Seismic 2D Reflection Processing and Interpretation of ... - Posiva

22Figure 18. First shot from the line S28 before and after NMO. Red line demonstrateshow NMO straightens up first breaks.After NMO data can be stacked (Table 2, item 14). First it must be sorted intocommon depth point gathers, which means that data is sorted by its CDP position, andCDP positions must be changed into CDP numbers. Traces with the same CDP numberare stacked. CDP numbers are integers and calculated based on a position of eachCDP. All traces having their CDP position within a bin length are stacked into the fold.Length of a bin was 2,5 meters and consequently maximum fold is eight and minimumfold one. Figure 19 demonstrates principle of stacking. In the line 342 geophonespacing was smaller so bin is 1 meter. Each stacked sample is divided by the squareroot of non-zero values stacked. Final stacked section from the line S28 is shown inFigure 21 a). Only the first 300 ms of the data are displayed because of a low signalto-noiseratio in the lower parts of the data.