沂沭断裂带北段全新世活动断层的发现及其意义

摘要

Yishu fault is a large scale active fault.It is the largest earth quake activity belt in eastern China.Regional geological survey with the scale of 1∶ 50000 has been carried out in northern Weifang.2 Holocene faults have been found in Yujiashanxia and Tianzhuang.Its distribution, occurrence, characteristics, activity time and its relationship with shallow earthquake have been studied.It is showed that the Holocene faults are normal faults formed under the action of tension.It has the same characteristics with the faults in bedrock areas.It is regarded that Anqiu-Juxian fault and Tangwu-Gegou fault have obvious inheritance or derivative relations.At the same time, based on the fact that faults cut through late Pleistocene Dazhan group, Holocene Heituhu group and Baiyunhu group, and covered with artificial deposits, it is determined that fault formation time is in about 2.1Ka, and has good correlation with seismic activity.The discovery of Holocene faults in northern section of Yishu fault zone has important significance to study the Neotectonic movement and seismic hazard assessment in southern Laizhou Bay.%沂沭断裂带是一条至今仍在活动的大型活动断层,也是中国东部最大的地震活动带.潍坊北部开展了1∶5万区域地质调查,在于家山下及田庄一带新发现了2条全新世断层,对其分布、产状、运动性质、活动时间及其与浅层地震的关系进行了研究.结果表明,全新世断层多为拉张作用下形成的正断层,具有与基岩区断裂相一致的特征,认为其与沂沭断裂带主干断裂安丘-莒县断裂和鄌郚-葛沟断裂有明显的继承性或派生性关系.同时,依据断层切割了晚更新世大站组、全新世黑土湖组及白云湖组,又被人工堆积物所覆盖,判断断层形成时间距今2.1Ka,并且与地震活动有很好的相关性.沂沭断裂带北段全新世断层的发现,对莱州湾南岸的新构造运动研究和地震危险性评价有重要意义.