Recent Evidence of Slip Deformation of the Nankou-Sunhe Fault Based on Paleoseismic Results
-
摘要: 南口-孙河断裂是北京地区重要的全新世活动断裂之一，也是张家口-渤海地震带的重要组成部分。该断裂总体走向310°，全长约80 km。前人通过大量的活动构造研究揭示，其全新世以来存在明显活动，发生了3次古地震事件，单次地震事件的垂直位错约为1.3 m，断裂的垂直滑动速率约为0.3 mm/a。但由于直接观察证据和测年精度限制，前人对南口-孙河断裂最近一次强震事件离逝时间的约束相对薄弱。同时，针对南口-孙河断裂可能存在的最新走滑变形特征，缺乏相对可靠的地表变形证据支撑。为此，本研究在南口-孙河断裂全新世活动段东南端进行了古地震研究，系统分析了强震事件造成的沉积地层和构造变形，采集了探槽内主断层面构造定向样品，并开展了扫描电镜分析。通过古地震探槽研究揭示，南口-孙河断裂的活动造成了沉积地层显著构造变形，表现为标志地层的错断、地层厚度的变化以及崩积楔的发育等。对探槽内沉积地层的对比分析表明，南口-孙河断裂的活动错断了探槽内1.3 m以下的沉积地层。14C测年结果揭示，南口-孙河断裂最新一次地震事件的离逝时间为2820～3700 a BP。依据古地震探槽内崩积楔、错断层位分布、地层厚度变化以及地层的倾斜变形等古地震事件识别标志分析，南口-孙河断裂在本探槽内共揭示了4次古地震事件，10020 a BP 以来发生了3次古地震事件。依据显微构造分析揭示，断裂主断层面存在平行于断层走向的黏土矿物的定向排列，揭示断层可能存在左旋水平运动，这也被探槽内揭示的主断裂约75°的陡倾角和显著的花状构造所验证。因此，南口-孙河断裂全新世以来表现为显著的走滑运动特征，启示北京地区发震构造分析需要考虑华北地区的走滑构造变形。Abstract: The Nankou-Sunhe Fault is a relatively significant Holocene active fault in Beijing and an important part of the Zhangjiakou-Bohai seismic zone. The strike of the rupture is 310°, and the total length is ～80 km. The elapse time for the most recent event is relatively weak. At the same time, there is lack of relatively reliable surface deformation evidence to support the possible latest slip deformation of the Nankou-Sunhe fault. In this study, a paleoseismic trench was excavated at the southeast end of the Holocene active section of the Nankou-Sunhe Fault, and the sedimentary stratigraphy and tectonic deformation features within the trench were analyzed, and the mechanically oriented samples of the main fault surface were collected and analyzed by scanning electron microscopy. The paleoseismic trenching revealed that the activity of the Nankou-Sunhe Fault caused significant tectonic deformation of the sedimentary stratigraphy, which is manifested by the misalignment of the layers, the change of stratigraphic thickness and the development of the colluvial wedge. According to the comprehensive analysis of the sedimentary stratigraphy in the trench, the Nankou-Sunhe Fault has misplaced the sedimentary stratigraphy below 1.3m in the trench. According to the 14C dating results, the latest seismic event of the Nankou-Sunhe Fault is 2820～3700 a BP, and the analysis of the identification marks of paleoseismic events, such as the distribution of colluvial wedges, fault location, stratigraphic thickness change and tilting deformation of strata in the trench, reveals that the Nankou-Sunhe Fault has revealed three seismic events during the past 10020 a in this trench. The presence of directional alignment of clay minerals parallel to the fault strike on the main fault surface reveals that the fault may have had left-rotation horizontal motion, which is also verified by the steep dip of ～75° of the main fault revealed in the trench. Thus, all these results evidenced the strike-slip deformation and the highly potential seismic hazard for Nankou-Sunhe fault.
-
Key words:
- Nankou-Sunhe fault /
- Trenching /
- Paleoseismic /
- Scanning electron microscopy
1)1 2 胡平，徐锡伟，孟勇琦，2006. 北京市活动断层探测与地震危险性评价工程技术报告.2)2 3 赵帅，2021. 北京市昌平区地震灾害风险普查技术报告. -
图 2 探槽和南口-孙河断裂空间相对位置示意图
Figure 2. Schematic diagram of the spatial relative position of trenching and the Nankou-Sunhe fault
图 3 探槽南壁沉积地层拼接照片及解释结果
Figure 3. Sedimentary stratigraphic splice photo and interpretation result for the south wall of the trenching
图 4 探槽北壁沉积地层拼接照片及解释结果
Figure 4. Sedimentary stratigraphic splice photo and interpretation result for the north wall of the trenching
图 5 识别的4次古地震事件及其层位分布
Figure 5. Recognized paleoseismic events and its occurrence horizon
图 6 本研究与前人古地震事件对比
Figure 6. Paleoseismic events comparison between this study and previous research
-
