滇西实验场区地壳密度时变特征与强震机理研究

利用重力与水准资料分析研究了滇西背景单层密度变化图像和1985～1992年单层密度时变特征，结果显示其与断裂活动、地震活动明显相关，特别是1996年丽江地震的孕育可能与洱源至剑川或鹤庆的串珠状低波数时变异常带及背景地壳密度变化梯级带有关。基于此，结合已有地震前兆或孕育模式，从地壳运动角度初步提出了地壳内部密度时变的强震前兆模式或发震机制。

The Characterastics of Crustal Density Change in Time and Strong Earthquake Causal Mechanism in Western-Yunnan

The repeated gravity and leveling data in the Western Yunnan are analyzed.The background density changes′ picture and 1985～1992′s picture of the single layer density changes are computed in this area.The results show that they are related to the fault motion and the seismic activity,and the gestation of Lijiang earthquake (1996,ML=7.0) may be related to the gradient belt of the background density changes and the belt of time change density anomaly from Eryuan to Jianchuan in which the wave numbers are low and the anomalies distribute like a string of beats.Based on the above,the strong earthquake precursor or causal mechanism on the time changes of crustal density is provided preliminarily from the crustal movement combining with previous earthquake precursor or gestation mode.