Wet and dry sample weights and volumes were determined for the calculation of porosity as well as bulk and grain densities. After measuring the wet weights, samples were dried at 110°C for a period of 24 hr to drive off water.
Velocity measurements were made at pressures up to 200 MPa by placing the samples in a core holder that consisted of two titanium end pieces. Each end piece houses a stacked plumbum (lead) zirconate titanate ceramic composite transducer containing a compressional and two orthogonally polarized shear elements. The ultrasonic compressional wave and shear waves were sequentially generated from one stack and received by the other stack, and the resulting waveforms recorded with a digital oscilloscope for processing. First arrivals were picked manually and travel times were corrected for known delays in the titanium end pieces (Coyner, 1984). The samples were coupled to each end piece using a non-water soluble resin. Confining and pore pressures were controlled using two hydraulically servo-controlled intensifiers. The samples were hydrostatically loaded, being separated from the confining medium with a soft rubber jacket. Pore pressure access to the sample was made through a small port in one of the core holder end pieces. Pressure history and data collection for each experiment was identical for all tests, being controlled via computer using a predefined script.
For vertical minicores, Vs1 was polarized perpendicular to the cut face as shown in Figure AF1 and Vs2 was always measured at 90° from Vs1. One exception is Sample 176-735B-96R-2 (54-58) v, for which the orientation markings were not clearly defined. However, this sample had a clear dipping fabric and S1 was oriented perpendicular to the strike of the fabric. In general, we had difficulties identifying fabrics in the cores, but since the cut face was made perpendicular to the strike of the fabric, the orientations are relatively good for all samples. For horizontal cores, Vs1 was horizontally polarized and Vs2 polarized vertically. A few of the horizontal cores were retested rotated 45° from vertical. Values for these types of measurements have a 45° note by the sample identifications in Table T1.
Ultrasonic compressional wave and shear wave Q values were computed using the procedure described by Toksöz et al. (1979). The procedure involves the comparison between the amplitude spectra of the measured waveforms and the spectra of reference waveforms measured on a high Q standard. Waveforms measured on a 2-in-long aluminum sample were used as the high Q reference. Reference waveforms were selected to match the pressure conditions of each measurement. All of the computations were performed using identical windowing parameters. A representative plot documenting the computations for each sample is shown in Figure AF2. In each plot, the entire recorded waveform, the windowed version that was used for the analysis, the reference waveform and its windowed version from a 2-in-long aluminum sample are shown. The amplitude spectra of the waveforms for the standard and the sample, the portion of the amplitude ratio versus frequency which was used for computing Q, and a line indicating the inferred slope are also represented.
An example of the processed cross-dipole data from the upper 600 m of Hole 735B is shown in Figure AF3. Definitions of curves in the shear wave cross-dipole analyses are the following: