地震研究

基于多期累积岩石圈磁场变化分析唐山M_S5.1地震震磁异常

王朝景^1,2,李博^1,2,苏树朋^1,2

(1.河北红山巨厚沉积与地震灾害国家野外科学观测研究站,河北邢台 054000; 2.河北省地震局流动测量队,河北保定 071000)

Analysis of the Seismomagnetic Anomaly of the Tangshan M_S5.1 Earthquake Based on the Accumulative Variation of the Lithospheric Magnetic Field

WANG Zhaojing^1,2,LI Bo^1,2,SU Shupeng ^1,2

(1.Hebei Hongshan National Observatory on Thick Sediments and Seismic Hazards,Xingtai 054000,Hebei,China; 2.Mobile Survey Team of Hebei Earthquake Agency,Baoding 071000,Hebei,China)

Keywords：mobile geomagnetics; seismomagnetic anomaly; accumulative variation; the lithosphere magnetic field

DOI: 10.20015/j.cnki.ISSN1000-0666.2024.0043

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利用2016—2021年河北及周边地区的6期流动地磁矢量观测资料,针对2020年7月12日唐山M_S5.1地震,建立了震前1～4年和震后1年的岩石圈磁场变化模型,对比分析了研究区岩石圈磁场的总强度、磁偏角、磁倾角和水平矢量4个要素的时空演化过程。结果表明:①震前累积4年和3年的岩石圈磁场各要素变化中区域整体趋势强,与大地构造有一定的相关性; 震前2年和1年的岩石圈磁场变化中,局部特征显著; 震前1～4年变化中震中附近总强度、磁偏角、磁倾角变化量值均较小,且多有变化零值线分布,水平矢量呈现出持续的弱变化特征; 震后震中附近的磁偏角和变化量值大。②从震前岩石圈磁场变化的时空演化过程,可以看出,越接近发震时间,局部正、负变化空间分布将取代区域的整体趋势。

Based on 6 periods of mobile geomagnetic vector measurement from 2016 to 2021 in Hebei and its surrounding areas,this paper builds a model to illustrate the variation of the lithospheric magnetic field 4 years,3 years,2 years and 1 year before the July 12,2020 Tangshan M_S5.1 earthquake,and 1 year after the earthquake.The temporal and spatial evolution of the total strength,the magnetic declination,the magnetic inclination and the horizontal vector of the lithospheric magnetic field in the study area are compared and analyzed.The results show that:①The 4-year and 3-year cumulative variation of the 4 elements of the lithospheric magnetic field before the Tangshan M_S5.1 earthquake showed a significant trend in total in the region,which had a certain correlation with the geotectonic settings.Two-year and 1-year variation of the 4 elements of the lithospheric magnetic field before the Tangshan M_S5.1 earthquake showed significant characteristics in some parts of the study area.Four years,3 years,2 years,and 1 year before the Tangshan M_S5.1 earthquake,the variation of the total strength,the magnetic declination,and the magnetic inclination near the epicenter of the earthquake is insignificant,and most of the values distributed along the zero-value line.The horizontal vector showed continuous and weak variation.After the Tangshan M_S5.1 earthquake,the magnetic declination near the epicenter varied obviously,and so did the horizontal vector.②The temporal and spatial evolution of the lithospheric magnetic field variation before the earthquake showed that when approaching the original time of the Tangshan M_S5.1 earthquake,the trend of the spatial distribution of the local positive and negative variation would replace the overall variation trend in the region.