一种适用于地方震事件的S波到时自动拾取方法

An automatic S phase picking algorithm for local earthquake events

基于特征值分解方法,本文讨论了一种适用于地方震事件S波震相到时拾取的自动处理算法。该算法计算参数少、简便快捷、易于实现,通过选用七个不同长度的时间窗,有效地减小了窗长选择不合理所引起的震相拾取误差。利用福建地震台网记录的9855条三分向波形记录进行测试,结果表明:本文方法的S波平均拾取偏差为(0.003±1.34)s,其中79.6%的记录拾取偏差小于0.5 s,4.1%的记录拾取偏差超过2.0 s,说明本文方法能够满足日常工作基本需求。综上分析认为,波形记录质量是影响拾取算法结果精度的最主要因素,信噪比较高的记录,其S波到时拾取偏差显著优于信噪比较低的记录,对信噪比较低的部分记录进行带通滤波预处理后,S波震相拾取精度也有所提升。

Base on eigenvalue decomposition calculation,we discussed an automatic S phase picking algorithm suitable for local earthquake events.The algorithm needs few parameters,less computer resources and is easy to realize.By choosing seven time windows with different time length,it effectively reduce the S phase pick errors that caused by unreasonable time window selection.By taking 9855 three-component records of Fujian seismic monitoring network,we test the applicability and accuracy of this algorithm.The results show that average S phase picking error by this method is(0.003±1.34)s,79.6%of them are within 0.5 s,4.1%of them are greater than 2.0 s,which indicates that the algorithm can meet the demands for daily S phase picking.All above-mentioned suggests that the quality of records is the most important factor that affects the accuracy of picking results,the S phase picking errors for high signal-noise ratio records are usually smaller than those for low signal-noise ratio records,and the accuracy of S phase picking for some low signal-noise ratio records will be improved after a band-pass filter preprocess.