(1. 中南大學 地球科學與信息物理學院，長沙 410083；
2. 北京礦產(chǎn)地質研究院，北京 100012)
摘 要: 以大地電磁測深理論公式為基礎，給出了提取小極值信息的具體方法。然后以第二層斷面為例，編程計算小極值在不同斷面類型、不同地電參數(shù)條件下的視電阻率曲線。通過數(shù)值模擬分析小極值出現(xiàn)頻率、曲線特征、幅度大小與斷面參數(shù)的關系，發(fā)現(xiàn)這些小極值的特征含有關于地電斷面參數(shù)的豐富信息，而且只需要觀測較窄的頻段，與觀測包括全部漸近線的完整視電阻率曲線相比，其觀測頻點可減少很多；對于其他地電構造，根據(jù)視電阻率曲線的左支漸近線和小極值特征也能夠提取到關于斷面參數(shù)信息。只要測準小極值幅值和頻率，就能提取斷面信息。結果表明：該方法能極大地提高物探結果的準確性和穩(wěn)定性，節(jié)省野外觀測時間，提高野外工作效率，降低成本。
關鍵字: 大地電磁；小極值；有用信息；數(shù)值模擬
（1. School of Geosciences and Info-physics Central South University, Changsha 410083, China;
2. Beijing Institute of Geology for Mineral Resources, Beijing 100012, China）
Abstract:Based on magnetotelluric sounding theoretical formula, the specific method for extracting small extremum information was proposed. Then for example, the apparent resistivity curve of the second floor section was calculated on small extremum under the conditions of different section types and different electrical parameters. Through numerical simulation, the relationships among frequency, curve characteristics, magnitude and profile parameters of the small extremum were analyzed. It was found that the wealth information on the geoelectric section parameters was contained in the characteristics of small extremum. Comparing with the observation including all asymptote complete apparent resistivity curves, the observation of small extremum only needs to observe a narrow band, and the observation frequency can be reduced. For other ground structures, according to the apparent resistivity characteristics of left branch curve asymptotes and small extremum, the cross-section parameters information can be extracted. The results show that this method can greatly improve the accuracy and stability of geophysical field observation, save the field observation time, increase the field efficiency and reduce the costs.
Key words: magnetotelluric; small extreme; useful information; numerical simulation
