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 SUPHASEVEL - Multi-mode PHASE VELocity dispersion map computed
              from shot record(s)				

 suphasevel <infile >outfile [optional parameters]		

 Optional parameters:						
 fv=330	minimum phase velocity (m/s)			
 nv=100	number of phase velocities			
 dv=25		phase velocity step (m/s)			
 fmax=50	maximum frequency to process (Hz)		
		=0 process to nyquist				
 norm=0	do not normalize by amplitude spectrum		
		=1 normalize by amplitude spectrum		
 verbose=0	verbose = 1 echoes information			

 Notes:  Offsets read from headers.			 	
  1. output is complex frequency data				
  2. offset header word must be set (signed offset is ok)	
  3. norm=1 tends to blow up aliasing and other artifacts	
  4. For correct suifft later, use fmax=0			
  5. For later processing outtrace.dt=domega			
  6. works for 2D or 3D shots in any offset order		


 Using this program:						

 First: use 							
 	suspecfx < shotrecord.su | suximage			
 to see what the maximum bandwidth is in your data. This will	
 give you an idea about the possible value for fmax.		

 Second: Plot your data or some subset of your data via:	
     suxwigb < shotrecord.su key=offset			

 You can then estimate the range of phase velocities by looking
 at the maximum and minimum slopes of arrivals in your data.	
 This will allow you do set first velocity fv and the increment
 in velocity dv, that make sense for your data.		

 You can pick values of offset and time by placing the cursor  
 on the desired location on the plot and pressing the \'s\' key
 The picks will appear in your terminal window. 		

 When displaying, don't forget to use suamp to compute the	
 modulus of the complex values that this program puts out.	

   suphasevel < shotrecord.su [parameters] | suamp | suximage	



 Credits:

	UHouston: Chris Liner June2008 (cloned from suspecfk)

  This code implements the following integral transform
             _
            /
  u(w,v) = / k(w,x,v) u(w,x) dx
         _/
  where
	u(w,v) is the phase velocity dispersion image
	k(w,x,v) is the transform kernel.... exp(-i w x / v)
	u(w,x) = FT[u(t,x)] is the input shot record(s) 
         _/
 Reference: Park, Miller, and Xia (1998, SEG Abstracts)

 Trace header fields accessed: dt, offset, ns
 Trace header fields modified: nx,dt,trid,d1,f1,d2,f2,tracl