This study uses recorded ground motions at soil sites over a range of shaking intensities to investigate the effects of soil nonlinearity on the high-frequency spectral decay, as quantified by the parameter $\kappa$. Equivalent-linear site response analyses indicate that $\kappa$ should increase significantly with increasing shear strain and ground motion intensity due to increases in soil damping. However, using more than 2500 motions from 32 sites, this study shows that $\kappa$ does not vary systematically with the induced shear strain but instead remains at its small-strain value. This observation indicates that high-frequency components of motion are consistent with small-strain damping, rather than the strain-compatible damping used in site response analysis. It is demonstrated that equivalent-linear site response analyses for large strains can be modified to generate surface motions with more realistic high-frequency content by scaling the predicted surface motion to fit the small-strain $\kappa$ or by employing frequency-dependent soil properties that account for the frequency dependence of the induced strains.

这项研究使用记录的地面运动在一定范围的震动强度范围内的土壤运动，以研究土壤非线性对高频频谱衰减的影响，其量化参数为 $\kappa$。等效线性站点响应分析表明$\kappa$由于土壤阻尼的增加，应随着剪切应变和地面运动强度的增加而显着增加。但是，这项研究使用了32个站点的2500多个运动，表明$\kappa$不会随诱导的剪切应变而系统地变化，而是保持在其较小的应变值。该观察结果表明，运动的高频分量与小应变阻尼一致，而不是与站点响应分析中使用的应变兼容阻尼一致。结果表明，可以通过缩放预测的表面运动以适合小应变，对大应变的等效线性部位响应分析进行修改，以生成具有更逼真的高频成分的表面运动。$\kappa$ 或通过采用频率相关的土壤特性来解释诱导菌株的频率相关性。