SUINVZCO3D - Seismic INVersion of Common Offset data with V(Z) velocity function in 3D                       

     suinvzco3d <infile >outfile [optional parameters]                 

 Required Parameters:                                      
 vfile                  file containing velocity array v[nz]           
 nz=                    number of z samples (1st dimension) in velocity
 nxm=             number of midpoints of input traces      
 ny=              number of lines                    

 Optional Parameters:                                      
 dt= or from header (dt)      time sampling interval of input data     
 offs= or from header (offset)      source-receiver offset            
 dxm= or from header (d2)     sampling interval of midpoints           
 fxm=0                  first midpoint in input trace            
 nxd=5                  skipped number of midpoints (see note)         
 dx=50.0                x sampling interval of velocity                
 fx=0.0                 first x sample of velocity               
 dz=50.0                z sampling interval of velocity                
 nxb=nx/2         band centered at midpoints (see note)          
 fxo=0.0                x-coordinate of first output trace       
 dxo=15.0         horizontal spacing of output trace       
 nxo=101                number of output traces                   ",   
 fyo=0.0          y-coordinate of first output trace       
 dyo=15.0         y-coordinate spacing of output trace           
 nyo=101          number of output traces in y-direction         
 fzo=0.0                z-coordinate of first point in output trace    
 dzo=15.0               vertical spacing of output trace         
 nzo=101                number of points in output trace          ",   
 fmax=0.25/dt           Maximum frequency set for operator antialiasing
 ang=180          Maximum dip angle allowed in the image         
 verbose=1              =1 to print some useful information      

 Notes:                                                    

 This algorithm is based on formula (50) in Geophysics Vol. 51,  
 1552-1558, by Cohen, J., Hagin, F., and Bleistein, N.                 

 Traveltime and amplitude are calculated by ray tracing.         
 Interpolation is used to calculate traveltime and amplitude.           ",
 For each midpoint, traveltime and amplitude are calculated in the     
 horizontal range of (xm-nxb*dx, xm+nxb*dx). Velocity is changed by    
 linear interpolation in two upper trianglar corners whose width is    
 nxc*dx and height is nzc*dz.                               ",   

 Eikonal equation will fail to solve if there is a polar turned ray.   
 In this case, the program shows the related geometric information.    
 
 Offsets are signed - may be positive or negative.                ",