Eh4 System Electromagnetic Sounding Data Processing And Improvement

Cagnird resistivity sounding is a Widely used Geophysical Prospecting method in geological exploration and mine exploration. It is very important to estimate the Cagnird resistivity correctly. The methods of data processing and noise elimination for the EH4 system are studied and improved in this paper.The data processing for EH4 system, such as Fast Fourier-Transformation into Frequency domain, Computation of the Cross and Auto Power-spectral, Computation of the Apparent Resistivity and Tensor Impedance, is introduced in detail.To narrow the interruption frequency band caused by the fling data,the parzen-Weighted window is employed instead of the common used Rectangular Weighted window to do the spectral smoothing. The calibration frequency is interpolated to improve the estimation resolution of the powerspectral, by which much more information is available. EH4 system's Power-Line Interference Elimination mostly depends on 50 Hz,100 Hz,150 Hz notch by the receiver and the calibration, but do nothing to the High Order Harmonics of 50 Hz. In order to eliminate all the harmonics interruption, a parzen-window with zero weight on 50Hz and its harmonics is adopted to smooth the power spectrum. According to the stationary characteristic of the signal sampled by EH4 system, a run test of the variances of the time series, is applied to eliminate the non-stationary noise. The coherency characteristic of the signal sampled by EH4 system is studied, a high and a low coherency thresholds are applied to eliminate the coherent and noncoherent noise respectively.According to the processing result on actual EH-4 measured data, it proves that the improvement methods are feasible and valuable.