陈成沟, 邢成起, 胡乐银等, 2017. 北京及其邻区小震重定位与活动构造分析. 地震, 37（3）: 84—94 doi: 10.3969/j.issn.1000-3274.2017.03.009Chen C. G. , Xing C. Q. , Hu L. Y. , et al. , 2017. Relocation of small earthquakes and active tectonics in Beijing and its adjacent areas. Earthquake, 37(3): 84—94. (in Chinese) doi: 10.3969/j.issn.1000-3274.2017.03.009 方仲景, 段瑞涛, 郑炳华等, 1994. 河北省怀安盆地北缘断裂活动性研究. 华北地震科学, 12（4）: 25—33Fang Z. J. , Duan R. T. , Zheng B. H. , et al. , 1994. Research on activity of the northern margin fault of the Huaian Basin in Hebei Province. North China Earthquake Sciences, 12(4): 25—33. (in Chinese) 何付兵, 2019. 南口—孙河断裂几何学、运动学特征及与地裂缝关系研究. 北京: 中国地震局地质研究所. He F. B. , 2019.Study on geometry and kinematics of the Nankou-Sunhe fault and its relationship with ground fissures. Beijing: Institute of Geology, China Earthquake Administrator. (in Chinese) 江娃利, 侯治华, 谢新生, 2001. 北京平原南口-孙河断裂带昌平旧县探槽古地震事件研究. 中国科学（D辑）, 31（6）: 501—509.Jiang W. L. ali, Hou Z. H. hihua, Xie X. S. insheng, 20021. Research on paleoearthquakes in Jiuxian trenches across Nankou-Sunhe fault zone in Changping County of Beijing plain. Science in China (Series D: Earth Sciences), 45(2)31(6): 160—173. 林传勇, 陈孝德, 罗华春等, 2006. 北京顺义-前门-良乡断裂探槽的微观分析及其启示. 地震地质, 28（4）: 561—578 doi: 10.3969/j.issn.0253-4967.2006.04.004Lin C. Y. , Chen X. D. , Luo H. C. , et al. , 2006. Microscopic analysis of the trench across the Shunyi-Qianmen-Liangxiang fault at Shunyi, Beijing and its implications. Seismology and Geology, 28(4): 561—578. (in Chinese) doi: 10.3969/j.issn.0253-4967.2006.04.004 林向东, 袁怀玉, 徐平等, 2017. 华北地区地震震源机制分区特征. 地球物理学报, 60（12）: 4589—4622 doi: 10.6038/cjg20171206Lin X. D. , Yuan H. Y. , Xu P. , et al. , 2017. Zonational characteristics of earthquake focal mechanism solutions in North China. Chinese Journal of Geophysics, 60(12): 4589—4622. (in Chinese) doi: 10.6038/cjg20171206 王丹丹, 张世民, 刘旭东等, 2007. 北京南口—孙河断裂北西段晚第四纪活动特征研究. 见: 地壳构造与地壳应力文集. 北京: 中国地震局地壳应力研究所, 50—59. 向宏发, 方仲景, 张晚霞等, 1993. 北京平原区隐伏断裂晚第四纪活动性的初步研究. 地震学报, 15（3）: 385—388. 向宏发, 虢顺民, 张晚霞等, 1995. 中国大陆区一些主要活动断裂滑移方式的地质位错与地震位错对比研究. 中国地震, 11（3）: 195—203Xiang H. F. , Guo S. M. , Zhang W. X. , et al. , 1995. The determination of the slip mode of some major active faults in China through the comparative study of geologic and seismic dislocations. Earthquake Research in China, 11(3): 195—203. (in Chinese) 徐锡伟, 吴卫民, 张先康等, 2002. 首都圈地区地壳最新构造变动与地震. 北京: 科学出版社, 1—376. 徐锡伟, 于贵华, 冉勇康等, 2015. 探测城市地震构造环境与活动断层. 见: 徐锡伟, 于贵华, 冉勇康等主编, 中国城市活动断层概论——20个城市活动断层探测成果. 北京: 地震出版社, 1—484. 徐锡伟, 白鸾曦, 魏雷鸣等, 2019. 华北克拉通破坏区最新构造运动起始时间讨论. 地球科学, 44（5）: 1647—1660Xu X. W. , Bai L. X. , Wei L. M. , et al. , 2019. Discussion on initiation time of the latest tectonic movement in break-up region of the North China Craton. Earth Science, 44(5): 1647—1660. (in Chinese) 张磊, 白凌燕, 蔡向民等, 2014. 北京南口-孙河断裂北西段综合物探剖面定位及其活动性研究. 现代地质, 28（1）: 234—242 doi: 10.3969/j.issn.1000-8527.2014.01.027Zhang L. , Bai L. Y. , Cai X. M. , et al. , 2014. Study on the position of North West section of Nankou-Sunhe fault in Beijing and its activity. Geoscience, 28(1): 234—242. (in Chinese) doi: 10.3969/j.issn.1000-8527.2014.01.027 张世民, 王丹丹, 刘旭东等, 2007. 北京南口-孙河断裂带北段晚第四纪活动的层序地层学研究. 地震地质, 29（4）: 729—743 doi: 10.3969/j.issn.0253-4967.2007.04.004Zhang S. M. , Wang D. D. , Liu X. D. , et al. , 2007. Sequence stratigraphy study of late quaternary activities of Nankou-Sunhe fault in Its Northern Segment, Beijing. Seismology and Geology, 29(4): 729—743. (in Chinese) doi: 10.3969/j.issn.0253-4967.2007.04.004 张世民, 王丹丹, 刘旭东等, 2008. 北京南口-孙河断裂晚第四纪古地震事件的钻孔剖面对比与分析. 中国科学 D辑: 地球科学, 38（7）: 881—895.Zhang S. M. , Wang D. D. , Liu X. D. , et al. , 2008. Using borehole core analysis to reveal Late Quaternary paleoearthquakes along the Nankou-Sunhe Fault, Beijing. Science in China Series D: Earth Sciences, 51(8): 1154—1168. Wells D. L. , Coppersmith K. J. , 1994. New empirical relationships among magnitude, rupture length, rupture width, rupture area, and surface displacement. Bulletin of the Seismological Society of America, 84(4): 974—1002. doi: 10.1785/BSSA0840040974 -
下载:
点击查看大图
图(8)
计量
- 文章访问数: 133
- HTML全文浏览量: 86
- PDF下载量: 77
- 被引次数: 0
