This is the story of how I processed some "single channel" data from the Ewing. The data were converted into SEG-Y before being given to me. ls -l ew* -rwxr-xr-x 1 henkart 21 612263952 Nov 14 13:42 ew9513_line7.segy The data contain 4 channels, where the close group has a length of 12.5m and is 150m from the fantail. The next group is a 25m group and then there are two 50m groups. lsd ew9513_line7.segy 1 12 SHOT TR RP TR ID RANGE DELAY NSAMPS SI YR DAY HR MIN SEC 81884 1 0 0 1 0 0 6144 2000 96 13 13 50 5 81884 2 0 0 1 0 0 6144 2000 96 13 13 50 5 81884 3 0 0 1 0 0 6144 2000 96 13 13 50 5 81884 4 0 0 1 0 0 6144 2000 96 13 13 50 5 81884 5 0 0 1 0 0 6144 2000 96 13 13 50 5 81884 6 0 0 1 0 0 6144 2000 96 13 13 50 5 81884 7 0 0 1 0 0 6144 2000 96 13 13 50 5 81884 8 0 0 1 0 0 6144 2000 96 13 13 50 5 81885 1 0 0 1 0 0 6144 2000 96 13 13 50 20 81885 2 0 0 1 0 0 6144 2000 96 13 13 50 20 81885 3 0 0 1 0 0 6144 2000 96 13 13 50 20 81885 4 0 0 1 0 0 6144 2000 96 13 13 50 20 The first thing I did was to get just look a small 50 shots of each channel.
Notice that trace 3 and trace 4 are significantly better than trace 1 or trace 2. I worked with trace 4 only to determine some other processing parameters. Waterguns have higher frequency content than airguns and a typical filter bandpass is 30x130. Typically, the watergun precurser is around 35Hz.
Sometimes AGC make the data look noisy, so I tried GAINS instead.
That was a bad choice of GAINS parameter ALPHA, so try alpha .5
Change the plot scale so the plot isn't as "scrunched".
Now, let's look at 400 shots rather than 50
Stack (addition) of any type of signals reduces the random noise by the square root of the number of signals summed. E.G. Adding two traces together will reduce the random noise by SQRT(2). Trace 3 and trace 4 are quite good and are similar streamer sections, so just use those two traces in the stack. Trace 3 and 4 are 50 meters apart and the pop interval is 79m, so simply sum the adjacent traces rather than sorting (gathering) into CDPs or RPs. Process STACK sums traces until an "end of gather" flag is detected. Process DISKIN parameter NTRGAT sets the "end of gather" flag after NTRGAT traces are read.
Go to the list of seismic processes. Go to SIOSEIS introduction.