Drilling during Ocean Drilling Program (ODP) Leg 165 recovered core, velocity, and density information that can be used to correlate core lithologies and ages of sedimentary units with high-resolution single-channel seismic profiles crossing Sites 998, 1000, and 1001 (Fig. 1). Because predictions of velocities with depth derived from the empirical velocity vs. depth functions of Carlson et al. (1986) do not match either laboratory or log velocity measurements at these sites, a correlation of core to seismic data using such a function will have significant error. In the absence of check-shot survey data or vertical seismic profiles, synthetic seismograms provide a means to correlate seismic facies and seismic reflections with core lithologies.
Synthetic seismograms were constructed using velocity and density data obtained during Leg 165. Velocity and density estimates were acquired from downhole sonic and density logs and from physical properties measurements of recovered cores (Sigurdsson, Leckie, Acton, et al., 1997). Sonic and density log measurements were not available in the top and bottom portions of the hole, however. Core-derived velocity and density measurements can be merged with sonic and density logs to create a relatively continuous velocity and density profile extending from the seafloor to near the base of the hole. Synthetic seismograms were created for Sites 998, 1000, and 1001 from the velocity and density profiles. These synthetic seismograms are spliced into single-channel seismic reflection profiles crossing the sites and a comparison is made between core lithologies and seismic facies.