SEISMOLOGY AND GEOLOGY ›› 2017, Vol. 39 ›› Issue (2): 287-303.DOI: 10.3969/j.issn.0253-4967.2017.02.003

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NEW EVIDENCES FOR LATE QUATERNARY ACTIVITY IN THE SOUTHERN SEGMENT OF THE YISHU-TANGTOU FAULT, THE TAN-LU FAULT ZONE, AND ITS TECTONIC IMPLICATION

CAO Jun1,2, XU Han-gang3, RAN Yong-kang1, LIANG Ming-jian1, LEI Sheng-xue1, ZHANG Peng3, LI Li-mei3, GU Qin-ping3, ZHAO Qi-guang3   

  1. 1. Key Laboratory of Active Tectonics and Volcano, Institute of Geology, China Earthquake Administration, Beijing 100029, China;
    2. Earthquake Administration of Hebei Province, Shijiazhuang 050021, China;
    3. Earthquake Administration of Jiangsu Province, Nanjing 210014, China
  • Received:2015-11-11 Revised:2016-04-17 Online:2017-04-20 Published:2017-05-25

郯庐断裂带沂水-汤头断裂南段晚第四纪活动新证及构造意义

曹筠1,2, 许汉刚3, 冉勇康1, 梁明剑1, 雷生学1, 张鹏3, 李丽梅3, 顾勤平3, 赵启光3   

  1. 1. 中国地震局地质研究所, 活动构造与火山重点实验室, 北京 100029;
    2. 河北省地震局, 石家庄 050021;
    3. 江苏省地震局, 南京 210014
  • 通讯作者: 许汉刚,男,高级工程师,E-mail:hagnxu@126.com
  • 作者简介:曹筠,男,1982年生,2015年于中国地质大学(北京)和中国地震局地质研究所联合培养获构造地质学专业博士学位,研究方向为活动构造,电话:0311-85817646,E-mail:cjconan82@163.com。
  • 基金资助:
    中国地震局地质研究所基本科研业务专项(IGCEA1602)与宿迁市城市活动断层探测与地震危险性评价(SQZBTB20110162)共同资助

Abstract: The Tan-Lu Fault Zone(TLFZ), a well-known lithosphere fault zone in eastern China, is a boundary tectonic belt of the secondary block within the North China plate, and its seismic risk has always been a focus problem. Previous studies were primarily conducted on the eastern graben faults of the Yishu segment where there are historical earthquake records, but the faults in western graben have seldom been involved. So, there has been no agreement about the activity of the western graben fault from the previous studies. This paper focuses on the activity of the two buried faults in the western graben along the southern segment of Yishu through combination of shallow seismic reflection profile and composite drilling section exploration.
Shallow seismic reflection profile reveals that the Tangwu-Gegou Fault(F4)only affects the top surface of Suqian Formation, therefore, the fault may be an early Quaternary fault. The Yishui-Tangtou Fault(F3)has displaced the upper Pleistocene series in the shallow seismic reflection profile, suggesting that the fault may be a late Pleistocene active fault. Drilling was implemented in Caiji Town and Lingcheng Town along the Yishui-Tangtou Fault(F3)respectively, and the result shows that the latest activity time of Yishui-Tangtou Fault(F3)is between(91.2±4.4)ka and(97.0±4.8)ka, therefore, the fault belongs to late Pleistocene active fault.
Combined with the latest research on the activity of other faults along TLFZ, both faults in eastern and western graben were active during the late Pleistocene in the southern segment of the Yishu fault zone, however, only the fault in eastern graben was active in the Holocene. This phenomenon is the tectonic response to the subduction of the Pacific and Philippine Sea Plate and collision between India and Asian Plate. The two late Quaternary active faults in the Yishu segment of TLFZ are deep faults and present different forms on the surface and in near surface according to studies of deep seismic reflection profile, seismic wave function and seismic relocation. Considering the tectonic structure of the southern segment of Yishu fault zone, the relationship between deep and shallow structures, and the impact of 1668 Tancheng earthquake(M=8(1/2)), the seismogenic ability of moderate-strong earthquake along the Yishui-Tangtou Fault(F3)can't be ignored.

Key words: the Tan-Lu fault zone, Yishui-Tangtou Fault, late Pleistocene, tectonic response

摘要: 以往对郯庐断裂带沂沭段各条断层第四纪活动性研究工作都集中在有历史地震记录的东地堑断层,而对断裂带西地堑断层却极少涉及,仅有的关于西地堑2条断层活动性的研究也至今没有定论。针对沂沭断裂带南段西地堑2条断层开展系统的浅层地震勘探和钻孔联合剖面相结合的研究,明确了鄌郚-葛沟断裂(F4)可能是第四纪早期断裂,而活动性较强的沂水-汤头断裂(F3)属于晚更新世活动断裂,其最新1次活动时间发生在距今(91.2±4.4)~(97.0±4.8)ka。结合断裂带其他断层的最新研究成果,对比东、西地堑活动断层最新活动时间,揭示出沂沭断裂带南段晚第四纪活动是断裂带对来自两侧应力的构造响应。沂水-汤头断裂可能是该区域未来中强地震的潜在发震构造。

关键词: 郯庐断裂带, 沂水-汤头断裂, 晚更新世, 构造响应

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