兰州市地震活断层探测新进展
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摘要
文中综述了兰州市地震活断层探测的最新进展情况。通过航、卫片解译,地质地貌调查,地球化学探测,浅层人工地震探测,电法探测,钻孔探测,特别是大型探槽等综合研究,对兰州市7条目标断层的新活动性提出了新的认识。修改了4条断层的最新活动时代,即金城关断层、雷坛河断层、寺儿沟断层和西津村断层等前人提出为QP3活动断层,探测结果为Q1p-Q2P断层;特别是否定了穿过市区的晚第四纪活动的刘家堡断层(Qh)和深沟桥断层(Q3P),明确了马衔山北缘断层西段为晚更新世—全新世活断层,并为1125年兰州7级地震的发震断层。
This paper makes a comprehensive analysis of the recent progress of the seismic active fault prospecting in Lanzhou city. Based on the satellite and aerial photos interpretation,geological and geomorphic investigation,geochemistry prospecting,shallow seismic investigation,resistivity imaging,drilling,especially large-scale trenching along the 7 active fault zones in Lanzhou city,we have achieved very important progress and gained new knowledge about the recent activity of main active faults and deformation features in Lanzhou Basin. The main conclusions are summarized bellow: (1) The Jinchengguan Fault is a thrust fault,constituting the northern boundary of the Lanzhou Tertiary Basin. It is revealed by geophysical prospecting and drilling that the newest strata offset by the Jinchengguan Fault are the early-Pleistocene sandstone and conglomerate,and that the overlying second and third terraces of the Yellow River remain intact. So,it's an early and middle Pleistocene active fault.(2) The Liujiabu Fault and Shengouqiao Fault constitute the northern and western boundaries of the Qilihe Subsidence,respectively. Revealed by geophysical prospecting,drilling and large trenching,they are not faults but lithologic boundaries of different rocks between Pliocene and early Pleistocene.(3) The Leitanhe Fault is the eastern boundary of Qilihe Subsidence,a boundary fault separating the Tertiary Lanzhou Basin into the east and west basins. According to the geophysical prospecting and drilling,the Leitanhe Fault is a thrust fault and its newest activity age is early and middle Pleistocene. It is not active since late Quaternary and does not cut the third terrace of the Yellow River.(4) The Siergou Fault is the southwestern boundary of Lanzhou Basin,a thrust fault too. It's an early and middle Pleistocene active fault and does not offset the forth terrace of Yellow River. While the Xijincun Fault is much nearer to the south margin of Lanzhou Basin and forms the southern boundary of the Tertiary Lanzhou Basin. It's an early Pleistocene fault.(5) The northern margin of Maxianshan Mountains fault is a major seismic fault on the southern margin of Lanzhou Basin,and its movement is characterized by segmentation. The east segment,the Neiguanying sub-fault,is a late Pleistocene fault. The middle segment,the Maxianshan and Qidaoliang faults,are active during late Pleistocene and early Holocene. The west segment,the Wusushan sub fault,is active during late Pleistocene and Holocene,and it's also the seismic fault of the M7 Lanzhou earthquake.On the whole,we correct the previous recognitions about the activity times of 4 faults,i.e. the Jinchengguan Fault,Leitanhe Fault,Siergou Fault and Xijicun Fault. They are all early and middle Pleistocene instead of late Pleistocene active faults. Especially,we find that the Liujiabu Fault and Shengouqiao Fault directly across Lanzhou city are not late Pleistocene or Holocene active faults but lithologic boundaries between Pliocene mudstone and early Pleistocene conglomerate. The results are very important for the urban planning and engineering construction,and will produce obvious economical and social benefits.
