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首页> 外文期刊>Bulletin of the Seismological Society of America >Ground-motion modeling of the 1906 San Francisco earthquake, part I: Validation using the 1989 Loma Prieta earthquake
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Ground-motion modeling of the 1906 San Francisco earthquake, part I: Validation using the 1989 Loma Prieta earthquake

机译:1906年旧金山地震的地面运动模拟,第一部分:使用1989年Loma Prieta地震进行的验证

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摘要

We compute ground motions for the Beroza (1991) and Wald et al. (1991) source models of the 1989 magnitude 6.9 Loma Prieta earthquake using four different wave-propagation codes and recently developed 3D geologic and seismic velocity models. In preparation for modeling the 1906 San Francisco earthquake, we use this well-recorded earthquake to characterize how well our ground-motion simulations reproduce the observed shaking intensities and amplitude and durations of recorded motions throughout the San Francisco Bay Area. All of the simulations generate ground motions consistent with the large-scale spatial variations in shaking associated with rupture directivity and the geologic structure. We attribute the small variations among the synthetics to the minimum shear-wave speed permitted in the simulations and how they accommodate topography. Our long-period simulations, on average, under predict shaking intensities by about one-half modified Mercalli intensity (MMI) units (25%-35% in peak velocity), while our broadband simulations, on average, under predict the shaking intensities by one-fourth MMI units (16% in peak velocity). Discrepancies with observations arise due to errors in the source models and geologic structure. The consistency in the synthetic waveforms across the wave-propagation codes for a given source model suggests the uncertainty in the source parameters tends to exceed the uncertainty in the seismic velocity structure. In agreement with earlier studies, we find that a source model with slip more evenly distributed northwest and southeast of the hypocenter would be preferable to both the Beroza and Wald source models. Although the new 3D seismic velocity model improves upon previous velocity models, we identify two areas needing improvement. Nevertheless, we find that the seismic velocity model and the wave-propagation codes are suitable for modeling the 1906 earthquake and scenario events in the San Francisco Bay Area.
机译:我们计算了Beroza(1991)和Wald等人的地震动。 (1991年)使用四个不同的波传播代码和最近开发的3D地质和地震速度模型建立了1989年6.9级洛马普列塔地震的震源模型。在准备对1906年旧金山地震进行建模时,我们使用记录良好的地震来表征我们的地震动模拟再现了整个旧金山湾地区观察到的震动强度以及记录的运动的幅度和持续时间。所有模拟都生成与破裂方向性和地质结构相关的大范围空间振动变化一致的地震动。我们将合成材料之间的细微差异归因于模拟中允许的最小剪切波速度以及它们如何适应地形。我们的长期模拟平均预测的震动强度约为修正的Mercalli强度(MMI)单位的一半(峰值速度的25%-35%),而我们的宽带模拟平均预测的震动强度为四分之一的MMI单位(峰值速度为16%)。由于源模型和地质结构的错误,与观测值的差异会出现。对于给定的源模型,整个波传播代码中合成波形的一致性表明,源参数的不确定性往往会超过地震速度结构中的不确定性。与早期的研究一致,我们发现滑动源在震源西北和东南更均匀分布的源模型比Beroza和Wald源模型都更可取。尽管新的3D地震速度模型比以前的速度模型有所改进,但我们确定了两个需要改进的地方。尽管如此,我们发现地震速度模型和波传播代码适合于模拟1906年旧金山湾地区的地震和情景事件。

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