Oct. 2007Back to SIOSEIS Examples. Go to the list of seismic processes. Go to SIOSEIS introduction.
USGS Western-Geco San Diego Trough MCSmap (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 112http://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