KEY TECHNIQUES AND SEVERAL CASES ANALYSIS IN PALEO- SEISMIC STUDIES IN MAINLAND CHINA(5): NONVISIBILITY, DIEOUT OF FAULT STRANDS AND IDENTIFICATION OF YOUNG PALEOSEISMIC EVENTS

doi:10.3969/j.issn.0253-4967.2015.02.001

Abstract

Abstract:

Nonvisibility(dieout)of fault strands occurs primarily in stratigraphic units associated with young paleoseismic events, which may cause misidentification of the young events and bring more uncertainties for seismic risk assessment. Based on previous related studies, this paper integrates case studies in mainland China to discuss the nonvisibility of fault strands and identification of young paleoseismic events. Nonvisibility of fault strands is prevailing in sandy, soil, silty, loess, and clay-sandy units, and is more possibly associated with strike-slip faults comparing with normal and reverse faults. Case studies on several trenches across surface ruptures produced by the Wenchuan earthquake and others located at different regions suggest that trench siting, excavation, and comprehensive analysis are key technical points to identify young paleoseismic events in the stratigraphic units where nonvisibility of fault strands is prone to occur. Stratigraphic units with more sequences have been suggested to be good sites for trenching to avoid misidentification produced by nonvisibility of fault strands. Multiple trenching is facilitated to lower the influence of local nonvisibility. Assumed extending of upper and lower units, grain sizes, color, and soil horizon are the basic methods to identify nonvisibility. Analysis of microstructures, grain sizes and magnetic susceptibility is one of the future studies related to identification of nonvisibility of fault strands.

Key words: nonvisibility of fault strands, case study, young paleoseismic events, identification technique

摘要：

断层隐形或尖灭现象在年轻事件影响的地层中较为突出, 可能造成年轻事件识别的误判, 增大地震危险性评价的不确定性。文中在前人相关研究成果的基础上, 结合中国的研究实例, 讨论断层隐形与年轻事件识别的问题。断裂在砂层、土壤、粉砂层、黄土、黏土质砂中的隐形比较普遍。在走滑、逆断层和正断层3种构造类型中走滑断层出现隐形的比例最高。汶川地震破裂带及其他一些探槽研究的案例显示, 易 "隐形"地层中年轻事件的识别需要从探槽开挖地点选择、探槽开挖方式、探槽信息的综合分析等相关技术入手。选择多韵律地层开挖探槽是避免断层隐形影响事件识别的关键; 组合或3维探槽有利于减小断层局部隐形的影响; 上下层位推延、粒度、色度以及土壤发育程度等综合分析是识别隐形断层的基本手段; 显微构造、粒度和磁化率分析等是隐形断层识别的重要发展方向之一。

关键词: 断层隐形, 研究案例, 年轻事件, 识别技术

CLC Number:

P315.2

RAN Yong-kang, WANG Hu, Li Yan-bao. KEY TECHNIQUES AND SEVERAL CASES ANALYSIS IN PALEO- SEISMIC STUDIES IN MAINLAND CHINA(5): NONVISIBILITY, DIEOUT OF FAULT STRANDS AND IDENTIFICATION OF YOUNG PALEOSEISMIC EVENTS[J]. SEISMOLOGY AND GEOLOGY, 2015, 37(2): 343-356.

冉勇康, 王虎, 李彦宝. 中国大陆古地震研究的关键技术与案例解析(5)——断层隐形、尖灭与年轻事件识别[J]. 地震地质, 2015, 37(2): 343-356.

