(1. 中南大學 有色資源與地質(zhì)災(zāi)害探測湖南省重點實驗室，長沙 410083；
2. 中南大學 地球科學與信息物理學院，長沙 410083；3. 中南大學 地質(zhì)調(diào)查研究院，長沙 410083)
摘 要: 廣域電磁法采用均勻大地表面水平電偶源的全區(qū)精確表達式定義廣域視電阻率，與卡尼亞視電阻率相比，能更好地反映地電模型的電性特征。利用廣域視電阻率定義方法定義了E-Eφ方式的廣域視電阻率、遠區(qū)視電阻率及近區(qū)視電阻率，考慮觀測方位角的影響，同時得出了E-Eφ觀測裝置的裝置系數(shù)和電磁響應(yīng)函數(shù)。對3層介質(zhì)的A型、Q型、K型和H型的一維正演計算分析表明：E-Eφ觀測裝置的廣域電磁法的觀測方位角的影響相當于φ=90°時觀測坐標系的旋轉(zhuǎn)，通過適當?shù)男Ｕ我猞战堑臏y深曲線更能真實地反映地電斷面隨深度的客觀變化，綜合3種不同視電阻率的分析，能夠較好地識別人工源頻率域測深中電磁場不同的漸近特性。基于E-Eφ方式的廣域電磁法擴大了觀測范圍，具有更好的應(yīng)用前景。
關(guān)鍵字: 廣域電磁法；E-Eφ裝置；電磁響應(yīng)函數(shù)；視電阻率；人工源頻率測深
（1. Key Laboratory of Non-Ferrous Resources and Geological Hazard Detection,
Central South University, Changsha 410083, China;
2. School of Geosciences and Info-Physics, Central South University, Changsha 410083, China;
3. Research Institute of Geological Survey, Central South University, Changsha 410083, China）
Abstract:Wide field electromagnetic method defines the apparent resistivity by the accurate expression of full-zone of horizontal electric dipole source in homogeneous earth surface. Compared with the Cagniard apparent resisitivity, it can preferably show the electrical characteristics of geoelectric model. The computational formula of the improved apparent resistivity of E-Eφ array in the wide field electromagnetic method, near-zone apparent resistivity and far-zone apparent resisitivity is defined, the influence of observed azimuth is considered and the coefficient of the observation array and electromagnetic response function is obtained by the pattern of wide field electromagnetic apparent resistivity definition. Based on the calculation and analysis of curve A, curve Q, curve K and curve H of three-layer model in 1-D forward modeling, the influence of observation azimuth (φ) is equal to the rotation of the coordinate system at φ=90° in the wide field electromagnetic sounding of the E-Eφ array. Through proper calibration, the sounding curve of the arbitrary angle azimuth (φ) can more truly show the objective change of geoelectric section with the depth. Through comprehensive analysis of three different apparent resistivities, the different asymptotic characteristics of electromagnetic field in the controlled source frequency sounding method can be well identified. The wide field electromagnetic sounding method based on the observation of E-Eφ array can expand the observed scope, and has better prospect of application.
Key words: wide field electromagnetic method; E-Eφ array; electromagnetic response function; apparent resistivity; controlled source frequency sounding
