Is Ground‐Motion Variability Distance Dependent? Insight from Finite‐Source Rupture Simulations
Is Ground‐Motion Variability Distance Dependent? Insight from Finite‐Source Rupture Simulations
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地面运动变化与距离有关吗？来自有限源破裂模拟的见解
DOI：
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发表时间：
2015
期刊：
影响因子：
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通讯作者：
F. Cotton
中科院分区：
文献类型：
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作者：
A. Imtiaz;M. Causse;E. Chaljub;F. Cotton
摘要 地面运动变异性西格玛是概率地震灾害评估的基本组成部分，因为它将灾害水平控制在非常低的超出概率下。到目前为止，大多数基于经验地面运动预测方程的分析都没有考虑西格玛的任何距离依赖性。本研究旨在分析地面运动变异性的潜在距离依赖性，特别是在近场区域，由于缺乏可用记录，变异性受到很差的限制。因此，我们通过对一些走滑事件进行地震动数值模拟来研究西格玛的距离依赖性。合成速度地震图（高达 3 Hz）是根据过去地震的一套有限源破裂模型生成的。使用离散波数技术计算一维速度结构的格林函数（Bouchon，1981）。然后根据合成数据评估地面运动变异性的事件内分量作为距离的函数。模拟表明，地震动的事件内分量表现出距离依赖性，具体取决于破裂类型。对于双侧破裂，变异性往往随着距离的增加而增加。相反，在单边事件的情况下，变异性随着距离的增加而减小。
Abstract The ground‐motion variability sigma is a fundamental component in probabilistic seismic‐hazard assessment because it controls the hazard level at very low probabilities of exceedance. So far, most of the analyses based on empirical ground‐motion prediction equations do not consider any distance dependency of sigma. This study aims to analyze the potential distance dependency of ground‐motion variability, especially in the near‐field region, where the variability is poorly constrained due to the lack of available records. We, therefore, investigate the distance dependency of sigma by performing numerical simulations of ground motion for some strike‐slip events. Synthetic velocity seismograms (up to 3 Hz) have been generated from a suite of finite‐source rupture models of past earthquakes. Green’s functions were calculated for a 1D velocity structure using a discrete wavenumber technique (Bouchon, 1981). The within‐event component of the ground‐motion variability was then evaluated from the synthetic data as a function of distance. The simulations reveal that the within‐event component of the ground motion shows a distance dependency, subject to the rupture type. For bilateral ruptures, the variability tends to increase with distance. On the contrary, in case of unilateral events, the variability decreases with distance.