Model for Basin Effects on Long-Period Response Spectra in Southern California
Model for Basin Effects on Long-Period Response Spectra in Southern California
复制标题
南加州长周期响应谱盆地效应模型
DOI：
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发表时间：
2008
期刊：
影响因子：
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通讯作者：
L. Ramírez
中科院分区：
文献类型：
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作者：
S. Day;R. Graves;J. Bielak;D. Dreger;S. Larsen;K. Olsen;A. Pitarka;L. Ramírez
提出了沉积盆地深度对长周期反应谱影响的模型。该模型基于对洛杉矶盆地地区一组60次地震(MW6.3至MW7.1)的长周期(2-10 S)地面运动的三维数值模拟(有限元和有限差分)的分析。我们发现深度到1.5公里/S S波速等值面是一个合适的预报变量，并给出了基于深度的模型的替代版本。由此产生的平均盆地深度效应与周期有关，而且比当地一维模型的预测更平滑(作为周期和深度的函数)，幅度也更高。在建立衰减关系中使用结果的主要要求是确定本研究中定义和量化的盆地效应在多大程度上已经被隐含地考虑到现有的衰减关系中，通过(1)平均“岩石”位置与我们理想的参考模型的偏离，以及(2)盆地深度与其他预测变量(如Vs30)的相关性。
We propose a model for the effect of sedimentary basin depth on long-period response spectra. The model is based on the analysis of 3-D numerical simulations (finite element and finite difference) of long-period (2–10 s) ground motions for a suite of sixty scenario earthquakes (Mw 6.3 to Mw 7.1) within the Los Angeles basin region. We find depth to the 1.5 km/s S-wave velocity isosurface to be a suitable predictor variable, and also present alternative versions of the model based on depths to the 1.0 and 2.5 km/s isosurfaces. The resulting mean basin-depth effect is period dependent, and both smoother (as a function of period and depth) and higher in amplitude than predictions from local 1-D models. The main requirement for the use of the results in construction of attenuation relationships is determining the extent to which the basin effect, as defined and quantified in this study, is already accounted for implicitly in existing attenuation relationships, through (1) departures of the average “rock” site from our idealized reference model, and (2) correlation of basin depth with other predictor variables (such as Vs30).