Program sfgroll | Add linear-chirp ground-roll noise to the data 
[SYNOPSIS]
sfgroll < in.rsf > out.rsf begf=10. endf=5. theta=0.2 alpha=0.1 beg1=0. beg2=0. rep=n
[PARAMETERS]
float   | alpha | =0.1 |   | 	width parameter of ground roll 
float   | beg1 | =0. |   | 	radial beginning point at first axis 
float   | beg2 | =0. |   | 	radial beginning point at second axis 
float   | begf | =10. |   | 	beginning frequency of ground roll 
float   | endf | =5. |   | 	ending frequency of ground roll 
bool    | rep | =n |  [y/n] | 	if y, replace data with noise 
float   | theta | =0.2 |   | 	direction of central ground roll 
[DIRECTORY]
user/yliu
