趋势面分析在高原地区音频大地电磁测深中的应用

Application of trend surface analysis to audio-magnetotelluric sounding in plateau region

常规音频大地电磁法,如EH-4电磁成像系统,在资料处理时通常不能有效分辨部分异常区域。以青海海北某公路隧道勘探为例,研究趋势面分析法在音频大地电磁测深中的应用。结果表明:通过拟合趋势面方程,可获取研究区内任一位置的视电阻率值,在拟合度较高的情况下可对区外的视电阻率值进行预测与估计;野外观测数据通常受随机因素的影响,可通过趋势面分析法对随机噪声进行平滑滤波处理;剩余值反映了视电阻率异常特征,绘制剩余值等值线图可以在去除区域背景视电阻率值后对异常区域进行凸显。音频大地电磁探测成果与趋势面分析法结合能更充分地利用地质信息。

Conventional audio-frequency magnetotellurtic method,such as EH-4 electromagnetic imaging system,is usually unable to effectively distinguish some abnormal areas during data processing.Taking a highway tunnel exploration in Haibei,Qinghai Province as an example,the application of trend surface analysis in audio-magnetotelluric sounding is studied.The results show that,firstly,the apparent resistivity values of any location in the study area can be obtained by fitting the trend surface equation,and the apparent resistivity values outside the area can be predicted and estimated when the degree of fitting is high.Secondly,the field observation data is usually affected by random factors,while the trend surface analysis can be used to smooth and filter the random noise.Thirdly,the residual values reflect the abnormal characteristics of apparent resistivity,and the contour map of the residual values can be drawn to highlight the abnormal areas after removing the background apparent resistivity values.The combination of audio-frequency magnetotelluric detection and trend surface analysis can help make full use of geological information.