Velocity and density data from laboratory and downhole measurements were converted from mbsf to two-way traveltime (TWT) and resampled at a 1-ms sample interval. Impedance (velocity x density) and impedance contrasts were used to calculate reflection coefficients (Fig. F2). This calculation is simplified by assuming vertical incidence, horizontal interfaces, no multiples, and no energy loss from spherical spreading and attenuation. The water gun seismic-source wavelet was obtained from the average of 10 adjacent traces of the seafloor reflection at the drill site. The portion of the stacked signal from the first negative to positive deflection associated with the seafloor to a point interpreted as the end of the source wavelet (31 ms) was used as the seismic source (Fig. F2). The series of reflection coefficients was convolved with the source wavelet to produce a minimum-phase synthetic seismogram. The merge point of laboratory and logging data at 180 mbsf occurs at a major change in lithology and physical properties (Unit II/III boundary) (Figs. F2, F3), and therefore, joining the data at that depth does not create an artificial impedance contrast. The use of a constant velocity in the lowermost 59 m of the sedimentary section, stepping to a higher constant velocity interval within the ~40 m of oceanic crust, only serves to model the TWT to the top of oceanic crust and not the seismic character (facies) of this short depth interval. The seismic character of this portion of the synthetic is controlled by the density log, which continues to 398 mbsf. An examination of the downhole resistivity and density measurements, which, like velocity, are largely controlled by porosity, indicate that there are no large reflection-producing changes in physical properties in the section immediately above basement (Fig. F3). More importantly, the length of the source wavelet is comparable to this depth interval and convolution with any reasonable velocity series covering this short 59-m interval will result in nearly identical synthetic seismograms with only the total traveltime changing.