SYNOPSIS
PERL PROGRAM NAME:
AUTHOR: Juan Lorenzo (Perl module only)
DATE:
DESCRIPTION:
Version:
USE
NOTES
Examples
SYNOPSIS
SEISMIC UNIX NOTES SUALFORD - trace by trace Alford Rotation of shear wave data volumes
sualford inS11=file1 inS22=file2 inS12=file3 inS21=file4
outS11=file5 outS22=file6 outS12=file7 outS21=file8 [optional
parameters]
Required Parameters:
inS11= input data volume for the 11 component
inS12= input data volume for the 12 component
inS21= input data volume for the 21 component
inS22= input data volume for the 22 component
outS11= output data volume for the 11 component
outS12= output data volume for the 11 component
outS21= output data volume for the 11 component
outS22= output data volume for the 11 component
Optional parameters:
angle_inc= sets the increment to the angle by which
the data sets are rotated. The minimum is
set to be 1 degree and default is 5.
Az_key= to set the header field storing the azimuths
for the fast shear wave on the output volumes
Q_key= to set the header field storing the quality
factors of performed optimum rotations
lag_key= to set the header field storing the lag in
miliseconds the fast and slow shear components
xcorr_key= to set the header field containing the maxi-
mum normalized cross-correlation between the
and slow shear waves.
taper= 2*taper+1 is the length of the sample overlap
between the unrotated data with the rotated
data on the traces. The boundary between them
is defined by time windowning.
taper = -1, for no-overlap
taper = 0, for overlap of one sample
taper =>1, for use of cosine scale to
to interpolate between the
unrotated and rotated parts
of the traces
taperwin= another taper used to taper the data within
the window of analysis to diminish the effect
of data near the window edges.In this way one
can focus on a given reflector. Also given in
number of samples
maxlag= maximum limit in ms for the lag between fast
and slow shear waves. If this threshold is
attained or surpassed, the quality factor for
the rotation is zeroed as well as all the
parameters found for that certain rotation
ntraces= number of traces to be used per computation
ntraces=3 will use three adjacent traces to
compute the angle of rotation "
Notes:
The Alford Rotation is a method to rotate the four components
of a shear wave survey into its natural coordinate system, where
the fast and slow shear correspond to the inline to inline shear (S11)
and xline to xline (S22) volumes, respectively.
This Alford Rotation code tries to maximize the energy in the
diagonal volumes, i.e., S11 and S22, while minimizing the energy
in the off-diagonals, i.e., in volumes S12 and S21, in a trace by
trace manner. It then returns the new rotated volumes, saving the
the quality factor for the rotation and azimuth angle of the fast
shear wave direction for each trace headers of the new rotated S11
volume.
The fields in the header containing the Azimuth and Quality factor
and the sample lag between fast and slow shear are otrav, grnolf and
grnofr, respectively, by default. The values are multiplied by ten in
the case of the angles and by a thousand for quality factors. To
change this defaults use the optional parameters Az_key, Q_key and
lag_key
modified header fields:
the ones specified by Az_key, Q_key, lag_key and xcorr_key. By default
these are otrav, grnlof, tstat and grnors, respectively.
Credits:
CWP: Rodrigo Felicio Fuck
Code translated and adapted from original version in Fortran
by Ted Schuck (1993)
Schuck, E. L. , 1993, Multicomponent, three dimensional seismic
characterization of a fractured coalbed methane reservoir,
Cedar Hill Field, San Juan County, New Mexico, Ph.D. Thesis,
Colorado School of MinesUser'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 Az_key
sub Q_key
sub angle_inc
sub inS11
sub inS12
sub inS21
sub inS22
sub lag_key
sub maxlag
sub ntraces
sub outS11
sub outS12
sub outS21
sub outS22
sub taper
sub taperwin
sub xcorr_key
sub get_max_index
max index = number of input variables -1