基于经验参考场地的广义线性反演方法
A Generalized Inversion Technique Based on the Empirical Reference Site

为了克服广义线性反演方法（GIT）中理想的参考场地难以找到的局限性，本文将四分之一波长法计算的平均场地放大系数和谱衰减法计算的高频衰减参数作为GIT方法的经验参考场地（ERS）。以2008年5月至8月间28个强震动台站记录的95个汶川8.0级地震余震的615组强震动记录为例，通过与其他方法的比较，验证了ERS-GIT的合理性，并讨论了各类方法之间差异的原因。结果显示，ERS-GIT方法、传统GIT方法和非参数化GIT方法计算得到的平均应力降依次为1.15 MPa，0.78 MPa和0.52 MPa；ERS-GIT方法和传统GIT方法得到的品质因子分别为Q（f）=75.02f1.27和Q（f）=65.56f1.22。以场地的卓越频率为分界，ERS-GIT方法得到的局部场地响应在长周期和高频部分分别与H/V谱比法和传统GIT方法更为接近。
Ideal reference sites of the generalized inversion technique (GIT) are not always available. To overcome this limitation, in this article, average site amplification factor, calculated by the quarter wave-length method, and the high-frequency attenuation parameter, obtained from the spectral decay method, were adopted as the empirical reference site (ERS) of the GIT. Rationality of ERS-GIT was verified, through comparison with other methods, based on 615 groups of strong ground motion records of 95 aftershocks of the 2008 Wenchuan M8.0 earthquake, recorded by 28 strong motion stations during May and August 2008. Reasons for the differences among the various methods are discussed. Results showed that the average stress drop, as calculated by the ERS-GIT, classical GIT method, and nonparametric GIT method was 1.15 MPa, 0.78 MPa, and 0.52 MPa, respectively. Quality factors obtained from the results of the ERS-GIT and classical GIT methods were Q(f)=75.02f1.27 and Q(f)=65.56f1.22, respectively. Taking the predominant frequency of the site as a boundary, the local site responses calculated by the ERS-GIT coincided with those of the H/V spectral ratio method and classical GIT method at long period and high frequency, respectively