Open Data/Open Source: Seismic Unix scripts to process a 2D land line

First Pass Velocity analysis

I used a long script, iva.sh, that combines several SU programs for velocity interpretation. My iva.sh is a combination of the scripts iva.sh and velanQC.sh in sections 7.6.7.3 and 8.2.2.2 of Seismic Processing with Seismic Un*x (Forel et al., 2005). My script is more practical, because you can start from no velocity function, or review and update an existing velocity field. The script has more capabilities, is tidier, and is a little shorter than Forel's script.

Figure 9 is an example velocity analysis plot. It can be produced with the commands:

rm vbrute.txt 
scons vbrute.txt

Or using the tar file:

./vbrute.job

There are four components of the plot: semblance plot, constant velocity stack (CVS) plot, cmp gather without NMO, and cmp gather after NMO. The semblance plots and CVS plot have the velocity function over plotted. The velocity analysis can be picked by pointing on the semblance and 'selecting' by pressing the 's' key. To 'quit' the location press the 'q' key. If you have 'selected' any picks, the plots will be recreated with your new velocity function, otherwise processing will continue at the next location. (The brute analysis only has one velocity location, so 'q' just quits the velocity analysis.)

The velocities I picked are in the vbruteorig.txt file.

velanal
Figure 9. Example velocity analysis from iva.sh.

Open Data/Open Source: Seismic Unix scripts to process a 2D land line