工程活动断裂鉴定的时限标准讨论

DISCUSSION ON THE TIME CRITERION FOR IDENTIFYING ENGINEERING ACTIVE FAULTS

鉴定工程活动断裂时限标准的制订需考虑科学性与工程安全性原则。活动断裂时限的确定依赖于对构造活动阶段性与重复性的认识 ,通过对中国大陆晚第四纪以来构造变形与断裂活动性特点的综合分析研究 ,得出了晚更新世晚期 (约距今 3万年 ) ,中国大陆发生了一次广泛的构造变动 ,经历这次构造变动后 ,各地的构造变形特征进入了一个新的阶段 ,其总体活动性质与活动强度没有大的改变 ,这一结果是确定工程活动断裂时限的科学基础。从工程安全性考虑 ,在中国大陆将活动断裂的时限定为晚更新世以来活动过的断裂偏于保守 ;定义为全新世以来活动过的断裂又存在较大的风险。而将晚更新世晚期 (约距今 3万年 )作为鉴定活动断裂的时限从科学意义上有其合理性 ,并符合工程安全性需要。但对一些安全性要求极高的重大工程 ,相关活动断裂的鉴定时限以晚更新世 (约距今 12万年 )

In engineering geological practice, the evidence to identify a fault as an active one is the latest time at which the fault ruptured the surface or subsurface if no other data are available. So drafting of the time criterion in a region is a key work with had better be based on both scientific and engineering safety consideration. The time criterion depends on our understanding to some extent on the periodical and repeatable features of tectonic movements. There occurred a widespread tectonic movement in late Pleistocene (about 30 thousand years B.P.) in China. The tectonic deformation have entered a new stage since then. This fact is the scientific basis for determining the time criterion. Therefore, the time criterion determined on the basis of it means that fautl activated or reactivated in the past 30 thousand years could be identified as engineering active ones in continent of China.