Oct. 2007
USGS Western-Geco San Diego Trough MCS
map (2.7MB pdf)
Fledermaus scene file (98MB)

     This example is an attempt to instruct non-seismic users
how to create a plot of the USGS processed stacked SEG-Y data 
located at:
http://walrus.wr.usgs.gov/NAMSS/data_access.html
or
http://walrus.wr.usgs.gov/infobank

     There are two examples below.  The first example is for a 1981
Western Geco dataset and is simpler. The second example is from a 
1990 USGS cruise on the R/V Fred Lee and was my first attempt 
at using the USGS seismic archive.  Both are excellent data quality.
     I'm assuming the novice SIOSEIS user is somewhat familiar 
with Unix and executing scripts and a text editor.  Get and compile
sioseis from http://sioseis.ucsd.edu.
If you don't have ImageMagick routines "display" and "convert",  
get them also.  Follow the installation and test scripts at
http://sioseis.ucsd.edu/installation.html.
     Basic SIOSEIS documentation is at:
http://sioseis.ucsd.edu/flow.html
http://sioseis.ucsd.edu/syntax.html
http://sioseis.ucsd.edu/definitions.html
     The parameters for the seismic processes are at:  
http://sioseis.ucsd.edu/procs.html
     The seismic data may be found at http://walrus.wr.usgs.gov/NAMSS/gm.html
Download "w-31-81-sc.mig.segy.tar.gz"
(use tar -xzf w-31-81-sc.mig.segy.tar.gz to unpack the tar file)
and the ASCII navigation file "w-31-81-sc.420_051".  
(An ESRI licensed ArcGis program is required in order to read E00 files).
     Use Google Earth determine the lat/long of the end point of the
seismic line of interest (in Google Earth delete any unnecessary 
surveys by right click on a push button, then under the edit 
pull-down delete).  Convert degrees, minutes, seconds to decimal 
degrees, then search the ASCII nav file for the end point to lookup
what seismic line number (don't use all the decimal points when 
doing the search e.g. 32.63).  You should see the line:
19810490000001  32.63470 -117.69946 WSD81-754            100
The number on the right is the SEG-Y energy source point number.
This is not the same as the SEG-Y shot point number or rp number.
      While looking at the nav file, determine which direction the 
line was shot and whether the first shot should be on the left or 
right side of the plot (sioseis parameter DIR controls the plot 
direction.  RTL means the first trace is on the right and LTR means 
left-to-right).
     Create a script file such as:
sioseis << eof
procs diskin filter plot end
diskin
   ipath WSD81-754__14951.sgy end
end
 filter
    ftype 0 pass 5 80 dbdrop 48 end
 end
plot
   srpath sunfil.ras dir ltr 
  trpin 300 vscale 1 ann espn taginc 100 tlines .5 1
    plotter 2859 clip .003 def .003 wiggle 0 end
end
end
eof
convert -rotate 270 -resize 50% sunfil.ras 754.png
display 754.png &

     Remember to change the permissions on the file so it can be 
executed (e.g. chmod +x filename).  You may have to use the whole 
pathname (e.g. /Users/henkart/bin/sioseis  and 
/Users/henkart/bin/display).

     There are two sioseis parameters that will change between 
seismic lines; the input file name (sioseis parameter ipath and
the plot direction (sioseis parameter dir).
     Sioseis creates a Sun rasterfile and ImageMagick program 
"convert" converts it to a PNG file that PhotoShop can read. Note 
that if the plot direction is RTL, the plot should be rotated 90 
degrees rather than 270.
     A plot should appear on the screen and a plot file "754.png" 
should be created.

     "754.png" shows a very nice fault in the San Diego Trough at
annotation point 533.  Recall that the annotation is the SEG-Y 
"energy source point number".  The nav file shows:
19810490000434  32.67317 -117.59298 WSD81-754            533   

     Some seismic lines are very long and would produce plot files
that are impractically long, so the following shows how to relate
a USGS ASCII nav file to a SEG-Y data file.  Script "prout":
sioseis << eof
procs diskin prout end
diskin
  ipath WSD81-748__30842.sgy
  end
end
prout
   fno 0 lno 999999 ftr 0 ltr 999 trlist espn rpno end
end
end
eof

     The command:      prout >  WSD81-748__30842.prt
results in file WSD81-748__30842.prt.
     Some terminology:   Multichannel seismics (MCS) are recorded as shot
records.  Each shot record is numbered, usually but not always 
consecutively in marine work.  USGS uses a navigation system that is not
integrated into the seismic system and records the location of each
shot using it's own numbering scheme - the "energy source point number"
(ESPN).  The ESPN is recorded by the seismic system but the location
(lat/long) is not since the location is at the navigation antenna, not
the actual shot.  One of the first steps in seismic processing is
sorting or gathering traces from different shots into a "common
mid-point" (CMP) or "reflection point" (RP).  The sorted data are
renumbered with an "RP number" (RPNO).  The traces with the same RPNO
are "stacked" (added) together but retain the RPNO.
     These data were collected in a manner so that there are two RPs for
every shot.  The beginning end of a seismic line will have RPs but no
ESPN because the streamer is towed behind the ship and all hydrophones
are recorded on the first shot.

1990 R/V Fred Lee Line 112

http://walrus.wr.usgs.gov/infobank/l/l490sc/html/l-4-90-sc.seis.html

Using lsd:
      SHOT   TR       RP    TR ID  RANGE DELAY NSAMPS    SI   YR DAY HR MIN SEC
      3982    48    8100     1  1   -255     0   3000  4000   90 134 15  40 497
      4823    48    9800     1  1   -255     0   3000  4000   90 134 19  56 440

Using download nav file l-4-90-sc.051:
19901341500000  32.62817 -117.83967     0.0 RHO
19901342000000  32.86522 -117.39827     0.0 RHO

Using program distance:
  The distance between the two points is  49060.0736 meters.

That's 28.8m, which probably means 25m per trace and a streamer group spacing of 50m

The fkmigr script:
sioseis << eof
procs diskin tx2fk fkmigr fk2tx diskoa end
diskin
   fno 8000 lno 99999 set 0 7 ipath 8000-9600.segy end
end
tx2fk
   end
end
fkmigr
   vel 1500 deltax 25 end
end
fk2tx
   end
end
diskoa
   opath fkmigr.segy end
end
end
eof