Reports

Spectral Analyses of High-Frequency Pn and Sn Phases Observed at Great Distances in the Western Pacific

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Science  24 Mar 1978:
Vol. 199, Issue 4335, pp. 1333-1335
DOI: 10.1126/science.199.4335.1333-a

Abstract

Both Pn, and Sn, phases recorded at distances greater than 3000 kilometers in the western Pacific have substantial amounts of energy at high frequencies, in sorne instances as high as 12 hertz for Pn and 15 hertz for Sn, A comparison of Pn and Sn spectra reveals generally higher energy levels and higher proportions of high-frequency to low-frequency energy for Sn than for Pn. Estimates of the effective quality factor, Q, indicate that the efficiency of Sn propagation may be two or three times that of Pn. First arrivals of Pn and Sn have apparent velocities in agreement with values for the uppermost mantle, whereas maximum-energy arrivals have apparent velocities in agreement with values for the lower crust.