Full Waveform Ultrasonic Core Logging

To measure the P-wave velocity and attenuation illustrated by Biot-StolTs model an automated, PC-controlled logging system was developed which records and stores digital ultrasonic P-waveforms transmitted radially across marine sediment cores (Breitzke and Spieli 1993). These transmission measurements can be done at arbitrary small depth 

Core Segment Complete Core Log P-Wave. jtho- 

While P-wave velocities are determined online during core logging using a cross-correlation 

The resulting value (A(fjj, x)) is related to that part of the frequency band which predominantly contributes to the spectral sum, i.e. to the arithmetic mean frequency (f j) of the spectral amplitude distribution within the i band. Subsequently, for a continuously moving window a series of attenuation coefficients (ot(f j)) is computed from the natural logarithm of the spectral ratio of the attenuated and reference signal 

Plotted in a log a - log f diagram the power (n) and logarithmic attenuation factor (log k) can be determined from the slope and intercept of a linear least square fit to the series of (f j,a(f j)) pairs (Fig. 2.14b). Finally, a smoothed attenuation coefficient a(J) = k f is calculated for the frequency (f) using these values for (k) and (n). 

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