How do I...

The TDCONV1 module can be used to convert seismic or velocity data from a time to a depth domain or vice versa.

To begin use the DISCREAD module to read in the seismic or velocity data followed by the TDCONV1
module. To run this latter module -

1. the SDEFILE parameter contains the *.nmo file. This should be a smoothed version of the file used to
   stack the data.
2. MODE this can be Vint, Vav or Vrms, for velocity files that are already depth converted the options are Vint(z) or Vav(z).
   
3. the FINALDEPTH parameter sets the maximum depth in metres, or for the inverse conversion the final time in ms.
   
4. SR_METERS is the new sample-rate in metres, or for the inverse conversion the output sample-rate in ms.
   
5. the FACTOR parameter is a value which all the velocities are multiplied by.
6. INVERSE is set to no for a time to depth conversion or yes for a depth to time conversion.
   
7. the DATATYPE parameter will be set to seismic to convert a seismic file or vels to convert a velocity file.

If you want to convert an *.nmo file you will first need to create a file of velocity traces that can be read in by DISCREAD. You can use a module like NMOTRACE to create this file. This module takes an NMO file and overwrites the seismic data in a stacked CDP file creating a file of velocity traces (see also How do I ..... ...create a segy velocity field.). If at the end of converting a velocity file you want an *.nmo file you can use isovels to open the segy velocity file (created by TDCONV1) and then save it as a *.nmo file from this application using the Re-pick button.

If converting a velocity file from a time to a depth domain you could use the TDCONV1 module _ though an easier method is to use the V(z) button in the isovels application, However, the reverse conversion of the a velocity file (i.e. a depth to a time domain) or the conversion of a seismic file would require the use of the TDCONV1 module.