Automatic NMO Correction and Full Common Depth Point NMO Velocity Field Estimation in Anisotropic Media

• Published in: Pure and applied geophysics Vol. 174; no. 1; pp. 305 - 325
• Main Authors: Sedek, Mohamed, Gross, Lutz, Tyson, Stephen
• Format: Journal Article
• Language: English
• Published: Cham Springer International Publishing 2017; Springer Nature B.V
• Subjects: Anisotropy; Automation; Background noise; Earth and Environmental Science; Earth Sciences; Estimating techniques; Flattening; Geophysics/Geodesy; Isotropy; Offsets; Seismic phenomena; Seismic surveys; Seismology; Velocity; INE, USA, Alaska; NMO correction; Velocity analysis; Velocity variation with offset; NMO velocity; Seismic anisotropy
• ISSN: 0033-4553; 1420-9136
• DOI: 10.1007/s00024-016-1356-2

We present a new computational method of automatic normal moveout (NMO) correction that not only accurately flattens and corrects the far offset data, but simultaneously provides NMO velocity ( v nmo ) for each individual seismic trace. The method is based on a predefined number of NMO velocity sweeps using linear vertical interpolation of different NMO velocities at each seismic trace. At each sweep, we measure the semblance between the zero offset trace (pilot trace) and the next seismic trace using a trace-by-trace rather than sample-by-sample based semblance measure; then after all the sweeps are done, the one with the maximum semblance value is chosen, which is assumed to be the most suitable NMO velocity trace that accurately flattens seismic reflection events. Other traces follow the same process, and a final velocity field is then extracted. Isotropic, anisotropic and lateral heterogenous synthetic geological models were built to test the method. A range of synthetic background noise, ranging from 10 to 30 %, was applied to the models. In addition, the method was tested on Hess’s VTI (vertical transverse isotropy) model. Furthermore, we tested our method on a real pre-stack seismic CDP gathered from a gas field in Alaska. The results from the presented examples show an excellent NMO correction and extracted a reasonably accurate NMO velocity field.