Abstract: In this paper, the definition of the lower-limit magnitude is recommended, then on the basis of analysis of its determination in connection with real data of some earthquakes, the difference between the lower-limit magnitude and the minimum magnitude considered in seismic harzard evaluation is pointed out. The lower-limit magnitude is commonly 4, but the minimum magnitude may be lower. Thus, for the facilities with specific safety requirement, such as nuclear power plant, a substitution of lower-limit magnitude 4 for the minimum magnitude may be unsafe.

Key words: Nuclear power plant siting, Lower-limit magnitude, Minimum magnitude

摘要： 从起算震级的定义出发,在分析其确定依据的基础上,结合实际震例,指出起算震级与工程场地地震危险性评价所关心的最小震级是两个不同的概念,起算震级可以取为4.0,但是,最小震级可能会是更小的震级,因此,对核电厂这类具特殊安全性要求的设施,以起算震级4.0代替最小震级,是偏于不安全的。

关键词: 核电厂选址, 起算震级, 最小震级