HR: 0800h
AN: S31B-1051    [Abstracts]
TI: Time-Frequency analysis of seismic signals using the Wigner-Ville Spectrum
AU: * Prieto, G A
EM: gprieto@ucsd.edu
AF: University of California San Diego, 9500 Gilman Drive, La Jolla, CA 92093-0225
AU: Vernon, F
EM: vernon@epicenter.ucsd.edu
AF: University of California San Diego, 9500 Gilman Drive, La Jolla, CA 92093-0225
AU: Parker, R L
EM: rlparker@ucsd.edu
AF: University of California San Diego, 9500 Gilman Drive, La Jolla, CA 92093-0225
AB: Fourier analysis and the spectral characterization of time series have played an important role in modern seismological studies. The frequency contents of a stationary time series are generally expressed by the use of the power spectrum. In seismology, we deal with earthquake records that are non-stationary transient time sequences. The usual spectral analysis fails to provide an acceptable estimate of the frequency contents of the signal with time because temporal information is lost and thus it is unsuitable for earthquake records. Different approaches have been proposed in the last 25 years to obtain an appropriate time-frequency representation, with the restriction imposed by the uncertainty principle, precluding one to obtain arbitrarily fine resolution in time and frequency. The Wigner-Ville distribution (or its stochastic counterpart the Wigner-Ville spectrum) has many of the desired properties for a power distribution: reduces to the PSD for stationary signals, its real-valued everywhere and is capable of correctly reflecting input-output relationship for linear filters. It has also some drawbacks, mainly the positivity of all its values cannot be guaranteed, which would be desirable property in terms of a density function. We apply the Wigner-Ville spectrum estimation to earthquakes ($M = 1-5$) recorded by the ANZA seismic network in Southern California and discuss the results. A measure of the degree of non-stationarity of the stochastic process is estimated, to test if the assumption of locally stationarity of the earthquake record is acceptable.
DE: 7299 General or miscellaneous
DE: 7200 SEISMOLOGY
DE: 7209 Earthquake dynamics and mechanics
DE: 7215 Earthquake parameters
SC: Seismology [S]
MN: 2004 AGU Fall Meeting