合肥盆地中郯庐断裂带西支乌云山-合肥断裂最新活动特征

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郑颖平, 杨晓平, 疏鹏, 路硕, 方良好, 石金虎, 黄雄南, 刘春茹. 合肥盆地中郯庐断裂带西支乌云山-合肥断裂最新活动特征[J]. 地震地质, 2020,42(1): 50-64.
ZHENG Ying-ping, YANG Xiao-ping, SHU Peng, LU Shuo, FANG Liang-hao, SHI Jin-hu, HUANG Xiong-nan, LIU Chun-ru. STUDY ON THE LATEST ACTIVITY OF WUYUNSHAN-HEFEI FAULT IN HEFEI BASIN, THE WESTERN BRANCH OF THE TANLU FAULT ZONE[J]. SEISMOLOGY AND GEOLOGY, 2020,42(1): 50-64. 复制到剪切板

DOI:10.3969/j.issn.0253-4967.2020.01.004
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合肥盆地中郯庐断裂带西支乌云山-合肥断裂最新活动特征

郑颖平¹⁾, 杨晓平²⁾, 疏鹏^1,²⁾, 路硕¹⁾, 方良好¹⁾, 石金虎³⁾, 黄雄南²⁾, 刘春茹²⁾

1) 安徽省地震局, 合肥 230031

2) 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

3) 中国地震局地球物理勘探中心, 郑州 450002

〔作者简介〕郑颖平, 女, 1980年生, 2006年于安徽理工大学获地质工程专业硕士学位,高级工程师, 主要从事活断层探测、地震安全性评价和地震地质等相关工作, E-mail: ypzheng2006@163.com。

收稿日期: 2018-08-31

基金项目: “合肥市地震活断层探测及地震危险性分析”项目和中国地震局地震科技星火计划青年项目(XH19017Y)共同资助

摘要

前人对于郯庐断裂带安徽段出露部分的活动性开展了不同程度的研究, 并获得了丰富的成果, 而对于隐伏于合肥盆地中的段, 其活动性如何, 甚至断裂是否存在一直未能取得明确认识。文中利用浅层地震勘探及钻探联合地质剖面探测方法, 对隐伏于合肥盆地中的郯庐断裂带西分支断层——乌云山-合肥断裂开展了详细的探测研究工作, 在合肥城区由北向南跨断裂布设了4条浅层地震勘探测线和2排联合钻孔剖面, 采用¹⁴C、 OSL和ESR 3种测年手段共获得了34个钻孔地层剖面样品的年龄数据, 结果显示乌云山-合肥断裂错动的最新地层为中更新统青灰色黏土层, 断层活动表现为逆断性质, 最大垂直错距达2.4m, 最新活动时代为中更新世晚期, 上断点最浅埋深达17m。文中研究证实了郯庐断裂带穿切合肥盆地, 且第四纪以来仍有活动, 所得成果充实了对郯庐断裂带安徽段总体活动的认识。

关键词: 郯庐断裂带; 隐伏断层; 钻探联合地质剖面探测; 最新活动; 合肥盆地

中图分类号:P315.2 文献标志码:A 文章编号:0253-4967(2020)01-0050-15

STUDY ON THE LATEST ACTIVITY OF WUYUNSHAN-HEFEI FAULT IN HEFEI BASIN, THE WESTERN BRANCH OF THE TANLU FAULT ZONE

ZHENG Ying-ping¹⁾, YANG Xiao-ping²⁾, SHU Peng^1,²⁾, LU Shuo¹⁾, FANG Liang-hao¹⁾, SHI Jin-hu³⁾, HUANG Xiong-nan²⁾, LIU Chun-ru²⁾

1) Anhui Earthquake Agency, Hefei 230031, China

2) Key Laboratory of Active Tectonics and Volcano, Institute of Geology, China Earthquake Administration, Beijing 100029, China

3) Geophysical Exploration Center, China Earthquake Administration, Zhengzhou 450002, China

Abstract

Tanlu fault zone is the largest strike-slip fault system in eastern China. Since it was discovered by aeromagnetics in 1960s, it has been widely concerned by scholars at home and abroad, and a lot of research has been done on its formation and evolution. At the same time, the Tanlu fault zone is also the main seismic structural zone in China, with an obvious characteristic of segmentation of seismicity. Major earthquakes are mostly concentrated in the Bohai section and Weifang-Jiashan section. For example, the largest earthquake occurring in the Bohai section is M7.4 earthquake, and the largest earthquake occurring in the Weifang-Jiashan section is M8.5 earthquake. Therefore, the research on the active structure of the Tanlu fault zone is mainly concentrated in these two sections. With the deepening of research, some scholars carried out a lot of research on the middle section of Tanlu fault zone, which is distributed in Shandong and northern Jiangsu Province, including five nearly parallel fault systems, i.e. Changyi-Dadian Fault(F₁), Baifenzi-Fulaishan Fault(F₂), Yishui-Tangtou Fault(F₃), Tangwu-Gegou Fault(F₄)and Anqiu-Juxian Fault(F₅). They find that the faults F₃ and F₅ are still active since the late Quaternary. In recent years, we have got a further understanding of the geometric distribution, active age and active nature of Fault F₅, and found that it is still active in Holocene. At the same time, the latest research on the extension of F₅ into Anhui suggests that there is a late Pleistocene-Holocene fault existing near the Huaihe River in Anhui Province.
The Tanlu fault zone extends into Anhui Province and the extension section is completely buried, especially in the Hefei Basin south of Dingyuan. At present, there is little research on the activity of this fault segment, and it is very difficult to study its geometric structure and active nature, and even whether the fault exists has not been clear. Precisely determining the distribution, active properties and the latest active time of the hidden faults under urban areas is of great significance not only for studying the rupture behavior and segmentation characteristics of the southern section of the Tanlu fault zone, but also for providing important basis for urban seismic fortification. By using the method of shallow seismic prospecting and the combined drilling geological section, this paper carries out a detailed exploration and research on the Wuyunshan-Hefei Fault, the west branch fault of Tanlu fault zone buried in Hefei Basin. Four shallow seismic prospecting lines and two rows of joint borehole profiles are laid across the fault in Hefei urban area from north to south. Using¹⁴C, OSL and ESR dating methods, ages of 34 samples of borehole stratigraphic profiles are obtained. The results show that the youngest stratum dislocated by the Wuyunshan-Hefei Fault is the Mesopleistocene blue-gray clay layer, and its activity is characterized by reverse faulting, with a maximum vertical offset of 2.4m. The latest active age is late Mesopleistocene, and the depth of the shallowest upper breaking point is 17m. This study confirms that the west branch of Tanlu fault zone cuts through Hefei Basin and is still active since Quaternary. Its latest activity age in Hefei Basin is late of Middle Pleistocene, and the latest activity is characterized by thrusting. The research results enrich the understanding of the overall activity of Tanlu fault zone in the buried section of Hefei Basin and provide reliable basic data for earthquake monitoring, prediction and earthquake damage prevention in Anhui Province.

