Earthquake Migration Codes and Examples
J. Louie, 1/31/2001
Task 0: Download the Archived Example For Solaris
- example.tar.Z, 18.7 Mbytes
- Unpack with:
zcat example.tar.Z | tar xvf -
Task 1: Read About Work on Weber Sequence, New Zealand
- A poster summarizing results (Acrobat 4).
- A manuscript submitted to
Tectonophysics that gives tests of the imaging method (Acrobat 3).
- Louie's research
links for the Weber imaging project.
Task 2: Outline of the Contents of This Archive
- The example folder contains data, scripts,
parameter files, migration source code, executables, and example plots for a
3-d P-P migration from the Weber II sequence.
- The rg folder contains a part of Louie's Resource
Geology Seismic Processing System, both source and Solaris 2.5 Sun-4 SPARC
executables. These codes are run by the scripts in the example folder.
- The JRG folder contains Louie's RG Seismic
Processing System for Java. JRG make it possible to do many of the
things available in the RG system, on any computer platform. JRG
includes a more user-friendly graphical interface, so no scripting is
- For the Weber project, JRG is mainly used for display and plotting
of seismic records and migrated sections. It also will animate the
migrated volumes, and can apply filtering and equalization.
- JRG can handle geographic coordinates and SEG-Y headers.
- JRG requires a Java Runtime Environment equivalent to JDK version
1.1.3 or higher.
- To start up JRG, go into the JRG folder and run:
a class exercise using JRG, for additional instructions
Task 3: Run the Example 3-D Migration
- The Weber II example folder already contains
11 common-receiver gathers in ``old RG'' format.
- Make the traveltime volume (with Vidale's 1988 method):
This will create a gridded, interpolated velocity section robinson-hz.vel
from a parametric velocity profile in the ascii file robinson.vmod .
Then it runs the rfast2d program 40 times to create travel-time sections
for 0-40 km depths and reflector offsets of 0-75 km. Each section is
for a different source depth. The 10-Mb binary traveltime volume file is
- Start the migration:
csh all3dmig.sh >& mon &
- The mon file will contain runtime messages and any error messages.
- The complete migration takes about 2 hours on a Sun 340-MHz Ultra10.
Check the mon file to assess progress and correct operation.
- The all3dmig.sh script runs the 3dmig.sh script on each of the
11 receiver gathers from the 11 local stations.
- The 3dmig.sh script does bandpass filtering and muting of the
traces in the receiver gather, then runs the aalatmig3dsz code.
- The aalatmig3dsz.c code is in the example folder, not rg .
- The aalatmig3dsz-cc.sh script will compile the code.
- aalatmig3dsz reads the 3dmigpar parameter file.
- Additional parameters are set in 3dmig.sh on the aalatmig3dsz command line.
- At the end of the all3dmig.sh script the cat3dmig.sh script
runs to do the final stack of the migration volumes from all
receiver gathers, and compute Harlan et al. (1984) statistical
- The final enhanced migration volume is ex.3dmigIIsum.flt .
Read this into JRG as raw float with 125 planes of 125 vectors with
100 depth samples each. In JRG apply the parameter file plex.3dmigpar
for proper plot labeling.
- In the example folder any file with the name pl*par is a JRG
plot parameter file for a different type of data.
Task 4: Prepare Your Data for 3-D Migration
- All scripts and parameter files have to be edited for your dataset.
Parameters defining trace sizes, section locations, time and depth sampling,
source-receiver geometry, etc. are found throughout all the scripts
and parameter files mentioned above.
- You can put your 1-d velocity model in the format of robinson.vmod
and create the traveltime volume with makett.sh as above.
- The crucial weber.zyx file, listing locations of earthquakes, stations,
and section origins, must be remade for your dataset in the same format.
The segyindex program will extract coordinates from a SEG-Y gather.
- The recgather.sh script repeatedly invokes the ignstorg script,
to convert source records in CUSP GRM and ASCII-MEM format to RG format,
and to re-sort them into receiver gathers.
- Raw seismograms can be brought into JRG, labeled with geometry,
sorted into shot or receiver gathers, and then written out into ``new RG''
format. If you go this route, contact me for a conversion from new to
- SEG-Y records can be converted to ``old RG'' with the segy2rg code.
Searches through large multi-record SEG-Y files can be speeded by
indexing them first with the segyindex program, and then converting
with indexsegy2rg .