Study On E-hz Wide-field Electromagnetical Method

Wide-field electromagnetic sounding method is a new and efficient artificial source frequency domain electromagnetic sounding method proposed by He Ji-shan Academician. It uses a high-performance and special pseudo-random multi-frequency signal as the field source to transmit and receive equivalent intensity multi-frequency signals at the same time. In contrast, the method rejects the variable frequency proposal and odd harmonic proposal of the inefficient CSAMT, achieves one transmitter, multiple receivers, uses the uniformity of electromagnetic field to measure one component (electricity component or magnetic component) in the artificial source electromagnetic field but not to measure the mutually perpendicular E and H at the same time. It is an accurate expression of calculating wide-field apparent resistivity in the electric filed (magnetic field), can measure and extract resistivity information in conditions that satisfies the dipole source in vast regions. Furthermore, the method puts emphasis on realizing the measurement of transmitting and receiving in a short distance, or deepening the exploration depth in the same level of transmitting and receiving distance. It shakes off the unfavorable factors such as weak signals, random changes of natural field source in MT method, can measure the total field when power supplies and overcome the weakness of needing high-current large equipment in measuring secondary filed in TEM measurement, so the speed of the ground observation has been greatly increased. The method expands the range of applications in frequency domain electromagnetic sounding, improves the survey results and has a very important theoretical significance and application value.Using pseudo-random multi-frequency signal as E-Hz Wide-field electromagnetic method's exciting field source, the author has comprehensively demonstrated the field source signals'time domain expression of the coding principles and coding rules, spectral analysis of frequency domain, and hardware implementation. According to the observation program that uses horizontal electric dipole source to excite earth in E-Hz Wide-field electromagnetic sounding method, the paper uses the basic theory of the electromagnetic field, and detailedly deduces the answers to the horizontal electric dipole source in stratified media space, analyzes the field response characteristics of the horizontal electric couple source under the influence of different factors in homogeneous half-space, carries out numerical modeling by using Hankel transform under the homogeneous half-space medium electromagnetic field of horizontal electric dipole and verifies the correctness of the algorithm. The thesis puts forward E-Hz wide-field apparent resistivity which meets the principle of apparent resistivity definition, uses inverse spline interpolation of electromagnetic fields on homogeneous half-space resistivity of the existence of complex and implicit function to calculate E-Hz wide-field sounding method's apparent resistivity, analyzes the feature of the simulated curves under the influence of different models and different factors. At the same time, comparing the characteristics of the theoretical curve both the present artificial source with electromagnetic sounding methods in natural field source, the author gives E-Hz wide-field apparent resistivity calculation which is fit to the practical application of a vertical magnetic field correction in the wild. Then, the paper proposes an adaptive inversion method that is fit to Wide-domain electromagnetic sounding method. The method is one of the most optimal inversion method based on the combination of Bostick direct inversion principle and the classic least-squares method. It uses Bostick direct inversion principle to establish the initial model, uses dimensionless parametric of differential mode to solve Jacobian matrix. The adaptive inversion method can well solve Layer problem of the initial model for inversion layer in layered media and avoid the problem that it is hard to get Partial derivative matrix of analytical expression for implicit function of wide-field apparent resistivity expression.Finally, by analyzing the existing frequency-domain sounding actual wild configurations, the thesis proposes a new field observations for region-wide configuration----E-Hz Wide-field electromagnetic sounding method configuration. The configuration measures only the vertical component (Hz) of the magnetic field in one direction, meeting dipole source conditions, is able to achieve full-field observation, well avoid the static effect caused by measuring electric field previously, and not subject to restrictions on the direction of survey lines just like traditional CSAMT wild configuration, which makes artificial source electromagnetic method more portable, flexible and efficient.