Keyword: Tanlu fault zone; buried fault; composite drilling geological section; latest activity; Hefei Basin

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0 引言

郯庐断裂带是中国东部最大的走滑断裂系, 自20世纪60年代通过航磁发现其存在以来, 受到了国内外学者的广泛关注, 并对其形成、演化过程进行了大量的研究(Xu et al., 1987; 徐嘉炜等, 1992, 1995; Yin et al., 1993; Gilder et al., 1999; 朱光等, 2005)。郯庐断裂带还是中国主要的地震构造带, 其地震活动分段特征明显, 大地震多集中在潍坊— 嘉山段和渤海段, 如在渤海段曾发生1597年和1548年M7地震、 1975年M7.3地震和1969年M7.4地震等, 潍坊— 嘉山段发生过70BC安丘M7地震和1668年郯城M81/2地震等, 因此关于郯庐断裂活动构造的研究多集中于这2段(方仲景等, 1987; 李家灵等, 1994; 施炜等, 2003)。随着研究的深入, 不同学者对郯庐断裂分布在山东及苏北境内的中段, 即昌邑-大店断裂(F₁)、白芬子-浮来山断裂(F₂)、沂水-汤头断裂(F₃)、鄌郚-葛沟断裂(F₄)和安丘-莒县断裂(F₅)等5条近平行的断裂系开展了丰富的研究工作(晁洪太等, 1994; 李家灵等, 1994; 王志才等, 2005; 曹筠等, 2017), 认为F₃和F₅断裂在晚第四纪以来仍有活动。尤其是近年来, 对F₅断裂的几何展布、活动时代和活动性质有了进一步认识(张鹏等, 2015; 许汉刚等, 2016; 曹筠等, 2018), 发现其在全新世仍有活动。同时, 对于F₅延入安徽境内的最新研究认为, 在安徽淮河附近存在晚更新世— 全新世破裂(郑颖平等, 2014; Shu et al., 2016; 杨源源等, 2017; 姚大全等, 2017)。然而, 郯庐断裂带在安徽境内, 尤其在定远以南为全隐伏段, 对其几何结构和活动性质等开展研究的难度较大, 目前未有关于其活动构造方面的成果报道。本文针对郯庐断裂带西支(F₄)位于合肥盆地的隐伏段, 通过人工地震反射、钻孔联合剖面的方法获得该隐伏断裂的几何展布、活动性质、活动特征等重要的活动构造学定量参数, 以期为更系统全面地讨论郯庐断裂带的破裂分段提供依据, 同时为区域地震危险性评价和城市规划提供重要的科学依据。

1 郯庐断裂合肥盆地段概况

郯庐断裂合肥盆地段主要由4支断裂构成, 自东向西分别为藕塘-清水涧断裂、池河-西山驿断裂、桑涧子-广寒桥断裂和乌云山-合肥断裂(图 1中的F₁— F₄)。据安徽省地质志(安徽省地质矿产局, 1987)记载, 乌云山-合肥断裂自五河县向S, 经合肥市、舒城县, 消失于大别山区的七里河一带, 长约350km, 倾向SEE, 倾角70° ~80° , 主要发育在五河群中, 基岩出露区可见沿线地层揉皱、岩石破碎并糜棱岩化。在遥感影像上, 断裂北段及南段出露较好, 在合肥盆地中呈隐伏状(图1)。然而其南延至合肥盆地中的活动特征等尚不明确, 尤其是西支断层在合肥盆地内均呈隐伏状, 开展研究的难度大, 难以进行直观有效的地表调查工作。而精细厘定城市内隐伏断裂的分布、活动性质和最新活动时代, 对研究郯庐断裂南段的破裂习性和分段特征以及城市抗震设防工作等均具有十分重要的意义。本文采用浅层地震和钻探联合地质剖面探测相结合的方法, 对郯庐断裂带的西分支断层— — 乌云山-合肥断裂开展深入研究工作, 获得其在合肥盆地内的展布特征、最新活动时代、活动性质等, 为综合评价郯庐断裂带在合肥盆地中的地震危险性提供依据。

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	图 1 郯庐断裂带分支断层在合肥盆地中的展布略图 F₁藕塘-清水涧断裂; F₂池河-西山驿断裂; F₃桑涧子-广寒桥断裂; F₄乌云山-合肥断裂Fig. 1 The distribution of the subsidiary faults of Tanlu fault zone in Hefei Basin.

2 浅层地震探测

2.1 数据采集

为查明第四系覆盖区隐伏断裂的位置, 进行了浅层地震反射勘探工作, 跨乌云山-合肥断裂共布设了4条测线, 由北向南分别标记为CF1-2、 CF1-1、 CF1-3和CF1-4(图1)。地震数据使用德国DMT公司生产的SUMMIT数字地震仪进行采集, 采样长度为1s, 采样间隔为0.5ms。地震波激发源采用美国M18/612型可控震源, 扫描频带为30~200Hz, 扫描长度为8s, 使用4个固有频率为60Hz的检波器串接收地震波。选取观测系统参数时, 依据现场试验结果, 最终采用道间距2m、炮间距10m、 160道接收、覆盖次数16次的观测系统。

2.2 探测结果

CF1-2测线长3.588km(图1)。在测线的反射波时间剖面图中可识别出4组反射波组, 自上而下分别为第四系底界的反射界面T_Q和基岩(白垩纪地层)内部的反射界面T₁、 T₂及T₃(图2)。

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	图 2 CF1-2测线的反射波时间剖面(a)和深度剖面(b)Fig. 2 The time-section(a) and depth-section(b) of reflection waves of line CF1-2.

在测线桩号2 264m附近, T₁、 T₂及T₃反射同相轴存在扭曲和错断现象, 根据反射波组特征和断层判别依据, 在此解释1个断点, 在剖面图中用F_P8 标出(图2), 是1条向E倾的正断层, 其可分辨的上断点埋深约35m, 该深度处垂直断距不大, 为2~3m, 向上切割第四系底界T_Q。在测线桩号1 808m附近, T₁、 T₂及T₃反射同相轴存在扭曲和错断现象, 根据反射波组特征和断层判别依据, 在此解释1个断点, 在剖面图中用F_P9 标出(图2), 是1条向W倾的正断层, 其可分辨的上断点埋深约65m, 该深度处的垂直断距达5~7m, 未切割第四系底界。

CF1-1测线长14km。图 3为该测线的反射波时间剖面图, 通过该剖面可识别出2组反射波组, 自上而下分别为第四系底界的反射界面T_Q和基岩(早白垩纪地层)反射界面T₃。

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	图 3 CF1-1测线的反射波时间剖面Fig. 3 The time-section of reflection waves of line CF1-1.

在测线桩号14 478m附近, T₃反射同相轴存在扭曲和错断现象, 根据反射波组特征和断层判别依据, 在此解释1个断点, 在剖面图中用F_P2 标出(图3), 是1条向E倾的正断层, 其可分辨的上断点埋深约28m, 该深度处的垂直断距最大约3m, 向上切割第四系底界T_Q。在测线桩号15 022m附近解释出另1个断点F_P3, 是1条向W倾的正断层, 其可分辨的上断点埋深约60m, 该深度处的垂直断距为4~6m, 向上未切割第四系。

CF1-3测线长4.478km。图 4为该测线的反射波时间剖面图, 从图中可识别出2组反射界面, 为第四系底界T_Q和基岩反射界面(古近系)T₁。

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	图 4 CF1-3测线的反射波时间剖面(a)和深度剖面(b)Fig. 4 The time-section(a) and depth-section(b) of reflection waves of line CF1-3.

