56 Seismic Imaging Figure 2.16 shows the velocity distribution at different depths (15 and 20 m), the 2,500 m/s iso-velocity depth map, and a 3D block with vertical velocity sections located at distances of 0 m, 60 m and 180 m in the cross-line direction and a velocity map located at 20 m in depth. A strong correlation can be seen between the 2,500 m/s iso-velocity depth map (Figure 2.16-c) and the Wz depth map (Figure 2.15-b). The correlation coefficient reaches 0.96. a b c 0 0 100 200 (m) 60 120 180 240 300 500 1000 1500 2000 2500 3000 3500 m/s 0 0 0 d Figure 2.16 Results of 3D tomography. a) Velocity distribution at 15 m in depth, b) Velocity distribution at 20 m in depth, c) 2,500 m/s iso velocity depth map, d) 3D block with vertical velocity sections located at distances of 0 m, 60 m and 180 m in the cross-line direction and a velocity map located at 20 m in depth. The results obtained by the Plus-Minus tomographic inversion joint method can also be used effectively to compute the static corrections in 3D. For that purpose, the thickness H of the weathering zone is given by the 2,500 m/s iso-velocity depth
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