青藏高原东南缘深部地壳流与地磁日变化短时畸变源电流的联系

章鑫, 姚丽, 冯志生. 2020. 青藏高原东南缘深部地壳流与地磁日变化短时畸变源电流的联系. 地球物理学报, 63(10): 3804-3817, doi: 10.6038/cjg2020N0223
引用本文: 章鑫, 姚丽, 冯志生. 2020. 青藏高原东南缘深部地壳流与地磁日变化短时畸变源电流的联系. 地球物理学报, 63(10): 3804-3817, doi: 10.6038/cjg2020N0223
ZHANG Xin, YAO Li, FENG ZhiSheng. 2020. Relationship between deep crustal flows and source currents of short time geomagnetic diurnal-variations distortion in southeast margin of Qinghai-Tibet Plateau. Chinese Journal of Geophysics (in Chinese), 63(10): 3804-3817, doi: 10.6038/cjg2020N0223
Citation: ZHANG Xin, YAO Li, FENG ZhiSheng. 2020. Relationship between deep crustal flows and source currents of short time geomagnetic diurnal-variations distortion in southeast margin of Qinghai-Tibet Plateau. Chinese Journal of Geophysics (in Chinese), 63(10): 3804-3817, doi: 10.6038/cjg2020N0223

青藏高原东南缘深部地壳流与地磁日变化短时畸变源电流的联系

  • 基金项目:

    地震科技星火计划青年项目(XH18035Y),国家重点研发计划(2017YFC1500502)资助

详细信息
    作者简介:

    章鑫, 男, 助理研究员, 主要从事地球电磁学研究.E-mail:zxdqwl@163.com

  • 中图分类号: P318;P319

Relationship between deep crustal flows and source currents of short time geomagnetic diurnal-variations distortion in southeast margin of Qinghai-Tibet Plateau

  • 在青藏高原东南缘,前人使用大地电磁探测和地震学方法得出的结果都揭示了可能存在部分熔融状态的地壳流,而这种地下熔融体与周围物质的作用可能引起了地下强电流异常,进一步导致地表地磁响应.基于连续的地磁观测,发现2018年7月31日在川滇块体周边出现大范围的地磁Z分量日变化短时畸变,畸变发生后100天内发生了4次5级以上地震.为了定量研究这一现象,本文基于Biot-Savart定理和采用SVD(Singular Value Decomposition,奇异值分解)的阻尼最小二乘法对地磁日变化短时畸变数据开展反演.结果显示:(1)以大地电磁测深给出的电性模型作为初始条件,反演得到的电流强度为3700~5000 A,有效深度为25~60 km;(2)地下畸变电流的空间分布位置和深度和地下电性高导体分布一致,与前人给出的地壳流位置吻合;(3)地壳流偶然微小运动可能引起了大范围的强电流,这种短时存在的高强度电流沿高导带分布,可能是地磁日变化短时畸变的源电流;(4)推测深部地壳流的运动具有传递应力作用,参与诱发了100天内发生多次5级以上地震.对源电流进行反演的定量化工作,以地下电流的方式佐证了可能存在地壳流.

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  • 图 1 

    研究区域的地磁站分布及地震构造要素

    Figure 1. 

    Distribution of geomagnetic stations and seismic structural elements in the study area

    图 2 

    2018年7月31日的地磁Z分量反相位畸变(a, b)及幅度(c)

    Figure 2. 

    The inverse phase distortion (a, b) and amplitudes (c) of geomagnetic Z component on July 31, 2018

    图 3 

    模型反演的下降速度和误差分析

    Figure 3. 

    The descent speed of inversion and the error analysis

    图 4 

    地磁Z分量反相位畸变正演拟合结果

    Figure 4. 

    Forward fitting result of geomagnetic Z component inverse phase distortion

    图 5 

    景谷—江油剖面(a)反演的电流深度(b)

    Figure 5. 

    Inversed depth (b) of current from Jinggu-Jiangyou profile (a)

    图 6 

    察隅—富源剖面(a)反演的电流深度(b)

    Figure 6. 

    Inversed depth (b) of current from Chayu-Fuyuan profile (a)

    图 7 

    盈江—马关剖面(a)反演的电流深度(b)

    Figure 7. 

    Inversed depth (b) of current from Yingjiang-Maguan profile (a)

    图 8 

    地磁畸变源电流约束下的地壳流可能分布

    Figure 8. 

    Distribution of crustal current limited by source currents of geomagnetic distortion

    图 9 

    川滇块体周边4次大于5级地震的时间空间相对关系

    Figure 9. 

    The temporal-spatial relationship of 4 earthquakes (MS≥5) around Sichuan-Yunnan block

    表 1 

    川滇块体周边4次MS≥ 5.0地震参数

    Table 1. 

    Parameters of 4 earthquakes (MS≥5.0) around the Sichuan-Yunnan block

    震级MS 发震时间 纬度(°N) 经度(°E) 深度(km) 与前一次地震间隔(天) 震中位置
    5.0 2018-08-14 03:50:36 24.19 102.71 14 - 云南通海
    5.0 2018-08-13 01:44:24 24.19 102.71 6 1 云南通海
    5.9 2018-09-08 10:31:29 23.26 101.53 17 26 云南墨江
    5.1 2018-10-31 16:29:56 27.62 102.09 20 53 四川西昌
    下载: 导出CSV

    表 2 

    反演的测试结果

    Table 2. 

    The result of inversion testing

    点序号 原始内插/nT 拟合结果/nT 深度反演结果/km 初始电流强度/nT 初始深度值/km
    1 13.091 13.0396 51.6917 120 30
    2 12.5806 12.5345 57.2987 120 30
    3 12.0369 11.9944 63.2168 120 30
    4 11.468 11.428 69.4277 120 30
    5 10.8787 10.8404 75.9568 120 30
    6 10.2731 10.1802 83.4966 160 40
    7 9.6541 9.5556 90.9245 160 40
    8 9.0231 8.9189 98.8949 160 40
    9 8.378 8.3556 106.3766 120 30
    10 7.7083 7.6997 115.7309 120 30
    11 6.9806 6.9976 126.7186 120 30
    下载: 导出CSV
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收稿日期:  2020-02-06
修回日期:  2020-09-01
上线日期:  2020-10-05

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