Interferometric Interpolation for Coarse OBS Data



Figure 1. The raw data used to test interferometric interpolation. The receiver interval is 160 meters.

Figure 2. The virtual shot gather generated by interferometric interpolation. The receiver interval of the virtual traces is 8 meters. Notice that there exist very strong artifacts.

Figure 3. The virtual shot gather after using matching filter.Notice that the artifacts are reduced, and most events are accurate predicted compared to the true shot gather.

Figure 4. The true shot gather with a 8 meters receiver interval.

Objective: Learn to use OBS Interferometric Interpolation codes, and study how a matching filter improve the accuracy of the interpolated data.

Procedure:

  1. Download data.tgz and decompress it by typing "tar xzvf data.tgz". It contains all the needed data files.
    vel.mat is the velocity model for all synthetic data used in this lab. This file is not needed in this exercise, but you can generate all synthetic data by yourself if interested. There are 801 grids in X direction and 601 grids in Z direction. Sources are located just beneath the free surface; receivers are located on the sea floor. Totally 201 shot gathers are generated by this model.
    raw data is the original OBS data set with a coarse receiver interval of 160 meters, where sources are located just beneath free surface and receivers are located on sea floor.
    truedata is the true data set with a dense receiver interval of 8 meters.
    dat_grn are the SWP Green's functions, which are generated by putting sources and receivers on sea floor, and only the water layer model is needed.
  2. Download codes.tgz and decompress it by typing "tar xzvf codes.tgz".
    obs_interp.m is the main program for OBS data interpolation.
    mute_direct.m,xcorr.m are functions used by obs_interp.m.
    matchfilter are the fortran codes of the matching filter.
  3. Go to directory 'codes', in matlab, run "obs_interp" to generate the interpolated virtual shot gather.
  4. In a linux terminal (make sure the intel fortran compiler is installed in the computer), goto directory 'codes/matchfilter', type "ifort -llapack -lg2c main.f90" or "ifort -llapack main.f90", to compile the codes and get the a.out.
  5. Type './a.out' to apply the matching filter to the virtual shot gather.
  6. Change the parameters in main.f90, try to use different filter parameters to see the results changes.

Questions to think about:

  1. What are the advantages of interferometric interpolation?
  2. Are the amplitudes of virtual traces correct?
  3. How to set the parameters for the matching filter to get the best results?

Designed by Shuqian Dong