岩石圈磁场与地质构造和地震活动性之间的关系——以漾濞地震为例

doi:10.3969/j.issn.0253-4967.2024.02.012

摘要/Abstract

摘要：

文中利用2018—2021年漾濞及周边地区的地磁矢量数据, 构建了5期岩石圈磁场曲面样条模型, 并计算得到相邻期的岩石圈磁场变化。在此基础上, 分析了岩石圈磁场的空间分布与区域地质构造和历史地震震中的对应关系, 并针对漾濞 M_S6.4 地震, 研究了磁偏角和地磁总强度在震前、震后的磁场变化特征。研究发现: 岩石圈磁场的空间展布能够反映地壳块体构造特征和主要断裂走向, 同时也与地震活动的分布存在相关性。通过对比分析历史地震的震中分布发现, 地震多发生在弱磁区, 尤其是磁异常零值区附近, 且地震震中分布偏向于高梯度带上。漾濞 M_S6.4 地震发生前后, 震中附近的岩石圈磁场发生显著变化, 震前、震中持续位于磁偏角负变化区, 震后则位于正变化区, 且震中位于震前一年磁偏角变化的零变线附近; 震前研究区内相邻期地磁总强度的正负变化大致均衡, 随后逐渐演变为整个研究区均呈负值, 而地震后研究区又恢复了正负变化大致均衡的分布。

关键词: 漾濞地震, 岩石圈磁场, 震磁异常

Abstract:

The lithospheric magnetic field is an important part of the earth’s magnetic field, which is affected by many factors, such as rock’s magnetization environment, underground geological structure, rock mineralogical composition, thermal and pressure state, and the deep tectonic evolution process. Most earthquakes occur in the crust and uppermost mantle, known as the lithosphere. The preparation and occurrence of earthquakes are usually accompanied by long-term accumulation and sudden release of energy, which will lead to changes in the thermal and pressure state of rocks, causing magnetic susceptibility variation in the lithosphere. Previous studies show that seismic activities can cause abnormal changes in the geomagnetic field, and there is an obvious correlation between the lithospheric magnetic field and seismic activities. The M_S6.4 Yangbi earthquake on May 21, 2021, provided a unique opportunity to study the dynamic evolution of seismo-magnetic anomaly.

Five-term repeat station vector geomagnetic data observed in Yangbi and surrounding areas from 2018-2021 were used in this paper, the first four terms were observed before the earthquake, and the fifth term was observed after the earthquake. After data processing and model calculation, the lithospheric magnetic fields before and after the earthquake are obtained, lithospheric magnetic field models are established using the Surface Spline method, and annual variations are calculated. Based on the analysis of lithospheric magnetic field combined with the regional geological structure, the Northwest Sichuan Subblock shows negative magnetic anomalies, which is consistent with the geological structural characteristics in the study area, altitude and crustal thickness increase sharply from Central Yunnan Subblock to Western Sichuan Plateau. Small areas of positive and negative magnetic anomalies are alternatively distributed in the Central Yunnan Subblock, which reflects the heterogeneity of deep lithosphere structure. The negative magnetic anomaly in the western boundary of the study area is also consistent with the geological characteristics of the Qingzang Plateau. There is also a correspondence between lithospheric magnetic field anomalies and faults, especially the total intensity. Negative magnetic anomaly strips are distributed along the strike of the Honghe Fault and Lijiang-Xiaojinhe Fault, while Weixi-Qiaohou-Weishan Fault appears at the junction of positive and negative magnetic anomalies. The statistical analysis of the M_S6.0 and above seismic events from 1970 to 2021 shows that there is a correlation between lithospheric magnetic anomalies and seismic activities. Most earthquakes occur in the weak magnetic anomaly area, especially near zero contour. The earthquakes tend to be distributed in anomaly gradient belts, and the number of earthquakes in the negative anomaly area is higher than that in the positive anomaly area. Analyzing the characteristics of the pre- and post-seismic changes of declination and total intensity near the epicenter of Yangbi M_S6.4, it is found that the epicenter of the Yangbi earthquake is located near the zero-contour-line of declination. During the preparation of the Yangbi earthquake, the total intensity gradually changed from a balanced distribution of positive and negative anomalies to the overall negative changes, and the magnetic anomalies recovered the trend of the balanced distribution of positive and negative changes after the earthquake.

Key words: Yangbi earthquake, lithospheric magnetic field, seismo-magnetic anomaly

陈政宇, 倪喆, 周思远, 金云华, 杨薪俊. 岩石圈磁场与地质构造和地震活动性之间的关系——以漾濞地震为例[J]. 地震地质, 2024, 46(2): 449-461.

