【摘要】 通过对2008年5月12日发生的汶川8.0级地震的发震构造——中央断裂映秀—南坝段地震地表破裂、地表形变及断裂上余震迁移等特征的详细调查和分析,结果表明:(1)自映秀至南坝,断层活动方式表现为由逆冲逐渐过渡为逆冲-右旋走滑、再到走滑分量与逆冲分量大致相当,同时断层两盘滑动伴有相对弱旋转活动;(2)在断层总体走向NE向、逆冲为主兼右旋走滑活动方式下,局部表现为走向NW向、逆冲为主兼左旋走滑活动方式;(3)地震裂缝与单侧破裂面关系,以及地表重叠缩短形变特征表明,断层活动、应变能释放是在近EW向区域构造应力及NE向局部构造应力综合作用下的结果.依据断层沿线地表裂缝产状的变化,粗略推出映秀至南坝段主应力方向由SEE向NEE方向变化,与前人使用CAP(Cut and Pasate)方法求出的主余震源机制方向基本一致.更多还原

【Abstract】 According to the surface rupture belts,deformation characteristics,kinematic characteristics and aftershock migration characteristics formed by Wenchuan M_S8.0 earthquake along the Yingxiu-Nanba segment of Central Fault Belt on May 12^th 2008,the research result shows.（1） From Yingxiu to Nanba,the faulting mode changes from reverse-thrusting to reversethrusting with right lateral slipping of comparable amplitude,and is accompanied by a weak rotation between the two walls of the fault;（2） On the whole the NE striking fault is dominated by thrusting with right lateral slipping,while locally there is NW striking thrusting with left lateral slipping;（3） The relation between earthquake cracks and the rupture surface,and the deformation characteristics of the overlapping shortening on the earth’s surface reveal that the rupture and strain energy release resulted from the combined action of regional tectonic stress in near E-W direction and local tectonic stress in NE direction.Based on the attitude change of surface cracks along the fault,we deduce that the direction of principal stress changes from SEE in Yingxiu to NEE in Nanba,which accords with the focal mechanism solutions of the mainshock and aftershocks determined with the CAP （Cut and Pasate） method.更多还原