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本文是“地震的感应磁效应(一)——三维电磁感应的数值理论”一文的继续。首先从理论和实际计算两个方面证明了三维电磁感应数值方程解的唯一性、收敛性和稳定性,从而充实了作为研究地壳、上地幔电性结构横向不均匀性理论基础的“三维数值方法”。作为这一理论方法的实际应用,文中对不同源场周期和具有不同埋藏深度的三维电导率异常体进行了模拟计算,以研究地震感应磁效应的大小、空间分布特征和频率特性。模拟计算结果表明,对于周期从数秒到数分钟的地磁短周期变化,若电导率异常体的线度与5至7级地震的震源体积大体相当,其电导率较原背景电导率高近一个量级,其感应磁效应主要特征为:在异常体正上方,地面磁场的水平分量变化最大,相对变化量约30％;在异常体于源场方向一致的两侧,垂直分量变化最大,相对变化量约40—50％。因此,观测短周期地磁场的异常变化,有可能是监测地震孕育过程地下电性变化的一种试验途径。但由于上述异常强度在空间上衰减迅速,所以观测必须接近震源区,这对测点的选择是个不利的因素。
This article is the continuation of “The Induced Magnetic Effect of Earthquake (1) - Numerical Theory of Three-dimensional Electromagnetic Induction”. First of all, the uniqueness, convergence and stability of the three-dimensional electromagnetic induction numerical equation are proved theoretically and practically. As a result, the three-dimensional numerical method ". As a practical application of this theoretical method, three-dimensional conductivity anomalies with different source field periods and different burial depths are simulated to study the size, spatial distribution and frequency characteristics of seismic induced magnetic effect. The simulation results show that for the short-period change of geomagnetic period from a few seconds to a few minutes, if the conductivity anomalies have the same magnitude as the focal volume of 5 to 7 earthquakes, the conductivity is higher than the original background conductivity by one The main characteristics of the induced magnetic effect are as follows: the horizontal component of the ground magnetic field changes the most with the relative change about 30% just above the abnormal body; and the vertical component changes most at both sides where the anomalous body is in the same direction of the source field, About 40-50%. Therefore, observing the abnormal change of the short-period geomagnetic field may be a test way to monitor the change of the underground electricity during the process of earthquake gestation. However, since the anomalous intensity decays rapidly in space, the observation must be close to the source region, which is an unfavorable factor for the selection of measuring points.