CHEN Zheng-yu, NI Zhe, ZHOU Si-yuan, JIN Yun-hua, YANG Xin-jun. STUDY ON THE RELATIONSHIP BETWEEN LITHOSPHERIC MAGNETIC FIELD AND GEOLOGICAL STRUCTURE AND SEISMIC ACTIVITY: TAKING THE 2021 M_S6.4 YANGBI EARTHQUAKE AS AN EXAMPLE[J]. SEISMOLOGY AND GEOLOGY, 2024, 46(2): 449-461.

图/表 7

图1 研究区的地质构造简图 F1则木河断裂; F2普渡河断裂; F3安宁河断裂; F4金河-箐河断裂; F5丽江-小金河断裂; F6红河断裂; F7金沙江断裂; F8维西-乔后-巍山断裂; F9澜沧江断裂; F10怒江断裂

Fig. 1 Schematic tectonic map around the study area.

表1 漾濞地区数据通化精度统计表

Table1 Accuracy statistical results of diurnal variation reduction in the Yangbi region

测量日期	测量期数	测点数	日变通化台	F_σ/nT	D_σ/(')	I_σ/(')
2018年4—5月	1	51	LIJ	0.31	0.11	0.06
2019年4—5月	2	54	LIJ	0.38	0.12	0.06
2020年4—5月	3	54	LIJ	0.31	0.10	0.07
2021年4—5月	4	54	LIJ	0.32	0.13	0.08
2021年5—6月	5	27	LIJ	0.47	0.17	0.08

图2 研究区测点分布图

Fig. 2 Distribution of measurement stations in the study area.

图3 2018.0岩石圈磁场空间分布图 a 地磁总强度; b 磁偏角

Fig. 3 Distribution of lithospheric magnetic field in the study area in 2018.0.

图4 1970—2021年MS≥6.0地震的震中统计分析 a 地磁总强度; b 磁偏角

Fig. 4 Statistical distribution of earthquake epicenters with MS≥6.0 from 1970 to 2021.

图5 岩石圈磁场磁偏角变化分布图 a 2018—2019年; b 2019—2020年; c 2020—2021年; d 2021年震前—震后

Fig. 5 Distribution of the declination variation.

图6 岩石圈磁场地磁总强度变化分布图 a 2018—2019年; b 2019—2020年; c 2020—2021年; d 2021年震前—震后

Fig. 6 Distribution of the total intensity variation.

