The April 20, 2013, Ms 7.0 Lushan Earthquake was a major earthquake that followed the Ms 8.0 Wenchuan Earthquake on May 12, 2008. Frequent earthquakes have caused heavy casualties and property loss in Western Sichuan. Earthquake disasters are often closely related to the amplification effect of ground motion. Studying the ground motion characteristics of near-surface geological structures helps to understand the distribution of potential earthquake disasters. In this study, we investigated ground motion amplification in the downtown area of Lushan using numerical simulation and aftershock data from the Lushan Earthquake. Using the Lushan earthquake aftershock data from nine seismic stations distributed in the area, the amplification effect of the sites was determined using the “reference site spectral ratio” method. The results show that the frequency of the ground motion amplification in the area was in the range 5–10 Hz, and the corresponding amplification peak was from 3 to 14. Among the study sites, the amplification (14 times) at L07 was the most prominent. To study further the amplification characteristics, shear-wave velocity models for the structures under these sites were established using passive-source Rayleigh surface-wave exploration. One-dimensional (1D) and two-dimensional (2D) seismic amplification effects were simulated using horizontally propagating shear-wave modeling. Except Site L07, the 1D simulation results of each site well reflected the variation feature of the seismic amplification on the frequency band below the observed peak frequency, although the overall simulated amplification peaks were smaller than the observed results. The 2D simulation of the remarkable amplification phenomenon at L07 was in better agreement with the observation result than was the 1D simulation, indicating that the seismic amplification in the Modong area is influenced by lateral variation of the Quaternary sediments.

中文翻译：

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庐山磨洞地区地震动放大的数值模拟

2013年4月20日，庐山7.0级地震是继2008年5月12日汶川8.0级地震之后的一次重大地震。频发的地震在四川西部造成了严重的人员伤亡和财产损失。地震灾害通常与地震动的放大效应密切相关。研究近地表地质结构的地震动特征有助于了解潜在的地震灾害的分布。在这项研究中，我们使用数值模拟和来自庐山地震的余震数据研究了庐山市区的地震动放大。利用分布在该地区的9个地震台站的庐山地震余震数据，使用“参考站谱比率”方法确定了站点的放大效果。结果表明，该区域的地震动放大频率在5-10 Hz范围内，相应的放大峰值在3到14之间。在研究地点中，L07的放大倍数最大（14倍）。突出。为了进一步研究放大特性，使用被动源瑞利面波勘探建立了这些位置下的结构的横波速度模型。使用水平传播剪切波模型模拟一维（1D）和二维（2D）地震放大效应。除了L07站点外，每个站点的一维模拟结果都很好地反映了地震放大在低于观测峰值频率的频带上的变化特征，尽管总体模拟放大峰值小于观测结果。