汶川8.0级地震的余震触发作用和对断层的应力加卸载作用

Earthquake triggering and stress loading/unloading effect on faults induced by the M_s8.0 Wenchuan earthquake,Sichuan,China

采用可变滑动震源模型,计算和研究了汶川M_S 8.0地震产生的应力变化及对后续6次强余震的应力触发作用,并定量分析了汶川地震对附近活动断裂带的库仑应力加卸载作用。结果显示:汶川地震产生的库仑破裂应力变化分布图案复杂性强,主要由发震断裂复杂的空间展布形态以及震源断层活动具有逆冲兼右旋走滑两种性质决定。汶川地震产生的库仑破裂应力变化对多数强余震存在一定的触发作用。汶川地震的发生对附近的断裂带有不同程度的影响,其中青川断裂中段和北段、岷江断裂南段和灌县-江油断裂南段,主要是以强烈的库仑破裂应力加载作用占主导地位,有利于强余震序列的孕育、加速以至于发生;东昆仑断裂带和鲜水河断裂带受到了轻微的应力加载作用;龙泉山断裂带、华莹山断裂带和西秦岭北缘断裂带主要受到了轻微的卸载作用。

Using the variable slip source models, the Coulomb failure stress change caused by the Ms 8.0 Wenchuan earthquake and its stress triggering effect on aftershocks are calculated. The stress loading/unloading effects imposed by Wenchuan earthquake on nearby active faults are also studied. The results show that： the distribution pattern of Coulomb failure stress changes is complex, due both to the complicated spatial pattern of source rupture, and thrust motion with right-lateral strike slip of source fault. Most of aftershocks are subjected to the triggering effect of Wenchuan earthquake. The stress triggering effect induced by Wenchuan earthquake on nearby active faults are different from each others, the middle and northern segment of Qingchuan fault, the southern segment of Minjiang fault and the southern segment of Guanxian-Jiangyou fault are mainly effected by strong loading, this effects favor to increase seismicity. The loading of East Kunlun fault and Xianshuihe fault are weak. Longquan Mount fault, Huaying Mount fault and West Qinling fault are mainly effected by weak unloading.