Research On The Micro-Earthquake Detection And Seismic Phase Automatic Identification

With the rapid development of economic and seismic observation network, especially, after China Earthquake Administration finishes constructing the"China digital earthquake observation network project"of the"five year plan"of Chinese central government. There are about 800 professional seismologic observation and many of local and enterprise seismologic stations have been built up for monitoring the natural and man-made earthquake, because every station is real-time sending and recording the seismic data, there are a lot of record data accumulated. The analyzers always expecting the automatic processing come true and the method is credible. We all know about the huge earthquake happened in Indonesia in 2004 and the"5.12"big earthquake happened in Sichuan in 2008. Big earthquake can destroy everything and the scientist still can not forecast, so people have to pay more attention to build the earthquake warning system. No matter the real-time automatic processing system and early warning system, they are all base on the credible automatic seismic event detection and phase identification.This paper sums up the general seismic event detection and phase identification methods. Focusing on the STA/LTA check arithmetic, earthquake polarization character and base on Akaike information criterion for application on small earthquake detection and PG and SG phase identification. What I have done is:1. Briefly summarized some seismic event detection methods, analyzed the STA/LTA detection method and polarization character. The research results indicates: the eigvalue method which is based on the covariance of the three channel record data can distinguish the noise and seismic clearly, SVD (singularity value decompose) method can also show this character and can show cleaner when the small earthquake recorded by broadband seismometer.2. In this paper, I summarized the phase identification method used by researchers, and continue research the AR-AIC(automatic regressive),VAR-AIC(based on the variance),TOC(High)-AIC(tall or high order statistics),AOC-TOC(based on Amplitude or Power), compared the different AIC method detect result. The VAR-AIC and AOC-AIC method need the least time and calculate fastest. When the SNR is high, every method can get the satisfying PG and SG start time. The polarization method is based on three channel seismic record, the detection result is credible, but when use the method to identify the phase the result is lie on the data window you chosen. the window is small the result is higher.3. We use the P wave data window and S wave data window of three components record get the principal axes of the polarization ellipsoid respectively, Using 175 three channel events records of WuJiang reservoir telemetering seismic network we get the Vertical/Horizontal, (2*Z/(Y+X)),Vertical/Radial(Z/Y),Radial /Transverse(Y/X) ratio statistics distributing characterics of P wave and S wave on their polarization axes, the results show Z/H ratios has the most difference, the V/R and R/T ratio also have obvious difference, We still take the P wave's polarization axes as the model standard, rotate the subsequent data of Pg phase, then detect the phase using AIC method automatically. We hope this will help us identify the automatic phase detection result.