STA/LTA方法拾取天然地震波初至及其改进分析  

STA/LTA method for picking up the first arrival of natural seismic waves and its improvement analysis

作　　者：邱磊 李彩华[3] QIU Lei;LI CaiHua(School of Electronic Science and Control Engineering,Institute of Disaster Prevention,Sanhe 065201,China;Hebei Key Laboratory of Seismic Disaster Instrument and Monitoring Technology,Institute of Disaster Prevention,Sanhe 065201,China;Institute of Geophysics,China Earthquake Administration,Beijing 100081,China)

机构地区：[1]防灾科技学院电子科学与控制工程学院,三河065201 [2]防灾科技学院,河北省地震灾害仪器与监测技术重点实验室,三河065201 [3]中国地震局地球物理研究所,北京100081

出　　处：《地球物理学进展》2023年第4期1497-1506,共10页Progress in Geophysics

基　　金：国家重点研发计划项目(2019YFC1511000)资助。

摘　　要：长短时窗均值比(Short Term Average/Long Term Average,STA/LTA)方法因原理简单、实时性强,在地震波初至拾取中应用最为广泛.传统STA/LTA方法阈值选取依赖于人工经验,且其针对单一信号设定的阈值无法适用于不同类型的地震记录.针对此问题,本文通过建立阈值与背景噪声之间的联系,提出两种基于参考阈值拾取地震波初至新方法,即基于参考阈值的STA/LTA方法与基于参考阈值的STA/LTA改进法.首先,分析不同特征函数拾取地震波初至的灵敏度,引用关于信噪比(Signal-to-Noise Ratio,SNR)的特征函数抑制背景噪声干扰,降低阈值选取的难度;其次,给出不同背景噪声环境下阈值的计算公式,将阈值选取建立在严密的数学推导之上,提出基于参考阈值的STA/LTA方法;最后,针对天然地震背景噪声复杂,地震波初至拾取受短时强噪声干扰大的问题,通过改进时窗位置并加入取消时窗的方法提高算法的抗干扰能力,提出了基于参考阈值的STA/LTA改进法.实际地震数据处理结果表明,本文提出的两种方法能够克服固定阈值不能适用于所有地震记录的缺点,相较于传统STA/LTA方法拾取正确率及精度均有所提升.Short Term Average/Long Term Average(STA/LTA)method is widely used in seismic wave first break picking because of its simple principle and strong real-time performance.The threshold selection of the traditional STA/LTA method depends on artificial experience,and the threshold set for a single signal cannot be applied to different types of seismic records.Aiming at this problem,this paper proposes two new methods for picking up the first arrival of seismic waves based on reference threshold by establishing the relationship between threshold and background noise,namely STA/LTA method based on reference threshold and STA/LTA improvement method based on reference threshold.Firstly,the sensitivity of different characteristic functions to pick up the first arrival of seismic waves is analyzed,and the characteristic function of Signal-to-Noise Ratio(SNR)is used to suppress background noise interference and reduce the difficulty of threshold selection.Secondly,the calculation formula of threshold under different background noise environments is given.The threshold selection is based on strict mathematical derivation,and the STA/LTA method based on reference threshold is proposed.Finally,in view of the complex background noise of natural earthquakes and the problem that the first arrival picking of seismic waves is greatly disturbed by short-term strong noise,the anti-interference ability of the algorithm is improved by improving the time window position and adding the method ofcanceling the time window,and the STA/LTA improvement method based on the reference threshold is proposed.The actual seismic data processing results show that the two methods proposed in this paper can overcome the shortcomings that the fixed threshold cannot be applied to all seismic records.Compared with the traditional STA/LTA method,the accuracy and precision are improved.

关 键 词：地震波初至拾取 STA/LTA方法 特征函数 信噪比 时窗 

分 类 号：P315[天文地球—地震学]