References

晁洪太. 1998. 第四纪地层中活断层显微构造标志、隐形活断层及其应用研究【D】. [学位论文]. 北京: 中国地震局地质研究所.
CHAO Hong-tai. 1998. Microstructural indicators of active faults and their applications to determine the invisible faults in Quaternary unconsolidated sediments 【D】. Dissertation. Institute of Geology, China Earthquake Administration, Beijing(in Chinese).
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特征滑动行为与特征地震【J】. 内陆地震, 8(4): 297—304.
CHAO Hong-tai, LI Jia-ling, CUI Zhao-wen, et al. 1994. Characteristic slip behavior of the Holocene fault in the central section of the Tanlu Fault zone and the characteristic earthquakes 【J】. Inland Earthquake, 8(4): 297—304(in Chinese).
邓起东, 陈立春, 冉勇康. 2004. 活动构造定量研究与应用【J】. 地学前缘, 11(4): 383—392.
DENG Qi-dong, CHEN Li-chun, RAN Yong-kang. 2004. Quantitative studies and applications of active tectonics 【J】. Earth Science Frontiers, 11(4): 383—392(in Chinese).
方仲景, 计凤桔, 向宏发, 等. 1976. 郯庐带中段第四纪断裂活动特征与地震地质条件论评【J】. 地质科学, 4: 354—365.
FANG Zhong-jing, JI Feng-ju, XIANG Hong-fa, et al. 1976. The characteristics of Quaternary movements along the middle segment of the old Tancheng-Lujiang fracture-zone and their seismogeologic conditions 【J】. Scientia Geologica Sinca, 4: 354—365(in Chinese).
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).
林传勇, 史兰斌, 陈孝德, 等. 2008. 松散沉积物中活动断层的微观探测方法【J】. 地学前缘, 15(3): 324—336.
LIN Chuan-yong, SHI Lan-bin, CHEN Xiao-de, et al. 2008. Microscopic observation method for active faults in soft sediments 【J】. Earth Science Frontiers, 15(3): 324—336(in Chinese).
冉勇康. 1997. 中国几个典型地点的古地震精细研究和大地震重复行为探讨【D】. [学位论文]. 北京: 中国地震局地质研究所.
RAN Yong-kang. 1997. Detailed research of paleoearthquakes at several typical regions in China and exploration of recurrence behavior of large earthquakes 【D】. Dissertation. Institute of Geology, China Earthquake Administration, Beijing(in Chinese).
冉勇康, 陈立春, 陈桂华, 等. 2008. 汶川M_S8.0地震发震断裂大地震原地重复现象初析【J】. 地震地质, 30(3): 630—643.
RAN Yong-kang, CHEN Li-chun, CHEN Gui-hua, et al. 2008. Primary analysis of in-situ recurrence of large earthquake along seismogenic fault of the M_S8.0 Wenchuan earthquake 【J】. Seismology and Geology, 30(3): 630—643(in Chinese).
冉勇康, 王虎, 李彦宝, 等. 2012a. 中国大陆古地震研究的关键技术与案例解析(1): 走滑活动断裂的探槽地点、布设与事件识别标志【J】. 地震地质, 34(2): 197—210.
RAN Yong-kang, WANG Hu, LI Yan-bao, et al. 2012a. Key techniques and several cases analysis in paleoseismic studies in mainland China(1): Trenching sites, layouts and paleoseismic indicators on active strike-slip faults 【J】. Seismology and Geology, 34(2): 197—210(in Chinese).
冉勇康, 陈立春, 陈文山, 等. 2012b. 中国大陆古地震研究的关键技术与案例解析(2): 汶川地震地表变形特征与褶皱逆断层古地震识别【J】. 地震地质, 34(3): 385—400.
RAN Yong-kang, CHEN Li-chun, CHEN Wen-shan, et al. 2012b. Key techniques and several cases analysis in paleoseismic studies in mainland China(2): Surface deformation characteristics of Wenchuan earthquake and paleoseismic indicators on fold-reverse fault 【J】. Seismology and Geology, 34(3): 385—400(in Chinese).
冉勇康, 李彦宝, 杜鹏, 等. 2014a. 中国大陆古地震研究的关键技术与案例解析(3): 正断层破裂特征、环境影响与古地震识别【J】. 地震地质, 36(2): 287—301.
RAN Yong-kang, LI Yan-bao, DU Peng, et al. 2014a. Key techniques and several cases analysis in paleoseismic studies in mainland China(3): Rupture characteristics, environment impact and paleoseismic indicators on normal faults 【J】. Seismology and Geology, 36(2): 287—301(in Chinese).
冉勇康, 王虎, 杨会丽, 等. 2014b. 中国大陆古地震研究的关键技术与案例解析(4): 古地震定年技术的样品采集和事件年代分析【J】. 地震地质, 36(4): 939—955.
RAN Yong-kang, WANG Hu, YANG Hui-li, et al. 2014b. Key techniques and several cases analysis in paleoseismic studies in mainland China(4): Sampling and event analysis of paleoseismic dating methods 【J】. Seismology and Geology, 36(4): 939—955(in Chinese).
任金卫. 1994. 则木河断裂晚第四纪位移及滑动速率【J】. 地震地质, 16(2): 146.
