sumigprefd.su.main

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SUMIGPREFD --- The 2-D prestack common-shot 45-90 degree   		
                     finite-difference migration.       		
Usage:                                                                 
sumigprefd <indata >outfile [parameters] 	                        ", 

Required Parameters:                                                   ",  

nxo=           number of total horizontal output samples               
nxshot=        number of shot gathers to be migrated                   
nz=            number of depth sapmles                                 
dx=            horizontal sampling interval                            ",   
dz=            depth sampling interval                                 
vfile=         velocity profile, it must be binary format.             
  
Optional Parameters:                                                   

dip=79       the maximum dip to migrate, it can be 45,65,79,80,87,89,90", 
	      The computation cost is 45=65=79<80<87<89<90		

fmax=25      the peak frequency of Ricker wavelet used as source wavelet

f1=5,f2=10,f3=40,f4=50         frequencies to build a Hamming window   

lpad=9999,rpad=9999            number of zero traces padded on both    
				sides of depth section to determine the	
				migration aperature, the default values 
				are using the full aperature.           

 Notes:								
 The input velocity file \'vfile\' consists of C-style binary floats.  
 The structure of this file is vfile[iz][ix]. Note that this means that
 the x-direction is the fastest direction instead of z-direction! Such a
 structure is more convenient for the downward continuation type       
 migration algorithm than using z as fastest dimension as in other SU  
 programs.                                                     	

 Because most of the tools in the SU package (such as  unif2, unisam2, ", 
 and makevel) produce output with the structure vfile[ix][iz], you will
 need to transpose the velocity files created by these programs. You may
 use the SU program \'transp\' in SU to transpose such files into the  
 required vfile[iz][ix] structure.                                     



 Credits: CWP, Baoniu Han, [e-mail], April 19th, 1998


 Trace header fields accessed: ns, dt, delrt, d2
 Trace header fields modified: ns, dt, delrt