Tau-P Analysis Tool




Seismic Unix






Womble is a tool that can help to understand where specific regions (events, energy) in seismic data end up when the data is transformed into a different domain. It was developed for the analysis of radon transformed data , e.g. linear Radon transform (slant stack), hyperbolic Radon transform, or parabolic Radon transfom. 

Womble allows to pick one or more polygons that define regions on a seismic shot record in the t-x domain. The input data has to be in SEGY-format.

The regions of interest are selected by drawing a polygon with the mouse. For each selected polygon are separate SEGY-files created with the amplitude zero outside the selected area and the amplitude 1 inside the polygon.

The user can then transform these SEGY-files by using a transform/program of his/her choice. Equally can regions be selected in transformed data, to study the effect of an inverse transformation.

The difference to surgical muting (as possible for example with ProMAX) and subsequent transformation of the data is, that the amplitudes of an event are not considered.

However, Womble allows for the creation of SEGY-files with the true amplitude inside the polygons while the amplitude is zero outside the polygon.


Womble can be obtained here (Size: 3.77 MB) .


Womble makes use of Seismic Unix and pgplot . Both packages need to be installed in order to compile and run Womble.


To install Womble download the compressed archive and execute the following command sequence:

tar zxvf womble.tgz
cd womble

Set the size (width, height, x-offset and z-offset in pixels) of the display-window by editing your .Xdefaults file: just add the following line at the bottom of the .Xdefaults file

pgxwin.Win.geometry:                               800x600+50+50

and run

xrdb .Xdefaults


Once Womble is compiled start it with

womble input.dat

If pgplot is installed correctly you should get the following request in your terminal window:

Graphics device/type (? to see list, default /xserve):

Just hit Enter.

Next the data window will pop up and you should be able to pick polygons with the mouse.
Use the left mouse button to pick the polygon points. Use the right mouse button to close a polygon.
After closing the last polygon that you want to define, hit again the right mouse button and Womble will proceed with the creation of the individuall phase-SEGY files.

All output is stored in the same directory where the input-SEGY file is located. In addition to SEGY-files for each picked phase you will find binary (.bin) and Seismic Unix (.su) files for each phase. The pick-points of each phase are written to the files ending with .dat . The format of the .dat-files is the following:

number of pick points in total
trace number       sample number
trace number       sample number
trace number       sample number

Here you can see a screengrab with several polygons picked on a seismic shot-gather:

Wish list

  • Various colour tables for data display.
  • Zoom function for the data display.


From left to right you can see the original shot record, the selected polygon, the slant-stack (linear Radon transform) of the polygon, and the original data in the transform (tau-pi) domain. Click on the images with the right mouse button and select "View Image" to see an enlarged version.

The seafloor reflection:

         original data                        selected polygon              transformed polygon      transformed data

A refracted event:

         original data                        selected polygon              transformed polygon      transformed data

Some blub in the cone of reflected, refracted, and multiple energy:

         original data                        selected polygon              transformed polygon      transformed data

Go home !