The Instantaneous Amplitude, Phase and Frequency in Seismic Event Detection, Timing and Identification

Abstract

The essential time-domain information of seismic waveforms is quantized in terms of the instantaneous amplitude, phase and frequency. The quantized information is used in the automatic detection, timing and identification of seismic event signals. Phase detection is in principle 6 dB better than amplitude (envelope) detection, and can be applied successfully to automatically detect and time well-dispersed long-period surface waves. Interference by early multiple signals precludes phase detection of short-period signals. For the latter, it is feasible to design an efficient, automatic envelope detector and timer with a controllable false alarm rate, based on a Gaussian noise model. For Eurasian events, short-period phase and frequency related identification parameters, produced automatically by the envelope detector, are believed to show an inverse relation between the size and the amount of tectonic energy release ruptures; the ruptures triggered by explosions then appear to be smaller than the spontaneous ruptures in earthquakes.