Dissipation of Rayleigh wave energy

Records of long-period vertical seismographs from 14 stations in the standardized world-wide seismograph network were used to determine the energy dissipation of Rayleigh waves. Records of Rayleigh waves produced by the nuclear explosion of September 19, 1962, near Novaya Zemlya, were digitized and Fourier analyzed, and the dissipation was computed for waves of periods between 10 and 100 seconds. The coefficient of energy dissipation was found to have a maximum value of about 150×10−6 km−1 at about 50-sec period, decreasing to about 80×10−6 km−1 at 20-sec period, and increasing for shorter waves to about 650×10−6 km−1 at 10-sec period. The high energy dissipation at periods larger than 40 sec is probably caused by high absorption of wave energy in a layer in the vicinity of the upper mantle low-velocity layer. Absolute values of the dissipation are uncertain because of the few stations used in this study. This possible error will, however, not affect the variations of dissipation with frequency.