Ocean Drilling Program, United States

Five analyses of seismic velocity employing acoustic tomography were conducted across the location of the sites proposed for Ocean Drilling Program (ODP) drilling on the continental shelf of the Pacific margin of the Antarctic Peninsula. The resulting interval velocities were supplied to the ODP Site Survey Panel before drilling and are now presented in light of the results of ODP Leg 178 drilling, during which three of the five proposed sites were drilled, as a tie between traveltimes and depths at all sites, and as a tool to aid genetic interpretation of seismic units in future studies. We present details of the methodology, the five stack sections across each site, and the picked horizons used for the velocity analysis. The results of the analysis are presented as interval tomographic velocity sections on a depth scale. Finally, we compare tomographic and stacking velocity profiles for each site location. We summarize the main features of the velocity fields obtained in this study in a short concluding section.