Application Of Strong-motion Data In Earthquake P-wave Early Warning

Destructive earthquakes cause disastrous consequences to human society,which makes seismologists all over the world work hard to explore the methods of earthquake disaster reduction.Nowadays,people realize the importance and practical value of earthquake early warning,earthquake disaster quick report gradually in earthquake prevention and disaster reduction.The key technologies of earthquake early warning is to determine the source parameters using the limited information of P wave quickly.With the characteristics of high sensitivity,high resolution,wide band response,large dynamic range,strong-motion data has important practical significance in such aspects as seismic P wave monitoring,determination of the epicenter and warning magnitude,seismic intensity field determine quickly and so on.In order to improve the stability and accuracy of earthquake early warning system,this paper discusses some qustions about determinationing the earthquake warning parameters by strong-motion data,such as automatic picking up of p-wave,early warning magnitude by Pd method,displacement conversion algorithm of strong-motion data and joint inversion.The following conclusions are obtained:(1)In view of the shortcomings of the STA/LTA+AIC method for automatic recognition of P waves,by bring in the concepts of SNR and relative power,the SNR-based STA/LTA+AIC method is given physical significance,which better improves the stability and accuracy of the earthquake warning system in the context of strong noise.And provides a more appropriate the length of time window and threshold value,The new p-wave automatic picking method has better filtering effect on sharp but short duration noise and improves the stability of the warning system.(2)Determinationing the warning magnitude is an important link in earthquake early warning.Based on the analysis and summary of the advantages and disadvantages of the existing methods of early warning magnitude,it is suggested that Pd method be the preferred for calculating early warning magnitude in China's early warning system.Re-fitting the relationship between Pd and Mw with the strong-motion network data in China's mainland,and take shimian earthquake of 16 May 2018 as an example to verify.(3)Although baseline drift exists in the strong-motion data,it is confirmed that reliable coseismic displacement and near-field displacement time series can be obtained by relying on the robust automatic baseline correction method.In this paper,wenchuan earthquake is taken as an example to obtain its coseismic displacement field and displacement time series using strong-motion data.With the advantage of high frequency,the coseismic displacement sequences obtained from the strong-motion data contain more abundant seismic information,which can provide reference for the research of near-fault ground motion after the earthquake.A variety of data(GPS,strong-motion,In SAR)were used to inverson the fault slip distribution of wenchuan earthquake,to provide better data constraints for understanding the wenchuan earthquake.