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首页> 外文期刊>Geochemistry, geophysics, geosystems >Rock record and magnetic response to large earthquakes within Wenchuan Earthquake Fault Scientific Drilling cores
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Rock record and magnetic response to large earthquakes within Wenchuan Earthquake Fault Scientific Drilling cores

机译：汶川地震故障科学钻井岩石中大地震岩石记录与磁反应

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摘要

Fault-related pseudotachylytes are often considered to be produced by large seismic events. To investigate the rock record and magnetic response to large earthquakes within cores from the Wenchuan Earthquake Fault Scientific Drilling borehole 2 (WFSD-2), we carried out microstructural, geochemical, and rock-magnetic analyses of representative cores. Based on microstructural observations and powder X-ray diffraction analyses, we found 21 layers of melt-origin pseudotachylytes from 579.62 to 599.31 m-depth in the cores. The presence of early-formed pseudotachylyte fragments in the new layer suggests that seismic faulting processes exploited the same fault strand more than once. Pseudotachylyte veins have higher values of magnetic susceptibility relative to wall rocks. Rock-magnetic results indicate that the magnetic minerals within the pseudotachylyte veins are magnetite with varying amounts of paramagnetic minerals. Magnetic hysteresis loops show that a reduction of the grain size of ferromagnetic minerals is not a plausible explanation for the higher magnetic susceptibility values in pseudotachylyte veins. Rock-magnetic analyses indicate that frictional heating (>500 degrees C) occurred in the pseudotachylyte veins during large earthquakes. The resulting high temperatures induced thermal decomposition of paramagnetic minerals, forming magnetite and contributing to the higher magnetic susceptibility values. Different generations of pseudotachylytes and numerous high magnetic susceptibility zones together demonstrate that ancient powerful earthquakes may have occurred repeatedly in the Longmen Shan thrust belt.
机译：与大量地震事件常常被认为具有与故障相关的假辐射术。为了调查来自汶川地震故障科学钻井钻孔2（WFSD-2）的核心内大地震的岩石记录和磁响应，我们进行了代表性核心的微观结构，地球化学和岩石磁性分析。基于微观结构观察和粉末X射线衍射分析，我们发现21层熔体源性裂解物，在核心中的579.62至599.31 m深度。新层中早期的假辐射碎片的存在表明，地震断裂过程不止一次地利用相同的故障链。 Pseudotachylyte静脉相对于壁岩具有更高的磁敏感值。岩石磁性结果表明，假壳静脉内的磁性矿物是具有不同量的顺磁矿物质的磁铁矿。磁滞回路表明，铁磁矿物质的晶粒尺寸的降低不是假辐射纹理中较高磁化率值的合理解释。摇滚磁性分析表明，在大地震期间，伪辐射岩静脉发生摩擦加热（> 500℃）。由此产生的高温诱导顺磁性矿物的热分解，形成磁铁矿并有助于较高的磁化率值。不同一代的假阴影术和许多高磁性敏感区一起表明，在龙门山推力皮带中可能反复发生古代强大的地震。

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  • 作者

    Zhang Lei; Sun Zhiming; Li Haibing; Zhao Laishi; Song Sheng-Rong; Chou Yu-Min; Cao Yong; Ye Xiaozhou; Wang Huan; He Xiangli;

  • 作者单位

    Chinese Acad Geol Sci Inst Geomech Key Lab Paleomagnetism &

    Tecton Reconstruct Minist Land &

    Resources Beijing Peoples R China;

    Chinese Acad Geol Sci Inst Geomech Key Lab Paleomagnetism &

    Tecton Reconstruct Minist Land &

    Resources Beijing Peoples R China;

    Chinese Acad Geol Sci Inst Geol Beijing Peoples R China;

    China Univ Geosci Wuhan Peoples R China;

    Natl Taiwan Univ Dept Geosci Taipei Taiwan;

    South Univ Sci &

    Technol Dept Ocean Sci &

    Engn Shenzhen Peoples R China;

    Chinese Acad Geol Sci Inst Geomech Key Lab Paleomagnetism &

    Tecton Reconstruct Minist Land &

    Resources Beijing Peoples R China;

    Chinese Acad Geol Sci Inst Geomech Key Lab Paleomagnetism &

    Tecton Reconstruct Minist Land &

    Resources Beijing Peoples R China;

    Chinese Acad Geol Sci Inst Geol Beijing Peoples R China;

    China Univ Geosci Beijing Peoples R China;

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  • 原文格式 PDF
  • 正文语种 eng
  • 中图分类 地球物理学;
  • 关键词

    frictional heating; pseudotachylyte; microstructure; rock magnetism; Wenchuan Earthquake Fault;

    机译：摩擦加热;假壳;微观结构;岩石磁性;汶川地震故障;

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