丽江地震前后西南地区定点形变变化的特点分析

研究了1996年2月3日丽江7．0级地震前后西南地区地倾斜观测的特点及与中强地震活动之间的关系。研究结果表明，丽江地震后西南地区地倾斜变化幅度与区域地震活动水平具有逐年减弱的趋势，丽江地震后5年内中强地震都发生在快速变形以后回复的时间段内，而5年之后，中强地震则往往发生在一些快速变化的极值点时刻。在对每次中强地震前形变特征分析的基础上，还研究了短期形变前兆对地震的触发机制，给出了每次地震前短期形变迁移的速度分布。最后讨论了短期形变前兆的非同步性、非遍历性、不可重复性及无记忆性等特性。尽管这些特性可能使得经验地震预测变得更为艰难，但是认识这些特性将可能帮助找到新的预测途径。

THE CHARACTERISTICS OF DEFORMATION IN SOUTHWEST REGION BEFORE AND AFTER LIJIANG EARTHQUAKE

Author has studied the characteristics of ground tilt changes in southwest region before and after Lijiang earthquake occurred on Feb.3, 1996, and their relations with mid-strong earthquakes. The result shows that the annual amplitudes of ground tilt change and seismic activity in southwest china region were decreased after Lijiang earthquake. In 5 years after Lijiang earthquake, all of mid-strong earthquakes occurred beyond a few months interval while the rapid ground tilt changes ended; however, some mid-strong earthquakes occurred around the extremum point of ground tilt rapid change beyond 5 years after the Lijiang earthquake. This phenomenon can be explained by the relaxation time after Lijiang earthquake.This paper also paid much attention to the trigger mechanism of short-term ground tilt changes, and a range of 0.3-1.3km/d velocity of ground tilt migration has been estimated.Finally, the author discussed the characteristics of the short precursory ground tilt before earthquakes that it is inharmony, inergodicity, unrepeatability and dismemorability. Although these characteristics make the experiential earthquake prediction be more difficult, but it can help us to seek for a scientific way.