NAME
bdmute - module to do record variable muting of seismic
data
SYNOPSIS
bdmute [ -Nntap ] [ -Ootap ] [ -Ppfile ] [ -nsnstr ] [
-nenetr ] [ -rsnrst ] [ -renred ] [ -Mmtype ] [ -hwmnemonic]
[ -rpramp ] [ -mdmdist ] [ -vvmul ] [ -dtmul ] [ -fsisp ] [
-incspinc ] [ -noextrap ] [ -nointerp ] [ -A ] [ -V ] [ -? ]
DESCRIPTION
bdmute is a record variable mute routine. Mute control
datums are input through an xsd pick file. The program per-
forms a linear interpolation between control locations. A
user defined taper may be specified.
INPUT
bdmute gets both its data and parameters from command line
arguments. These arguments specify the input, output, pick
file, mute type flag, ramp length, mute velocity, start and
end traces, start and end record, pick file time unit over-
ride, the initial shot point and shot point interval over-
rides. Verbose printout is available.
Command line arguments
-N ntap
Enter the input data set name or file immediately after
typing -N unless the input is from a pipe in which case
the -N entry must be omitted. This input file should
include the complete path name if the file resides in a
different directory. Example -N/b/vsp/dummy tells the
program to look for file 'dummy' in directory '/b/vsp'.
-O otap
Enter the output data set name or file immediately
after typing -O. This output file is not required when
piping the output to another process. The output data
set also requires the full path name (see above).
-P pfile [default: none]
Enter the input pick file name immediately after typing
-P. The input file name also requires the full path
name (see above). The pick file indexing should
correspond to the trace header index chosen below. If
this is not true unpredictable results are sure to fol-
low.
-ns nstr [default: first trace]
Enter start trace.
-ne netr [default: last trace]
Enter end trace.
-rs nrst [default: first record]
Enter start record.
-re nred [default: last record]
Enter end record.
-M mflag [default: none]
For a full description of these options refer to on
section below.
Enter : on (mute before the pick)
off (mute after the pick)
nearon (mute above line)
nearoff (mute below line)
diston (mute above the pick in header file)
distoff (mute below the pick in header file)
-hw mnemonic [default: RecNum]
Enter the trace header mnemonic used to index the pick-
file.
-rp ramp [default: 48 ms]
Enter the temporal linear taper length in ms to apply.
This taper will be used in front of the pick so for ON
type mutes the pick represents the point at which 100
percent of the input data amplitude is preserved while
for OFF type mutes the pick represents the point at
which 0 percent of the input data amplitude is
preserved.
-v vmul [default: 99999 units/s]
Enter the mute velocity (units/second) to used with the
nearon or nearoff options above. If you are not using
either of these options this entry is neither required
nor used.
-md mdist [default: 0 units]
Enter the minimum offset at which to apply the mute.
Traces containing DstSgn entries whose absoulute value
is equal to or less than this entry will be passed un-
muted.
-dt mul [default: 1]
Enter pick file time unit multiplier. If unused, pick
file times will be unaffected.
-fs isp [default: option not used]
Enter the record number to be used in place of the
first pick file record value.
WARNING ...... if you use this option you must also
include -inc.
-inc spinc [default: option not used]
Enter the shot point increment to use between input
pick segments (see -fs).
-noextrap
Enter the command line argument -noextrap to prevent
bdmute from extrapolation of the mute start times out-
side the record boundaries described in the attached
mute parameters file.
-nointerp
Enter the command line argument -nointerp to prevent
bdmute from interpolation of the mute start times
between record boundaries described in the attached
mute parameters file. In this case only records actu-
ally picked will be muted.
-A Enter the command line argument '-A' to use abs(DstSgn)
when using a mute type of diston or distoff. The
default is to honour the signed trace distance for
these options
-V Enter the command line argument '-V' to get additional
printout.
-? -h -help
Enter the command line argument '-?' -h or -help to
get online help. The program terminates after the help
screen is printed.
DISCUSSION
Taper or Ramp
The temporal taper in this program is applied before
the pick so that the pick time represents the 100 per-
cent pass or delete point.
