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Frequency Dependence of Q in the Mantle Underlying the Shield Areas of Eurasia
Final technical rept. 15 Nov 1982-30 Dec 1984
TELEDYNE GEOTECH ALEXANDRIA VA ALEXANDRIA LABS
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In Part I the results of short and intermediate period data analyses for the determination of a frequency dependent Q model of the mantle under the shield areas of Eurasia are presented. The spectra of short period P waves from nuclear explosions in the 1-8 Hz frequency range give t sub p approx. 0.15-0. 2 seconds. Part II presents analyses of long period data. Long period multiple S and ScS phases observed in northern Europe were analyzed to determine mantle attenuation in the 0.02 to 0.2 Hz range under the Eurasian shield. Two groups of events are used deep Far-Eastern earthquakes and large earthquakes near the edges of the shield areas of Eurasia. Part III provides the Q model. A large set of broad band data was analyzed to determine the frequency and depth dependence of Q for P and S waves under the northern shield areas of Eurasia. A wide range of techniques utilizing spectra, amplitude ratios and waveform modeling were used to derive apparent and absolute t estimated for P and S waves covering the seismic band between 0.01 to 10 Hz. A supplement discusses methodologies for estimating tf from Short Period Body Waves and Regional Variations of tf in the United States. Keywords include Attenuation.
APPROVED FOR PUBLIC RELEASE