Script to weight smute plot shot 29.
plot of shot 29 after weight and smute
The above C shell script is executed by using the first shot
number at the first argument and the last shot number to plot as
the second argument. e.g. plt 29 29 plots just shot 29.
I plotted each shot on the screen, one at a time, to check that
I got all the bad traces. Good thing too, because I'd missed a few.
Script to weight smute plot all shots.
Note that xloadimage is terminated by typing the letter q
in the plot window. Also note that the pause between plots is
caused by xloadimage being in the foreground. Continuous plots
(without a pause between shots) may be obtained by doing xloadimage
in background (by placing the ampersand sign (&) on the xloadimage
command line.
Each SEG2 shot is a separate file, so I callected them all
together into one SEG-Y file using this script.
The next step shown in script is to:
1) edit the data (kill bad traces, invert traces with reverse polarity
and surgically mute noise bursts).
2) Assign the shooting and geophone geometry as well as assigning
the topographic corrections.
3) Do a CMP gather (collect traces according to common mid points)
The final script is short, but took a great deal of analysis to derive.
1) Only the traces near the shot were retained. Traces further than
40cm from the shot don't appear to have reflections and have some
other mode (surface waves or shear waves or ???); so ranges 45cm and
greater are eliminated from the stack by weighting them to zero.
2) Filter was applied before NMO because the low frequencies didn't
move-out correctly. I never determined why.
3) The datum or topographic corrections are applied via process SHIFT.
4) A 100x800 Hz bandpass filter was applied.
5) The plot is done in reverse direction since the first shot was on
the southe end of the line. The plot annotation is by meters with
the top of the mound being zero.
final plot
User Discussion
New (2001) Analysis
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The recording unit clipped some of the traces on some of the shots,
so it was decided to mute the clipped data first thing. Script is
the sioplt script used to pick the mutes. The tsets were then used to
create a new set of cmp gathers using (script).
The cmp gathers can be plotted with script.
The cmp gathers were moved out and stacked with script.
The stack was fk migrated with script.
The final plot was generated with script.
The plot of the filtered agced shot directly over the mound was generated
by script.
Tomography Survey
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The tomography survey geophone layout has "Geometrics" channel 2-48,
LeRoy channel 1-32, Alistair channels 1-34.
1) Create a SEGY file of all 72 shots
Script to combine all three Geometrics recorders
2) Create a file with the "closest" trace to the vibrator.
Note: There is confusion about the polarity between the two series
of Geometrics. After step 1 above, traces 1-47 are from the rental
Geometrics and traces 48-105 are from LeRoy and Alistair. The polarity
of the pilot traces of all "closest" traces of the Geometrics are
reversed in this script.
Script to collect the trace "closest" to each vibrator point.
3) Pick and print the time of the largest positive amplitude after
correlating with the trace closest to the vibrator. SIOSEIS does not
permit specifying a different pilot trace on every shot when the pilot
is in a different file, so each shot is correlated in a new sioseis
job. The first sioseis job created the output file and subsequent
jobs positioned after the last shot in the output file.
The special lprint value of 4 was created in process WBT to print
the picks and a perl script was run to write the pick in the "Cornuelle"
format and to only print if the time of the pick was greater than .05
seconds.
Script to correlate and pick.
Perl script to reformat the picks
Plot of the first shot after correlation. (62KB)
GPR (Ground Penetrating Radar) Survey
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Larry Conyers of the University of Denver collected and processed
a bunch of GPR data. I will try some seismic processing techniques on
these data. The digital data were recorded in the GSSI DZT format.
GPR uses nanosecond sampling and SEG-Y can do no better than micro-
seconds, so all processing units have been scaled by 10**3. Individual
GPR traces are displayed here. A typical GPR line is displayed here
GPR line 59, meters 26 to 33 corresponds to the location
of the seismic reflection line. A simple plot doesn't reveal
anything useful. (plot script).
A common GPR processing technique is to use a "background"
filter, which subtracting the average trace from all the
traces. SIOSEIS found the average trace through process STACK
and process UADD then subtracted it (script).
The plot does help!
A plot with a bandpass filter of 500 2000.
A plot with a bandpass filter of 500 1000.
A plot with the background filter and 500x1000 bandpass.
A plot and script for filter and migration.
A plot with background filter, filter and migration.
A plot with filter, migration and topography corrections.
A plot with background filter, filter, migration and topography corrections.
The units used in GPR processing in SIOSEIS are confusing:
1) DZT2SEGY uses a sample interval in microseconds rather than nanoseconds
since the SEG-Y standard (and SIOSEIS) expect it that way. DZT2SEGY
sets the sample interval to 59, where it should be .059.
2) The elevations in SEG-Y are also integers, but they need to be in
millimeters, so the elevations are multiplied by 1000. Thus GEOM
parameters datume 600 datumv 200000 are in millimeters and mm/sec.
3) The FK migration was done using a sample interval of .001 so the
program wouldn't bomb. The migration velocity was 2500. The
distance between traces in migration was set to 16 rather than the
.016m actually recorded.
Go to the list of seismic processes.
Go to SIOSEIS introduction.