Compressional and shear wave velocity data at increasing pressures are presented in Table T1. VP/VS values and Poisson's ratios (s) calculated from these velocities at each pressure are presented in Table T2. Compressional wave velocities were measured for all 14 samples, and shear waves were measured for 8 samples. The estimated errors in the measurements are ±0.5% for compressional velocity, ±1% for shear velocity, and ±6% for Poisson's ratio (Christensen and Shaw, 1970). Although serpentinites may be anisotropic, it was not possible to prepare several samples from the core with different orientations because of the limited amount of rock. Therefore, it was not possible to determine seismic anisotropy of these samples from the velocity measurements. The anisotropy in serpentinites may be due to preferred alignment of relict olivine grains (Birch, 1961; Christensen, 1966), and values of Poisson's ratio may vary in excess of ±6% because the velocities were not measured in more than one direction. All of the rocks fall into a narrow density range between 2548 and 2701 kg/m3.