【摘要】 根据对龙高半岛主要断裂与上覆地层的切割关系考察、浅层地震勘探、断裂两侧等时地貌面的分布调查等资料,分析了断裂第四纪以来的活动特征,并探讨了地震活动与断裂活动的关系。研究结果表明:中楼-东瀚断裂(F1)、高山断裂(F2)和海口-江阴断裂(F4)属有地质、地貌证据的中更新世活动断裂;三山断裂(F3)属浅层地震勘探确定的早中更新世活动断裂;福清断裂(F5)和东张断裂(F6)属断层物质TL测年结果确定的早中更新世活动断裂。从区内≥3级中小地震沿龙田-江镜地堑边界的分布特点看,可能与三山断裂和海口-江阴断裂活动有关。更多还原

【Abstract】 The paper discusses the characteristics of the fault activities since Quaternary and the relation between the seismicity and faults activities,basing on the analysis of Quaternary strata overlying the main faults of Longgao peninsula,shallow seismic exploration,distribution of geomorphic surfaces on both sides of the faults.The results show:1)The Zhonglou-Donghan Fault(F1),Sanshan Fault(F3)and Haikou-Jiangyin Fault(F4)are the middle Pleistocene active faults instead of the late Pleistocene active faults as considered before.2)The Zhonglou-Donghan Fault(F1),Gaoshan Fault(F2)and Haikou-Jiangyin Fault(F4)incise the middle Pleistocene eluvial-deluvium,and the late Pleistocene deluvium overlying the faults wasn’t offset.The geomorphic surfaces of terrace T3 formed in the middle or late stage of the late Pleistocene((4～1.8)×104aBP)and distributed on both sides of the faults have an elevation of 50m above sea level,and they haven’t differential changes.These indicate that they belong to the middle Pleistocene active faults and have been inactive since the late Pleistocene.The Sanshan Fault(F3)controls the eastern border of the Longtian-Jiangjing horst.The shallow seismic exploration results show that the bedrock surface is undulate slightly,the east side of the fault is higher,while the west side is lower,relatively.But the fault doesn’t incise the overlying middle Pleistocene eluvium or the late Pleistocene marine deposit.The elevation above sea level of geomorphic surfaces of terrace T3 is 50m on both sides of the fault without any change,showing that the fault is the early or middle Quaternary active fault and inactive since the late Pleistocene.The Fuqing Fault(F5)controls the development of the Fuqing basin and the Yuxi bay plain.According to the TL dating result of selvage and quartz vein,the latest active age of the fault is the middle or late stage of the middle Pleistocene.The geomorphic surfaces of terrace T3 on both sides of the fault keep the same elevation of 50m,showing that the fault belongs to the early or middle Pleistocene active fault and has been inactive since the late Pleistocene.The Dongzhang Fault is the border line between the middle or low mountains in the west and the hills in east,topographically.On some segments,it also controls the strike of mountains and the development of valleys.According to the TL dating result of fault material,the latest active age of the fault is the middle Pleistocene,so it belongs to the early or middle Pleistocene active fault.3)The grade Ⅲ isochronous geomorphic surfaces formed in the middle or late stage of the late Pleistocene((4～1.8)×104aBP)are used as an important marker for discriminating fault activities,it provides reliable foundation for determining the age of faults activities.4)The regional historical or modern moderate and small earthquakes of magnitude equal to or larger than 3.0 always occurred in the vicinity of the Sanshan Fault(F3)and the Haikou-Jiangyin Fault(F4)developed on the two boundary sides of the Longtian-Jiangjing horst.Although the magnitude isn’t large,the earthquakes are probably related to the activities of the two faults.There exists the possibility of occurrence of moderate or strong earthquakes of magnitude 4.0～5.0 in the region in the future,therefore,monitoring should be reinforced.更多还原