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基于大深度(2 000 m)3层H型模型,采用MATLAB模拟了可控源音频大地电磁法(CSAMT)中不同地质模型的电磁场响应和视电阻率曲线,根据曲线特征探讨了各地质参数对CSAMT法分辨能力的影响,研究了如何提高电磁场响应强度从而真正实现分辨深部低阻.结果表明:当覆盖层和低阻层电阻率比值大于2时可以分辨低阻,且分辨能力随覆盖层厚度的降低,低阻层厚度的增加及其电阻率的降低而增加;各地质模型均存在分辨低阻的最佳发射频率,且采用该频率作为最小发射频率进行勘探,可使电磁场幅值随该频率的1.5次幂增长,从而解决电场响应幅值微弱(nV),接收机难以分辨的问题.
Based on the 3-layer H-type model with large depth (2 000 m), the electromagnetic response and apparent resistivity curves of different geologic models in CSAMT are simulated by MATLAB, and the relationships among geologic parameter pairs CSAMT method, and how to improve the response strength of electromagnetic field so that the deep low-resistivity discrimination can truly be realized.The results show that the low resistivity can be distinguished when the resistivity ratio of the overburden and the low resistivity layer is greater than 2, and the resolving power varies with the thickness of the overburden , The increase of low resistivity layer and the increase of resistivity. The best emission frequency with low resistivity exists in each geological model, and using this frequency as the minimum transmitting frequency can make the amplitude of electromagnetic field increase with The 1.5-power increase in frequency resolves the problem of weak electric field response (nV) and poor receiver resolution.