He showed that it is exact to fourth Converted-wave (P to S or S to P) traveltime order and'a very close approximation to sixth order, that data have a nonhyperbolic characteristic that is most is: significant at high offset-to-depth ratios. If the standard two-term NM0 equation of Taner and Koehler(1969) is T. T,(l-l/S) '/((TJS)Z X'/SV',J, (2) used in velocity analysis of converted-wave data, and far offsets are included, this characteristic impedes accurate where V,,,,, is the root-mean-square velocity and S is the moveout corrections and RMS velocity estimates. For ratio of the fourth time-weighted moment of the velocity this reason, valuable far-offset data are often muted out.