2008年汶川MS8.0地震对周边断层地震活动的影响

为分析2008年5月12日四川汶川M_S8.0级地震对周边断层地震活动的影响,本文首先基于Burgers体黏滞松弛模型计算汶川M_S8.0级地震引起的库仑应力动态演化,分析认为2008年汶川M_S8.0级地震在周边断层上引起的库仑应力显著增加的主要有四个断层段,分别为鲜水河断裂道孚-康定段、东昆仑断裂东段玛曲段、青川断裂和龙门山断裂南段.而且震后4年内黏滞松弛引起的库仑应力变化量可能与同震变化相当,相当于再发生一次汶川地震所造成的影响,因此震后效应在分析强震影响时不应忽略.本文基于强震引起的库仑应力变化动态演化,结合背景地震发生率、由Dieterich(1994)模型给出地震发生概率,结合相关构造地质、历史地震、余震活动等方面资料的综合分析认为,上述4个断裂段地震危险性由高到低依次为鲜水河断裂道孚-康定段、龙门山断裂南段、东昆仑断裂东段玛曲段和青川断裂.

The impact of Wenchuan Ms8.0 earthquake on the seismic activity of surrounding faults

In order to analyze the effect of Wenchuan M_S8.0 earthquake on the seismic activity of surrounding faults, we calculate the dynamic changes of Coulomb stress caused by the Wenchuan M_S8.0 earthquake with a Burgers viscous relaxation model. Simulation result shows significant increase of Coulomb stress on four majors fault segments, which are Daofu-Kangding section in the Xianshuihe fault, Maqu section in the East Kunlun fault, the southern section of the Longmen Shan fault, and the Qingchuan fault respectively. Furthermore, the Coulomb stress change caused by the post-seismic relaxation during 4 years after Wenchuan M_S8.0 earthquake is so strong that it almost matches to that caused by the co-seismic rupture. That is to say, the effect of the postseismic relaxation is nearly equal to that caused by the Wenchuan earthquake itself. This is a strong evidence that the postseismic relaxation is critically important so it should not be neglected on evaluating the effects of strong earthquake. Taking the postseismic effect into consideration, the probability of seismicity is evaluated by the Dieterich (1994) model based on the dynamic evolution of Coulomb stress and the background seismic rate. Combining the relevant structural geology, historical earthquake, aftershocks activities and some other minor factors, a comprehensive analysis shows that the seismic hazards on the above four fault segments are ranked from high to low as Daofu-Kangding section in Xianshuihe fault, the southern section of the Longmen Shan fault, the Maqu section in East Kunlun fault and the Qingchuan fault.