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首页> 外文会议>Coupled site and soil-structure interaction effects with application to seismic risk mitigation >THE NATURE OF SITE RESPONSE DURING EARTHQUAKES
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THE NATURE OF SITE RESPONSE DURING EARTHQUAKES

机译：地震现场响应的性质

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摘要

The traditional approach for empirical scaling of the amplitudes of strong earthquake ground motion revolves around the linear representation of the amplification of seismic waves when they propagate through soft surface sediments and soil. However, in the near field, when the amplitudes of shaking become large, the soil experiences nonlinear strains, and tensile cracks, fissures, and pounding zones form, resulting in highly nonlinear response characteristics. This means that the characteristic site response, and the patterns of amplifications measured via small earthquake records, or by analysis of microtremors, will disappear, departing from the linear amplification characteristics completely. This leads to chaos and creates a problem for seismic zoning because the nonlinear response is strongly dependent upon the amplitudes and on the time history of shaking, so that it becomes virtually impossible to predict the distribution of amplification from the local site conditions. If we assume that the observed damage distribution is a useful indication of the distribution and of the nature of shaking amplitudes, we can conduct a full-scale experiment every time a moderate or large earthquake leads to some damage. Analyses of these patterns, combined with detailed maps of the properties of the soil and of surface geology, suggest that there are reappearing patterns of nonlinear site response from one earthquake to the next. We show one such example for two earthquakes in the Los Angeles metropolitan area. This example implies that the relative movement along the boundaries of the blocks of soil, and along the cracks formed by previous strong shaking, may recur during future earthquakes. The implication is significant for all engineering analyses of response and for engineering design in the near field because it means that in the vicinity of these cracks the complexity of strong shaking is further increased by large differential motions and by large transient and permanent strains and tilts.
机译：根据经验按比例缩放强地震地震动幅度的传统方法围绕着地震波在软地表沉积物和土壤中传播时放大线性表示。但是，在近场中，当振动幅度变大时，土壤会经历非线性应变，并且会形成张裂，裂隙和撞击区，从而产生高度非线性的响应特性。这意味着特征点响应以及通过小地震记录或通过微震分析测得的放大模式将消失，完全脱离线性放大特性。由于非线性响应强烈地依赖于振幅和振动的时间历程，这导致混乱并给地震分区带来了问题，因此实际上不可能从本地现场条件预测放大的分布。如果我们假设观察到的损伤分布是分布的分布和振动幅度性质的有用指示，那么每当中度或大地震导致某种程度的损伤时，我们都可以进行一次全面的实验。对这些模式的分析，再加上详细的土壤特性和表面地质图，表明从一次地震到下一次地震，非线性场地响应的再现模式不断出现。我们为洛杉矶都会区的两次地震展示了这样一个例子。这个例子表明，在未来的地震中，可能会沿着土壤块的边界以及先前强烈震动形成的裂缝发生相对运动。这对所有工程响应分析和近场工程设计都具​​有重要意义，因为这意味着在这些裂缝附近，大的差动运动以及大的瞬态和永久性应变和倾斜会进一步增加强震动的复杂性。

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