This paper makes a comprehensive analysis of the recent progress of the seismic active fault prospecting in Lanzhou city. Based on the satellite and aerial photos interpretation,geological and geomorphic investigation,geochemistry prospecting,shallow seismic investigation,resistivity imaging,drilling,especially large-scale trenching along the 7 active fault zones in Lanzhou city,we have achieved very important progress and gained new knowledge about the recent activity of main active faults and deformation features in Lanzhou Basin. The main conclusions are summarized bellow: (1) The Jinchengguan Fault is a thrust fault,constituting the northern boundary of the Lanzhou Tertiary Basin. It is revealed by geophysical prospecting and drilling that the newest strata offset by the Jinchengguan Fault are the early-Pleistocene sandstone and conglomerate,and that the overlying second and third terraces of the Yellow River remain intact. So,it's an early and middle Pleistocene active fault.(2) The Liujiabu Fault and Shengouqiao Fault constitute the northern and western boundaries of the Qilihe Subsidence,respectively. Revealed by geophysical prospecting,drilling and large trenching,they are not faults but lithologic boundaries of different rocks between Pliocene and early Pleistocene.(3) The Leitanhe Fault is the eastern boundary of Qilihe Subsidence,a boundary fault separating the Tertiary Lanzhou Basin into the east and west basins. According to the geophysical prospecting and drilling,the Leitanhe Fault is a thrust fault and its newest activity age is early and middle Pleistocene. It is not active since late Quaternary and does not cut the third terrace of the Yellow River.(4) The Siergou Fault is the southwestern boundary of Lanzhou Basin,a thrust fault too. It's an early and middle Pleistocene active fault and does not offset the forth terrace of Yellow River. While the Xijincun Fault is much nearer to the south margin of Lanzhou Basin and forms the southern boundary of the Tertiary Lanzhou Basin. It's an early Pleistocene fault.(5) The northern margin of Maxianshan Mountains fault is a major seismic fault on the southern margin of Lanzhou Basin,and its movement is characterized by segmentation. The east segment,the Neiguanying sub-fault,is a late Pleistocene fault. The middle segment,the Maxianshan and Qidaoliang faults,are active during late Pleistocene and early Holocene. The west segment,the Wusushan sub fault,is active during late Pleistocene and Holocene,and it's also the seismic fault of the M7 Lanzhou earthquake.On the whole,we correct the previous recognitions about the activity times of 4 faults,i.e. the Jinchengguan Fault,Leitanhe Fault,Siergou Fault and Xijicun Fault. They are all early and middle Pleistocene instead of late Pleistocene active faults. Especially,we find that the Liujiabu Fault and Shengouqiao Fault directly across Lanzhou city are not late Pleistocene or Holocene active faults but lithologic boundaries between Pliocene mudstone and early Pleistocene conglomerate. The results are very important for the urban planning and engineering construction,and will produce obvious economical and social benefits.
引文
①甘肃省地质矿产局第二水文地质队,1980,甘肃省中部兰州—永登—皋兰地区水文地质普查报告。
②甘肃省地质矿产局第一水文地质工程地质队,1987,兰州市区环境地质勘察报告。
①甘肃省地震局,2006,兰州市活断层探测与地震危险性评价施工设计。
①同237页②。
②国家地震局兰州地震研究所,1987,兰州大震区地震地质填图总结报告。
①见240页②。
②见237页②。
安特生.1925.甘肃考古记[J].地质专报,甲种第5号.AN Te-sheng.1925.Archaeological records in Gansu province[J].Geological Journal.The first volume,No.5(inChinese).
陈梦熊.1947.甘肃中部之地文[J].地质评论,12:545—556.CHEN Meng-xiong.1947.The physiographical epoch in middle area of Gansu province[J].Geology Reviews,12:545—556(in Chinese).
侯珍清,王多杰,董治平.1985.兰州金城关断裂的新活动性与地震[J].西北地震学报,7(2):95—98.HOU Zhen-qing,WANG Duo-jie,DONG Zhi-ping.1985.Activities and earthquakes of Lanzhou Jinchengguan Faultsince Holocene epoch[J].Northwestern Seismological Journal,7(2):95—98(in Chinese).
潘保田,苏怀,刘小丰,等.2007.兰州东盆地最近1·2Ma的黄河阶地序列与形成原因[J].第四纪研究,27(2):172—180.PAN Bao-tian,SU Huai,LIU Xiao-feng,et al.2007.River terraces of the Yellow River and their genesis in easternLanzhou Basin during Last1·2Ma[J].Quaternary Sciences,27(2):172—180(in Chinese).
宋方敏,袁道阳,陈桂华,等.2006.甘肃马衔山北缘断裂西北段几何结构及其新活动[J].地震地质,28(4):547—560.SONG Fang-min,YUAN Dao-yang,CHEN Gui-hua,et al.2006.Geometric structures and recent activity along thenorthwest segment of north marginal fault of Maxianshan Mountains,Gansu province[J].Seismology andGeology,28(4):547—560(in Chinese).
