断层系统中危险断层识别的频次-能量方法及数值模拟

A Frequency-energy method to determine the hazard faults among faults and numerical simulation

断层系统中危险断层的确定对于地震及矿震等自然灾害的预防具有重要的实际意义.在过去通过编写FISH函数对FLAC-3D多方面二次开发的基础上,本文针对实验室尺度含4条断层的岩石标本,开展数值计算工作,阐明了标本在拉伸位移控制加载条件下,五个典型阶段(长期阶段、短期阶段、短临阶段、失稳阶段及失稳后阶段)能量释放的分布规律,统计了标本整体及各条断层上的频次-能量关系(其斜率的绝对值称之为b0值),并确定了断层系统中的危险断层.研究发现,在标本整体失稳之前,在一条长且平直的断层上b0值发生下降及缺失现象,即大事件集中出现或违反常规.本文的研究方法对于复杂断层系统中危险断层识别具有一定的参考价值.

Determination of the hazard faults among a fault system is especially significant for natural hazards ＇ prevention, such as natural and mining earthquakes. Based on the previous written FISH functions in FLAC-3D on several aspects by the first author of the paper, for a sample comprising four faults at a laboratory scale, numerical simulation is conducted. The distribution of the released energy within the sample at five typical stages is presented under the condition of tensile displacement-controlled loading. These five stages include the long-term stage, short- term stage, impending stage, unstable stage, and post-instability stage. The relation between frequency of events and released energy （the absolute value of the slope of the relation is called b0 value） for the overall sample and each fault is calculated respectively, and then the hazard fault is determined. It is found that prior to the sample instability, the decreasing and diminishing b0 value phenomena are observed on a long and straight fault. This means that large events occur simultaneously or they are abnormal. The present method can be used to assess the hazard fault among a complex fault system.