汶川地震对龙泉山断裂地震发生概率的影响研究  

The research in the change of the earthquake occurrence probability in Longquan Shan fault after the Wenchuan earthquake

作　　者：钱琦[1] 韩竹军[1] 

机构地区：[1]中国地震局地质研究所国家地震活断层研究中心,北京100029

出　　处：《地球物理学进展》2011年第2期489-497,共9页Progress in Geophysics

基　　金：科学技术部国际科技合作项目;汶川地震区活动断层发震习性鉴定与重建避让带宽度研究(2009DFA21280)资助

摘　　要：通过构建汶川M_s8.0级地震震源断层模型和龙泉山断裂模型,计算龙泉山断裂在汶川地震后的库仑应力变化,结果显示:汶川地震使龙泉山断裂北部(A区)库仑应力增大0.46～0.58 bars,中部(B区)库仑应力增加0.12～0.17 bars,南部(C区)基本上无库仑应力变化.汶川地震后至2010年1月龙泉山断裂沿线的M_s≥1.6级小震活动频度变化与库仑应力变化量分布特征相一致,汶川地震对龙泉山地区的地震活动具有明显的触发作用.应用速率/状态摩擦定律,计算了汶川地震后龙泉山断裂未来10年的预期地震发生概率.其中,A区5.0≤M_s<6.0级地震发生概率为63～77%,汶川地震前为18～32%;B区未来10年5.0≤Ms<6.0级地震发生概率为33～50%,汶川地震前为18～32%;C区在汶川地震前后5.0≤M_s<6.0级地震发生概率基本无变化,为18～28%.龙泉山断裂沿线的库仑应力变化量明显地改变了该地区不同区段未来地震的发生概率.通过预期地震活动率与背景地震活动率的比值图像分析,表明汶川地震后该区域94.2%的小震都发生在地震活动率增加区,这也部分地验证了未来10年地震发生概率预测结果的合理性.For calculating the change of the Coulomb Stress in Longquan Shan area during the Wenchuan earthquake, we establish the seismic source fault model and the Longquan Shan fault model. The result indicate that the Coulomb stress change of the northern section of the Longquan Shan fault （Zone A） is increased by 0.46-0.58 bars, that of the middle section （Zone B） by 0. 1240.17 bars, and that of the southern section （Zone C） shows almost no change. The epicenter distribution feature of Ms≥1. 6 small earthquake after the Wenchuan earthquake is consistent with the distribution of the Coulomb stress change. Obviously, the seismicity in the Longquan Shan area is triggered by the Wenchuan earthquake. We then use the rate/state friction law to forecast the occurrence probability of future earthquakes in the study region for the next decade. The result is： The earthquake occurrence probability in Zone A is estimated to be 63-77% for 5.0≤Ms〈6.0 shocks during the next decade, and it is 18-32% before the Wenchuan earthquake~ The earthquake probability in Zone B is to be 33~50% for 5.0≤Ms〈6.0 shocks during the next 10 years, and it is 18- 32 % before the Wenchuan earthquake; The earthquake probability in Zone C is estimated to be 18-28% for 5.0≤Ms〈6.0 shocks during the next decade, and it is the same as it before the Wenchuan earthquake. The change of the Coulomb stress change the earthquake probability obviously in different section along I.ongquan Shan fault. The ratio image between the expected seismicity rate and the background seismicity rate, shows that 94. 2 %0 small earthquake after the Wenchuan earthquake is in the increased seismicity zone, which is validating the result of the expected seismicity rate next decade is resonable.

关 键 词：汶川地震 龙泉山断裂 库仑应力变化 速率/状态摩擦定律 地震活动率 地震发生概率 

分 类 号：P315[天文地球—地震学]