非均匀半无限介质中振荡电偶极子地表电场的数值模拟

NUMERICAL SIMULATION OF GEOELECTRICAL FIELD RESPONSE TO OSCILLATING DIPOLE SOURCE IN HETEROGENEOUS CRUST

以数值模拟方法对层状介质中振荡电偶极子电场进行了研究 .结果表明 :(1)在典型层状介质结构下 ,地表不可能观测到此种信号源产生的电场信息 .(2 )有断层存在时地表偶极子电场值可增大 2～ 3个量级 .在常见的地壳电性结构中 ,地表可得到零点几至几毫伏每公里的异常 ;在特殊电性结构中可达上百毫伏每公里 .电场强度的最大点并不在震中 ,而是在断层带上 .这表明地下介质的不均匀性一方面有利于地电异常的观测 ,另一方面也是引起地表电场异常出现复杂性的原因 .

The geoelectrical fields induced by oscillating dipole source are numerically simulated in different heterogeneous models.The results show that for the model of ordinary layered media it is impossible to observe such electrical signals on earth surface.It is found that the surface field can be enhanced 2 or 3 orders if these is high conductive fault in the layered model.The surface abnormal electrical signals of ordinary electric structure is about several mV/km or less, however it could reach hundreds mV/km in special electrical structure. It is deserved to point out that the area of strongest abnormal signals is not over the epicenter, but is in some points of fault. This means the heterogeneity of electric structure is advantageous to detect abnormal electrical signals, on the other hand, it leads to the complex phenomena of abnormal electrical signals distribution on surface.