A fast algorithm for 3D azimuthally anisotropic velocity scan |
Finally we consider a field-data example. A subset of the McElroy dataset from West Texas was formed in a supergather (Figure 7). This dataset was studied by Burnett and Fomel (2009), in which they proposed a velocity-independent moveout correction to avoid costly velocity scan. With the fast algorithm, we are now able to compute the semblance efficiently: only 45 s for a single Radon transform when , , and ; direct computation at this sampling would take approximately 30 hours.
Although the original data have been isotropically NMO corrected, the time slice still shows a subtle directional trend to flatness (Figure 7). From the semblance plot (Figure 8), we observe some nonzero values of anisotropic parameters.
super
Figure 7. An isotropically NMO-corrected supergather from the McElroy dataset, West Texas. , . s, m. |
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semb
Figure 8. Semblance plot computed by the fast algorithm. , . |
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A fast algorithm for 3D azimuthally anisotropic velocity scan |