音频大地电磁远参考点信号特征及远参考大地电磁法在信号处理中的应用研究

Signal Characteristics of Remote Reference Point of Audio-magnetotelluric Sounding Method (AMT) and Application of Remote Reference MT Method in Signal Processing

音频大地电磁测深法(AMT)利用天然交变的电磁场为场源,探测的频率范围为0.35~10^4 Hz,其解决地质问题的深度通常在2 km以内。然而天然电磁场频带范围宽,信号微弱,极化方向随机,在实际测量中大地电磁信号很容易受到各种电磁噪声干扰,音频大地电磁远参考法可以压制随机噪声,恢复“死频带”数据,改善音频大地电磁法数据质量,该方法的应用越来越受到各单位的重视,以实测远参考点数据为基础,通过对其时间序列特征、频谱特征、相干度特征及视电阻-相位曲线特征进行分析研究,总结归纳了远参考点特征,时间序列电磁场信号平稳,无干扰噪声信号,频谱无明显震荡,相干度接近1,视电阻率-相位曲线光滑连续,频点功率谱文件数值稳定,基本一致。同时选取受噪数据进行远参考技术处理,分析其有效性,结果表明,远参考法可以有效压制干扰噪声对视电阻率-相位曲线的影响,改善受噪数据质量。

The audio-magnetotelluric sounding method(AMT)uses the natural alternating electromagnetic field as the field source.The frequency range of the detection is 0.35~10^4 Hz,and the depth of solving the geological problem is usually within 2km.However,the natural electromagnetic field has a wide frequency band,weak signal,and random polarization.In actual measurement,the magnetotelluric signal is easily interfered by various electromagnetic noises.The audio geodetic remote reference method can suppress random noise and restore“dead band”data.The data quality of audio magnetotelluric method is improved.The application of this method has been paid more and more attention by all units.Based on the measured far reference point data,this paper analyzes its time series,spectral features,coherence characteristics and apparent resistance-phase curve characteristics.The analysis and research are carried out,and the characteristics of the far reference point are summarized.The time series electromagnetic field signal is stable with no interference noise signal;the spectrum has no obvious oscillation;the coherence is close to 1;the apparent resistivity-phase curve is smooth and continuous;the frequency power spectrum file is stable,basically consistent.At the same time,the noise-receiving data is selected for long-reference technology processing,and the validity is analyzed.The results show that the far-reference method can effectively suppress the influence of interference noise on the apparent resistivity-phase curve and improve the quality of the noise-received data.