The high‐frequency decay term of the acceleration spectrum κ is a commonly used parameter in engineering seismology. In recent years, the assumption of a linearly decaying spectrum in log–linear space has been recognized to not always be valid as the value of κ depends on the analyzed frequency band. We present an alternative model for the spectral falloff in which the frequency dependence is explicitly taken into account. This is motivated by observations that the quality factor Q has a power‐law dependence on frequency at high frequencies. The new model describes the spectral decay with the help of two variables, opposite to the single parameter κ⁠. The approach is applied to borehole data of the EUROSEISTEST site in Greece. The misfit between modeled and observed spectra is reduced with the new approach compared with the classical kappa model. The new estimates compare well with κ estimates if the same frequency interval is considered but additionally allows for the capture of the frequency dependence of the spectral shape.

中文翻译：

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高频加速度傅立叶振幅谱形状的频率依赖模型

加速度谱κ的高频衰减项是工程地震学中常用的参数。近年来，人们认识到对数线性空间中线性衰减谱的假设并不总是成立，因为κ的值取决于所分析的频带。我们为频谱衰减提出了一种替代模型，其中明确考虑了频率依赖性。这是由于观察到的，即品质因数Q在高频下具有幂律对频率的依赖性。新模型借助两个变量来描述光谱衰减，这与单个参数κ⁠相反。该方法适用于希腊EUROSEISTEST站点的钻孔数据。与传统的kappa模型相比，使用新方法减少了建模光谱和观测光谱之间的不匹配。