Program sfepisort | Sort microseismic surface array recording traces by their distances or azimuths to a given epicenter. 
[SYNOPSIS]
sfepisort < in.rsf x=x_file.rsf y=y_file.rsf > out.rsf dist=dist_file.rsf theta=theta_file.rsf epi_x= epi_y= sort=
[PARAMETERS]
file    | dist | = |   | 	auxiliary output file name
float   | epi_x | = |   | 	referenced epicenter coordinate x. 
float   | epi_y | = |   | 	referenced epicenter coordinate y. 
string  | sort | = |   | 	sort distance[d] (default) or angle[a] 
file    | theta | = |   | 	auxiliary output file name
file    | x | = |   | 	auxiliary input file name
file    | y | = |   | 	auxiliary input file name
[DIRECTORY]
user/yunzhi