在测线桩号1 590m附近, T₁反射同相轴存在扭曲和错断现象, 根据反射波组特征和断层判别依据, 在此解释1个断点, 在剖面图中用F_P10 标出(图4), 是1条向SE倾的逆断层, 其可分辨的上断点埋深42m, 该深度的垂直断距为3~5m, 向上未切割第四系。

CF1-4测线长10.578km。图 5为该测线的反射波时间剖面图, 从图中可识别出4组反射界面, 为第四系底界T_Q和基岩反射界面(白垩系)T₁、 T₂及T₃。

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	图 5 CF1-4测线的反射波时间剖面(a)和深度剖面(b)Fig. 5 The time-section(a) and depth-section(b) of reflection waves of line CF1-4.

在测线桩号4 700m附近, T₁及T₃的反射同相轴存在扭曲和错断现象, 根据反射波组特征和断层判别依据, 在此解释1个断点, 在剖面图中用F_P13 标出(图5), 且在T₂界面附近出现反转, 下部表现为正断性质, 上部表现为逆断性质, 倾向SE, 上断点埋深约21m, 在该深度其垂直断距很小, 不易分辨, 向上切割第四系。在测线桩号3 615m附近解释另1个断点F_P12, 为倾向SE的正断层, 上断点埋深为29m, 该深度处其垂直断距为4~6m, 向上至第四系底界。在测线桩号2 577m附近解释1个断点F_P11, 为倾向NW的逆断层, 上断点埋深约60m, 在该深度其垂直断距为4~6m; 在测线桩号3 178m处解释断点F_P11.1, 为F_P11的次级断裂, 是倾向SE的正断层, 上断点埋深约60m, 在该深度其垂直断距为4~6m, 断点均在基岩内部。

3 钻探联合地质剖面探测

3.1 钻孔布置

为进一步确定乌云山-合肥断裂的上断点埋深及活动时代, 在浅层地震勘探结果的基础上, 跨CF1-1和CF1-4测线的断点位置分别在瑶海公园南门和合铜路布设了7个和11个钻孔。本次工作中, 最大钻孔间距49m, 最小钻孔间距0.5m。

3.2 瑶海公园南门钻孔联合剖面

该联合剖面以150° 走向布置于瑶海公园南门北西侧湖边, 横跨浅震测线CF1-1解释出的F_P2 断点。从北西向南东共布置了7个钻孔, 孔深34.46~40.71m, 孔间距1~14m, 共对3个¹⁴C样品、 9个OSL样品及7个ESR样品进行测年(图6)。

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	图 6 瑶海公园南门钻孔联合地质剖面 1 淤泥; 2 黏土; 3 粉砂质黏土; 4 泥岩; 5 粉砂质泥岩; 6 泥质粉砂岩; 7 泥质细砂岩; 8 粉砂岩; 9 铁锰结核; 10 钙质结核; 11 断层; 12 ¹⁴C样品; 13 光释光样品; 14 电子自旋共振测年样品Fig. 6 The composite drilling geological section at south gate of Yaohai Park.

3.2.1 钻孔揭示的地层特征

7个钻孔揭示的地层层序基本相同, 根据各钻孔岩心特征可分为7层, 自上而下描述为: 全新统(Qh)①为黑色淤泥、灰褐色黏土, 含零星铁锰结核, 埋深1.91~2.89m。晚更新统( $Q_{P}^{3}$ )分为2层, 上部②为黑褐、灰褐色黏土, 埋深4.09~6.43m; 下部③为青灰、棕褐、黄色黏土, 夹铁锰结核密集带和钙质结核, 埋深10.67~11.29m。中更新统( $Q_{P}^{2}$ )分为3层, 上部④为棕褐、青灰色黏土, 夹铁锰结核密集带, 埋深15.67~16.77m; 中部⑤为黄色夹青灰或棕色黏土, 夹数层铁锰结核密集带, 埋深26.33~27.41m; 下部⑥为浅灰色黏土, 发育钙结核, 埋深33.32~34.91m。下白垩系(K₁)⑦为红褐、棕色— 浅黄色近水平条纹泥质粉砂— 细砂岩。

3.2.2 标志层断错分析及钻孔地层剖面年代学分析

由瑶海公园南门钻孔联合剖面(图6)可见, 富含铁锰结核密集带的更新世地层可作为标志层, 且在更新世地层中段⑤内至少可以分辨出3层铁锰结核层, 埋深分别约17m、 20m和26m, 均未被断错。

钻孔F_P2-3和F_P2-8间仅距1m, 但其基岩⑦的顶面落差达1.2m, 且钻孔F_P2-3深32m处, 在层⑥黏土中还钻遇2个断面, 倾向SE, 倾角40° ~45° , 其上擦痕明显, 反映出逆冲的运动性质, 判定钻孔F_P2-3和F_P2-8间发育断层f₁, 该断层可能继续向上延伸, 终止于灰色黏土层⑥与黄色、棕色黏土层⑤之间的分界线以下; 钻孔F_P2-5和F_P2-3间距14m, 2钻孔的基岩顶面落差为1.3m, 推测其间可能发育断层f₂; 钻孔F_P2-1和F_P2-6间距10.5m, 2钻孔的基岩顶面落差为0.6m, 且在钻孔F_P2-6深26.5m处发现断面, 判定钻孔F_P2-1和F_P2-6间发育断层f₃, 因断层两侧基岩顶面落差仅0.6m, 推测f₃断层应终止于深约26m的棕红色黏土中。

根据F_P2-5钻孔系列样品测试结果(表1和表2), 深26m以下的黏土层的堆积年龄是(324± 24)ka。深26m以上(接近26m)的黏土层的堆积年龄是(158.29± 19.27)ka。因此可以推测f₁、 f₂和f₃的最新活动年代在(324± 24)ka BP之后、 (158.29± 19.27)ka BP之前的中更新世晚期。

表1 联合钻孔地层剖面¹⁴C测年结果 Table1 ¹⁴C dating of the strata of the composite drilling section

表2 联合钻孔地层剖面光释光(OSL)测年及电子自旋共振(ESR)测年结果 Table2 OSL and ESR dating of the strata of the composite drilling section

