SUKDMIG2D - Kirchhoff Depth Migration of 2D poststack/prestack data	

    sukdmig2d  infile=  outfile=  [parameters] 			

 Required parameters:							
 infile=stdin		file for input seismic traces			
 outfile=stdout	file for common offset migration output  	
 ttfile=		file for input traveltime tables		
   The following 9 parameters describe traveltime tables:		
 fzt= 			first depth sample in traveltime table		
 nzt= 			number of depth samples in traveltime table	
 dzt=			depth interval in traveltime table		
 fxt=			first lateral sample in traveltime table	
 nxt=			number of lateral samples in traveltime table	
 dxt=			lateral interval in traveltime table		
 fs= 			x-coordinate of first source			
 ns= 			number of sources				
 ds= 			x-coordinate increment of sources		

 Optional Parameters:							
 dt= or from header (dt) 	time sampling interval of input data	
 ft= or from header (ft) 	first time sample of input data	
 dxm= or from header (d2) 	sampling interval of midpoints 		
 fzo=fzt                z-coordinate of first point in output trace 	
 dzo=0.2*dzt		vertical spacing of output trace 		
 nzo=5*(nzt-1)+1 	number of points in output trace		",	
 fxo=fxt                x-coordinate of first output trace 		
 dxo=0.5*dxt		horizontal spacing of output trace 		
 nxo=2*(nxt-1)+1  	number of output traces 			",	
 off0=0               	first offest in output 				
 doff=99999		offset increment in output 			
 noff=1       		number of offsets in output 			",	
 fmax=0.25/dt		frequency-highcut for input traces		
 offmax=99999		maximum absolute offset allowed in migration 	
 aperx=nxt*dxt/2  	migration lateral aperature 			
 angmax=60		migration angle aperature from vertical 	
 v0=1500(m/s)		reference velocity value at surface		",	
 dvz=0.0  		reference velocity vertical gradient		
 ls=1	                flag for line source				
 jpfile=stderr		job print file name 				
 mtr=100  		print verbal information at every mtr traces	
 ntr=100000		maximum number of input traces to be migrated	
 npv=0			flag of computing quantities for velocity analysis
   ...if npv>0 specify the following three files:			
 tvfile=tvfile		input file of traveltime variation tables	
			tv[ns][nxt][nzt]				
 csfile=csfile		input file of cosine tables cs[ns][nxt][nzt]	
 dataout1=dataout1	file containning additional migration output   	
			with extra amplitude				

 Notes:								
 1. Traveltime tables were generated by program rayt2d (or other ones)	
    on relatively coarse grids, with dimension ns*nxt*nzt. In the	
    migration process, traveltimes are interpolated into shot/gephone 	
    positions and output grids.					
 2. Input seismic traces must be SU format and can be any type of 	
    gathers (common shot, common offset, common CDP, and so on).	", 
 3. Migrated traces are output in CDP gathers if velocity analysis	
    is required, with dimension nxo*noff*nzo.  			", 
 4. If the offset value of an input trace is not in the offset array 	
    of output, the nearest one in the array is chosen. 		
 5. Memory requirement for this program is about			
    	[ns*nxt*nzt+noff*nxo*nzo+4*nr*nzt+5*nxt*nzt+npa*(2*ns*nxt*nzt   
	+noff*nxo*nzo+4*nxt*nzt)]*4 bytes				
    where nr = 1+min(nxt*dxt,0.5*offmax+aperx)/dxo. 			
 6. Amplitudes are computed using the reference velocity profile, v(z),
    specified by the parameters v0= and dvz=.				
 7. Input traces must specify source and receiver positions via the header
    fields tr.sx and tr.gx. Offset is computed automatically.		


 Author:  Zhenyue Liu, 03/01/95,  Colorado School of Mines 

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