REN Jin-wei. 1994. Late Quaternary displacement and slip rate of Zemuhe Fault in Sichuan, China 【J】. Seismology and Geology, 16(2): 146(in Chinese).
田勤俭, 任志坤, 张军龙. 2008. 则木河断裂带大箐梁子附近古地震组合探槽研究【J】. 地震地质, 30(2): 400—411.
TIAN Qin-jian, REN Zhi-kun, ZHANG Jun-long. 2008. Study of paleoearthquakes by combined trench on Zemuhe Fault around Daqingliangzi, Xichang, Sichuan 【J】. Seismology and Geology, 30(2): 400—411(in Chinese).
王虎, 冉勇康, 李彦宝. 2011. 小型拉分盆地的生长与走滑断层的位移速率: 以青藏高原东南缘则木河断裂带为例【J】. 地震地质, 33(4): 818—827.
WANG Hu, RAN Yong-kang, LI Yan-bao. 2011. Growth of a small pull-apart basin and slip rate of strike-slip fault: With the example of Zemuhe Fault on the southeastern margin of the Tibetan plateau 【J】. Seismology and Geology, 33(4): 818—827(in Chinese).
王虎, 冉勇康, 李彦宝, 等. 2013. 则木河断裂上古地震破裂与小型三角状拉分盆地演化【J】. 中国科学(D辑), 43(7): 1106—1114.
WANG Hu, RAN Yong-kang, LI Yan-bao, et al. 2013. Paleoseismic ruptures and evolution of a small triangular pull-apart basin on the Zemuhe Fault 【J】. Science in China(Ser D), 56(3): 504—512.
王挺梅, 李建平. 1984. 唐山大地震的重复间隔【J】. 地震地质, 6(3): 77—83.
WANG Ting-mei, LI Jian-ping. 1984. The recurrence intervals of the strong earthquakes in Tangshan 【J】. Seismology and Geology, 6(3): 77—83(in Chinese).
闻学泽. 1995. 活动断裂地震潜势的定量评估【M】. 北京: 地震出版社.
WEN Xue-ze. 1995. Quantitative Assessment of Seismic Potential of Active Faults 【M】. Seismological Press, Beijing(in Chinese).
徐锡伟, 闻学泽, 叶建青, 等. 2008. 汶川M_S8.0地震地表破裂带及其发震构造【J】. 地震地质, 30(3): 597—629.
XU Xi-wei, WEN Xu-ze, YE Jian-qing, et al. 2008. The M_S8.0 Wenchuan earthquake surface ruptures and its seismogenic structure 【J】. Seismology and Geology, 30(3): 597—629(in Chinese).
殷志强, 秦小光, 赵无忌, 等. 2013. 黄河上游官亭盆地红黏土层成因机制再探讨【J】. 第四纪研究, 33(5): 995—1004.
YIN Zhi-qiang, QIN Xiao-guang, ZHAO Wu-ji, et al. 2013. Reexploration on the formation mechanism of the red clay layer in the Guanting Basin of the upper reaches of Yellow River 【J】. Quaternary Sciences, 33(5): 995—1004(in Chinese).
张培震, 毛凤英. 1996. 活动断裂定量研究与中长期强地震危险性概率评价【A】. 见: 中国地震局地质研究所编. 活动断裂研究(5). 北京: 地震出版社. 12—31.
ZHANG Pei-zhen, MAO Feng-ying. 1996. Active faulting and fault specific probabilistic seismic hazard assessment 【A】. In: Institute of Geology, China Earthquake Administration(ed). Research of Active Fault (5). Seismological Press, Beijing. 12—31(in Chinese).
Bonilla M G, Lienkaemper J J. 1990. Visibility of fault strands in exploratory trenches and timing of rupture events 【J】. Geology, 18(2): 153—156.
Bonilla M G, Lienkaemper J J. 1991. Factors affecting the recognition of faults exposed in exploratory trenches 【J】. U S Geological Survey Bulletin, 1947(54): 1—54.
He Hong-lin, Ren Jin-wei. 2003. Holocene earthquakes on the Zemuhe Fault in southwestern China 【J】. Annals of Geophysics, 46(5): 1035—1051.
Ran Yong-kang, Chen Li-chun, Chen Jie, et al. 2010. Paleoseismic evidence and repeat time of large earthquakes at three sites along the Longmenshan Fault zone 【J】. Tectonophysics, 491(1-4): 141—153.
Ran Yong-kang, Chen Wen-shan, Xu Xi-wei, et al. 2013. Paleoseismic events and recurrence interval along the Beichuan-Yingxiu Fault of Longmenshan Fault zone, Yingxiu, Sichuan, China 【J】. Tectonophysics, 584: 81—90.
Ran Yong-kang, Chen Wen-shan, Xu Xi-wei, et al. 2014. Late Quaternary paleoseismic behavior and rupture segmentation of the Yingxiu-Beichuan Fault along the Longmen Shan Fault zone, China 【J】. Tectonics, 33(11). doi: 10.1002/2014tc003649.
Wang Hu, Ran Yong-kang, Li Yan-bao, et al.,
2013. Holocene palaeoseismologic record of earthquakes on the Zemuhe Fault on the southeastern margin of the Tibetan plateau 【J】. Geophysical Journal International, 193(1): 11—28.

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