2-D Specular Interferometric Imaging

Objective: To learn how to apply the specular interferometric imaging condition (i.e., migration with semi-natural Green's functions) to VSP data to obtain ghost migration images.

Skill Learned: Compile and run a Fortran program for ghost migration with specular interferometry; Analyze the migration results; QC data.

Procedure:

Load data. Load the synthetic VSP data file_crgmutedirect.tar, traveltime tables time_s.tar and the picked first arrival time ta.tar.

To observe the data. To observe the common receiver gathers and traveltime tables with "SU":

            ximage < file_crgmutedirect/crg/crg1  n1=12000 d1=0.00025 label1='Time (s)' perc=99 title='crg1 ' & 
            ximage < file_crgmutedirect/crg/crg45 n1=12000 d1=0.00025 label1='Time (s)' perc=99 title='crg45' & 
            ximage < file_crgmutedirect/crg/crg91 n1=12000 d1=0.00025 label1='Time (s)' perc=99 title='crg91' & 

            ximage < time_s/ts/ts1  n1=521 d1=2.5 d2=2.5 label1='Depth (m)' label2='Dist (m)' title='ts1 ' & 
            ximage < time_s/ts/ts46 n1=521 d1=2.5 d2=2.5 label1='Depth (m)' label2='Dist (m)' title='ts46' & 
            ximage < time_s/ts/ts92 n1=521 d1=2.5 d2=2.5 label1='Depth (m)' label2='Dist (m)' title='ts92' &

Load Fortran programs. Load the specular interferometric migration codes, parameter files, and readme files SI.mig.tar.
Run the code. After unzipping the tar files, go to the directory "SI.mig" and type "f77 mig_1stgh_IM6.f -o mig_1stgh_IM6.exe -O3" to compile the code. Then issue "./mig_1stgh_IM6.exe" to run the executable file. When the jobs are finished, the migration results will be written to the directory "SI.mig/image".

To observe the migration images. To observe the migration results with "SU":

            ximage < SI.mig/image/image_file1  n1=521 d1=2.5 d2=2.5 label1='Depth (m)' label2='Dist (m)' title='image_file1'  &
            ximage < SI.mig/image/image_file45 n1=521 d1=2.5 d2=2.5 label1='Depth (m)' label2='Dist (m)' title='image_file45' &
            ximage < SI.mig/image/image_file91 n1=521 d1=2.5 d2=2.5 label1='Depth (m)' label2='Dist (m)' title='image_file91' &

Something to think about:

To sum the migration images. After migration we get one image for each receiver. User can sum all the images into a final image. For reference here is the code segment for writing files, which is taken from the migration code:
```
       open(unit=5, file=filename2,form='unformatted',
     +       access='direct', recl=nz*4)
       do ix=1,nx
          write(5,rec=ix) ( image(ix,iz),iz=1,nz )
       enddo
       close(5)
```
To plot the final migration images. With "SU" plot the final migration image we obtained by summation.