名称	样品编号	测年方法	取样深度 /m	U /ug· g	Th /ug· g	K₂O /%	含水量 /%	古剂量 /Gy	年剂量 /Gy· ka^-1	年龄 /ka
F_P2 联合剖面	F_P2-52.10	OSL	2.10	2.33	13.4	1.62	17.44	69.65± 6.46	3.56	19.58± 2.67
	F_P2-55.00	OSL	5.00	2.54	12.7	1.18	16.54	221.26± 22.87	3.15	70.27± 10.11
	F_P2-57.95	OSL	7.95	2.11	12.5	1.48	14.91	343.58± 32.67	3.29	104.47± 14.42
	F_P2-510.65	OSL	10.65	2.35	13.2	1.45	16.64	362.93± 8.37	3.34	108.81± 11.81
	F_P2-513.35	OSL	13.35	2.86	14.6	1.47	16.49	497.57± 44.70	3.58	138.95± 18.68
	F_P2-515.85	OSL	15.85	3.33	13.6	0.78	14.41	562.71± 105.34	3.14	179.25± 38.04
	F_P2-519.50	OSL	19.50	2.93	13.6	0.98	16.38	665.05± 52.39	3.15	211.46± 26.92
	F_P2-522.35	OSL	22.35	2.61	13.4	1.25	16.36	552.42± 72.71	3.24	170.27± 28.15
	F_P2-525.30	OSL	25.30	2.69	12.5	1.43	18.00	508.23± 35.28	3.21	158.29± 19.27
	F_P2-519.65	ESR	19.65	3.84	17.0	1.44	16.22	1 873± 164	3.08	608± 53
	F_P2-522.50	ESR	22.50	3.00	14.2	1.69	15.91	874± 161	2.95	296± 55
	F_P2-525.45	ESR	25.45	3.17	14.8	1.96	17.05	1 026± 204	3.17	324± 64
	F_P2-527.00	ESR	27.00	2.81	14.3	1.40	16.54	4 287± 1 238	2.67	1 606± 461
	F_P2-529.50	ESR	29.50	2.71	14.4	1.33	15.49	1 074± 344	2.64	407± 130
	F_P2-531.90	ESR	31.90	1.66	8.9	1.28	12.46	1 331± 302	2.14	622± 141
	F_P2-532.80	ESR	32.80	2.01	9.84	1.12	12.14	1 301± 230	2.15	605± 107
F_P13 联合剖面	F_P13-71.70	OSL	1.70	3.28	13.30	1.54	13.12		0.16	57.8± 2.81
	F_P13-73.50	OSL	3.50	1.72	8.84	1.32	12.76		0.13	75.42± 5.98
	F_P13-716.65	OSL	16.65	3.00	14.40	0.97	11.69		0.04	212.92± 11.07
	F_P13-719.15	OSL	19.15	1.66	11.20	0.96	12.11		0.03	265.67± 19.51
	F_P13-714.00	ESR	14.00	2.25	12.2	1.37	13.58	1 991± 424	2.50	796± 170
	F_P13-716.80	ESR	16.80	2.65	13.3	1.14	13.50	1 391± 175	2.47	563± 71
	F_P13-115.05	OSL	5.05	2.24	11.00	1.41	13.39		0.10	99.92± 9.87
	F_P13-117.45	OSL	7.45	2.05	10.50	1.29	16.59		0.08	177.45± 12.97
	F_P13-119.45	OSL	9.45	2.10	11.90	1.03	13.25		0.06	193.81± 15.99
	F_P13-1112.55	OSL	12.55	1.77	9.03	1.37	12.75		0.05	237.62± 21.39
	F_P13-1115.15	OSL	15.15	2.53	11.70	1.25	8.86		0.04	192.12± 18.77
	F_P13-1116.15	OSL	16.15	1.81	12.20	1.10	11.44		0.04	212.49± 21.58
	F_P13-1117.25	OSL	17.25	1.75	9.57	1.11	9.33		0.03	253.68± 19.61
	F_P13-1119.50	OSL	19.50	1.56	9.42	0.91	11.02		0.03	270.35± 25.69
	F_P13-1120.50	OSL	20.50	1.54	10.40	0.36	14.80		0.03	402.72± 57.46

注 ESR测试单位为中国地震局地质研究所地震动力学国家重点实验室; F_P2联合剖面中OSL测试单位为中国地震局地壳应力研究所地壳动力学重点实验室; F_P13联合剖面中OSL测试单位为中国科学技术大学科技考古实验室。

表2 联合钻孔地层剖面光释光(OSL)测年及电子自旋共振(ESR)测年结果 Table2 OSL and ESR dating of the strata of the composite drilling section

3. 3 合铜路钻孔联合剖面

该联合剖面为SE走向, 布置于合铜路两侧的金岗村苗圃地, 横跨浅震测线CF1-4解释出的F_P13断点。从北西向南东共布置了11个钻孔, 孔深21.34~34.38m, 孔间距0.5~49m, 共完成13个OSL样品及2个ESR样品的测年工作(图7)。

	Figure Option View Download New Window
	图 7 合铜路钻孔联合地质剖面 1 淤泥; 2 黏土; 3 粉砂质黏土; 4 细砂质黏土; 5 泥岩; 6 粉砂质泥岩; 7 泥质粉砂岩; 8 粉砂岩; 9 细砂岩; 10 中粗砂岩; 11 砾石; 12 铁锰结核; 13 钙质结核; 14 断层; 15 光释光样品; 16 电子自旋共振测年样品Fig. 7 The composite drilling geological section at Hetong road.

3.3.1 钻孔揭示的地层特征

11个钻孔揭示的地层层序基本相同, 根据各钻孔的岩心特征可分为7层, 自上而下描述为: 全新统(Qh)①为灰黑色、灰褐色黏土质耕作土, 埋深0.25~0.4m。晚更新统( $Q_{P}^{3}$ )②为灰黄、黄褐、黑褐色黏土, 底部发育铁锰结核密集带, 埋深5.60~6.94m。中更新统( $Q_{P}^{2}$ )分为4层, 上部层③为青灰-黄色斜纹状黏土, 富含铁锰结核, 埋深9.9~10.39m; 中上部层④为青灰-黄色斑纹状黏土, 含铁锰氧化物, 埋深13.07~14.89m; 中下部层⑤为黄色黏土, 夹铁锰结核密集带, 埋深16.70~18.23m; 下部层⑥为青灰色黏土夹铁锰结核, 埋深19.74~22.64m。上白垩系(K₂)⑦为灰黄色砂岩、砂质泥岩夹红褐色泥岩。

3.3.2 标志层断错分析及钻孔地层剖面年代学分析

由合铜路钻孔联合剖面(图7)可见, 富含铁锰结核密集带的更新世地层可作为标志层, 且在中更新世地层③、 ④、 ⑤和⑥内至少可以分辨出3层铁锰结核层, 埋深分别约10m、 14m和17m, 均未被断错。

钻孔F_P13-4和F_P13-9相距仅0.5m, 但其基岩顶面⑦的落差达2.4m, 且在F_P13-9钻孔25.5m深处的白垩纪砂岩中钻遇断层破碎带, 判定在F_P13-4和2钻孔间发育断层f₁, 在钻孔F_P13-4深约22.3m处的黄土中钻遇断层, 断面倾角30° ~35° , 可能是f₁向NW逆冲时发育的1条分支断层; 钻孔F_P13-11和F_P13-10相距3.5m, 但其基岩顶面⑦的落差达0.6m, 且在钻孔F_P13-10深19.4~20m处的黄土中钻遇2个断面, 倾角为40° ~45° , 推测在钻孔F_P13-11和F_P13-10之间发育1条逆冲断层f₂。

