福建福清龙高半岛断裂活动性研究
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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。
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.
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.
引文
[1]中国地震局地球物理研究所防灾减灾工程技术研究院,福建地震地质工程勘察院,2004,福建核电后续厂址(前薛、万安)地震初步调查及其安全性评价工作报告。
[2]郑晓云等,1995,福建玄武岩的形成年代。
[1]同433页[1]。
[1]国家地震局地球物理研究所,国家地震局地质研究所,福建省地震局,福建省核电站建设领导小组办公室,1994,福建省惠安山前核电厂厂址地震详细调查及其安全性评价报告。
[1]同436页[1]。
[1]福建省地质局,1977,福州幅、福清幅、南日岛幅区域地质调查报告(1/20万)。
[2]同436页[1]。
丁祥焕,黄卿团,庄进耀.1992.福建省长乐-诏安断裂带晚第四纪活动性的分析[A].见:国家地震局地质研究所编.活动断裂研究(2).北京:地震出版社.224—235.DING Xiang-huan,HUANG Qing-tuan,ZHUANG Jin-yao.1992.Activity of Changle-Shaoan Fault zone in late Quater-nary,Fujian[A].In:Institute of Geology,SSB(ed).Research on Active Faults(2).Seismological Press,Bei-jing.224—235(in Chinese).
丁祥焕,王耀东,叶盛基,等.1999.福建东南沿海活动断裂与地震[M].福州:福建科学技术出版社.DING Xiang-huan,WANG Yao-dong,YE Sheng-ji,et al.1999.Active Faults and Seismicity in the Southeast CoastalAreas of Fujian Province[M].Science and Technology Press of Fujian Province,Fuzhou(in Chinese).
黄卿团,丁祥焕,庄进耀.1999.福建东南沿海晚第四纪断陷构造的形成和发育[A].见:国家地震局地质研究所编.活动断裂研究(7).北京:地震出版社.67—80.HUANG Qing-tuan,DING Xiang-huan,ZHUANG Jin-yao.1999.Formation and development of fault-subsidence tec-tonics in late Quaternary along coastal region of eastern Fujian Province[A].In:Institute of Geology,SSB(ed).Research on Active Faults(7).Seismological Press,Beijing.67—80(in Chinese).
黄卿团,郑韶鹏.2006.福建东南沿海及邻区活动断裂的微地貌研究[J].地球物理学进展,21(4):1099—1107.HUANG Qing-tuan,ZHENG Shao-peng.2006.Micro-relief research on active fault in the coast of southeast Fujian andadjacent area[J].Advances in Geophysics,21(4):1099—1107(in Chinese).
黄卿团,付萍,郑韶鹏.2007.福建东南沿海50m以下的地貌面与断裂活动性[J].地震地质,29(3):578—596.HUANG Qing-tuan,FUPing,ZHENG Shao-peng.2007.The geomorphic surfaces below50metres in Fujian southeast-ern coastal region and the fault activity[J].Seismology and Geology,29(3):578—596(in Chinese).
[2]郑晓云等,1995,福建玄武岩的形成年代。
[1]同433页[1]。
[1]国家地震局地球物理研究所,国家地震局地质研究所,福建省地震局,福建省核电站建设领导小组办公室,1994,福建省惠安山前核电厂厂址地震详细调查及其安全性评价报告。
[1]同436页[1]。
[1]福建省地质局,1977,福州幅、福清幅、南日岛幅区域地质调查报告(1/20万)。
[2]同436页[1]。
丁祥焕,黄卿团,庄进耀.1992.福建省长乐-诏安断裂带晚第四纪活动性的分析[A].见:国家地震局地质研究所编.活动断裂研究(2).北京:地震出版社.224—235.DING Xiang-huan,HUANG Qing-tuan,ZHUANG Jin-yao.1992.Activity of Changle-Shaoan Fault zone in late Quater-nary,Fujian[A].In:Institute of Geology,SSB(ed).Research on Active Faults(2).Seismological Press,Bei-jing.224—235(in Chinese).
丁祥焕,王耀东,叶盛基,等.1999.福建东南沿海活动断裂与地震[M].福州:福建科学技术出版社.DING Xiang-huan,WANG Yao-dong,YE Sheng-ji,et al.1999.Active Faults and Seismicity in the Southeast CoastalAreas of Fujian Province[M].Science and Technology Press of Fujian Province,Fuzhou(in Chinese).
黄卿团,丁祥焕,庄进耀.1999.福建东南沿海晚第四纪断陷构造的形成和发育[A].见:国家地震局地质研究所编.活动断裂研究(7).北京:地震出版社.67—80.HUANG Qing-tuan,DING Xiang-huan,ZHUANG Jin-yao.1999.Formation and development of fault-subsidence tec-tonics in late Quaternary along coastal region of eastern Fujian Province[A].In:Institute of Geology,SSB(ed).Research on Active Faults(7).Seismological Press,Beijing.67—80(in Chinese).
黄卿团,郑韶鹏.2006.福建东南沿海及邻区活动断裂的微地貌研究[J].地球物理学进展,21(4):1099—1107.HUANG Qing-tuan,ZHENG Shao-peng.2006.Micro-relief research on active fault in the coast of southeast Fujian andadjacent area[J].Advances in Geophysics,21(4):1099—1107(in Chinese).
黄卿团,付萍,郑韶鹏.2007.福建东南沿海50m以下的地貌面与断裂活动性[J].地震地质,29(3):578—596.HUANG Qing-tuan,FUPing,ZHENG Shao-peng.2007.The geomorphic surfaces below50metres in Fujian southeast-ern coastal region and the fault activity[J].Seismology and Geology,29(3):578—596(in Chinese).
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