Automatic P-wave Arrival Detection For Earthquake Early Warning System

Earthquake early warning(EEW) can quickly release early-warning information after a earthquake and reduce the disaster effectively. So far, some countries have built earthquake early warning system(EEWS) which played a direct role. Automated determination of P-phase arrival times is the most basic and crucial technology. This paper introduced different types of seismic phases identification methods, and developed a convenient composite method, suitable for use in real time. The work is as follows:(1) Summarized the current methods of P-phase arrival time determination. This paper reviewed STA/LTA algorithm, energy analysis, polarization analysis, short term Fourier transform, wavelet transform method, artificial neural network method which were divided into four categories. Research status and development tendency of the current methods were presented in detail.(2) Described principles of STA/LTA algorithm combined with AIC parameter, polarization analysis, energy analysis, FFT amplitude-ratio method and kurtosis. Five methods are used to detect the P-wave arrival time of Fujian seismic records. The statistical analysis show that any individual method is based on separation of signal and noise in a particular domain and cannot ensure consistent onset time picking under all source, receiver, path, and noise conditions. The results also show that, the high error trigger rate of STA/LTA algorithm combined with AIC parameter and energy analysis method is unacceptable, and the leakage trigger of polarization analysis and FFT amplitude-ratio method is need to be reduced.(3) In order to avoid recognition error caused by interference, this paper develop a convenient composite method, which is suitable for use in real time, by full use of amplitude, frequency, polarization characteristics of seismic signals. The method was used to detect the P-wave arrival time of Fujian seismic records. The statistical analysis show that the anti-interference ability of composite method is obviously raised and the result is more reliable, compared to any individual method.Composite method will markedly enhance its capability of anti-jamming signal, which can effectively avoid false trigger caused by the interference signal.What’s more, For part of records, the false trigger caused by S seismic phase.To avoid such mistake, composite method use DR function, which can effectively distinguish between P seismic phase and S seismic phase.