontal layers I can compute the velocity spectrum from the shot gather. The velocity spectrum of the data before and after processing are shown in Figure 5 for comparison. It is seen that the energy of the water-bottom multiples is greatly reduced.

 

fieexa
Figure 4 A field data example: (a) a shot gather recorded in a marine survey in the Arctic; (b) the same gather after the removal of the water-bottom multiples. At far offsets, refracted waves are seen.

 

velspe
Figure 5 Velocity spectra: (a) before and (b) after the removal of low-velocity events.