Figure 12. Velocity profiles based on the results of the zero-offset VSP at Sites 994, 995, and 997. From the flank of the Blake Ridge to the crest, the profiles show similar, possibly slightly increasing, velocities above the hydrate stability zone (~450 mbsf) and a significant decrease in velocity toward the crest below this zone. These preliminary velocity-depth functions were produced by inverting the air gun first-arrival times using a weighted, damped, least-squares inversion that weights mean traveltimes by the inverse of their standard error. The velocity-depth curves were produced by assigning equal weight to fitting the traveltime data and to producing a smooth velocity-depth function.

To Figure 13