Abstract: The 14 November 2001 M_S 8.1 Kunlun earthquake at northern Tibet is the largest earthquake that occurred in the Chinese continent since 1950.We apply a three-dimensional(3-D)finite element numerical procedure to model the coseismic displacement and stress fields caused by the earthquake dislocations,which are constrained by field investigations.We then further investigate the stress interaction between the M_S 8.1 earthquake and the intensive aftershocks.Our primary calculation shows that the coseismic displacement field is centralized around the east Kunlun Fault zone.And the attenuation of coseismic displacements on the south side of Kunlun Fault zone is larger than that on the north side.The calculated coseismic stress field also indicates that the calculated maximal shear stress field is centralized around the east Kunlun Fault zone,and the directions of the coseismic maximal principal stress are contrary to that of the background crustal stress filed of Tibet Plateau.It indicates that the earthquake relaxes the crustal stress state in Tibet Plateau.Finally,we study the stress interaction between the M_S 8.1 earthquake and its intensive aftershocks.The calculated Coulomb stress changes of the M_S8.1 great earthquake are in favor of triggering 3 aftershocks.

Key words: Kunlun Shan M_S8.1 earthquake, coseismic displacement, coseismic stress, numerical simulation

摘要： 根据野外调查得到的地震破裂以及同震位错分布,利用三维有限元模型研究了昆仑山口西M_S8.1地震的同震位移场和同震应力场的分布,讨论了震后地震活动与同震应力场变化的关系。模拟的M_S8.1地震同震位移场显示,东昆仑断裂带南北两侧的同震位移衰减程度存在差异,断裂带南部的同震位移衰减大于北部同震位移的衰减;同震应力场研究结果则表明,M_S8.1地震的同震最大剪切应力主要集中在东昆仑断裂带的周边地区,最大剪切应力等值线沿断裂带密集分布,形成了高梯度带。M_S8.1地震的发生使青藏活动地块区的地壳应力发生了剧烈的变化,可能导致研究区的地壳应力场得到松弛。库伦破裂应力的研究表明,昆仑山地震对其后发生的5次强余震有一定的触发作用,昆仑山口西M_S8.1地震可能也触发了2003年的德令哈6.6级地震。

关键词: 昆仑山口西M_S8.1地震, 同震位移, 同震应力, 数值模拟