SYNOPSIS

PERL PROGRAM NAME:

AUTHOR: Juan Lorenzo (Perl module only)

DATE:

DESCRIPTION:

Version:

USE

NOTES

Examples

SYNOPSIS

SEISMIC UNIX NOTES SUTIFOWLER VTI constant velocity prestack time migration

	      velocity analysis via Fowler's method			



 sutifowler ncdps=250 vmin=1500 vmax=6000 dx=12.5			



 Required Parameter:							

 ncdps=		number of input cdp's				

 Optional Parameters:							

 choose=1	1 do full prestack time migration			

		2 do only DMO						

		3 do only post-stack migrations				

		4 do only stacking velocity analysis			

 getcvstacks=0	flag to set to 1 if inputting precomputed cvstacks	

		(vmin, nvstack, and ncdps must match SUCVS4FOWLER job)	

 vminstack=vmin	minimum velocity panel in m/s in input cvstacks	

 etamin=0.		minimum eta (see paper by Tariq Alkhalifah)	

 etamax=0.5	maximum eta (see paper by Tariq Alkhalifah)		

 neta=1	number of eta values to image				

 d=0.		Thomsen's delta						

 vpvs=0.5	assumed vp/vs ratio (not critical -- default almost always ok)

 dx=25.	cdp x increment						

 vmin=1500.	minimum velocity panel in m/s to output			

 vmax=8000.	maximum velocity panel in m/s to output			

 nv=75	 number of velocity panels to output				

 nvstack=180	number of stacking velocity panels to compute		

		     ( Let offmax be the maximum offset, fmax be	

		     the maximum freq to preserve, and tmute be		

		     the starting mute time in sec on offmax, then	

		     the recommended value for nvstack would be		

		     nvstack = 4 +(offmax*offmax*fmax)/(0.6*vmin*vmin*tmute)

		     ---you may want to make do with less---)		

 nxpad=0	  number of traces to padd for spatial fft		

		     Ideally nxpad = (0.5*tmax*vmax+0.5*offmax)/dx	

 lmute=24	 length of mute taper in ms				

 nonhyp=1	  1 if do mute at 2*offset/vmin to avoid non-hyperbolic 

				moveout, 0 otherwise			

 lbtaper=0	length of bottom taper in ms				

 lstaper=0	length of side taper in traces				

 dtout=1.5*dt	output sample rate in s,   note: typically		

				fmax=salias*0.5/dtout			

 mxfold=120	maximum number of offsets/input cmp			

 salias=0.8	fraction of output frequencies to force within sloth	

		     antialias limit.  This controls muting by offset of

		     the input data prior to computing the cv stacks	

		     for values of choose=1 or choose=2.		

 file=sutifowler	root name for temporary files			

 p=not		Enter a path name where to put temporary files.		

	  	specified  Can enter multiple times to use multiple disk

		systems.						

		     The default uses information from the .VND file	

		     in the current directory if it exists, or puts 	

		     unique temporary files in the current directory.	

 ngroup=20	Number of cmps per velocity analysis group.		

 printfile=stderr    The output file for printout from this program.	



 Required trace header words on input are ns, dt, cdp, offset.		

 On output, trace headers are rebuilt from scratch with		

 ns - number of samples						

 dt - sample rate in usec						

 cdp - the output cmp number (0 based)					

 offset - the output velocity						

 tracf	- the output velocity index (0 based)				

 fldr - index for velocity analysis group (0 based, groups of ngroup cdps)

 ep - central cmp for velocity analysis group				

 igc - index for choice of eta (0 based)				

 igi - eta*100								

 sx=gx	- x coordinate as icmp*dx					

 tracl=tracr -sequential trace count (1 based)				



 Note: Due to aliasing considerations, the small offset-to-depth	

 ratio assumption inherent in the TI DMO derivation, and the		

 poor stacking of some large-offset events associated with TI non-hyperbolic

 moveout, a fairly stiff initial mute is recommended for the		

 long offsets.  As a result, this method may not work well		

 where you have multiple reflections to remove via stacking.		



 Note: The temporary files can be split over multiple disks by building

 a .VND file in your working directory.  The .VND file is ascii text	

 with the first line giving the number of directories followed by	

 successive lines with one line per directory name.			



 Note: The output data order has primary key equal to cdp, secondary	

 key equal to eta, and tertiary key equal to velocity.			



 Credits:

	CWP: John Anderson (visitor to CSM from Mobil) Spring 1993

User's notes (Juan Lorenzo) untested

CHANGES and their DATES

Import packages

instantiation of packages

Encapsulated hash of private variables

sub Step

collects switches and assembles bash instructions by adding the program name

sub note

collects switches and assembles bash instructions by adding the program name

sub clear

sub choose

sub d

sub dtout

sub dx

sub etamax

sub etamin

sub file

sub fmax

sub getcvstacks

sub lbtaper

sub lmute

sub lstaper

sub mxfold

sub ncdps

sub neta

sub ngroup

sub nonhyp

sub nv

sub nvstack

sub nxpad

sub p

sub printfile

sub salias

sub sx

sub tracl

sub vmax

sub vmin

sub vminstack

sub vpvs

sub get_max_index

max index = number of input variables -1

cpanm App::SeismicUnixGui

perl -MCPAN -e shell
install App::SeismicUnixGui