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FIG. 6. (A) Common-source gathers along Line 2 (Fig. 4). Steeply dipping reflections are evident from backdipping moveout (e.g., transmitter [TX] = 45 m). A significant decrease in surface velocity past 145 m is evident where the dips of the direct ground arrival steepen, as indicated by the dashed lines (e.g., TX = 198 m). (B) The normal moveout common midpoint (CMP) stack reveals dipping strata in the near surface and a clear reflection from the water table. At distances >145 m, the signal is severely degraded due to increased attenuation. Note the approximately 40-ns push down of the water table reflection at distances >145 m. (C) Prestack depth migration (PSDM) with the laterally variable velocity model places the water table at the correct position in depth across the entire profile.
