Amplification of seismic response of a large deep-seated landslide in Tokushima, Japan
Amplification of seismic response of a large deep-seated landslide in Tokushima, Japan
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DOI：
10.1016/j.enggeo.2019.01.002
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发表时间：
2019-01
影响因子：
7.4
通讯作者：
Ning Ma;Gong-hui Wang;T. Kamai;I. Doi;M. Chigira
中科院分区：
文献类型：
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作者：
Ning Ma;Gong-hui Wang;T. Kamai;I. Doi;M. Chigira
为了更好地了解深层滑坡的地震现场反应，我们对2004年台风“南天”（Namtheun）在日本德岛县中町（Naka Town）引发的暴雨重新激活的目标滑坡进行了长期地震监测。在不同海拔的滑坡区不同位置安装了5台高灵敏度地震仪。通过研究大量的地震事件记录，我们区分了不同地区的物质对比和地形对这些局部放大的影响，并在详细的地质和地球物理调查的帮助下总结了它们的特征。为了分析放大的差异，采用了HVSR方法（计算地面运动的水平与垂直频谱比）。地形导致的HVSR峰值振幅小于5的滑坡块体放大主要垂直于山脊延伸方向。然而，在多个地层中，由于材料对比引起的放大（HVSR峰值幅度为3 ~ 5）呈现出不同的放大方向。通过分析HVSR峰值振幅与剪切速度曲线的关系，我们发现不同频率下的振幅受材料对比程度的影响很大。这也许可以解释为什么有古滑坡沉积的坡脚部分通常表现出最大的地面运动（其特征为HVSR峰值振幅通常为bb10）。这种由物质对比引起的强放大可能会在地震中对山区的居民区造成严重破坏，在滑坡地区建造建筑物时应考虑这种放大。
To better understand seismic site responses of deep-seated landslides, we carried out long-term seismic monitoring of a target landslide reactivated by a rainstorm in 2004 accompanying Typhoon Namtheun in Naka Town, Tokushima Prefecture, Japan. Five seismometers with high sensitivity were installed at different locations on landslide areas with different elevations. By examining numerous records of earthquake events, we distinguished the effects of material contrast and topography on these localized amplifications for different areas, and summarized their features, with help of detailed geological and geophysical surveys. To analyze differences in amplification, the HVSR method (calculating the horizontal to vertical spectral ratio of ground motion) was applied. The amplification on a landslide block with an HVSR peak amplitude smaller than 5 and resulting from topography is predominantly perpendicular to the direction of elongation of the mountain ridge. However, the amplification (revealed by HVSR peak amplitude of 3 to 5) resulting from material contrasts in multiple strata showed differing amplification directions. By examining the relationship between the HVSR peak amplitude and shear velocity profiles, we found that the amplifications at different frequencies are greatly affected by the extent of material contrasts. This may explain why the toe part of the slope, with ancient landslide deposits, generally shows the greatest ground motion (characterized by HVSR peak amplitude normally >10). This type of strong amplification due to material contrasts may result in severe damage to residential areas in mountainous areas during an earthquake and should be considered for the construction of buildings on landslide areas.