| 汶川地震断裂带滑移行为、物理性质及其大地震活动性——来自汶川地震断裂带科学钻探的证据 |
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| 引用本文： | 李海兵,许志琴,王焕,张蕾,何祥丽,司家亮,孙知明.汶川地震断裂带滑移行为、物理性质及其大地震活动性——来自汶川地震断裂带科学钻探的证据[J].地球物理学报,2018,61(5):1680-1697. |
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| 作者姓名： | 李海兵 许志琴 王焕 张蕾 何祥丽 司家亮 孙知明 |
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| 作者单位： | 1. 自然资源部深地动力学重点实验室, 中国地质科学院地质研究所, 北京 100037;2. 南京大学地球科学与工程学院, 南京 210046;3. 自然资源部古地磁与古构造重建重点实验室, 中国地质科学院地质力学研究所, 北京 100081 |
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| 基金项目： | 国家自然科学基金项目（41620104006，41330211）和中国地质科学院基本科研业务费项目（YYWF201601）联合资助. |
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| 摘 要： | 断裂带物质组成、结构及其物理性质是理解断裂变形机制和地震破裂过程的基础和关键，断裂带地震（黏滑）和非地震（蠕滑）滑移行为不仅对了解地震活动性和山脉隆升过程具有重要意义，而且直接为防震减灾提供科学依据.我们以穿过龙门山映秀—北川和灌县—安县断裂带的汶川地震断裂带科学钻探（WFSD）岩心和地表出露的断裂带为研究对象，通过对断裂岩组成、结构、显微构造和钻孔物性测井数据进行分析研究，确定了龙门山逆冲断裂带滑移行为和物性特征，初步探讨了大地震活动性和有关断裂带的隆升作用：（1）映秀—北川断裂带倾向NW，浅部倾角~65°，发育的断裂岩厚约180~280 m，由碎裂岩、假玄武玻璃（地震化石）、断层泥和断层角砾岩组成.断裂带具有高自然伽马、高磁化率值、低电阻率、低波速等物理性质以及对称型破碎结构.断层泥普遍具有摩擦热效应的高磁化率值和石墨化作用特征，是古地震滑动的岩石记录.表明映秀—北川断裂带为经常发生大地震的断裂带，晚新生代以来类似汶川地震的大地震复发周期小于6000—10000年，具有千年复发周期特征.（2）灌县—安县断裂带倾向NW，浅部倾角~38°，发育的断裂岩厚约40~50 m，仅由断层泥和断层角砾岩组成，具有典型的"压溶"结构，表现出蠕滑性质.除压溶作用外，定向富集的层状黏土矿物和微孔隙的发育使断层强度变弱.断裂带具上盘破碎的非对称型破碎结构，除具低磁化率值特征外，其他物性与映秀—北川断裂带一致.（3）根据断裂岩厚度与断层滑移量相关经验公式关系，以及断层产状，粗略估算映秀—北川断裂带自中生代以来累积垂直位移量大于9 km，灌县—安县断裂带累积垂直位移量小于3 km.映秀—北川断裂带长期大地震产生的累积垂直位移量是龙门山隆升的主要贡献.
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| 关 键 词： | 汶川地震断裂带 滑移行为 断裂带物理性质 大地震活动性 汶川地震断裂带科学钻探 龙门山 |
| 收稿时间： | 2018-04-20 |
Fault behavior,physical properties and seismic activity of the Wenchuan earthquake fault zone: evidences from the Wenchuan earthquake Fault Scientific Drilling project (WFSD) |
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| LI HaiBing,XU ZhiQin,WANG Huan,ZHANG Lei,HE XiangLi,SI JiaLiang,SUN ZhiMing.Fault behavior,physical properties and seismic activity of the Wenchuan earthquake fault zone: evidences from the Wenchuan earthquake Fault Scientific Drilling project (WFSD)[J].Chinese Journal of Geophysics,2018,61(5):1680-1697. |
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| Authors: | LI HaiBing XU ZhiQin WANG Huan ZHANG Lei HE XiangLi SI JiaLiang SUN ZhiMing |
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| Institution: | 1. Key Laboratory of Deep-Earth Dynamics of Natural Resources Ministry, Institute of Geology, Chinese Academy of Geological Sciences, Beijing 100037, China;2. School of Earth Sciences and Engineering, Nanjing University, Nanjing 210046, China;3. Key Laboratory of Paleomagnetism and Tectonic Reconstruction of Natural Resources Ministry, Institute of Geomechanics, Chinese Academy of Geological Sciences, Beijing 100081, China |
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| Abstract: | Fault zone composition, structures and physical properties are the keys to understand the fault deformation mechanisms and earthquake generation processes. Seismic and aseismic slip behaviors are essential to learn about fault zone seismicity and mountain uplift processes, which provide scientific basis for Earthquake prevention and disaster reduction. Based on surface outcrop investigation and detailed research on the drilling cores of the Wenchuan earthquake Fault Scientific Drilling (WFSD), fault zone characteristics, microstructures and physical properties of fault rocks were determined, and new knowledge about the fault zone deformation mechanisms and related Longmen Shan uplift are suggested: (1) The Yingxiu-Beichuan fault (YBF) dips to NW with an angle of 65° at shallow depth, consisting of ~180—280 m-wide fault rocks of cataclasite, pseudotachylyte (fossil earthquake), fault gouge and fault breccia. The fault zone has higher natural gamma and magnetic susceptibility, lower electrical resistivity and wave velocity, and a symmetrical fracture structure. Gouge graphitization and high magnetic susceptibility are observed in the fault zone due to the high temperature generated by ancient seismic faulting, indicating large earthquakes happened frequently along this fault. Large earthquakes (as Wenchuan earthquake) recurrence period is less than 6000—10000 years since late Cenozoic, charactered with millennium recurrence period. (2) The Guanxian-Anxian fault (GAF) dips to NW with an angle of 38°, consisting of ~40—50 m-thick fault breccia and fault gouge with lower magnetic susceptibility. Multi-scale structural analyzes show that the brittle fault rocks display characteristics of pressolution and ductile-like structures, indicating that the GAF is an aseismic fault with long-term creeping properties. Besides, phyllosilicates-rich gouge and pervasive micropores are responsible for weakening the GAF. The physical properties of the GAF are similar to that of the YBF, except the lower magnetic susceptibility. (3) Based on the empirical formula between fault displacement and fault core thickness, and taking the fault occurrences into consideration, a cumulative vertical displacement of >9 km is roughly estimated for the YBF, whereas that of the GAF is <3 km. Therefore, the accumulative vertical displacement generated by the long-term seismicity of the YBF is the main contribution to the Longmen Shan uplift. |
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| Keywords: | Wenchuan earthquake fault zone Slip behavior Fault zone physical properties Large earthquake activities WFSD Longmen Shan |
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