由图 7可见, f₁向上延伸且应位于F_P13-4和F_P13-9钻孔之间, 但2个钻孔中层⑥的顶面埋深皆为16.7m, 不存在落差, 因此断层没有错断层⑥的顶面。 f₂向上延伸且应位于F_P13-10和F_P13-4之间, 2个钻孔中层⑥的顶面埋深分别为17.6m和16.7m, 而该断层是逆断层, 故该断层也没有错断层⑥的顶面。

F_P13-7和2个钻孔的系列样品测试结果(表2)反映, 层⑥顶面以下样品的最新年龄为(265.67± 19.51)~(253.68± 19.61)ka, 顶面以上样品的最老年龄为(212.92± 19.51)~(212.49± 21.58)ka。由前述分析可知, 2条断层错断了层⑥, 但没有影响层⑤。因此f₁、 f₂ 2条断层的最新活动应在(265.67± 19.51)~(253.68± 19.61)ka BP之后、 (212.92± 19.51)~(212.49± 21.58)ka BP之前的中更新世晚期。

4 结论及讨论

通过研究发现, 合肥盆地隐伏区郯庐断裂带的西支断层— — 乌云山-合肥断裂在钻探联合地质剖面上为逆断层, 在浅层地震剖面上为走滑断层; 经地层分析和年代测试工作可知, 乌云山-合肥断裂的最新活动时代在中更新世晚期, 上断点埋深最浅为17m, 最深达26m, 最大垂直错距达2.4m。

浅层地震探测揭示, 乌云山-合肥断裂切割白垩纪以来的地层, 在剖面中或表现为陡倾的多支或单支断裂, 或表现为陡倾的主干断裂与倾角稍缓的次级断裂的组合。从反射层位的断错来看, 有的表现为正断性质, 有的表现为逆断性质, 有的下部表现为正断性质而上部又反映出逆冲性质。而联合钻孔剖面揭示断层为逆冲性质, 反映了郯庐断裂带经历了多期构造运动的叠加, 也可能是走滑运动在倾向滑动上不均一性的表现。

本研究证实郯庐断裂带穿切合肥盆地, 且第四纪以来仍有活动, 但活动强度不及安徽北段淮河附近, 活动性具有明显的分段特征, 揭示了郯庐断裂带作为中国东部最有影响的断裂系具有复杂性的一面。该断裂向S延入大别山一带的活动特征有待进一步研究工作。

致谢本文得到中国地震局地质研究所宋方敏研究员的悉心指导和帮助, 在此表示衷心感谢!

参考文献

文献列表

[1]	安徽省地质矿产局. 1987. 安徽省区域地质志 [M]. 北京: 地质出版社. Bureau of Geology and Mineral Resources of Anhui Province. 1987. Regional Geology of Anhui [M]. Geological Publishing House, Beijing(in Chinese). [本文引用:1]
[2]	曹筠, 冉勇康, 许汉刚, 等. 2018. 郯庐断裂带江苏段安丘-莒县断裂全新世活动及其构造意义[J]. 地球物理学报, 61(7): 2828—2844. CAO Jun, RAN Yong-kang, XU Han-gang, et al. 2018. Holocene activity of the Anqiu-Juxian Fault on the Jiangsu segment of the Tanlu fault zone and its tectonics implication[J]. Chinese Journal of Geophysics, 61(7): 2828—2844(in Chinese). [本文引用:1]
[3]	曹筠, 许汉刚, 冉勇康, 等. 2017. 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[J]. 地震地质, 39(2): 287—303. doi: DOI: 103969/j. issn. 0253-4967. 2017. 02. 003. CAO Jun, XU Han-gang, RAN Yong-kang, et al. 2017. New evidences for late Quaternary activity in the southern segment of the Yishu-Tangtou Fault, the Tan-Lu fault zone, and its tectonic implication[J]. Seismology and Geology, 39(2): 287—303(in Chinese). [本文引用:1]
[4]	晁洪太, 李家灵, 崔昭文, 等. 1994. 郯庐断裂带中段全新世活断层的几何结构与分段 [G]∥国家地震局地质研究所. 活动断裂研究(3). 北京: 地震出版社: 180—190. CHAO Hong-tai, LI Jia-ling, CUI Zhao-wen, et al. 1994. Geometry and segmentation of the Quaternary fault in the middle segment of Tanlu fault zone [G]∥ Institute of Geology, State Seismological Bureau. Research of Active Fault (3). Seismological Press, Beijing: 180—190(in Chinese). [本文引用:1]
[5]	方仲景, 丁梦林, 向宏发, 等. 1987. 郯庐断裂带 [M]. 北京: 地震出版社. FANG Zhong-jing, DING Meng-lin, XIANG Hong-fa, et al. 1987. The Tanlu Fault Zone [M]. Seismological Press, Beijing(in Chinese). [本文引用:1]
[6]	李家灵, 晁洪太, 崔昭文, 等. 1994. 郯庐活断层的分段及其大震危险性分析[J]. 地震地质, 16(2): 121—126. LI Jia-ling, CHAO Hong-tai, CUI Zhao-wen, et al. 1994. Segmentation of active fault along the Tancheng-Lujiang fault zone and evaluation of strong earthquake risk[J]. Seismology and Geology, 16(2): 121—126(in Chinese). [本文引用:2]
[7]	施炜, 张岳桥, 董树文. 2003. 郯庐断裂带中段第四纪活动及其分段特征[J]. 地球学报, 24(1): 11—18. SHI Wei, ZHANG Yue-qiao, DONG Shu-wen. 2003. Quaternary activity and segmentation behavior of the middle portion of the Tan-Lu fault zone[J]. Acta Geoscientica Sinica, 24(1): 11—18(in Chinese). [本文引用:1]
[8]	王志才, 贾荣光, 孙昭民, 等. 2005. 沂沭断裂带安丘-莒县断裂安丘—朱里段几何结构与活动特征[J]. 地震地质, 27(2): 212—220. WANG Zhi-cai, JIA Rong-guang, SUN Zhao-min, et al. 2005. Geometry and activity of the Anqiu-Zhuli segment of the Anqiu-Juxian Fault in the Yishu fault zone[J]. Seismology and Geology, 27(2): 212—220(in Chinese). [本文引用:1]
[9]	许汉刚, 范小平, 冉勇康, 等. 2016. 郯庐断裂带宿迁段F₅断裂浅层地震勘探新证据[J]. 地震地质, 38(1): 31—43. doi: DOI: 103969/j. issn. 0253-4967. 2016. 01. 013. XU Han-gang, FAN Xiao-ping, RAN Yong-kang, et al. 2016. New evidences of the Holocene fault in Suqian segment of the Tanlu fault zone discovered by shallow seismic exploration method[J]. Seismology and Geology, 38(1): 31—43(in Chinese). [本文引用:1]
[10]	徐嘉炜, 马国锋. 1992. 郯庐断裂带研究的十年回顾[J]. 地质论评, 38(4): 316—324. XU Jia-wei, MA Guo-feng. 1992. Review of the years(1981—1991) of the research on the Tancheng-Lujiang fault zone[J]. Geological Review, 38(4): 316—324(in Chinese). [本文引用:1]
[11]	徐嘉炜, 朱光. 1995. 中国东部郯庐断裂带构造模式讨论[J]. 华北地质矿产杂志, 10(2): 121—134. XU Jia-wei, ZHU Guang. 1995. Discussion on the tectonic models for the Tan-Lu fault zone, eastern China[J]. Journal of Geology and Mineral Resources of North China, 10(2): 121—134(in Chinese). [本文引用:1]
[12]	杨源源, 赵朋, 郑海刚, 等. 2017. 郯庐断裂带安徽紫阳山段发现全新世活动证据[J]. 地震地质, 39(4): 644—655. doi: DOI: 103969/j. issn. 0253-4967. 2017. 04. 002. YANG Yuan-yuan, ZHAO Peng, ZHENG Hai-gang, et al. 2017. Evidence of Holocene activity discovered in Anhui Ziyangshan segment of Tanlu fault zone[J]. Seismology and Geology, 39(4): 644—655(in Chinese). [本文引用:1]
[13]	姚大全, 郑海刚, 赵朋, 等. 2017. 郯庐断裂带淮河南到女山湖段晚第四纪以来的新活动[J]. 中国地震, 33(1): 38—45. YAO Da-quan, ZHENG Hai-gang, ZHAO Peng, et al. 2017. New activity of the Tanlu fault zone from Huaihe to the Nüshanhu since the Late Quaternary[J]. Earthquake Research in China, 33(1): 38—45(in Chinese). [本文引用:1]
[14]	张鹏, 李丽梅, 冉勇康, 等. 2015. 郯庐断裂带安丘-莒县断裂江苏段晚第四纪活动特征研究[J]. 地震地质, 37(4): 1162—1176. doi: DOI: 103969/j. issn. 0253-4967. 2015. 04. 018. ZHANG Peng, LI Li-mei, RAN Rong-kang, et al. 2015. Research on characteristics of Late Quaternary activity of the Jiangsu segment of Anqiu-Juxian Fault in the Tanlu fault zone[J]. Seismology and Geology, 37(4): 1162—1176(in Chinese). [本文引用:1]
[15]	郑颖平, 姚大全, 张毅, 等. 2014. 郯庐断裂带新沂—五河段晚第四纪活动的新证据[J]. 中国地震, 30(1): 23—29. ZHENG Ying-ping, YAO Da-quan, ZHANG Yi, et al. 2014. New evidence of Late Quaternary activity in the segment from Xinyi to Wuhe in the Tancheng-Lujiang fault zone[J]. Earthquake Research in China, 30(1): 23—29(in Chinese). [本文引用:1]
[16]	朱光, 牛漫兰, 刘国生, 等. 2005. 郯庐断裂带肥东段走滑运动的 ⁴⁰Ar/³⁹Ar法定年[J]. 地质学报, 79(3): 303—316. ZHU Guang, NIU Man-lan, LIU Guo-sheng, et al. 2005. ⁴⁰Ar/³⁹Ar dating for the strike-slip movement on the Feidong part of Tanlu fault belt[J]. Acta Geologica Sinica, 79(3): 303—316(in Chinese). [本文引用:1]
[17]	Gilder S A, Leloup P H, Courtillot V, et al. 1999. Tectonic evolution of the Tancheng-Lujiang(Tan-Lu)Fault via Middle Triassic to Early Cenozoic paleomagnetic data[J]. Journal of Geophysical Research: Solid Earth, 104(B7): 15365—15390. [本文引用:1]
[18]	Shu P, Fang L H, Zheng Y P, et al. 2016. Geological evidence and characteristics of activity of the Wuhe-Mingguang section of Tancheng-Lujiang fault zone in Late Pleistocene[J]. Earthquake Research in China, 30(4): 485—499. [本文引用:1]
[19]	Xu J W, Zhu G, Tong W X, et al. 1987. Formation and evolution of the Tancheng-Lujiang wrench fault system: A major shear system to the northwest of the Pacific Ocean[J]. Tectonophysics, 134(4): 273—310. [本文引用:1]
[20]	Yin A, Nie S Y. 1993. An indentation model for the North and South China collision and the development of the Tan-Lu and Honam fault systems, eastern Asia[J]. Tectonics, 12(4): 801—813. [本文引用:1]

