Abstract: During the post-disaster recovery in Maoxian country,we found that lacustrine sediments are exposed intermittently ～30km north of the present Diexi barrier lake(Xiaohaizi)along the Minjiang River and its tributaries.According to the study on lacustrine sediments around Qiangyang village,we obtained the evidence of activities of the Minjiang Fault in the Holocene.It is concluded that the tectonic deformation of paleo-lacustrine sediments in Qiangyang possibly reflects multi-time ancient seismic activity of Minjiang Fault zone.It is more accepted that the 1st seismic activity resulted in the formation of dammed paleolake in Qiangyang,and accumulation of the 1st set of lacustrine facies deposits;the 2nd seismic activity led to deformation of the lacustrine facies stratum;the 3rd seismic activity caused the deformation of the 1st and 2nd set of lacustrine facies strata;and the 4th seismic activity ruptured the youngest deposit overlying the lacustrine facies stratum.Total Station Instrument measurements indicate that the vertical displacement of the last ancient seismic activity is about 2.6～3.6m.

Key words: Minjiang Fault, paleo-dammed lake, the Holocene, paleoearthquake

摘要： 在支援茂县汶川地震灾后恢复重建期间,发现在现今叠溪堰塞湖(小海子)上游30km的岷江沿岸及其支流断续有第四纪湖相层出露。通过对羌阳村一带古堰塞湖沉积层的研究,获得了岷江断裂全新世活动的证据。分析认为:岷江断裂沿线古堰塞湖相沉积及其构造变形反映了岷江断裂的多次活动。羌阳桥古堰塞湖沉积及其构造变形可能反映岷江断裂的多次古地震活动。较肯定的是:第1次地震活动导致羌阳桥堰塞湖的形成,堆积第1套湖相沉积;第2次地震活动使湖相层变形;第3次地震活动使第1,2套湖相地层变形;第4次地震活动错断了湖相层之上最新的堆积物。全站仪实测结果表明最后一次古地震活动的垂直位移约为2.6～3.6m。

关键词: 岷江断裂, 古堰塞湖, 全新世, 古地震