Data Processing Of Time-and Frequency-domain In EH4 System And Its Application

The Stratagem system is a magnetotelluric system made by EMI Inc. The device can use not only the natural source magnetotelluric filed, but also the user workshops source of electromagnetic signals, through collecting geophysical electric and magnetic field components, the apparent resistivity is calculated, in order to obtain the geological structure and resistivity contour of geoelectric section. In U.S Stratagem measurements may be effectively applied in ground water investigation, research in environment, mineral and geothermal exploration, and in civil engineering studies. In recently years EH4 system become more and more popular in magnetotelluric filed because of abundance data collection, portability equipment and high work efficiency. Although EH4 has been widely used in china, in the current actual production, it's data processing mostly depend on IMAGEM which is manufacturer's software of data collecting and data processing.The background and purposes of research are introduced in this paper, research status of EH4 electromagnetic at home and abroad is presented briefly. It is mainly for the time domain data and frequency domain data to analysis, and use the regularization inversion method to research and analysis. EH4 electromagnetic sounding system principle is based on high-frequency magnetotelluric theory, the basic theory of homogeneous half-space, layered medium is derived. Reading of time series, time and frequency conversion, power spectrum and impedance estimation have been studied in time domain.Specifically including the reading process of Y documents, FFT time-frequency conversion principle, Han-ning window filtering of field survey data and the calculation of power spectrum, etc. In frequency domain, one-dimensional continuous medium inversion is derived and the program is written using Matlab programming. Finally, to illustrate the practicality of this field, through specific examples-Coal Mine detection, the abnormal distribution of several regions is determined by measuring geological, geophysical conditions. So the effectiveness of the time domain and frequency domain data processing is verified.