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本文分析了渤海周围25个地磁台站1973—1979年急始、湾扰等短周期事件,以及静日、抗日和磁暴的频谱成分,发现包括唐山震区在内的渤海地区存在地磁短周期变化异常。北部的昌黎、宁河、宝坻一带异常最强,垂直分量的变化△Z为正,南部的烟台附近异常最强,△Z为负,周期为5分钟至2小时的异常变化最为明显。应用三维电磁感应的数值理论,拟合了与这种短周期地磁异常变化相应的上地幔高导层电性结构,发现渤海地区有一上地幔高导层的局部隆起,唐山地震位于隆起部位的北侧边缘。与隆起构造相应的附加热应力,其量级高达千巴,很可能是唐山地震的重要动力来源。
In this paper, we analyzed the short-period events of 1973 geochronological and geomagnetic disturbance from 25 geomagnetic stations around the Bohai Sea in 1973-1979 as well as the static composition, the anti-Japanese and the magnetic storms. It was found that the short-period changes of the geomagnetic field in the Bohai Sea area including the Tangshan earthquake area abnormal. The northern part of Changli, Ninghe and Baodi are the most anomalous regions. The vertical component △ Z is positive, the southern region near Yantai is the strongest, and the negative △ Z is the region with the most obvious change from 5 minutes to 2 hours. Using the numerical theory of three-dimensional electromagnetic induction, fitting the electrical structure of the upper mantle high conductivity layer corresponding to such short-period geomagnetic anomaly changes, we found that there is a local uplift of the upper mantle high conductivity layer in the Bohai Sea region. The Tangshan earthquake is located north of the uplift Side edge. Additional thermal stresses corresponding to uplift tectonics, up to 1,000 bar, are likely to be an important source of power for the Tangshan earthquake.