Interferometric Extrapolation for Narrow Aperture OBS Data
Figure 1. The original single shot profile. The receiver aperture is about one half of the full aperture.
Figure 2. The virtual shot gather generated by interferometric extrapolation. The receiver aperture is almost doubled, and the missing traces are accurately predicted compared to the true CSG with a full receiver aperture.
Figure 3. The true shot gather with a full receiver aperture.
Learn to use Interferometric Extrapolation codes, and study its advantage of enlarging the aperture for narrow aperture OBS profile. Using a matching filter can improve the accuracy of the extrapolated data, but that part is not included in this lab.
- 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 narrow receiver aperture, where sources are located just beneath free surface and receivers are located on sea floor.
truedata is the true data set with full aperture used for comparison;
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.
- Make a directory and name it as 'codes'. Load matlab codes to this directory:
obs_extrap.m is the main program for OBS extrapolation.
mute_direct.m,xcorr.m are functions used by obs_extrap.m.
- Go to directory 'codes', in matlab, run "obs_extrap" to generate the extrapolated virtual shot gather. Compare the virtual shot gather with the raw data and the true full aperture data.
Questions to think about:
- What are the advantages of interferometric extrapolation?
- Are the amplitudes of virtual traces correct? If not, how to correct them?
Designed by Shuqian Dong