关键词: 滑动分布, 汶川M_S 8.0地震, 库仑破裂应力变化, 断层相互作用

Abstract: Using the focal mechanisms and slip distribution model of the M_S 8.0 Wenchuan earthquake,we inverted the co-seismic Coulomb failure stress change.The inverted Coulomb stress change based on Chen J's slip distribution model shows that about 83%of its aftershocks lie in regions where the Coulomb stress increased by 0.01MPa,given the receiver fault' strike/dip/rake as 204?/56?/98? respectively.In contrast,the distribution of aftershocks is sparse in areas where the inverted Coulomb stress change is decreased by 0.01MPa.From this we can tell that aftershocks are abundant where the Coulomb stress change rose by more than 0.01MPa,and aftershocks are sparse where the Coulomb stress dropped by a similar amount.This study and the forerunner,Ma et al(2005),demonstrate that even when the source geometry and slip distribution are complex,Coulomb stress change is correlated with the distribution of aftershocks.And its main characteristic is that for most of the region in the northern wall of the fault the Coulomb stress dropped by 0.01MPa and for most of the region in the southern wall of the fault,it increased by 0.01MPa.The tendency of change of the Coulomb stress field is progressed to the direction of N-E and S-W.At last,we calculated the Coulomb stress change on most of the existing faults based on Deng's active fault data.The results show that the Coulomb stress change on several strike-slip faults is decreased by about 0.01MPa,including Maerkang Fault,southeast Chengdu thrust fault,Huya Fault,Min Jiang Fault,west Qinling north-edge fault and Qinling north-edge fault.This means these faults may be less dangerous in future earthquakes.There are several strike-slip faults on which the Coulomb stress change are increased by about 0.01MPa,including eastern Kunlun Fault,northern part of Chengdu thrust fault,Wenxian Fault,and western part of west Qinling north-edge fault.These results are consistent with that of Tom Parsons et al.What brings contradiction is that when comes to Xianshuihe Fault,our results show an increase by about 0.01MPa in the middle part of Xianshuihe Fault,at longitude 101.2皌o 102癊 and latitude 30皌o 31.04癗.The Coulomb stress change in most part of Xianshuihe Fault is decreased,which means the Xianshuihe Fault system has a potential seismic risk lower that it had before the M_S 8.0 Wenchuan earthquake.

Key words: slip distribution, the M_S 8.0 Wenchuan earthquake, Coulomb failure stress change, fault interaction