A Note on the Attenuation of Short Period P and S Waves in the Mantle

The reciprocal dissipation factor Q of P and S waves is determined by spectral analysis of records of earthquakes whose epicentral distance from Tsukuba ranges from 36 to 76 degrees, with special emphasis on that of short period S waves. A constant velocity radiated spectrum near the source is assumed. The value of QƒÀ(Q for S waves) is found between 300 to 2400 in the period range from 0.1 to 1 second, and its average QƒÀ is 800, whereas Qƒ¿ (Q for P waves) ranges from 600 to 5000, and its average Qƒ¿ is 2000. The ratio Qƒ¿/QƒÀ is 2.5. Also obtained are Qƒ¿ and QƒÀ for the period range from 1 to 10 seconds in order to compare with those of short period P and S waves. It is found that Qƒ¿ ranges from 150 to 4800, while QƒÀ is between 150 and 2400 in the period range from 1 to 10 seconds. The average value is 1000 for Qƒ¿ and 600 for QƒÀ. The ratio Qƒ¿/QƒÀ is 1.7.