Synopsis
		sfsqsanaly < in.rsf > out.rsf iq= gx= gz= sc= xc= zc=

Parameters
		float gx= x-gradient of slowness^2   float gz= z-gradient of slowness^2   int iq= switch for escape variable 0=x, 1=a, 2=t, 3=z   float sc= slowness constant   float xc= x reference   float zc= z reference