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There are four kinds of methods used in low-frequency shear wave logging. They are the downhole method, uphole method, cross-hole method, and suspension PS logging. Among these methods, the downhole method is commonly used in Japan. Hundreds of shear wave measurements using the downhole method have been carried out since it was established in the 1970s. Suspension PS logging is a recently developed method in which a nonsymmetric seismic source and two receivers are built into a single probe. Source-to-receiver spacing is 2 and 3 m and the logging frequency ranges from 100 to 1000 Hz. Shear waves generated by the seismic source in the probe are detected with the receivers installed 1 m apart, and the shear wave velocity is calculated from the difference of the arrival time between the two receivers. Because the distance between the two receivers is fixed in the probe and the shear wave source produces a repeatable signal, velocity values obtained by suspension PS logging have less errorsxompared with the other methods. Shear wave velocity measurements have important applications in earthquake engineering. In this paper, shear wave velocity measurements are shown to give a useful indication of soil liquefaction potential and shear moduli that can be used to predict the amplitude of surface soil motions during earthquakes.

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