The conventional method used to estimate velocities for converted-wave (C-wave) prestack time migration is awkward because the P-wave velocity comes from P-wave processing, the velocity ratio gamma is estimated from C-wave data, and the S-wave velocity is then derived from and gamma. Instead, by using the C-wave velocity , effective gamma , and anisotropy parameter , velocity updating becomes straightforward and more reliable. To update for converted-wave time migration, one can carry out hyperbolic moveout analysis on the hyperbolic-moveout-migrated-common-midpoint (HMO-MCMP) gathers. However, the errors in initial and anisotropy parameter can only be corrected by trial and error. In this article, we propose to remove the effects of initial and in the HMO-MCMP gathers by inverting the moveout related to the initial and . This enables a full nonhyperbolic velocity analysis to update not only but also and . To obtain reliable , we also develop a simultaneous PP/PS anisotropic-parameter estimation method so the estimated from P-wave data is compared immediately with the derived from by using C-wave data. This provides a better constraint for estimating anisotropy parameters. The method has been tested and shows consistent improvement in converted-wave prestack time-migration velocity estimations.