(1. 北京礦產(chǎn)地質(zhì)研究院，北京 100012；2. 中南大學(xué) 地球科學(xué)與信息物理學(xué)院，長(zhǎng)沙 410083)
摘 要: 提出一種在近區(qū)測(cè)量磁場(chǎng)垂直虛分量提取視電阻率的頻率域電磁測(cè)深方法，通過(guò)分析其特性并進(jìn)行數(shù)值模擬，初步建立近區(qū)頻率域電磁測(cè)深理論體系，為觀測(cè)系統(tǒng)的設(shè)計(jì)提供理論基礎(chǔ)。通過(guò)研究線圈中心均勻大地電磁場(chǎng)，推導(dǎo)相關(guān)解析表達(dá)式并將成熟的雙頻和偽隨機(jī)合成電流移植到本方法中。根據(jù)一定近似條件下電磁場(chǎng)的理論公式，深入研究載流線圈中心垂直磁場(chǎng)虛分量提取視電阻率的方法特性，并編寫相應(yīng)正演程序，對(duì)二層、三層和四層等地電模型進(jìn)行數(shù)值模擬，分析其對(duì)地下電性分布變化的分辨力。最后，根據(jù)模擬結(jié)果揭示本方法的可行性及實(shí)際意義。
關(guān)鍵字: 垂直磁場(chǎng)虛分量；線圈中心；數(shù)值模擬；頻域電磁法
（1. Beijing Institute of Geology for Mineral Resources, Beijing 100012, China;
2. School of Geoscience and Info-physics, Central South University, Changsha 410083, China）
Abstract:A new frequency domain electromagnetic sounding method of extracting apparent resistivity was put forward through measuring its near zone magnetic field vertical virtual component, and a theoretical system of near zone frequency domain electromagnetic sounding method was conatructed 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 pseudorandom synthetic current by studying the coil center homogeneous magnetotelluric field and deducing the related analytical expression. According to the theoretical formula fo 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 was analyzed through numerical simulation on two-layered, three-layered, four-layered geoelectric models. The feasibility and significance of the method were revealed based on the simulation results.
Key words: imaginary component vertical to magnetic field; loop center; numerical simulation; frequency domain electromagnetic sounding
