Abstract

Coda waves are used to determine the Q value of short-period waves in the Beijing area and in Yun-nan Province, China, and the seismic moments of the earthquakes studied. For the Beijing area the Q0, or 1-Hz value, is found to be approximately 400, with little or no indication of frequency dependence of Q for frequencies near 1 Hz in that region. For Yun-nan Province, the Q0 value is about 180, and the data suggest that Q(f) = Q0f0.2, where f is wave frequency. These values are in fairly good agreement with short-period Q estimates made for those regions by Chen and Nuttli (1984), on the basis of attenuation of seismic intensity values.

Hermann's (1980) application of Aki's (1969) coda wave theory is extended, to provide simple equations for calculating master curves for coda wave studies. Two types of master curves provide independent estimates of Q0 and of the dependency of Q on wave frequency. For the data analyzed the two methods gave similar results. A third type of master curves gives estimates of the seismic moments of the earthquakes studied. The moments obtained by this means agree with values obtained by the conventional methods of analysis that use the spectrum of body waves or surface waves.

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