参考文献 28

[1]	安振昌, 徐元芳, 夏国辉, 等. 1982. 表示局部地区地磁场及其长期变化分布的数学方法[J]. 地球物理学报, 25(S1): 711—717.
	AN Zhen-chang, XU Yuan-fang, XIA Guo-hui, et al. 1982. Mathematical method to express the distribution of geomagnetic field and its secular variation in a local area[J]. Chinese Journal of Geophysics, 25(S1): 711—717(in Chinese).
[2]	常祖峰, 常昊, 臧阳, 等. 2016. 维西-乔后断裂新活动特征及其与红河断裂的关系[J]. 地质力学学报, 22(3): 517—530.
	CHANG Zu-feng, CHANG Hao, ZANG Yang, et al. 2016. Recent active features of Weixi-Qiaohou Fault and its relationship with the Honghe Fault[J]. Journal of Geomechanics, 22(3): 517—530(in Chinese).
[3]	陈斌, 袁洁浩, 王粲, 等. 2017. 流动地磁监测数据处理流程[J]. 地震研究, 40(3): 335—339.
	CHEN Bin, YUAN Jie-hao, WANG Can, et al. 2017. Data processing flowchart of Chinese mobile geomagnet monitoring array[J]. Journal of Seismological Research, 40(3): 335—339(in Chinese).
[4]	邓起东, 张培震, 冉勇康, 等. 2002. 中国活动构造基本特征[J]. 中国科学(D辑), 32(12): 1020—1030.
	DENG Qi-dong, ZHANG Pei-zhen, RAN Yong-kang, et al. 2002. Basic characteristics of active tectonics of China[J]. Science in China(Ser D), 32(12): 1020—1030(in Chinese).
[5]	丁新娟. 2017. 2015年新疆皮山6.5级地震前岩石圈磁场局部异常特征分析[J]. 地震研究, 40(3): 362—367.
	DING Xin-juan. 2017. Analysis of local lithospheric magnetic field anomalies characteristics before Xinjiang Pishan M_S6.5 earthquake in 2015[J]. Journal of Seismological Research, 40(3): 362—367(in Chinese).
[6]	董超, 陈斌, 袁洁浩, 等. 2021. 2021年5月22日玛多 M_S7.4 地震震前岩石圈磁场变化特征分析[J]. 地震学报, 43(4): 453—462.
	DONG Chao, CHEN Bin, YUAN Jie-hao, et al. 2021. Characteristic analysis of the lithospheric magnetic anomaly before the Maduo M_S7.4 earthquake on 22th May 2021[J]. Acta Seismologica Sinica, 43(4): 453—462(in Chinese).
[7]	顾春雷, 张毅, 顾左文, 等. 2012. 华北地震区岩石圈磁异常场零值线与中强震震中分布关系[J]. 西北地震学报, 34(2): 174—179.
	GU Chun-lei, ZHANG Yi, GU Zuo-wen, et al. 2012. Relationship between zero-value-line abnormal geomagnetic field in lithosphere and strong-moderate earthquake epicenters in north China seismic region[J]. Northwestern Seismological Journal, 34(2): 174—179(in Chinese).
[8]	顾春雷, 张毅, 徐如刚, 等. 2010. 地震前后岩石圈磁场变化特征分析[J]. 地球物理学进展, 25(2): 472—477.
	GU Chun-lei, ZHANG Yi, XU Ru-gang, et al. 2010. Analysis of the variation characteristic in the lithospheric geomagnetic field before and after earthquakes[J]. Progress in Geophysics, 25(2): 472—477(in Chinese).
[9]	顾左文, 陈斌, 高金田, 等. 2009. 应用NOC方法研究中国地区地磁时空变化[J]. 地球物理学报, 52(10): 2602—2612.
	GU Zuo-wen, CHEN Bin, GAO Jin-tian, et al. 2009. Research of geomagnetic spatial-temporal variations in China by the NOC method[J]. Chinese Journal of Geophysics, 52(10): 2602—2612(in Chinese).
[10]	顾左文, 张毅, 姚同起, 等. 2006. 九江-瑞昌 M_S5.7 地震地磁异常的观测与分析[J]. 地震学报, 28(6): 611—621.
	GU Zuo-wen, ZHANG Yi, YAO Tong-qi, et al. 2006. Observation and analysis of geomagnetic abnormity associated with the M_S5.7 Jiujiang-Ruichang earthquake[J]. Acta Seismologica Sinica, 28(6): 611—621(in Chinese).
[11]	韩渭宾, 蒋国芳. 2004. 川滇地区强震活动分布特征及其与地壳块体构造背景关系的研究[J]. 地震学报, 26(2): 211—222.
	HAN Wei-bin, JIANG Guo-fang. 2004. Study on distribution characteristics of strong earthquakes in Sichuan-Yunnan area and their geological tectonic background[J]. Acta Seismologica Sinica, 26(2): 211—222(in Chinese).
[12]	皇甫岗, 秦嘉政, 李忠华, 等. 2007. 云南地震类型分区特征研究[J]. 地震学报, 29(2): 142—150.
	HUANGFU Gang, QIN Jia-zheng, LI Zhong-hua, et al. 2007. Subarea characteristics of earthquake types in Yunnan[J]. Acta Seismologica Sinica, 29(2): 142—150(in Chinese).
[13]	李传友, 张金玉, 王伟, 等. 2021. 2021年云南漾濞6.4级地震发震构造分析[J]. 地震地质, 43(3): 706—721. doi: 10.3969/j.issn.0253-4967.2021.03.015.
	LI Chuan-you, ZHANG Jin-yu, WANG Wei, et al. 2021. The seismogenic fault of the 2021 Yunnan Yangbi M_S6.4 earthquake[J]. Seismology and Geology, 43(3): 706—721(in Chinese). DOI
[14]	李家发, 吴一柱, 安振昌, 等. 1992. 中国地区地磁异常与地震分布关系[J]. 华南地震, 12(1): 11—16.
