Abstract

In this paper, the computation of seismic responses of complex ridge topography is documented that can provide a reliable scenario of ridge amplification. This research work is inspired by the topography of the great Himalaya, wherein the increase of height from the south to north is in form of ups (anticlines) and downs (synclines). The viscoelastic SH- and SV-wave responses of triangular and elliptical complex ridge topography models are simulated using fourth-order finite-difference method. The complexity in the model is augmented by adding more number of sub-ridges and sub-valleys along the flanks of the reference mega-ridge. An increase in ridge amplification is obtained with an increase of complexity in both the triangular and elliptical ridge models for both the polarization of S-wave. The increase of amplification with complexity is drastically very high for the horizontal components of the SV-wave in the case of triangular ridges. It is concluded that the horizontal ground motion simulated at the crest of ridge very much depends on the shape and complexity of the topography as well as the polarization of the incident S-wave. It is concluded that the computed topography effects using the spectral ratio of earthquake records at the top and near its base generally overpredicts spectral amplifications and may not be reliable.

Research highlights

In this paper, the increase of S-wave amplification at the crest of sub-ridges as well as the base of subvalleys with an increase of complexity in the topography models is observed. The increase of amplification of the horizontal components of the SV-wave with complexity was larger to that of the SH-wave in the case of triangular sub-ridges. The predicted ridge amplification using earthquake records at the top and base of a ridge generally over-predicts the ridge amplification.

中文翻译：

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脊形地形的形状和复杂性对SH波和SV波的比较放大场景的影响

摘要

在本文中，记录了复杂脊形地形的地震响应的计算，可以提供可靠的脊形放大方案。这项研究工作的灵感来自大喜马拉雅山的地形，其中，从南到北的高度以起伏（背斜线）和起伏（向斜线）形式增加。利用四阶有限差分法模拟了三角形和椭圆形复杂脊形地形模型的粘弹性SH波和SV波响应。通过沿着参考巨型山脊的侧面添加更多数量的子山脊和子谷，可以增加模型的复杂性。对于S波的偏振，在三角形和椭圆形脊模型中，随着脊复杂性的增加，脊放大的增加也得到了提高。在三角脊的情况下，对于SV波的水平分量，放大的复杂度增加非常大。结论是，在脊顶模拟的水平地震动很大程度上取决于地形的形状和复杂性以及入射S波的极化。可以得出结论，使用顶部和底部附近地震记录的频谱比率计算出的地形效应通常会过度预测频谱放大，因此可能并不可靠。

研究重点

在本文中，随着地形模型中复杂度的增加，观察到子脊顶部和子谷底部的S波放大率增加。在三角形子脊的情况下，SV波的水平分量的放大增加的复杂度比SH波的复杂度大。使用在山脊顶部和底部的地震记录进行的预测山脊放大通常会过度预测山脊放大。