Ground Motion Prediction Equations in the San Jacinto Fault Zone: Significant Effects of Rupture Directivity and Fault Zone Amplification
Ground Motion Prediction Equations in the San Jacinto Fault Zone: Significant Effects of Rupture Directivity and Fault Zone Amplification
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DOI：
10.1007/s00024-014-0855-2
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发表时间：
2014-05
影响因子：
2
通讯作者：
I. Kurzon;F. Vernon;Y. Ben‐Zion;G. Atkinson
中科院分区：
文献类型：
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作者：
I. Kurzon;F. Vernon;Y. Ben‐Zion;G. Atkinson
我们提出了一套新的地面运动预测方程 (GMPE)，用于水平峰值地面加速度、峰值地面速度和 5% 阻尼伪谱加速度 (PSA)，是为圣哈辛托断层带 (SJFZ) 区域开发的。除了使用这些方程来量化该地区的地震震动外，这些结果还使我们能够检查控制观测到的地面运动的物理和局部特性。分析的数据集包括约 800 个事件的约 30,000 个观测结果，震级范围为 1.5 <M< 6.0，由震中距离基本为零到 150 公里的多达 140 个观测站记录。局部 GMPE 是通过应用经典回归技术为 SJFZ 开发的，预测变量首先包括距离和震级，然后是场地特征、破裂方向性和断层带放大。这些影响的重要性是通过测量每个因素导致的 GMPE 不确定性降低来确定的。结果表明，与许多区域研究相比，传统的场地特征对我们研究区域的峰值幅度的影响相对较小。然而，破裂方向性是控制地震动振幅的重要因素，即使对于小事件也是如此。密集的地震网络和新开发的方向性工具使我们能够在回归分析过程中使用地面运动数据集有效地提取具有统计意义的方向性效应。获得的破裂方向性与其他研究中已知的主要震源机制方向和表面痕迹方向以及 SJFZ 三分叉区域双材料破裂的预测一致。断层带放大是第二个重要因素，显示出对峰值地震动值的强烈影响，并且在 5% 阻尼 PSA 值中检查的较低频率范围（<10 Hz）的作用越来越大。我们还观察到大振幅方差的特征，这表明在时间和地点接近 2013 年 3 月 ML5.1 地震的余震中，对振幅分布（除了破裂方向性）进行了额外的震源相关控制。利用全套记录，我们为 SJFZ 地区提供了最完整的 GMPE 集，包括对破裂方向区域的更高振幅预测。
We present a new set of Ground Motion Prediction Equations (GMPEs) for horizontal Peak Ground Acceleration, Peak Ground Velocity, and 5 % damped pseudo-spectral acceleration (PSA), developed for the San Jacinto Fault Zone (SJFZ) area. Besides using these equations to quantify seismic shaking in the area, the results allow us to examine the physics and local properties controlling the observed ground motions. The analyzed dataset includes ~30,000 observations from ~800 events spanning a magnitude range of 1.5 <M< 6.0 and recorded by up to 140 stations at epicentral distances ranging from essentially zero to 150 km. The local GMPE is developed for the SJFZ by applying classical regression techniques with predictive variables that include first distance and magnitude, and then site characteristics, rupture directivity, and fault zone amplification. The significance of these effects is determined by measuring the uncertainty-reduction of the GMPE due to each factor. The results show that, in contrast to many regional studies, traditional site characteristic has a relatively minor effect on peak amplitudes in our study area. However, rupture directivity is a significant factor controlling the amplitudes of ground motion even for small events. The dense seismic network and newly developed directivity tool enable us to extract efficiently directivity effects with statistical significance, using the ground-motion dataset during the regression analysis process. The obtained rupture directivities are consistent with the main focal mechanism orientations and surface trace orientations, known from other studies, and predictions for bimaterial ruptures in the trifurcation area of the SJFZ. Fault zone amplification is a second important factor, showing strong impact on the peak ground motion values, with increasing role for the lower frequency range (<10 Hz) examined in the 5 % damped PSA values. We also observe signatures of large amplitude-variances, which indicate additional source-related control on the distribution of amplitudes (besides rupture directivity) for aftershocks close in time and location to theML5.1 earthquake of March 2013. Using the full set of records we present the most complete set of GMPEs for the SJFZ area, including a higher-amplitude prediction for regions in the direction of rupture.