一种实时场地校正方法及其在地震预警中的应用

地震预警系统对地震数据处理的实时性要求极高。其系统数据来源除布设在基岩的测震台站外,还有大量非基岩场地的强震动台站和地震烈度仪台站,其场地影响不容忽视。为了考虑震级估算和地震动场预测中的场地影响,需实时对各种场地条件下的地震波形进行校正。目前处理一般使用某个标量来表征场地放大效应。本文采用一种实时的场地校正方法,首先计算目标场地与参考场地的谱比,然后通过最小二乘法、双线性变换将谱比转化为因果递归的无限冲激响应(IIR)时域滤波器,之后可以应用该滤波器进行实时场地校正。该方法考虑了场地放大系数的频率依赖性,相比于标量校正提高了准确度。应用我国四川和日本部分强震动台站记录,验证并讨论了这种实时场地校正方法在地震预警中的应用效果。

A real-time site correction method and its application in earthquake early warning

The earthquake early warning system has extremely high requirements on the real-time processing of seismic data.The waveforms are not only from the seismic station installed in the bedrock,but also from a large number of strong motion stations and seismic intensity meters stations which are installed in soil rather than bedrock.The amplification of the site cannot be ignored.In order to consider the site amplification effect in magnitude estimation and ground motion field prediction,it is necessary to correct the seismic waveforms under various site conditions in real time.A scalar is currently used to characterize the site amplification effect.In this paper,a real-time site correction method is adopted,in which the spectral ratio of the target site and the reference site is first calculated,and then converted into a causal recursive infinite impulse response(IIR)time domain filter by least squares method and bilinear transformation.The IIR filter can be used to correct the site amplification in real time.This method considers the frequency dependence of the site amplification factor and improves the accuracy compared to the scalar correction.Based on the records of some strong motion stations in Sichuan province and Japan,the application effect of this real-time site correction method in earthquake early warning is verified and discussed.