【摘要】 芦山地震的发震构造迄今为止仍不明确。文中基于中国地震局地震预测研究所2008—2009年间布设于龙门山断裂带南段的流动地震台站观测剖面、芦山地震余震精定位结果等地球物理资料对深部构造单元进行了分析;同时基于阶地变形资料、遥感资料、区域地质资料等手段对地表构造变形进行了分析;综合两者建立芦山地震的构造变形模式并研究芦山地震的发震构造。初步认为由于断层面倾角的差异,芦山地震的构造变形模式和中北段与汶川地震有关的主要破裂段的变形模式有所不同。南段前山断裂近直立的断层面最终以对下盘的挤压作用为主,并在下盘地块内形成逆冲断层引发了芦山地震;而北段中央断裂陡倾的断层面使得仍然以上盘的逆冲作用为主。新生逆冲断层的上盘形成了1个活动背斜,第四纪以来该活动背斜之上的阶地面已经发生了显著的变形,该断层最新的1次活动导致了芦山地震的发生。大溪乡与太平镇之间向SE方向凸出的弧形断层段长期以来已经累积了巨大的位移量或构造变形量,是应变释放、构造运动都集中发生的段。芦山地震只是这种构造模式的长期演化过程中的1次地震事件,未来南段前山断裂下盘的这些新生活动逆冲断层仍然具有发生类似地震的危险性。更多还原

【Abstract】 The seismogenic structure of the Lushan earthquake has remained in suspensed until now. Several faults or tectonics,including basal slipping zone,unknown blind thrust fault and piedmont buried fault,etc,are all considered as the possible seismogenic structure. This paper tries to make some new insights into this unsolved problem. Firstly,based on the data collected from the dynamic seismic stations located on the southern segment of the Longmenshan fault deployed by the Institute of Earthquake Science from 2008 to 2009 and the result of the aftershock relocation and the location of the known faults on the surface,we analyze and interpret the deep structures. Secondly,based on the terrace deformation across the main earthquake zone obtained from the dirrerential GPS meaturement of topography along the Qingyijiang River,combining with the geological interpretation of the high resolution remote sensing image and the regional geological data,we analyze the surface tectonic deformation. Furthermore,we combined the data of the deep structure and the surface deformation above to construct tectonic deformation model and research the seismogenic structure of the Lushan earthquake. Preliminarily,we think that the deformation model of the Lushan earthquake is different from that of the northern thrust segment ruptured in the Wenchuan earthquake due to the dip angle of the fault plane. On the southern segment,the main deformation is the compression of the footwall due to the nearly vertical fault plane of the frontal fault,and the new active thrust faults formed in the footwall. While on the northern segment,the main deformation is the thrusting of the hanging wall due to the less steep fault plane of the central fault. An active anticline formed on the hanging wall of the new active thrust fault,and the terrace surface on this anticline have deformed evidently since the Quaterary,and the latest activity of this anticline caused the Lushan earthquake,so the newly formed active thrust fault is probably the seismogenic structure of the Lushan earthquake. Huge displacement or tectonic deformation has been accumulated on the fault segment curved towards southeast from the Daxi country to the Taiping town during a long time,and the release of the strain and the tectonic movement all concentrate on this fault segment. The Lushan earthquake is just one event during the whole process of tectonic evolution,and the newly formed active thrust faults in the footwall may still cause similar earthquake in the future.更多还原