Abstract
—Borehole seismograms from local earthquakes in the aftershock region of the 1984 western Nagano Prefecture, Japan earthquake were analyzed to measure the frequency-dependent characteristics of P- and S-wave attenuation in the upper crust. The records from a three-component velocity seismometer at the depth of 145m exhibit high S/N-ratio in a wide frequency range up to 100 Hz. Extended coda normalization methods were applied to bandpass-filtered seismograms of frequencies from 25 to 102 Hz. For the attenuation of high-frequency P and S waves, our measurements show Q P -1≃ 0.052ƒ-0.66 and Q S -1≃ 0.0034ƒ-0.12 respectively. The frequency dependence of the quality factor of S waves is very weak as compared with that of P waves. The ratio of Q P -1/Q S -1 is larger than unity in the entire analyzed frequency range.
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Received January 13, 1998, revised June 5, 1998, accepted June 23, 1998
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Yoshimoto, K., Sato, H., Iio, Y. et al. Frequency-dependent Attenuation of High-frequency P and S Waves in the Upper Crust in Western Nagano, Japan. Pure appl. geophys. 153, 489–502 (1998). https://doi.org/10.1007/s000240050205
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DOI: https://doi.org/10.1007/s000240050205