| 2017年西藏米林MS6.9地震前地磁垂直强度极化异常特征 |
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| 引用本文： | 李霞,冯丽丽,赵玉红,刘磊,苟智栋,樊文杰,贺曼秋,廖晓峰,艾萨·伊斯马伊力.2017年西藏米林MS6.9地震前地磁垂直强度极化异常特征[J].地震学报,2021,43(5):584-594. |
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| 作者姓名： | 李霞 冯丽丽 赵玉红 刘磊 苟智栋 樊文杰 贺曼秋 廖晓峰 艾萨·伊斯马伊力 |
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| 作者单位： | 中国西宁 810001 青海省地震局;中国西宁 810001 中国地震局青海格尔木青藏高原内部地球动力学野外科学观测研究站;中国西宁 810001 青海省地震局;中国昆明 650224 云南省地震局;中国重庆 401147 重庆市地震局;中国成都 610041 四川省地震局;中国乌鲁木齐 830011 新疆维吾尔自治区地震局 |
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| 基金项目： | 中国地震局科技星火计划（XH21037Y）%中国地震局震情跟踪定向工作任务（2021010413，2021010308）%青海省地震局格尔木青藏高原内部地球动力学野外科学观测研究站专项课题和青海省地震局基金课题（2021A03）联合资助 |
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| 摘 要： | 基于中国大陆65 个地磁台站秒采样观测资料，利用地磁垂直强度极化方法提取了2017年西藏米林MS6.9 地震震中及附近区域超低频电磁异常信号并分析其时空演化特征。结果显示:米林MS6.9 地震前在青藏高原出现了大范围的地磁垂直强度极化高值异常，异常过程共持续9天；高值异常开始于2017 年10 月30 日，高值持续3 天之后出现短时间下降，随即转折上升，再次出现高值异常并持续了4 天，在此过程中各高值台站的时序曲线呈现出单峰或双峰的形态。空间分布图显示高值异常在中国大陆西部区域反复出现，尤其是在青藏高原巴颜喀拉地块与羌塘地块的交界处。异常呈“出现—扩大—收缩—消失—扩大—消失”的演化过程，10月31日异常面积达到最大值。异常过程结束后10天发生了西藏米林MS6.9地震，震中距离10 月31 日异常阈值线5 km。综合分析认为，此次异常与米林地震具有较强的时空相关性，是可靠的地震电磁前兆异常。
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| 关 键 词： | 地震磁扰动异常 西藏米林MS6.9地震 电磁辐射信号 地磁垂直强度极化方法 |
| 收稿时间： | 2020-12-03 |
Anomalous characteristics of geomagnetic vertical strength polarization before the 2017 Milin MS6.9 earthquake in Tibet |
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| Li Xia,Feng Lili,Zhao Yuhong,Liu Lei,Gou Zhidong,Fan Wenjie,He Manqiu,Liao Xiaofeng,Aisa Yisimayili.Anomalous characteristics of geomagnetic vertical strength polarization before the 2017 Milin MS6.9 earthquake in Tibet[J].Acta Seismologica Sinica,2021,43(5):584-594. |
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| Authors: | Li Xia Feng Lili Zhao Yuhong Liu Lei Gou Zhidong Fan Wenjie He Manqiu Liao Xiaofeng Aisa Yisimayili |
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| Affiliation: | 1.Qinghai Earthquake Agency，Xining 810001，China2.Geodynamics Field Observation and Research Station of Qinghai-Tibet Plateau，Golmud，China Earthquake Administration，Xining 810001，China3.Yunnan Earthquake Agency，Kunming 650224，China4.Chongqing Earthquake Agency，Chongqing 401147，China5.Sichuan Earthquake Agency，Chengdu 610041，China6.Xinjiang Earthquake Agency，Urumqi 830011，China |
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| Abstract: | Based on the second sampling data from 65 geomagnetic stations in Chinese mainland, we extracted the ultra-low frequency electromagnetic anomaly signals from the epicenter of the 2017 Milin MS6.9 earthquake in Tibet and its vicinity using geomagnetic vertical strength polarization method, and analyzed their spatio-temporal evolution characteristics. The results show that a large range of geomagnetic vertical strength polarization high value anomalies appeared in the Qinghai-Xizang （Tibetan） Plateau before the MS6.9 earthquake, and the abnormal process lasted for nine days. The high value anomaly began on October 30, 2017. The high value lasted for three days, followed by a short period of decline, a turning point and an increase. Afterwards the high value anomaly appeared again and lasted for four days. In this process, the time-series curves of each high-value station show single peak or double peak. The spatial distribution map shows that high value anomalies occur repeatedly in the western part of Chinese mainland, especially at the junction of Bayankhara and Qiangtang blocks on the Tibetan Plateau. The anomaly appeared, expanded, contracted, disappeared, expanded and disappeared, and the abnormal area reached its maximum value on October 31. Ten days after the end of the abnormal process, the Milin MS6.9 earthquake occurred, with its epicenter 5 km from the anomaly threshold line of October 31. Comprehensive analysis indicates that this anomaly has strong temporal and spatial correlation with the Millin earthquake and can be regarded as reliable seismic electromagnetic precursor. |
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| Keywords: | seismic magnetic disturbance anomaly MS6 9 Milin Tibet earthquake electromagnetic radiation signals geomagnetic vertical strength polarization method |
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