High-frequency Magnetotelluric Data Processing Method

The purpose of Magnetotelluric (MT) is to measure the conductivity structural of underground medium on different depth.The whole process includes data collection and processing and inversioning.It has been proved that the MT signal are non-liner,non-stationary and non-minimum phase.therefore, the classical time-frequency transform which based on fourier analysis is not suitable for MT signal,paper adopt a more efficiently method - Hilbert-Huang transform(HHT) to process MT signal, it can suppress the big scale disturb of MT signal and raise Signal Noise Ratio.In recently years EH-4 system become more and more popular in magnetotelluric filed because of abundance data collection, portability equipment, and high work efficiency. although EH-4 has been widely used in china, it's data processing mostly depend on IMAGEM which is manufacturer's software of data collecting and data processing.because IMAGEM work in DOS interface and have some disadvantages, it is not satisfy with data processing in practice, and it has some disadvantage: low-resolution factor, asymmetrical frequency distribution, cannot effectively suppress disturb (electromagnetism disturb with static and topography influence), In order to attain high quality data we are required mastering the overall process of EH-4 system data processing, importing some advanced means of restraining noise, improving the quality of data. EH-4 system's theory, out-file format and it's data processing has been detailedly researched in paper, according to those research, the author succeeds in designing the progaram of EH-4 data processing software by visual C++, .the main EH-4 data processing is as follow: reading time-sires file correctly and converting to decimal file in order to further study; citing HHT to analyze the MT signal; selecting data with the radio of signal correlation; then recalculating tensor impedance and resistivity resistance basis on Power spectrum estimation. The quantity of new impedance file is more 6 times than the original file, it heighten greatly resolution factor. According to actual measure EH-4 data analysis , the result is consistent with actual geological situation, it prove that the program is feasible and valuable.