研究了１９９５ 年苍山５２ 级地震前地震时空分布参数Ｒ （ｔ） 图的异常变化， 由Ｒ （ｔ）图清楚的反映出苍山５２ 级地震前地震活动的三个阶段性发展特征。即早期地震活动增强，形成大的孕震空区； 中期在上述背景上地震活动再次向外围扩散并收缩， 地震活动逐渐减弱， 孕震空区缩小； 晚期地震活动出现短平静（１８ 个月无ＭＬ≥２５ 级地震） ； 临震前１８ 天孕震空区内出现３ 个特征前震， 在孕震空区内形成临震地震线 The anomalous change of R (t) plot of the temporal and spatial distribution of earthquakes before the Cangshan MS 5.2 earthquake in 1995 was studied. The R (t) plots clearly reflected the three phases of the seismic activity before the MS 5.2 Cangshan earthquake . That is, the early seismic activity is enhanced to form a large zoning area. In the middle period, the seismic activity once again spreads and shrinks to the periphery, the seismic activity gradually weakened and the seismogenic vacancy shrinks. In the late period, the seismogenic activity is short and quiet (18 months ML≥25 earthquakes); three characteristic foreshocks occurred within 18 days before the earthquake projectile, forming a quake-prone seismic line