王金宝,戴华光,丁伯阳,等.1998.兰州市孔家崖断裂活动特征[J].西北地震学报,20(3):92—94.WANG Jin-bao,DAI Hua-guang,DING Bo-yang,et al.1998.Active characteristics of Kongjia ai Fault in Lanzhou city[J].Northwestern Seismological Journal,20(3):92—94(in Chinese).
袁道阳,雷中生,刘百篪,等.2002.兰州1125年7级地震考证与发震构造分析[J].中国地震,18(1):67—75.YUAN Dao-yang,LEI Zhong-sheng,LIU Bai-chi,et al.2002.Textual research on the1125M7Lanzhou earthquakeand the causative structure[J].Earthquake Research in China,18(1):67—75(in Chinese).
中华人民共和国建设部,国家质量监督检验检疫总局.2001.建筑抗震设计规范(GB50011-2001)[S].北京:中国建筑工业出版社.Ministry of Construction of the People s Republic of China,General Administration of Quality Supervision,Inspectionand Quarantine of the People s Republic of China.2001.Code for Seismic Design of Buildings(GB50011-2001)[S].China Architecture and Building Press,Beijing(in Chinese).
②甘肃省地质矿产局第一水文地质工程地质队,1987,兰州市区环境地质勘察报告。
①甘肃省地震局,2006,兰州市活断层探测与地震危险性评价施工设计。
①同237页②。
②国家地震局兰州地震研究所,1987,兰州大震区地震地质填图总结报告。
①见240页②。
②见237页②。
安特生.1925.甘肃考古记[J].地质专报,甲种第5号.AN Te-sheng.1925.Archaeological records in Gansu province[J].Geological Journal.The first volume,No.5(inChinese).
陈梦熊.1947.甘肃中部之地文[J].地质评论,12:545—556.CHEN Meng-xiong.1947.The physiographical epoch in middle area of Gansu province[J].Geology Reviews,12:545—556(in Chinese).
侯珍清,王多杰,董治平.1985.兰州金城关断裂的新活动性与地震[J].西北地震学报,7(2):95—98.HOU Zhen-qing,WANG Duo-jie,DONG Zhi-ping.1985.Activities and earthquakes of Lanzhou Jinchengguan Faultsince Holocene epoch[J].Northwestern Seismological Journal,7(2):95—98(in Chinese).
潘保田,苏怀,刘小丰,等.2007.兰州东盆地最近1·2Ma的黄河阶地序列与形成原因[J].第四纪研究,27(2):172—180.PAN Bao-tian,SU Huai,LIU Xiao-feng,et al.2007.River terraces of the Yellow River and their genesis in easternLanzhou Basin during Last1·2Ma[J].Quaternary Sciences,27(2):172—180(in Chinese).
宋方敏,袁道阳,陈桂华,等.2006.甘肃马衔山北缘断裂西北段几何结构及其新活动[J].地震地质,28(4):547—560.SONG Fang-min,YUAN Dao-yang,CHEN Gui-hua,et al.2006.Geometric structures and recent activity along thenorthwest segment of north marginal fault of Maxianshan Mountains,Gansu province[J].Seismology andGeology,28(4):547—560(in Chinese).
王金宝,戴华光,丁伯阳,等.1998.兰州市孔家崖断裂活动特征[J].西北地震学报,20(3):92—94.WANG Jin-bao,DAI Hua-guang,DING Bo-yang,et al.1998.Active characteristics of Kongjia ai Fault in Lanzhou city[J].Northwestern Seismological Journal,20(3):92—94(in Chinese).
袁道阳,雷中生,刘百篪,等.2002.兰州1125年7级地震考证与发震构造分析[J].中国地震,18(1):67—75.YUAN Dao-yang,LEI Zhong-sheng,LIU Bai-chi,et al.2002.Textual research on the1125M7Lanzhou earthquakeand the causative structure[J].Earthquake Research in China,18(1):67—75(in Chinese).
中华人民共和国建设部,国家质量监督检验检疫总局.2001.建筑抗震设计规范(GB50011-2001)[S].北京:中国建筑工业出版社.Ministry of Construction of the People s Republic of China,General Administration of Quality Supervision,Inspectionand Quarantine of the People s Republic of China.2001.Code for Seismic Design of Buildings(GB50011-2001)[S].China Architecture and Building Press,Beijing(in Chinese).
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