汶川-映秀M_S8.0地震的地球物理场与动力过程  

Geophysical background field and deep dynamics of the Wenchuan-Yingxiu M_S8.0 earthquake

作　　者：滕吉文[1,2,3] 宋鹏汉 刘有山 Jiwen Teng;Penghan Song;Youshan Liu(Institute of Geology and Geophysics,Chinese Academy of Sciences,Beijing 100029,China;College ofGeoExploration Sicence and Technology,Jilin University,Changchun 100044,China;University of Chinese Academy of Sciences,Beijing 100049,China)

机构地区：[1]中国科学院地质与地球物理研究所,北京100029 [2]吉林大学地球探测科学与技术学院,长春130026 [3]中国科学院大学,北京100049

出　　处：《科学通报》2018年第19期1882-1905,共24页Chinese Science Bulletin

基　　金：国家重点基础研究发展计划(2008CB425700);国家科技支撑计划(0907804078)资助

摘　　要：汶川-映秀M_S8.0大地震发生在当今构造、地震远不如相邻地带的龙门山断裂系上,震间和震后在地表形成了一条长300 km,宽近80 km,发生了70000多次余震的长廊地带,造成了严重的地表破坏和大量人员伤亡,而震前却未见到可视为与大地震发生与发展有因果关系的征兆现象,可是大地震就在这里发生了.多年的研究表明,这次M_S8.0大地震的发生乃是由于印度洋板块与欧亚板块碰撞、挤压,且东构造结向北"顶进"插入青藏高原东北缘力系作用下导致的该区构造、地震均强烈活动,在此背景下:(1)高原腹地壳、幔物质向东运移受阻、应力集中,深部物质重新分异、调整,物质与能量进行强烈交换;(2)震源深处介质属性与结构变异、破裂,且导致重力场的高度不均衡;(3)川西高原,相对低速壳、幔物质在坚硬的四川盆地壳、幔物质阻隔下,沿龙门山陡峭主断裂面相上逆冲,并在龙门山3条不同角度西倾断裂向下收敛处强烈碰撞;(4)震源深处汇聚断裂的形成构成了汶川-映秀M_S8.0大地震的发震断裂.The Wenchuan-Yingxiu MS8.0 earthquake occurred along the Longmenshan fault system where the tectonic and seismic activities are relatively less inactive than its surroundings. After the great earthquake, a dynamic failure corridor zone was formed at the surface, which was about 300 km-long and 80 km-wide and more than 70000 aftershocks occurred. The earthquake caused serious surface damages and large numbers of casualties, but no confirmed precursor phenomena were reported. In the northeastern Tibetan Plateau, geophysicists had applied many kinds of geophysical methods, including the artificial seismic probing, the natural seismic imaging, the gravity probing, and the electric and magnetic methods. Many researchers believed that the crust or mantle shortening is the main dynamic of the MS8.0 Wenchuan-Yingxiu earthquake. However, the evidences were not enough, due to the disadvantage of the geophysical methods, such as the dubious resolution problem and the ambiguous interpretation from colorful results. Based on the previous results and our extensively study, we made a further study on the Wenchuan-Yingxiu MS8.0 earthquake which mainly concentrating on the three issues, including the highly isostatic equilibrium of the Longmenshan fault system, the fine structure and abrupt deep dynamics of the Longmenshan fault zone, and the force source system, the development and occurrence of the Wenchuan-Yingxiu MS8.0 great earthquake. First, we reviewed the gravity filed and response of the boundary in the northeastern margin of Tibetan Plateau. The free-space and Bouguer gravity anomaly were given. The distribution of the theoretical isostatic crustal thickness and the isostatic thickness difference were analyzed. Considering the topography and gravity field of eastern Tibetan Plateau, the Longmenshan zone was far from gravity isostasy. Second, the electrical structures and the S-wave velocity structures were reviewed. We reanalyzed the four artificial seismic sounding profiles. Third, we showed a diagram of the 15±5 km d

关 键 词：汶川-映秀MS8.0大地震 物质与能量交换 壳、幔结构突变 重力不均衡 深部汇聚断裂带-发震断裂 

分 类 号：P315[天文地球—地震学]