1987

0.0

... 据安徽省地质志(安徽省地质矿产局, 1987)记载, 乌云山-合肥断裂自五河县向S, 经合肥市、舒城县, 消失于大别山区的七里河一带, 长约350km, 倾向SEE, 倾角70#cod#x000b0 ...

2018

0.0

... 曹筠等, 2018), 发现其在全新世仍有活动 ...

2017

0.0

... 曹筠等, 2017), 认为F₃和F₅断裂在晚第四纪以来仍有活动 ...

1994

0.0

... 随着研究的深入, 不同学者对郯庐断裂分布在山东及苏北境内的中段, 即昌邑-大店断裂(F₁)、白芬子-浮来山断裂(F₂)、沂水-汤头断裂(F₃)、鄌郚-葛沟断裂(F₄)和安丘-莒县断裂(F₅)等5条近平行的断裂系开展了丰富的研究工作(晁洪太等, 1994 ...

1987

0.0

... 嘉山段发生过70BC安丘M7地震和1668年郯城M81/2地震等, 因此关于郯庐断裂活动构造的研究多集中于这2段(方仲景等, 1987 ...

1994

0.0

李家灵, 晁洪太, 崔昭文, 等. 1994. 郯庐活断层的分段及其大震危险性分析[J]. 地震地质, 16(2): 121—126.

Jia-ling

, CHAO

Hong-tai

, CUI

Zhao-wen

, et al. 1994. Segmentation of active fault along the Tancheng-Lujiang fault zone and evaluation of strong earthquake risk[J]. Seismology and Geology, 16(2): 121—126(in Chinese).

Based on systematic geologic mapping,we found that the active fault in the Tancheng-Lujiang fault zone is not continuous and can be divided into three independent rupture segments,which are Anqiu segment,Juxian-Tancheng segment and Xinyi-Sihong segment．The geometrical pattern,displacment amount and strong earthquake recurrence interval on these three seg-ments are obviously different．Each segment responds to the maximum rupture length of a strongearthquake.At the separation of the segments,the faults are arranged in left-stepover,where an 8～10km wide local uplift was formed．The local uplifts serve as the barriers between the segments.By analysing the strong earthquake recurrence intervals and the age of the latest activity ofeach segment,we suggest that the Xinyi-Sihong segment is the most dangerous segment in thefuture,the Anqiu segment is the secondary one and the Juxian-Tancheng segment has little possibility to suffer the strong earthquake.

Seismological Bureau of Shandong Province, Jinan 250021

郯庐活断层长360km,通过系统的填图可将其分为3个独立的活断层破裂段。对每段的几何形态、最新活动时代、大震复发间隔、现今活动状态以及分段障碍体等作了介绍,并对各段未来的大震危险性做了初步分析。

... 李家灵等, 1994 ...

