摘要
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Ms5.1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.
Abstract
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 Ms5.1 earthquake,and 1 year after the earthquake.The tem-poral and spatial evolution of the total strength,the magnetic declination,the magnetic inclination and the horizon-tal 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 Tangs-han Ms5.1 earthquake showed a significant trend in total in the region,which had a certain correlation with the ge-otectonic settings.Two-year and 1-year variation of the 4 elements of the lithospheric magnetic field before the Tangshan Ms5.1 earthquake showed significant characteristics in some parts of the study area.Four years,3 years,2 years,and 1 year before the Tangshan Ms5.1 earthquake,the variation of the total strength,the magnetic decli-nation,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 Tangs-han Ms5.1 earthquake,the magnetic declination near the epicenter varied obviously,and so did the horizontal vector.(2)The temporal and spatial evolution of the lithospheric magnetic field variation before the earthquake showed that when approaching the original time of the Tangshan Ms5.1 earthquake,the trend of the spatial distri-bution of the local positive and negative variation would replace the overall variation trend in the region.
万方数据