相对局部区域震源参数随机不确定性经验关系研究

Empirical relationship of stochastic uncertainty of source parameters in relative local area

  • 摘要: 在进行未来破坏性地震的强地面运动数值模拟时,震源参数选取的准确性对地震动预测的结果影响很大。震源参数的确定存在很多不确定性因素,既包含随机的不确定性因素,又包含认知的不确定性因素。本文在大量地震事件及文献调研的基础上,运用统计学方法对具备随机不确定性特征的震源参数进行统计研究,以震源参数经验公式的形态建立解释其随机性和不确定性的数学模型。为了研究局部地区震源参数的定标关系特征,获得更加适用于局部地震密集区域,尤其是包含中国大陆地区在内的局部区域的震源参数的经验关系,本文从GCMT地震目录中选取了1 700多个MW≥5.5的地震事件,运用统计学方法研究地震密集地区的震源参数经验关系,包括震级、地震矩、破裂面积等,增加了相对较大的局部范围内凹凸体的地震样本数量,从统计学角度计算更加适合局部区域的震源参数的经验关系。统计结果表明:局部区域震例获得的震源参数的经验关系与不限区域震例获得的经验关系存在差异,尤其是涉及到断层破裂面积、凹凸体相关参数时差异较大,局部区域内震例获得的震源参数的经验关系将更具有代表性。应用本文获得的相对局部区域的经验公式计算未来破坏性地震的强地面运动所需的震源参数时,获得的地震动预测结果将更能体现目标区域真实的地震动特征,进而提高地震动预测结果的可靠性。

     

    Abstract: In the numerical simulation of strong ground motion of future destructive earthquakes, the accuracy of source parameters selection has a great impact on the results of ground motion prediction. There are many uncertain factors in determining source parameters, including both random and cognitive uncertainties. Based on a large number of seismic events and literature researches, this paper focuses on statistical analysis of source parameters with random uncertainty characteristics by using statistical methods. Through regression analysis, a mathematical model is established to explain the randomness and uncertainty of source parameters in the form of empirical formula. In order to study the scaling relation characteristics of source parameters in local regions, we get more empirical relations which are more suitable for local seismic densely regions, especially those of the local regions including the Chinese mainland. This paper more than 1 700 seismic events with MW≥5.5 are selected from the global CMT catalogue. The empirical relationship of source parameters in earthquake intensive areas is studied by using statistical methods, including focal depth, magnitude, seismic moment, rupture area, etc. The number of seismic samples of asperity in a relatively large local range is increased, so as to obtain more suitable experience for local areas to calculate source parameters from the perspective of statistics relationship. The statistical results show that there are differences between the empirical relationship of source parameters obtained from local earthquake cases and those obtained from unlimited regional cases, especially when it comes to fault rupture area and asperity related parameters. The empirical relationship of source parameters obtained from local earthquake cases is more representative. When using the empirical formula obtained in this paper to calculate the focal parameters required for the strong ground motion of future destructive earthquakes, the ground motion prediction results will better reflect the real ground motion characteristics of the target area. It could improve the reliability of the ground motion prediction results.

     

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