2003

0.0

... 施炜等, 2003) ...

2005

0.0

王志才, 贾荣光, 孙昭民, 等. 2005. 沂沭断裂带安丘-莒县断裂安丘—朱里段几何结构与活动特征[J]. 地震地质, 27(2): 212—220.

WANG

Zhi-cai

, JIA

Rong-guang

, SUN

Zhao-min

, et al. 2005. Geometry and activity of the Anqiu-Zhuli segment of the Anqiu-Juxian Fault in the Yishu fault zone[J]. Seismology and Geology, 27(2): 212—220(in Chinese).

The Yishu Fault zone is a part of the Tanlu Fault zone that passes through Shandong Province and the northern area of Jiangsu. It is composed of 5 nearly parallel faults among which the Anqiu-Juxian Fault is the most important and prominent active fault since late Pleistocene and is usually considered to be the seismogenic fault of the 70 BC M 7 Anqiu earthquake and the 1668 AD M 8 1 / 2 Tancheng earthquake. By detailed research in recent years, e.g. the active fault mapping implemented during the “Eighth Five-Year Plan” period, we have gained thorough knowledge of the middle segment of the Anqiu-Juxian Fault to the south of Juxian, while the knowledge of the segment to the north of Juxian has been poor, even no active fault profiles have ever been found. Recent discoveries about the geometry and activity of the Anqiu-Zhuli segment of the Anqiu-Juxian Fault are introduced in this paper. The segment consists of the Nanliu sub-segment, the Shuangguan-Meicun sub-segment and the Zhuli sub-segment. All these sub-segments are distributed along the linear boundary line between hilly area and plain, or locate in the eastern slope of the NNE-trending hills. These fault segments are featured with right-lateral strike-slip movement combined with dip component, and their latest activity age is late Pleistocene to early Holocene. In conclusion, The Anqiu-Juxian Fault is the predominant active structure between Juxian and Changyi in the north of Shandong, and it should have some connections with the occurrence of the 70 BC M 7 Anqiu earthquake. Since the elapsed time is nearly 2100 years, the future earthquake risk in this area shall be emphasized.

1. Institute of Geology, China Earthquake Administration, Beijing 100029, China; 2. Institute of Earthquake Engieering of Shandoug Province Jinan 250014, China

安丘-莒县断裂是沂沭断裂带最主要的活动断裂,对强震的发生具有明显的控制作用。该断裂的安丘—朱里段由南流段、双官—眉村段和朱里段3条右阶斜列的次级断裂所组成,以右旋走滑活动为主,兼有正断或逆冲活动分量;其最新活动时代推断为晚更新世—全新世早期。根据断裂活动性的最新研究成果,认为在莒县至昌邑之间安丘-莒县断裂仍是占主导地位的活动断裂,与公元前70年安丘7级地震的发生具有密切关系。

... 王志才等, 2005 ...

2016

0.0

许汉刚, 范小平, 冉勇康, 等. 2016. 郯庐断裂带宿迁段F₅断裂浅层地震勘探新证据[J]. 地震地质, 38(1): 31—43. doi: DOI: 103969/j. issn. 0253-4967. 2016. 01. 013.

Han-gang

, FAN

Xiao-ping

, RAN

Yong-kang

, et al. 2016. New evidences of the Holocene fault in Suqian segment of the Tanlu fault zone discovered by shallow seismic exploration method[J]. Seismology and Geology, 38(1): 31—43(in Chinese).

The fault F 5 is considered as the most active fault in the Tanlu fault zone(Yi-Shu fault zone), which is located from Weifang of Shandong Province to Jiashan of Anhui Province, with a length of 360km. It has always been a focus of concern to many geoscientists because of its complexity and importance. But, for a long period of time, there exists biggish indetermination in the accurate position and active ages of the fault F 5 in Suqian section of Tanlu fault zone. Seismic reflection exploration is the main technique in present urban active faults detecting. In order to investigate the spatial distribution, characteristics and activities of the fault F 5 in covered terrains, we carried out a systematic survey to the fault with shallow seismic prospecting method and obtained the accurate position and development characteristics of the fault. The results show that the fault F 5 continues to develop toward south rather than ending at the Huancheng South Road of Suqian City. F 5 is mainly composed of two main faults, which dip in opposite directions and almost vertically. Near the Sankeshu town, F 5 is composed of three faults with right-stepping, forming a small pull-apart basin with length of 6km, width of 2.5km, controlling the deposition of Neogene and Quaternary strata. By combining the results of composite drilling section and trenching, we make a conclusion that the western branch of fault F 5 is a Holocene active fault, and the eastern branch is a Pleistocene active fault. Our general view is that fault F 5 is a Holocene active fault.

1. Earthquake Administration of Jiangsu Province, Nanjing 210014, China; 2. Institute of Geology, China Earthquake Administration, Beijing 10029, China

郯庐断裂带沂沭段最新活动的断层一般称之为F 5 断层,分布于潍坊至嘉山一带,长约360km。郯庐断裂带宿迁段F 5 断裂的准确位置、活动时代一直以来存在较大的不确定性。文中通过浅层地震勘探对F 5 断裂进行了系统性勘探,获取了准确的定位及其断裂发育特征。结果表明,F 5 断裂并未终止于原来认定的宿迁市环城南路处,而是继续向南延伸; F 5 断裂主要由2条相向而倾、近直立发育的主干断裂组成;在三棵树乡附近,F 5 断裂由3条断裂组成,且呈右阶排列,阶区长度约6km,宽度约2.5km,形成小的拉分盆地,控制了新近纪以来地层的沉积。结合钻孔联合剖面和槽探结果,判断F 5 断裂西边界断裂为全新世活动断裂,东边界断裂为晚更新世活动断裂,总体认为F 5 断裂为全新世活动断裂。

... 许汉刚等, 2016 ...

1992

0.0

徐嘉炜, 马国锋. 1992. 郯庐断裂带研究的十年回顾[J]. 地质论评, 38(4): 316—324.

Jia-wei

, MA

Guo-feng

. 1992. Review of the years(1981—1991) of the research on the Tancheng-Lujiang fault zone[J]. Geological Review, 38(4): 316—324(in Chinese).

Ten years have passed since the First All-China symposium on the TanchengLujiang Fault Zone. In the past ten years Chinese geologist have paid great atten-tion to this zone and written more than 200 papers on this subject.Several mono-graphs and contributions have been published. During this period this zone hasbeen well known in the international geoscience circle. In the paper the advances are introduced in the following aspects: distribu-tion of the fault zone, organization and attitude of the fault zone, fault rocks,associated structures, ductile shear zones, correlation of the blocks on both sides ofthe fault, large--scale strike-slip, kinematics of the strike--slip, timing of fault activ-ity and stages of evolution, mineralization, wrench fault system, transform marginalong the margin of the Northwest Pacific and the nature of the fault zone. The authors also point out that further work remains to be done on thefollowing problems; the existence of the fault zone in pre-Mesozoic time,correlation of different tectonic stages, strike--slip and adjustment of the northernsegment, nature of the fault, relationship between the fault and intrusions, miner-alization and isotopic geology.

