Abstract: We have investigated the ground rupture zone caused by the M 7.3 earthquake of Jiji,Taiwan in 1999 after occurrence of the event.The results indicate that the seismogenic structure of this event is associated with the Chelongpu fault which is an active fault with dominant reverse-dip-slip and a sinistral strike-slip component.The total length of the ground rupture zone is about 80km.The vertical displacement on the ground along the rupture zone is mostly 1.5～3.5m and the hori-zontal displacement 3.0m.It is suggested that decollement between the basement and the cover of the Taiwan foothills has played an important role to the seismogenic fault.

Key words: Jiji earthquake of Taiwan, Earthquake rupture, Active fault

摘要： 野外考察结果表明,1999年9月21日台湾集集大地震是由车笼埔断层发生逆冲作用造成的。地震产生的地表破裂长约80km,具有明显的挤压逆断层特征,其活动方式为具左旋性质的逆倾滑动。实测逆冲断层以30°～50°的角向西北逆冲而上。断层的垂直位移量,南段约2～3m,北段约3～8m;断层的水平位移量,南段0～3m,北段3～5m;垂直断层的水平缩短量,南段2～3m,北段3～6m。从台湾西部麓山带的地质构造剖面分析,地震震源恰好位于台湾西部麓山带中生代基底与其上的沉积盖层的界面的深度,而西部麓山带第三纪地层和其下的基底的分离面为一滑动面(decollement)。在菲律宾海板块的挤压作用下,沿该区中生代基底之上滑动面的错动导致了地震的发生。

关键词: 台湾集集大地震, 地震破裂, 活动断裂