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