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| | Abstract | | Downhole type S-wave velocity logging methods has been widely adopted for providing 1D velocity profile at a site of interest owing to its easiness of field measurements. However, it does not always provide precise or reliable velocity information affected by setting inappropriate measurement parameters or choosing inapt tools or methods. Comparative measurement is one of the most effective way to certify velocity structure as a logging result. The author has conducted such comparative study on S-wave logging in a total of 93 boreholes and has tested six tools or measurement methods since 1980. The tested tools consisted of a suspension PS logging tool, downhole type OYO3315 and NGP54 probes, a DH5 hydrophone array, two types of full wave sonic systems, and seismic NGP SC Q3036 probes as seismic cone penetration testing tools. As a result, synthetic seismograms generated from the records obtained in a borehole by using a downhole probe, hydrophone array, and seismic cone were quite concordant with each other. Moreover, they matched well with a seismogram synthesized from suspension PS logging data. Thus, comparative measurements were effective to pick first breaks and estimate Vs structure precisely. |
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