鲜水河断裂带地震活动特征及强震发生随时间增长概率

作者等仔细分析了鲜水河断裂带从１７２５年到现在的地震资料，并利用乌莫洛夫Ｔ─Ｓ、Ｍ为参数的作图法及强震发生随时间增长概率，绘制了地震活动图件及地震发生概率曲线以及Ｍ─Ｔ图和鲜水河断裂应变释放曲线。根据这些资料可以清楚地看出鲜水河断裂带自１７２５年到现在可分为两个大的活动周期，其中６．０级以上地震有由康定依次向甘孜迁移的特点。在每一个大的地震活动周期中，地震基本上两次重复由康定向甘孜迁移的过程，而且较强地震多发生在第二次迁移过程中，１９８２年甘孜地震标志着断裂带在第二幕地震活动高潮中，中强震已经完成了最后一次由断裂带东南端向西北端迁移的过程。同时考虑到断裂带应变释放曲线的特征，估计鲜水河断裂带目前已进入新的平静阶段。前两个大的活动周期之间，平静了近一个世纪。按历史上地震定向迁移规律，估计在新的活动期地震仍将从康定方向开始，逐步向甘孜发展。

THE SEISMICITY FEATURES OF THE XIANSHUIHE FAULT ZONE AND INCREASING PROBABILITY OF STRONG EARTHQUAKE OCCURRENCE WITH TIME

In this paper the authors analysed carefully the earthquake data of the Xianshuihe fault zone from year 1725 to present and drew seismicity map, probability curve of earthquake occurrence, M-T map and strain release curve of the Xianshuihe fault using Ulomv's drawing method of parameters T-S, M and increase probability of strong earthquake with time. According to these data, it can be clearly seen that there are two big active periods for the Xianshuihe fault zone from year 1725 to now and successive migration feature of more than M6 earthquakes from Kangding to Ganze. In every big active period earthquakes have migrated twice repeatly from Kangding to Ganze on the whole and stronger earthquakes occurred in the second migration process. The Ganze earthquake of 1982 is a sign that medium and strong earthquakes have finished last migration process from southwestern segment to northwestern one of the fault zone in the second episode of seismicity peak period. With considering the feature of strain release curve of the fault zone, we estimate that the Xianshuihe fault zone has entered a new quiet period. The quiet period between the early two big active periods continued for about one century. According to historical regularity of directional earthquake migration we reckon that seismicity will maintain to develop gradually from Kanding to Ganze in new active period.