	LI Jia-fa, WU Yi-zhu, AN Zhen-chang, et al. 1992. The relationship between magnetic anomaly and the distribution of earthquakes in China continent[J]. South China Journal of Seismology, 12(1): 11—16(in Chinese).
[15]	倪喆. 2014. 洱源5.5级地震前后地磁场变化异常特征分析[J]. 地震研究, 37(3): 426—432.
	NI Zhe. 2014. Analysis of anomalous characteristics of geomagnetic change before and after Eryuan M5.5 earthquake[J]. Journal of Seismological Research, 37(3): 426—432(in Chinese).
[16]	倪喆, 袁洁浩, 王粲, 等. 2014. 2014年云南鲁甸6.5级, 永善5.0级地震前岩石圈磁场局部异常特征分析[J]. 地震研究, 37(4): 537—541.
	NI Zhe, YUAN Jie-hao, WANG Can, et al. 2014. Analysis of local anomalous characteristics of lithospheric magnetic field before Ludian M6.5 and Yongshan M5.0 earthquakes in Yunnan in 2014[J]. Journal of Seismological Research, 37(4): 537—541(in Chinese).
[17]	邱耀东. 2017. 联合Champ和Swarm卫星磁测数据反演中国大陆区域岩石圈磁场[D]. 武汉: 武汉大学.
	QIU Yao-dong. 2017. Invert the lithospheric magnetic field in China mainland by combining Champ and Swarm satellite data[D]. Wuhan University, Wuhan(in Chinese).
[18]	宋成科, 张海洋. 2020. 2013年芦山 M_S7.0 地震同震地磁变化分析[J]. 地震地质, 42(6): 1301—1315. doi: 10.3969/j.issn.0253-4967.2020.06.003.
	SONG Cheng-ke, ZHANG Hai-yang. 2020. Analysis of coseismic variations in magnetic field of the Lushan M_S7.0 earthquake in 2013[J]. Seismology and Geology, 42(6): 1301—1315(in Chinese). DOI
[19]	王月, 胡少乾, 何骁慧, 等. 2021. 2021年5月21日云南漾濞6.4级地震序列重定位及震源机制研究[J]. 地球物理学报, 64(12): 4510—4525. DOI
	WANG Yue, HU Shao-qian, HE Xiao-hui, et al. 2021. Relocation and focal mechanism solutions of the 21 May 2021 M_S6.4 Yunnan Yangbi earthquake sequence[J]. Chinese Journal of Geophysics, 64(12): 4510—4525(in Chinese).
[20]	王朝景, 刘德强, 苏树朋, 等. 2021. 2018年永清 M_W4.3 地震前后岩石圈磁场变化特征[J]. 地震地磁观测与研究, 42(3): 129—136.
	WANG Zhao-jing, LIU De-qiang, SU Shu-peng, et al. 2021. Analysis of lithospheric geomagnetic field variation characteristics before and after the Yongqing M_W4.3 earthquake in 2018[J]. Seismological and Geomagnetic Observation and Research, 42(3): 129—136(in Chinese).
[21]	吴富春, 米秋霞, 姬建中, 等. 1995. 中国及其邻区地震深度的特征[J]. 华北地震科学, 13(3): 21—27.
	WU Fu-chun, MI Qiu-xia, JI Jian-zhong, et al. 1995. The characteristics of earthquake depth in China and its adjacent area[J]. North China Earthquake Sciences, 13(3): 21—27(in Chinese).
[22]	徐如刚, 张毅, 顾春雷, 等. 2010. 九江-瑞昌 M_S5.7 地震前后地磁场水平分量异常追踪与分析[J]. 地球物理学进展, 25(4): 1175—1179.
	XU Ru-gang, ZHANG Yi, GU Chun-lei, et al. 2010. Tracing and analyzing anomalies of horizontal geomagnetic component before and after the M_S5.7 Jiujiang-Ruichang earthquake[J]. Progress in Geophysics, 25(4): 1175—1179(in Chinese).
[23]	易桂喜, 闻学泽, 苏有锦. 2008. 川滇活动地块东边界强震危险性研究[J]. 地球物理学报, 51(6): 1719—1725.
	YI Gui-xi, WEN Xue-ze, SU You-jin. 2008. Study on the potential strong-earthquake risk for the eastern boundary of the Sichuan-Yunnan active faulted-block, China[J]. Chinese Journal of Geophysics, 51(6): 1719—1725(in Chinese).
[24]	张国民, 汪素云, 李丽, 等. 2002. 中国大陆地震震源深度及其构造含义[J]. 科学通报, 47(9): 663—668.
	ZHANG Guo-min, WANG Su-yun, LI Li, et al. 2002. Focal depth research of earthquakes in Mainland China: Implication for tectonics[J]. Chinese Science Bulletin, 47(9): 663—668(in Chinese).
[25]	张培震, 邓起东, 张国民, 等. 2003. 中国大陆的强震活动与活动地块[J]. 中国科学(D辑), 33(S1): 12—20.
	ZHANG Pei-zhen, DENG Qi-dong, ZHANG Guo-min, et al. 2003. Active tectonic blocks and strong earthquakes in the continent of China[J]. Science in China(Ser D), 33(S1): 12—20(in Chinese).
[26]	Alken P, Thébault E, Beggan C D, et al. 2021. International geomagnetic reference field: The thirteenth generation[J]. Earth, Planets and Space, 73(1): 49—73.
[27]	Lei Y, Jiao L, Chen H. 2018. Possible correlation between the vertical component of lithospheric magnetic field and continental seismicity[J]. Earth Planets and Space, 70(1): 179.
[28]	Thébault E, Purucker M, Whaler K A, et al. 2010. The magnetic field of the Earth’s lithosphere[J]. Space Science Reviews, 155(1-4): 95—127.