Correlations with synthetic seismograms indicate that the top of the sonic log begins at 4.335 s TWT, exactly between the TWTs predicted by corrected and uncorrected laboratory data, and show that total depth of 1066.4 mbsf reached at Site 999 corresponds to 4.711 s TWT on MCS Line CT1-12a, exactly matching the TWT predicted by analyses of uncorrected laboratory velocity-depth data and well within the range calculated using MCS velocity analysis. The top of volcanic basement lies at a depth of 1420-1473 mbsf, which is derived from extrapolation of average velocities determined by synthetic seismogram correlations and physical properties measurements, respectively. These values are comparable to those using the median to upper limits of MCS-derived interval velocities, which result in an estimated depth to volcanic basement between 1330 and 1467 mbsf.