Program sffdb1 | 1-D Finite-difference wave extrapolation 
[SYNOPSIS]
sffdb1 < in.rsf vel=vel.rsf > out.rsf dt= nt= nb=20 abc=0 order=2
[PARAMETERS]
int     | abc | =0 |   | 	absorbing boundary condition 1: cos 0: exp
float   | dt | = |   | 	
int     | nb | =20 |   | 	
int     | nt | = |   | 	
int     | order | =2 |   | 	FD order: 2,4
file    | vel | = |   | 	auxiliary input file name
[DIRECTORY]
user/songxl
