Using a comparison between a direct body-wave phase and its surface-reflected phase recorded on the same deep-borehole seismogram, 1/QP(f) and 1/QS(f) were measured in the frequency range from 1 to 10 Hz in a sedimentary layer-basement system at the SHM and FCH stations in the Kanto region, Japan. Estimated values of 1/QP(f) and 1/QS(f) decrease linearly with increasing frequency at low frequencies. This frequency dependence weakens with increasing frequency. The frequency points at which these two characteristics intersect are approximately 4 and 2 Hz for 1/QP(f) and 1/QS(f), respectively. The relation of QS(f)/QP(f)≥1 was measured over the frequency range from 1 to 10 Hz. However, QS(f)/QP(f) is in the range of 1.5–3 for frequencies lower than 3 Hz and QS(f)/QP(f)≈1 for frequencies higher than 4 Hz.

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