Program sfhelm2D_rtm | 2D Frequency Domain Reverse Time Migration. 
[SYNOPSIS]
sfhelm2D_rtm < in.rsf > out.rsf receiver=receiver.rsf source=source.rsf record=record.rsf nh=0 uts=0 npml=20 order=
[PARAMETERS]
int     | nh | =0 |   | 	
int     | npml | =20 |   | 	PML width 
string  | order | = |   | 	discretization scheme (default optimal 9-point) 
string  | receiver | = |   | 	auxiliary input file name
string  | record | = |   | 	auxiliary input file name
string  | source | = |   | 	auxiliary input file name
int     | uts | =0 |   | 	
[DIRECTORY]
user/hzhu
