关键词: 郯庐断裂带, 胡家孟晏地震破裂带, 古地震

Abstract: Tanlu Fault zone is one of the most important active faults in east China. Yishu Fault,the middle section of the Tanlu Fault zone,presents a graben system consisting of two grabens and four main boundary faults. The eastern graben between Weifang and Jiashan is the most active segment of the Tanlu fault zone,along which developed a 360km long Holocene active fault zone (F₅). The F₅ fault zone has been defined as what consists of all Holocene faults in the eastern graben. The Anqiu earthquake of AD 70 and the Tancheng earthquake of 1668 occurred along the northern and middle segments of the Holocene active fault,respectively. We found a 7km long surface rupture between the main boundary faults of the eastern graben in Juxian County,when we made an investigation on the Yishu Fault in 2003. As an active fault,it should belong to the F₅ fault zone. The carbon date of the un-faulted deposit covering the newly-found surface rupture shows that no earthquake has occurred along this rupture since 2 140?190 yr BP. Therefore,we infer that this newly-found surface rupture is independent of the surface rupture of 1668 Tancheng earthquake,although it is necessary to make a further research to verify this inference.

Key words: Tanlu fault zone, Hujiamengyan surface rupture, paleoearthquake