- job deck = fwd.job
- output = data30hz60x.sep

- job deck = migcv.job
- output = migcv.sep

Examination of 15 and 30 Hz jobs made clear that the origin of the noise is simply aliasing in the shot direction.

- job deck = fwd15.job
- output = testfwd15.sep
- job deck = mig15.job
- output = testmig15.sep
- job deck = fwd30.job
- output = testfwd30.sep
- job deck = mig30.job
- output = testmig30.sep

Aliasing analysed on pp. 105 ff. of Large Notebook 2. Max shot spacing permissible for 15 Hz and 45deg aperture is about 35m. Redesigned experiments with 24m shot spacing. Gives very clean migrations with 15Hz source. Not aliased at peak for 30Hz, but is aliased for high end of spectrum - which is obvious in migration - see mig 30 Hz 45 deg 24 m dshot, mig 15 Hz 45 deg 24 m dshot.

Some experimentation with offsets and prestack migrated image volume make clear that there is simply not much residual moveout for this velocity model, even at const. velocity - see the coherency panels mentioned before.

ALL OF THIS STUFF UP TO THIS POINT STORED IN masc39:datb/nlay60.

First try: set up line of 121 shots, 33 offsets, far offset = 1680m, offset spacing = shot spacing = 24m, 30Hz Ricker source, aperture = 65 degrees. Results of simulation and prestack migration stored in masc39:datb/nlay60a. Upshot: no significant amount of data or image until about trace 20, at offset roughly 1200. SO...

Second try: everything the same, but far offset = 1224. This time plenty of data at near and far offsets, also image at near and far offsets. Results stored in masc39:datb/nlay60b. image begins for all offsets slightly below 400m, whereas for the nearer offsets there is considerable aliased energy in the migrations above 400m. Coherency panels at constant velocity show lots of moveout; detail at trace 650 gives idea of noise in simulation + migration. Remember that the range of offsets here is only 456m (near) to 1224m (far), as opposed to the 160 - 1760 m. range of the earlier example.

OLS scans: go with second data set. Set reflectivity cutoff at 400m. Distribute scans amongst nodes on texas cluster, running on local disks. Scan records stored in scanx_sum.hdr, reflectivity estimates in r8esx.sep, x=0,...,20, where the scan offset in each case is h=0.05*x.

Image at 0.5(const. vel.)+0.5(target vel.)

Summary: data norm: .12087510E+02 h=0.0: ms error diffl semblance damping term total DSO cost .69762421E+02 .00000000E+00 .13808806E-05 .69762421E+02 rms error norm of inner state .11812063E+02 .16618547E+02 h=0.05: ms error diffl semblance damping term total DSO cost .69232315E+02 .00000000E+00 .16725306E-05 .69232315E+02 rms error norm of inner state .11767099E+02 .18289509E+02 h=0.1: ms error diffl semblance damping term total DSO cost .68611153E+02 .00000000E+00 .20308523E-05 .68611153E+02 rms error norm of inner state .11714192E+02 .20153671E+02 h=0.15: ms error diffl semblance damping term total DSO cost .68018181E+02 .00000000E+00 .25567965E-05 .68018181E+02 rms error norm of inner state .11663463E+02 .22613255E+02 h=0.2: ms error diffl semblance damping term total DSO cost .67509651E+02 .00000000E+00 .32013909E-05 .67509651E+02 rms error norm of inner state .11619781E+02 .25303719E+02 h=0.25: ms error diffl semblance damping term total DSO cost .67026131E+02 .00000000E+00 .41048329E-05 .67026138E+02 rms error norm of inner state .11578094E+02 .28652514E+02 h=0.35: ms error diffl semblance damping term total DSO cost .65687202E+02 .00000000E+00 .66334514E-05 .65687210E+02 rms error norm of inner state .11461867E+02 .36423759E+02 h=0.4: ms error diffl semblance damping term total DSO cost .64642380E+02 .00000000E+00 .84921476E-05 .64642387E+02 rms error norm of inner state .11370346E+02 .41212009E+02 h=0.5: ms error diffl semblance damping term total DSO cost .61503914E+02 .00000000E+00 .13260361E-04 .61503925E+02 rms error norm of inner state .11090889E+02 .51498276E+02 h=0.55: ms error diffl semblance damping term total DSO cost .59135445E+02 .00000000E+00 .16121054E-04 .59135460E+02 rms error norm of inner state .10875242E+02 .56782135E+02 h=0.7: ms error diffl semblance damping term total DSO cost .46103771E+02 .00000000E+00 .27037566E-04 .46103798E+02 rms error norm of inner state .96024761E+01 .73535797E+02 h=0.85: ms error diffl semblance damping term total DSO cost .23080196E+02 .00000000E+00 .41168321E-04 .23080238E+02 rms error norm of inner state .67941442E+01 .90739540E+02 h=1.0: ms error diffl semblance damping term total DSO cost .46885290E+01 .00000000E+00 .56574390E-04 .46885858E+01 rms error norm of inner state .30621982E+01 .10637141E+03William W. Symes (symes@rice.edu)