Abstract: Studies of the properties of seismogenic structures play an important role in delineation of potential earthquake source and in determination of parameters of seismic activity. The location,direction,size and the maximum potential earthquake magnitude of a seismogenic structure can be used separately to determine the location,direction,extent and upper limit magnitude of the related potential earthquake sources. The recurrence behavior of large earthquakes on seismogenic structures is closely related to the estimation of the annual average occurrence of the high magnitude grade earthquakes. In consideration of the spatial heterogeneity of seismicity,two-grade delineation of potential earthquake source has been adopted in seismic hazard assessment in China since the late 1980s. Moreover,a relatively large region is usually taken as the seismictiy statistical unit (seismic region or seismic zone) in order to gain sufficient seismic data,so that it might contain some seismotectonic blocks with different background earthquake magnitudes. For the sake of more reasonable seismic hazard assessment,it is necessary to consider these seismotectonic blocks as the second grade potential earthquake sources,which are then subdivided into the third grade potential earthquake sources. On the basis of research on the recurrence behavior of large earthquakes on seismogenic structures,this paper proposes a method for calculating the annual average occurrence of the high magnitude grade earthquakes by applying the equivalent probability transferring in the predicted time scale. This method may greatly enhance the reasonability of seismic risk assessment. The frequency insufficiency of the second grade magnitude earthquakes of potential earthquake sources and the spatial inhomogeneity of seismogenic structures,as well as their applications to determining the parameters of potential earthquake sources are also discussed in this paper.

Key words: potential earthquake sources, properties of seismogenic structures, seismic hazard assessment

摘要： 发震构造特性是潜在震源区划分及其地震年发生率确定的重要依据。潜在震源区除了反映“未来具有发生破坏性地震的地区”的内涵外,还应反映高震级档地震具有相似复发特征的涵义。由于在地震活动性参数统计单元内,有一些具有不同本底地震的活动构造块体,为更好地反映地震活动的空间不均匀性,考虑潜在震源区的三级划分是有必要的。通过分析潜在震源区内高震级档地震的复发特征,计算预测时段内潜在震源区的高震级档地震的发震概率,采用预测时段内概率等效转换获得地震年平均发生率的方法,有助于在中国地震危险性分析框架内考虑潜在震源区的强震复发特性。另外,文中还对潜在震源区内特征地震次级震级档频度不足的特性和发震构造上强震非均匀性在地震危险性分析中的应用问题进行了探讨。

关键词: 潜在震源区, 发震构造特性, 地震危险性分析