Velocity and VTI anisotropy scanning in multicomponent seismic data
Osareni Christopher Ogiesoba, James E. Gaiser, Robert R. Stewart
We present a prestack method that scans for the average vertical-velocity ratio 0, and the effective anisotropic parameter , using a new converted-wave (PS) non-hyperbolic traveltime equation. We tested our method using a numerical data set generated in ANIVEC (a frequency-wave number modeling package). The procedure entails computing semblance as a function of three variables: the PS velocity Vps, 0, and . Results are displayed in 3D plots as a function of the PS zero-offset time tps0. We observe that the derived equation is valid for an offset-depth ratio of up to 1.5 for the tested model. There is a tradeoff in resolving and the velocity ratio 0 since both parameters control far offset moveout. The accuracy of the scanning technique increases with depth. It is inaccurate at shallow depths where the offset-depth ratio is greater than 1.5. At deeper levels, where the offset-depth ratio is 1 to 1.5, the errors in scanned velocity ratio 0 and effective anisotropic parameter , range from +9 to +10% and +0.2 to +8%, respectively.