用7级以上强震的年次数表征的全球地震活动性变化的范围非常宽(图1)。地震频次变化曲线似乎是一个随机过程的体现,在几十年内这条曲线可能是稳定的。全球和局部地区地震活动动态总体统计稳定性的假定对地震区划和地震危险性评定是一个普遍的认识。然而,图1已显示出,在 The range of changes in global seismicity characterized by the annual number of earthquakes of magnitude 7 and above is very wide (Figure 1). The curve of seismic frequency seems to be a manifestation of a random process, which may be stable for decades. Assumptions on the overall statistical stability of seismic activity in the world and in parts of the world are generally recognized for seismic zoning and seismic hazard assessment. However, Figure 1 has shown that at