1980―1990的十年间,作者主要根据自己和参考国内外地学工作者对郯庐断裂带研究的地质成果,论述了该断裂带的范围、性质、产状、结构、形成时间、断裂两侧的水平位移、两侧地块的对比及其成矿作用等。

... 徐嘉炜等, 1992, 1995 ...

1995

0.0

... 徐嘉炜等, 1992, 1995 ...

2017

0.0

... 杨源源等, 2017 ...

2017

0.0

... 姚大全等, 2017) ...

2015

0.0

张鹏, 李丽梅, 冉勇康, 等. 2015. 郯庐断裂带安丘-莒县断裂江苏段晚第四纪活动特征研究[J]. 地震地质, 37(4): 1162—1176. doi: DOI: 103969/j. issn. 0253-4967. 2015. 04. 018.

ZHANG

Peng

, LI

Li-mei

, RAN

Rong-kang

, et al. 2015. Research on characteristics of Late Quaternary activity of the Jiangsu segment of Anqiu-Juxian Fault in the Tanlu fault zone[J]. Seismology and Geology, 37(4): 1162—1176(in Chinese).

Anqiu-Juxian Fault is an important fault in the Tanlu fault zone, with the highest seismic risk, the most recent activity date, and the most obvious surface traces. Due to lack of credible geological evidences, there is big controversy on the Holocene activity in the Jiangsu segment of this fault. Research on the characteristics of late Quaternary activity in the Jiangsu segment of Anqiu-Juxian Fault, particularly its latest activity time, is of great significance to assessment of its earthquake ability and seismic risk. Based on field investigations on the Jiangsu segment of Anqiu-Juxian Fault, and combining with the results of fault activities identification on this fault in Suqian City, we discussed the characteristics of its activities in late Quaternary. Multiple geological sections we found in this study and the results of fault activities identification in Suqian City all indicate that there was an ancient seismic event occurring in middle period of Holocene in the segment from southern Maling Mountain to Suqian City; but the trench at Houchen village did not show any evidence of Holocene activity on the Chonggangshan segment of this fault. Based on method of shallow seismic exploration, we carried out a systematic exploration of this fault to get its accurate position and activity characteristics. The results show that Anqiu-Juxian Fault in Suqian City is mainly characterized by dextral strike-slip, associated with both thrusting and extensional movement in different positions. A series of low hills were formed along the fault in the north of Suqian City, and a small graben basin was formed in the south of Suqian City, both are controlled by the dextral strike-slip movement of this fault. The Jiangsu segment of Anqiu-Juxian Fault in general is characterized by dextral strike-slip with thrusting movement. But some parts of it are characterized by dextral strike-slip with extensional movement. The Jiangsu segment of Anqiu-Juxian Fault experienced a number of activities since the late Quaternary, with an obvious activity in Holocene. The seismic activities of Jiangsu segment of Anqiu-Juxian Fault have the characteristic of high intensity and low frequency. Its activities decrease gradually from north to south as a whole.

1. Earthquake Administration of Jiangsu Province, Nanjing 210014, China; 2. Institute of Geology, China Earthquake Administration, Beijing 100085, China

安丘-莒县断裂是郯庐断裂带内活动时代最新、地表形迹最明显, 地震危险性最大的断裂。因缺少可信的地质证据, 前人对于该断裂江苏段的全新世活动情况存在较大争议。文中根据对郯庐断裂带安丘-莒县断裂江苏段开展的野外调查工作成果, 结合在宿迁市地区开展的断层活动性鉴定工作成果, 对该断裂的晚第四纪活动特征进行了探讨。本次发现的多个断裂剖面及宿迁地区的断层活动性鉴定成果都表明安丘-莒县断裂的南马陵山—宿迁段在全新世中期发生过1次古地震事件; 而后陈村探槽表明该断裂重岗山段无全新世活动迹象。安丘-莒县断裂江苏段晚第四纪活动总体以右旋走滑兼挤压逆冲为特征, 局部地区则以走滑正断为主。安丘-莒县断裂江苏段自晚更新世以来经历了多次活动, 在全新世也有明显活动, 其地震活动具强度大、频度低的特点, 其活动性总体自北向南逐渐减弱。

... 尤其是近年来, 对F₅断裂的几何展布、活动时代和活动性质有了进一步认识(张鹏等, 2015 ...

2014

0.0

... 全新世破裂(郑颖平等, 2014 ...

2005

0.0

朱光, 牛漫兰, 刘国生, 等. 2005. 郯庐断裂带肥东段走滑运动的 ⁴⁰Ar/³⁹Ar法定年[J]. 地质学报, 79(3): 303—316.

ZHU

Guang

, NIU

Man-lan

, LIU

Guo-sheng

, et al. 2005. ⁴⁰Ar/³⁹Ar dating for the strike-slip movement on the Feidong part of Tanlu fault belt[J]. Acta Geologica Sinica, 79(3): 303—316(in Chinese).

郯庐断裂带在华北与华南板块碰撞之后是否发生过大规模左行平移及其准确的时间,仍然是存在着争议的重要问题。郯庐断裂肥东段地表出露了大规模的、北北东走向的韧性剪切带。野外构造、显微构造与石英C轴组构分析皆指示为左旋走滑韧性剪切带。糜棱岩中变形矿物组合与矿物变形行为指示该韧性剪切带形成于中―高绿片岩相环境。通过对该段走滑糜棱岩中角闪石与黑云母的40Ar/39Ar年代学研究,本次工作中获得了一个角闪石(N14)的40Ar/39Ar坪年龄为143.3±1.3Ma(早白垩世初),据变形温度判断其代表了该断裂带左行平移中的变形年龄。该糜棱岩(N14)中新生的黑云母40Ar/39Ar坪年龄为134.1±0.6Ma,而同一采场中另一糜棱岩(N13)中新生黑云母40Ar/39Ar坪年龄为130.3±0.6Ma,皆指示了左行平移活动的冷却年龄。另外4处走滑糜棱岩中黑云母的40Ar/39Ar坪年龄分别为137.2±0.8Ma(N47)、135.6±0.6Ma(N17)、124.8±0.7Ma(N21)和125.9±0.4Ma(N22),也都属于冷却年龄,反映了该走滑韧性剪带内的不均匀冷却现象。由此变形年龄与冷却年龄可以判断该断裂带的左行平移持续时间不超过6Ma左右。由N14糜棱岩中的角闪石与黑云母坪年龄得到该处的平均冷却速率为21.7℃/Ma,属于较快速的冷却。本次40Ar/39Ar测年结果,更可靠地证实了郯庐断裂

... 朱光等, 2005) ...

1999

0.0

... Gilder et al ...

2016

0.0

... Shu et al ...

1987

0.0

... 0 引言郯庐断裂带是中国东部最大的走滑断裂系, 自20世纪60年代通过航磁发现其存在以来, 受到了国内外学者的广泛关注, 并对其形成、演化过程进行了大量的研究(Xu et al ...

1993

0.0

... Yin et al ...