Soil nonlinear behavior is often triggered in soft sedimentary deposits subjected to strong ground shaking and has led to catastrophic damage to civil infrastructure in many past earthquakes. Nonlinear behavior in soils is associated with large shear strains, increased material damping ratio, and reduced stiffness. However, most investigations of the high‐frequency spectral decay parameter κ⁠, which captures attenuation, have focused on low‐intensity ground motions inducing only small shear strains. Because studies of the applicability of the κ model when larger deformations are induced are limited, this article investigates the behavior of κ (both κr per record and site‐specific κ0 estimates) beyond the linear‐elastic regime. About 20 stations from the Kiban–Kyoshin network database, with time‐average shear‐wave velocities in the upper 30 m between 213 and 626 m/s⁠, are used in this study. We find that the classification scheme used to identify ground motions that trigger soil nonlinear behavior biases estimates of κ0 in the linear and nonlinear regimes. A hybrid method to overcome such bias is proposed considering proxies for in situ deformation (via the shear‐strain index) and ground shaking intensity (via peak ground acceleration). Our findings show that soil nonlinearity affects κr and κ0 estimates, but this influence is station dependent. Most κ0 at our sites had a 5%–20% increase at the onset of soil nonlinear behavior. Velocity gradients and impedance contrasts influence the degree of soil nonlinearity and its effects on κr and κ0⁠. Moreover, we observe that other complexities in the wave propagation phenomenon (e.g., scattering and amplifications in the high‐frequency range) impose challenges to the application of the κ0 model, including the estimation of negative values of κr⁠.

中文翻译：

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非线性土壤行为对 Kappa (κ) 的影响：来自 KiK-Net 数据库的观察结果

土壤非线性行为通常在受到强烈地面震动的软沉积沉积物中触发，并在过去的许多地震中对民用基础设施造成灾难性破坏。土壤中的非线性行为与大剪切应变、增加的材料阻尼比和降低的刚度有关。然而，对捕获衰减的高频频谱衰减参数 κ 的大多数研究都集中在仅引起小的剪切应变的低强度地面运动上。由于对 κ 模型在引起较大变形时的适用性的研究是有限的，本文研究了 κ（每个记录的 κr 和特定地点的 κ0 估计值）超出线性弹性机制的行为。Kiban-Kyoshin 网络数据库中的大约 20 个站点，本研究中使用了时间平均横波速度在 213 到 626 m/s 之间的上层 30 m。我们发现，用于识别触发土壤非线性行为的地面运动的分类方案会在线性和非线性状态下对 κ0 的估计产生偏差。考虑到原位变形（通过剪切应变指数）和地面震动强度（通过峰值地面加速度）的代理，提出了一种克服这种偏差的混合方法。我们的研究结果表明，土壤非线性影响 κr 和 κ0 估计值，但这种影响取决于站点。我们站点的大多数 κ0 在土壤非线性行为开始时增加了 5%–20%。速度梯度和阻抗对比影响土壤非线性程度及其对 κr 和 κ0 的影响。此外，我们观察到波传播现象中的其他复杂性（例如，