永登5.8级地震前后的重力场动态图像特征研究

STUDY OF THE DYNAMIC PATTERN CHARACTERISTICS OF GRAVITY FIELD AROUND YONGDENG EARTHQUAKE M s 5.8

对北祁连河西地区１９９２～１９９７年的重力资料进行了处理分析，从动态的观点研究了永登地震前后重力场的图像演化特征。结果表明：①重力场动态图像较清晰地反映了本区重力场由永登地震孕育的非均匀态（１９９２～１９９４）—发震（１９９４～１９９５）—震后恢复（１９９５～１９９７）的演化过程；②重力变化与构造环境有关；永登地震前后重力场动态图像较好地反映了永登地震孕育、发生过程中断层的控震和发震构造活动引起的重力变化；③重力变化与所处的区域布格重力异常背景场有关；④重力动态图像较清晰地反映了本区重力场在地震孕育、发生过程的重力“源兆”和“场兆”特征。

The gravity datum from 1992 to 1997 in North Qilian Hexi region are analyzed and the pattern evolution characteristics of gravity field before and after Yongdeng earthquake are studied by dynamic viewpoint. The results show that: (1) the dynamic patterns of gravity field mirror clearly the evolution process of gravity field: non homogeneous state (1992～1994)-earthquake occurrence (1994～1995)-postseismic recovery (1995～1997). (2) Gravity changement is related with tectonic environment before and after earthquake, and the dynamic pattern reflects well the control effect of fault movement and its influence on gravity changement in seismogenic process. (3) Gravity changement is correspended with abnormal background field of regional Bouguer gravity. If gravity changement is similar to background changement, the stress field is strengthened, otherwise, the stress field is weakened. (4) Gravity dynamic patterns reflect clearly the features of “source precurssor” and “field precussor” in seismogenic process.