State Key Laboratory for GeoMechanics and Deep Underground Engineering, School of Mechanics and Civil Engineering, China University of Mining and Technology, Xuzhou, Jiangsu, China.
PLoS One. 2021 Jul 30;16(7):e0254871. doi: 10.1371/journal.pone.0254871. eCollection 2021.
In this paper, considering the far-field seismic input, an accelerogram recorded in the bedrock at Wuquan Mountain in Lanzhou city during the 2008 Wenchuan Ms8.0 earthquake was selected, and numerical dynamic analyses were conducted. The one-dimensional equivalent linear method was implemented to estimate the ground motion effects in the loess regions. Thereafter, slope topographic effects on ground motion were studied by applying the dynamic finite-element method. The results revealed the relationship between the PGA amplification coefficients and the soil layer thickness, which confirmed that the dynamic response of the sites had obvious nonlinear characteristics. The results also showed that there was an obvious difference in the dynamic magnification factor between the short-period and long-period structures. Moreover, it was found that the amplification coefficient of the observation point at the free surface was greater than the point inside the soil at the same depth, which mainly occurred in the upper slope. Through this study, the quantitative assessment of ground motion effects in loess regions can be approximately estimated, and the amplification mechanism of the far-field ground motion mechanism can be further explained. In addition to the refraction and reflection theory of seismic waves, the resonance phenomenon may help explain the slope topographic effect through spectrum analysis.
本文考虑远场地震输入，选取了 2008 年汶川 Ms8.0 地震中兰州武泉山基岩上记录的加速度记录，并进行了数值动力分析。采用一维等效线性方法估算了黄土地区的地面运动效应。然后，通过动力有限元方法研究了边坡地形对地面运动的影响。结果揭示了 PGA 放大系数与土层厚度之间的关系，证实了场地的动力响应具有明显的非线性特征。结果还表明，在短周期和长周期结构之间存在明显的动力放大因子差异。此外，还发现自由表面观测点的放大系数大于同一深度内土壤内的点，这主要发生在上坡。通过这项研究，可以对黄土地区的地面运动效应进行定量评估，并进一步解释远场地面运动机制的放大机制。除了地震波的折射和反射理论外，通过频谱分析，共振现象可能有助于解释边坡地形效应。
