丽江7.0级地震重力前兆模式研究

STUDY ON A GRAVITY PRECURSOR MODE OF LUIANG EARTHQUAKE WITH Ms = 7. 0

为了研究1996年丽江M_s7.0地震前地震孕育过程或前兆表现,利用滇西地震实验场内高精度重复重力观测数据,结合地质调查和地球物理推断结果,并考虑到观测数据和模型粗差,采用稳健或抗差-贝叶斯最小二乘算法和多断层位错模型,首次初步反演获得了研究区主要活动断裂滑动的时间变化分布。结果表明,1990～1997年断层运动的时间变化,较好地反映了1996年丽江M_s7.0地震孕育过程。其主要前兆模式图象具有主震余震型特征,遵循地壳内部密度和地壳形变耦合运动模式(简称DD耦合运动模式)。

To study the seismogeny process or the precursory behavior of Lijiang earthquake with Ms= 7. 0 occurred in 1996, we analyze the repeat gravity data with high precision from the Western Yunnan Earthquake Prediction Experiment Area (WYEPEA) and the related results of geology and geophysics survey in this paper. Considering the gross errors caused by observation data and model difference, we have firstly inverted the slip distribution of the main active faults with time based on the robust Baye's least squares estimation and multi-fault dislocation model. The results show that the slip changes of the faults with time from 1990 to 1997 obviously reflect the preparation process of Lijiang earthquake. The images of main precursor mode have the characteristic of main shock-after shock type, which is agreement to the model of coupling movement between crust density and crust deformation (DD mode of coupling movement).