Rocks often showed an alteration in their first meters of depth, by the presence of weathered portion through variable thickness. Concentration of building damage near the edge of hard or dense cliff has been observed during a number of earthquakes. The numerical analysis of topographic effects of rocky steep slopes knowingly neglects the stratigraphic effect. In previous studies, it was evoked the fracturing of the upper parts of the site of ‘Rocher Noir’ in Boumerdes City, and the obtained HVSR curves were flat or presenting a peak over 10 Hz, explained by the fact that the metamorphic outcropping is overlaid by sediments. In this paper, interaction between the effects of stratigraphic and topographic amplification of this weathered rocky site is investigated through 1D and 2D numerical models.

The goal of these investigations is to provide a better understanding of the potential hazard that is represented by amplified ground motion due to the coupling effect (1D amplification and topographic amplification) and to quantify the weathering effects on topographic amplification. Seismic responses (amplification functions and response spectra) are calculated at representative points located in the upper surface of the rocky model, assumed either hard or weathered. The obtained results show that the presence of a weathered portion on the surface can modify the ground response in the sense of higher amplification, larger bandwidth (modifying of the mode vibration), multiple response spectra peaks and inducing a considerable vertical acceleration component. Ambient noise measurements were conducted, the HVSR results agree well with those obtained by modelling.

由于存在厚度可变的风化部分，岩石的第一米深度通常会发生变化。在多次地震中，观察到建筑物损坏集中在坚硬或密密的悬崖边缘附近。岩石陡坡地形效应的数值分析故意忽略了地层效应。在以前的研究中，它引起了Boumerdes City的'Rocher Noir'站点上部的破裂，并且获得的HVSR曲线平坦或出现了超过10 Hz的峰值，这可以解释为变质露头被覆盖了通过沉积物。本文通过一维和二维数值模型研究了该风化岩石站点的地层和地形放大效应之间的相互作用。

这些研究的目的是为了更好地理解由耦合效应（一维放大和地形放大）引起的放大地面运动所代表的潜在危害，并量化风化对地形放大的影响。在岩石模型上表面的代表点（假定是坚硬的或风化的）上计算地震响应（放大函数和响应谱）。所获得的结果表明，在更高的放大率，更大的带宽（模式振动的修改），多个响应谱峰以及诱导相当大的垂直加速度分量的意义上，表面上风化部分的存在可以改变地面响应。进行了环境噪声测量，