Eldholm, O., Thiede, J., Taylor, E., et al., 1989（Eldholm,O。）.pdfVIP

Eldholm, O., Thiede, J., Taylor, E., et al., 1989 Proceedings of the Ocean Drilling Program, Scientific Results, Vol. 104 45 . A N A L Y S I S O F F U L L WAVEFOR M A C O U S T I C L O G G I N G DAT A A T O D P S I T E 6 4 2 — O U T E R V O R I N G P L A T E A U 1 Colleen Barton , Danie l Moos , an d Jean-Pierr e Blangy2 ABSTRACT Formation compressional and shear-wave velocities were calculated from sonic full waveform logs in ODP Hole 642E. The data were recorded over a 710-m interval of a cyclic repetition of lava flows and volcaniclastic sediments which are intruded by tholeiitic dikes. Although compressional (p) and shear (s) velocities in the flows are above 5 km/s and 3 km/s, respectively, interval velocities are 4.14 km/s for/? and 2.25 km/s for s, resulting in an average V /V of p s 1.84 for the entire logged interval. This is a consequence of the much lower velocities in the volcaniclastics. The velocity results are interpreted in conjunction with the companion logs (density, porosity, natural gamma, and electrical resistiv­ ity) run in the drill hole in an attempt to determine the mechanisms causing the characteristic velocity response. The re­ sults show that porosity and microstructure have the primary influence on velocities. The degree o