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 source 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 earthquake 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 parts. Between the first corner frequency f1 and the second corner frequency f2, the high-frequency fall-off of the source spectra can be represented by f-5; above f2, the high-frequency fall-off can be represented by f-2.