No spacial taper is generated by this routine. This
may result in very sharp edges when using the more
surgical mute options of the program. If you are
suffering from this malady, and it is really important
that it be fixed use program polymute which utilizes
a radial taper.
ple Interval Concerns
If you are muting microsecond data [log data, waveform
data etc.] you must be certain that your pickfile also
contains pick times in microseconds. Bdmute expects
the sample units to be consistent in both the data and
the pickfile. If you have millisecond data [the norm]
then the pickfile must contain times in milliseconds.
This can be facilitated by making the sample units
entry in xsd conform to the sample units of your
data.
Mute Types
There are six options available at present to use in
muting your data (see above). In reality there are
three options with an on and off toggle for each.
on Data above the pick are muted. This is the old faith-
ful first break mute. Mute parameters are interpolated
between segments and the first and last segment are
used for data outside the range of the input control
pick file. For instance on a large dataset one might
have editt'd off a selection of data to facilitate the
digitization of mute control. Say every 50th record
was picked so that the first 49 and last few records
were not defined within the range of record numbers
recorded in the pick file. bdmute would use the first
pick segment to mute records 1 through 50 and the last
pick segment for the last few records on the line.
Mutes would be interpolated for the body of the
dataset.
Within each record should the picks not encompass the
range of traces present, the first and last pick will
be used for traces that fall outside the range of the
segment.
off Data amplitudes are ramped to zero at the pick. Data
below the pick are muted. This can be used to perform a
surgical mute of some portion of the data. Interpola-
tion and extrapolation between records is handled as
described above. Within the record however, only data
below the defined picks are muted. No attempt is made
to extend the first or last picks to the edge of the
record. If you want to mute out all near traces below
some time, be certain that the near trace is included
in the pick file. If you get sloppy, you will immedi-
ately notice the results.
nearon
Data above a line defined by the mute velocity is
muted. The line is hung from a zero offset time deter-
mined from the pick file. This option is handy in
areas with large changes in water bottom depth. One
may digitize the water bottom from a near trace stack
and feed the resulting pick file to bdmute along with a
mute velocity. The program will use the pick time
associated with each record (interpolation and extrapo-
lation between records is handled as described above)
as t(o) and mute all data above a line defined by t(x)
= t(o)+x/v where x is the trace distance as read from
the trace header and v is the mute velocity supplied on
the command line.
nearoff
Data below a line defined as with nearon is muted.
(see nearon for particulars).
diston
This option has the same functionality as on except
that the input parameter control comes from a trace
header output file generated by xsd. The diston flag
lets the routine know to expect this different type of
parameter file. When generating the trace header
parameter file with xsd be sure to detect the trace
header index of your choice [usually RecNum ] and
DstSgn as output. These are the pnemonics for record
number and signed trace distance from the trace
header. It is advisable to check that these entries
are defined for your dataset. If you wish to use abso-
lute value of DstSgn then use the command line flag -A
[see above].
distoff
This option has the same functionality as off except
that the input parameter control comes from a trace
header output file generated by xsd. The distoff flag
lets the routine know to expect this different type of
parameter file. When generating the trace header
parameter file with xsd be sure to detect the trace
header index of your choice [usually RecNum ] and
DstSgn as output. These are the pnemonics for record
number and signed trace distance from the trace header.
It is advisable to check that these entries are defined
for your dataset. If you wish to use absolute value of
DstSgn then use the command line flag -A [see above].
BUGS
It is impossible to check for all possible errors that could
be present in the users xsd pick or header file. There are
policemen in the code to detect the most common of these,
however there will always be a way to crash this routine.
It will not crash in the sense of throwing a core but may
mute your data in some very unpredictable fashion. When
picking mutes within records make sure that you don't hang a
pick over a record boundary. This is the most common error
and is the hardest to recover from since it is not always
obvious what the user intended to do. Always begin your
picking session by clearing the xsd pick register. This
assures one that there are no picks left over from a previ-
ous image that will cause mysterious problems down the line.
AUTHOR
Paul G.A. Garossino APR:3932
COPYRIGHT
copyright 2001, Amoco Production Company
All Rights Reserved
an affiliate of BP America Inc.
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