HIGH-FREQUENCY FALL-OFF OF SOURCE SPECTRA OF DEEP-FOCUS EARTHQUAKES FROM WIGNER-DISTRIBUTION ESTIMATION

Using Wigner-distribution estimation, the high-frequency fall-off of s ource spectra was estimated. The technique was applied to the analysis of the source spectra of the Vladivostok M=6.4 deep-focus earthquake of 22 July 1994 and the Northern Japan Sea, M=5.7 deep-focus earthquak e of 22 July 1994. It is shown that the high-frequency fall-off of the source spectra of these two earthquakes may be characterized by two p arts. Between the first corner frequency f(1) and the second corner fr equency f(2), the high-frequency fall-off of the source spectra can be represented by f(-5); above f(2), the high-frequency fall-off can be represented by f(-2).