利用四川省汶川M_S 8.0地震的震源机制解及滑动分布模型,反演了由汶川地震造成的同震库仑破裂应力变化;从余震效应与断层相互作用的角度对库仑破裂应力变化进行了分析。结果显示:基于滑动分布模型反演的库仑破裂应力变化能较好地反映与余震分布的对应关系,以最大余震断层面参数(走向/倾角/滑动角:204°/56°/98°)为接收断层,反演结果最佳,83%M>4的余震均发生于库仑应力增加约0.01MPa的区域;库仑破裂应力变化的主要特征为断层北盘大部分区域为库仑破裂应力下降区,断层南盘主要为增加区,断层两端均显示库仑破裂应力变化增加,且分别沿NE和SW两个方向发展。最后,基于活断层分布模型,计算由此次地震造成的已存断层面上的库仑破裂应力变化,结果显示多条左旋走滑断裂库仑破裂应力变化值增加。

    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.