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A Generalization of the Stochastic Summation Scheme of Small Earthquakes to Simulate Strong Ground Motions
Pure and Applied Geophysics ( IF 2 ) Pub Date : 2020-05-18 , DOI: 10.1007/s00024-020-02499-9
Farhad Sedaghati , Behrooz Tavakoli , Shahram Pezeshk

A generalization of the stochastic summation scheme of small earthquakes following a general form of the source spectrum ( ω − n ) model is developed to estimate the proper probability density functions for rupture propagation over the fault and to simulate site-specific strong ground motions in two independent stages. The probability density functions for rupture propagation are first developed for a single-corner-frequency source model, and then extended to multiplicative and additive double-corner-frequency source models to partially account for the effects of finite-fault rupture such as fault geometry, rise time, and rupture time on ground motions, and to better match observed Fourier amplitude spectra (FAS). The generalized two-stage stochastic summation scheme developed in this study can be used to simulate realistic strong-ground-motion time histories from small events, represented as empirical Green’s functions (EGFs), by specifying only two source parameters of the seismic moment and stress drop for a given site. The proposed two-stage stochastic summation schemes are tested using numerical examples following the theoretical source models as well as observed ground motions of the 2011 M w 9.0 Tohoku earthquake in Japan and the 1994 M w 6.7 Northridge earthquake in California to verify the applicability of the approach. Comparisons between the observed and simulated time histories for these two earthquakes, their response spectra, and FAS show satisfactory performance of the proposed approach for engineering purposes. The results of these comparisons indicate that the proposed stochastic summation of small events as EGFs can adequately replicate observed ground motions and evaluate uncertainties in ground motions with the generation of many time history realizations corresponding to a multitude of possible rupture processes . The proposed approach can also be used to generate multiple realistic acceleration time histories matched on average to the target response spectra for use in earthquake performance design, and to develop ground-motion models for low-seismicity regions, where there is a lack of recording of strong ground motions.

中文翻译:

模拟强地面运动的小地震随机求和方案的推广

开发了遵循震源谱 (ω-n) 模型的一般形式的小地震随机求和方案的推广,以估计断层上破裂传播的适当概率密度函数,并在两个阶段模拟特定地点的强地面运动。独立的阶段。破裂传播的概率密度函数首先是为单角频率源模型开发的,然后扩展到乘法和加法双角频率源模型,以部分考虑有限断层破裂的影响,如断层几何、上升时间和地面运动的破裂时间,并更好地匹配观察到的傅立叶振幅谱(FAS)。本研究中开发的广义两阶段随机求和方案可用于模拟来自小事件的真实强地震动时间历程,以经验格林函数 (EGF) 表示,通过仅指定地震矩和应力的两个源参数删除给定的站点。根据理论震源模型以及 2011 年日本 9.0 兆瓦东北地震和加利福尼亚州 1994 年兆瓦 6.7 北岭地震的观测地面运动,对所提出的两阶段随机求和方案进行了测试,以验证该方法的适用性。方法。这两次地震的观测和模拟时间历程、它们的响应谱和 FAS 之间的比较表明,所提出的方法在工程方面具有令人满意的性能。这些比较的结果表明,建议将小事件随机求和作为 EGF 可以充分复制观测到的地面运动并评估地面运动中的不确定性,并生成与多种可能的破裂过程相对应的许多时程实现。所提出的方法还可用于生成多个与目标响应谱平均匹配的真实加速度时间历程,以用于地震性能设计,并为缺乏记录的低地震地区开发地面运动模型。强烈的地面运动。
更新日期:2020-05-18
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