2008年汶川大地震对周围断层的影响  

The influence of 2008 Wenchuan earthquake on surrounding faults

作　　者：万永革[1,2] 沈正康[3] 盛书中[1] 徐晓枫[4] 

机构地区：[1]防灾科技学院,中国河北三河燕郊065201 [2]中国地震局地质研究所地震动力学国家重点实验室,中国北京100029 [3]北京大学地球与空间科学学院地球物理系,中国北京100871 [4]中国地震局地球物理研究所,中国北京100081

出　　处：《地震学报》2009年第2期128-139,共12页Acta Seismologica Sinica

基　　金：国家自然科学基金(40374012,40874022)资助

摘　　要：2008年5月12日的汶川地震明显地改变了区域地震的应力场.理解这种应力场的改变对周围断层构造加载进程和区域地震危险性的改变非常重要.本文以汶川地震的破裂为驱动源,计算了该地震造成周围断层上的静态库仑破裂应力变化.结果表明,汶川大地震的发生使得龙门山断裂北部和最南端、鲜水河断裂最南端、东昆仑断裂、陇县—宝鸡断裂、鄂拉山断裂、白玉断裂、日月山断裂南端、马边—盐津断裂南部、班公错—嘉黎断裂西部、则木河断裂的库仑破裂应力增加,量值达0.00001—0.06MPa.库仑破裂应力增加尤为显著的断裂量值分别为:龙门山断裂的地震断层南端最大增加0.01MPa、北端0.03MPa,秦岭南缘断裂的西南部最大增加0.03MPa,东昆仑断裂的东南部为0.007MPa,地震破裂断层西南部的鲜水河断裂为0.005MPa,西秦岭北缘断裂的天水—宝鸡段为0.004MPa,陇县—宝鸡断裂为0.003MPa.该地震还使得龙日坝断裂、怒江断裂、西秦岭北缘断裂西部、秦岭北缘断裂、庄浪河断裂、日月山断裂北部、海原断裂、岷江断裂、玉树—玛曲断裂、金沙江断裂的库仑破裂应力减少;减少尤为显著的断裂为龙门山断裂的断层破裂段、岷江断裂和鲜水河断裂的炉霍段,其库仑破裂应力减少分别达0.04—0.7MPa,0.001—0.1MPa和0.008—0.01MPa.本次地震在小金河、安宁河和大凉山断裂面上产生的库仑应力变化很小,对断层地震活动没有显著影响.The 12 May 2008 Mw 7.9 Wenchuan earthquake has changed the regional tectonic stress field significantly. It is important to know how such a change affects the tectonic loading process on regional faults and thenceforth the seismic potential of the region. Utilizing the slip distribution of the Wenchuan earthquake as the driving source, we computed the Coulomb stress changes on the neighborhood faults. Our result shows that the Coulomb stress has increased on northern and southern end of the Longmenshan, the southernmost Xianshuihe, East Kunlun, Longxian-Baoji, Elashan, Baiyu, southernmost Riyueshan, central segment of the Mabian-Yanjin, western segment of the Bangongcuo-Jiali, and Zemuhe fault. Most significant increases of the Coulomb stress are： 0.01 MPa and 0.03 MPa at southern and northern end of the Longmenshan fault, 0.03 MPa on western segment of the Qinling Southern Frontal fault, 0. 007 MPa at southeast end of the East Kunlun fault, 0. 005 MPa on the southernmost Xianshuihe fault, 0. 004 MPa on the Tianshui-Baoji segment of the West Qinling Northern Frontal fault, and 0. 003 MPa in Longxian-Baoji fault zone. The earthquake also decreased the Coulomb stress on the Longriba, Nujiang, western segment of the Qinling Northern Frontal, Zhuanglanghe, Haiyuan, Minjiang, and Yushu-Maqu fault. Large relaxation occurred on the ruptured part of the Longmenshan, Minjiang, and Luhuo segment of the Xianshuihe fault, with the Coulomb stress reduction ranging 0. 04--0. 7 MPa, 0. 001--0.1 MPa and 0. 008--0. 01 MPa, respectively. The Coulomb failure stress projected on fault plane of the Xiaojinhe, Anninghe and Xiaojiang fault is nearly zero, indicating no significant influence of the Wenchuan earthquake on these faults.

关 键 词：汶川地震 库仑破裂应力 断层相互作用 震源机制 

分 类 号：P315.727[天文地球—地震学]