汶川地震对周边断层的库仑应力和发震概率影响的定量研究

QUANTITATIVE STUDY ON INFLUENCE OF WENCHUAN EARTHQUAKE ON COULOMB STRESS AND EARTHQUAKE PROBABILITY OF THE FAULTS AROUND

利用2008年汶川震前的GPS速度场,计算青藏高原东部主要断层背景地震活动性和发震概率,然后根据密集的近场同震形变约束的精细的汶川地震破裂模型,分析汶川地震引起的周边断层库仑应力的变化,并对应力扰动后周边断层发震概率的变化进行定量估计。研究表明,鲜水河断裂道孚-康定段有明显的应力增加,最大应力增加值达0.67 bar;东昆仑断裂、嘉黎察隅断裂、岷江断裂南段和成都德阳断裂东北段应力增加值较小;而鲜水河断裂康定-泸定段、岷江断裂北段、成都德阳断裂西南段和虎牙断裂的应力积累则明显降低。综合震前发震概率和汶川地震应力变化影响估算的应力扰动后的发震概率表明,受汶川地震影响,鲜水河断裂道孚-康定段发震概率明显增加,大震发生概率接近震前的2倍。

Regional tectonic stress field was analyzed with focal mechanism of Wenchuan Earthquake and the fine rupture model which based on near-field displacement field,and probability of earthquake occurrence of the faults around Wenchuan was estimated.The result shows that the Coulomb stress in Daofu-Kangding segment of Xianshuihe Fault increased obviously with the maximum value of 0.67 bar.The stress in east Kunlun fault,Jialichayu fault,southern segment of Minjiang fault and northeast segment of Chengdu-Deyang fault increased a little.The Earthquake also reduced the stress in Maerkang fault,northern segment of Minjiang fault,southwest segment of Chengdu-Deyang fault and Huya fault.Analysis of earthquake occurrence probability based on changes of Coulomb stress indicates that the probability of earthquake occurrence in Xianshuihe fault is increased close to 2 times.