Technical Questions

Question 18   I want to resample my data so that I have half as many traces, and half as many samples. How do I do that?

Answer 18   To resample data, you must do the following:

1. Check that you won't have aliasing. Do this by viewing the amplitude spectra of your data. Do this with suspecfx

       suspecfx < data.su | suxwigb
   

2. If the bandwidth of your data extends beyond the new nyquist frequency of your data (which, in this example, will be half of the original nyquist frequency) then you will have to filter your data to fit within its new nyquist bandwidth. Do this with sufilter

        sufilter < data.su f=f1,f2,f3,f4  amps=0,1,1,0 > data.filtered.su
   

   Here, the f1 f2 f3 f4 are the filter corner frequencies and amps=0,1,1,0 indicate that the filter is a bandpass filter.
3. Now you may resample your data with suresamp:

       suresamp < data.filtered.su  nt=NTOUT dt=DTOUT > data.resampled.su
   

For your case, NTOUT is 1/2 of the original number of samples, and DTOUT is twice the time sampling interval (in seconds) of that in the original data. Your output data should look quite similar to your input data, with the exception that the bandwidth will change.