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

摘要： 郯庐断裂带是中国东部最主要的一条活动断裂带。在该断裂带中部,沂沭断裂东地堑的潍坊—嘉山段中发育了1条长360km的全新世活动断裂带(F₅),在该全新世断裂带的北段和中段分别发生了公元70年的安丘地震和公元1668年的郯城地震。2003年底我们考察沭河断裂带时,在莒县境内发现了1条长约7km的地震破裂带,作为活动断层应该归属于F₅断裂带,但其是一条独立的地震破裂段还是归属于1668年郯城8.5级地震破裂带有待于进一步的研究。尽管如此,探槽揭示出的上覆未经破坏的地层的¹⁴C年代表明,该破裂带在(2140±190)aBP以来没有过活动,因此我们认为其作为1条独立破裂段的可能性较大。

关键词: 郯庐断裂带, 胡家孟晏地震破裂带, 古地震