线圈中心测量垂直磁场虚分量频域电磁法数值模拟

Numerical simulation on frequency domain electromagnetic sounding method of measuring magnetic field vertical imaginary component in center of loop

提出一种在近区测量磁场垂直虚分量提取视电阻率的频率域电磁测深方法,通过分析其特性并进行数值模拟研究,建立近区频率域电磁测深理论体系。通过研究线圈中心均匀大地电磁场,推导相关解析表达式,并将成熟的双频和伪随机合成电流移植到本方法中。根据一定近似条件下电磁场的理论公式,研究载流线圈中心垂直磁场虚分量提取视电阻率的方法特性,并编写相应正演程序,对2层、3层、4层等地电模型进行数值模拟,分析结果显示其对地下电性分布变化的有较高分辨力。最后根据模拟结果揭示本方法可行性及实际意义。

A new frequency domain electromagnetic sounding method of extracting apparent resistivity was put forward through measuring its near of zone magnetic field vertical virtual component, and a theoretical system of near zone frequency domain electromagnetic sounding method was constructed by analyzing its characteristics and conducting numerical simulation, and a theoretical foundation was provided for the design of the observing system. The method integrates the mature formula of dual and pseudo-random synthetic current by studying the coil center homogeneous magnetotelluric field and deducing the related analytical expression. According to the theoretical formula of magnetic field under certain approximate conditions, the method characteristics on extracting apparent resistivity were studied by vertical virtual component of magnetic field at current-carrying coil center, the corresponding forward programs were written and its better resolution on underground electrical distribution changes through numerical simulation on two-layered, three-layered, four-layered geoelectric models. The feasibility and significance of the method are revealed based on the simulation results.