首页> 外文期刊>Bulletin of the Seismological Society of America >Broadband Ground Motions from Dynamic Models of Rupture on the Northern San Jacinto Fault, and Comparison with Precariously Balanced Rocks
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Broadband Ground Motions from Dynamic Models of Rupture on the Northern San Jacinto Fault, and Comparison with Precariously Balanced Rocks

机译:北部圣哈辛托断层破裂动态模型的宽带地震动及其与不稳定岩石的比较

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摘要

The Southern California San Jacinto fault is geometrically complex, consisting of several major strands with smaller scale complexity within each strand. The two northernmost strands, the Claremont and the Casa Loma-Clark, are separated by a 25-km-long extensional stepover with an average of 4 km separation between the strands. We use a combined modeling method to assess probable rupture and ground-motion behaviors for this stepover. First, dynamic rupture modeling on geometrically complex fault strands embedded in a state-of-the-art 3D crustal velocity model is used to generate a series of scenario earthquakes. We then use the resulting near-fault low-frequency (< 1 Hz) ground-motion time histories to generate broadband synthetic seismograms with a hybrid approach. These synthetics are then compared with a distribution of precariously balanced rocks (PBRs) near the fault to constrain our results and assess shaking hazard for the region surrounding the fault. Our dynamic models produce sources between M-w 5.4 and 6.9, with rupture limits imposed by sharp contrasts in fault stress or by geometrical barriers. The main stepover serves as a primary barrier to rupture in our model, producing event sizes that are consistent with the historical behavior of the San Jacinto fault. The largest broadband synthetics are a good match to leading ground-motion prediction equations and are generally consistent with the distribution of PBRs, none of which experience accelerations that produce toppling probabilities significantly higher than zero. Thus, although the PBRs do not rule out any of our model scenarios, they confirm that our models produce realistic rupture extents and shaking.
机译:南加利福尼亚州的圣哈辛托断裂在几何上是复杂的,由几条主要股构成,每条股中的尺度复杂度较小。两条最北端的链条,克莱蒙特和卡萨洛玛-克拉克,由25公里长的延伸跨步分开,两链之间平均间隔4公里。我们使用一种组合的建模方法来评估此过渡过程可能发生的破裂和地震动行为。首先,使用嵌入最新3D地壳速度模型中的几何复杂断层线上的动态破裂建模来生成一系列情景地震。然后,我们使用所得的接近故障的低频(<1 Hz)地面运动时间历史记录,通过混合方法生成宽带合成地震图。然后将这些合成物与断层附近不稳定平衡的岩石(PBR)的分布进行比较,以约束我们的结果并评估断层周围区域的摇晃危险。我们的动力学模型产生的M-w 5.4和6.9之间的源,断裂极限是由断层应力的强烈对比或几何屏障引起的。主跨步是我们模型破裂的主要障碍,产生的事件大小与圣哈辛托断层的历史行为一致。最大的宽带合成器与领先的地面运动预测方程式非常匹配,并且通常与PBR的分布保持一致,PBR的分布均未经历加速,产生的倾倒概率明显高于零。因此,尽管PBR并不排除我们的任何模型场景,但它们证实了我们的模型会产生实际的破裂程度和震动。

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