地震发生的成丛模式及其在地震危险性分析中的应用

为了反映地震发生过程中的非平稳和成丛特性,文中将考虑丛中心非平稳的成丛过程应用于地震危险性分析。在推导给定时间段内地震次数分布的计算公式时,文中假设丛过程的发生率随时间变化按幂指数和周期函数形式变化,丛中事件发生的次数分布服从截头的离散Pareto分布,丛中事件相对于丛的发生时间服从指数分布。文中给出了当地震发生为非平稳和成丛过程时进行地震危险性分析的一般方法和计算步骤。最后,文中还就一个震源的情况初步探讨了模型在特殊情况下各种参数对地震危险性分析结果的影响,指出忽略前震和余震的影响可能低估所考虑场地面临的危险性。

THE CLUSTERING MODEL OF EARTHQUAKE OCCURRENCE AND ITS APPLICATION IN SEISMIC RISK ANALYSIS

In order to reflect the non-stationary and clustering properties in the series of earthquake occurrence, a Rind of clustering random process concerned with non-stationary property of the process of clustering center has been used in sesimie risk analysis. It is assumed that the variation of occurrence rate of the process of clustering center with time follows power function and periodic function and that the probability distribution of number of events in a seismic cluster follows truncated discrete pereto distribution and that the relative occurrence times, counted from clustering center, of the events in series follow exponential distribution. The general methodology and computing steps for seismic hazard analysis have been pointed out when taking non-stationary and clustering process as recurrence model of earthquake. In addition the influences of the various parameters on the results of seisrnie hazard analysis have been discussed in a special case of clustering model. As a result it is pointed out that the seismic risk for a given site could be underestimated if the influence of pre-earthquakes and aftershocks are neglected.