中文摘要：

以大地电磁测深理论公式为基础，给出了提取小极值信息的具体方法。然后以第二层断面为例，编程计算小极值在不同断面类型、不同地电参数条件下的视电阻率曲线。通过数值模拟分析小极值出现频率、曲线特征、幅度大小与断面参数的关系，发现这些小极值的特征含有关于地电断面参数的丰富信息，而且只需要观测较窄的频段，与观测包括全部渐近线的完整视电阻率曲线相比，其观测频点可减少很多；对于其他地电构造，根据视电阻率曲线的左支渐近线和小极值特征也能够提取到关于断面参数信息。只要测准小极值幅值和频率，就能提取断面信息。结果表明：该方法能极大地提高物探结果的准确性和稳定性，节省野外观测时间，提高野外工作效率，降低成本。

英文摘要：

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.