Mobile Array Seismic Detection And Seismic Phase Automatic Picking Research

Earthquake arrival time is the basic data for seismological research.It is widely used in earthquake location,traveltime tomography,earthquake early warning and other fields.With the increasing of seismic stations and wide application of portable seismic array observations,the traditional phase picking methods can't meet the real-time requirements of modern society on the development of seismic information.Developing reliable,strong anti-interference automatic phase detection and picking technology has become one of the important research direction in the field of seismology.Based on the observation data of Xichang seismic array,we conducted the automatic detection of seismic events and the automatic picking of seismic phase in this research:1.We summarize the commonly used seismic phase picking methods.We compare STA/LTA,AIC,polarization analysis,singular value decomposition(SVD),wavelet analysis and artificial neuron method in detail and analyze the predominant advantages and disadvantages of these methods and research status.2.We propose a combination method using STA/LTA and VAR-AIC to pick phase data preliminarily,then using Delaunay triangulation method and traveltime difference of inter-stations to preclude noise inference.The new method can suppress noise effectively and improve earthquake detecting ability.3.A comparative study of STA/LTA,VAR-AIC and polarization analysis is conducted.We design a new detection method.The method determine the strength of signal on the basis of phase difference with STA/LTA and VAR-AIC and select VARAIC method or polarization method to obtain phase arrival time automatically.The new method has higher overall phase picking accuracy compared with the single VAR-AIC method or polarization method.4.Seismic phase picking method based on seismic detection results is designed.The method contains four steps:(1)using high SNR phase arrival data determing earthquake locations;(2)according to the earthquake location,then calculate theoretical arrival time at each station;(3)designing specific phase detection criterion to determine whether there are further prediction of near earthquake by setting the time window at each station;(4)if there is phase,using STA/LTA method,VAR-AIC method and polarization analysis method of phase picking.5.According to methods motioned above,we develop a seismic detection software under Matlab environment.We process and analyze 304 seismic events recorded by Xichang Seismic Array in 2013.Our results show that:(1)compared with the Delaunay triangulation method,the new method proposed in this research has better performance;(2)the new method can not only detect phase arrival data with high SNR missed by analysists,but also can detect phase arrival data with low SNR which are easy to neglect in manual picking process.