虎门地区的断裂构造特征及近期活动性

THE CHARACTERISTICS OF FAULTED STRUCTURE AT HUMEN REGION OF LOWER REACHES IN PEARL RIVER AND ITS RECENT ACTIVITY

本文以现场调查、岩芯切片分析、土壤汞气测量、^(14)C年代测定及地震台网观测资料为基础,参考前人的工作结果,对虎门区段的断裂发育特征、挽近地质时期的活动性作了分析和论证。发现虎门河道及其两岸发育有北北西、北东东、北西和北东四组断层,其中顺珠江河道发育的北北西组断层活动年代较新,但断续、成组出现,未见贯通性的深、大断裂。所有断裂主要活动于晚更新世晚期以前,晚更新世以来全区缓慢上升,平均上升速度为0.1～0.5毫米/年,某些北北西向断裂存在0.05～0.1毫米/年的逆时针方向的水平错动。历史上未发生破坏性地震,布台观测期间未记录到当地地震。认为虎门大桥区段的地震地质环境比较稳定,发生破坏性地震可能性很小。

Basing on the in situ investigation, core cutting analysis, measurement of soil mercury gas, dating dection of 14C and observating data of seismic network and consulting the results done by our predecessors, the characteristics about the rrft development at Humen region and its geologic activity in the late and recent period are analysed and proved. The results shows that there are four faults, namely, NWN, EEN, WN and EN in the two sides of Humen channel, among them, the fault of NWN at the channel of pearl River has develoed in a new type. It appears disjointed and there is not transfix of deep and big fracture.All of the faults delopee befor the late period of Epipleistocent. Since the Epipleistocent, the region has rised slowly, about 0. 1-0. 5 mm/year. Some faults of NWN stagger against the clockwise, about 0.05-0.1 mm/year. AS there is not any destructive earthquakes in the histroy and no earthquakes in this region were recorded during the investigation,so we think that the environmene of seismogeogy in Humen region is stable and it is not possible that the destructive earhquake will occur in this region.