Wide Field Electromagnetic Method Static Correction Research And Application

Wide field electromagnetic method, a new kind of artificial source frequency domain electromagnetic sounding method, is proposed by Academician He Ji-shan recently, Central South University. The method gets rid of weak and random variation natural field source signal of MT by using one plant source. It unifies near area, transitive area and remote area according to uniformity of field and defines wild field apparent resistivity and reduces distortion in non-remote area, so the method can measure in the vast, non-remote areas and expand the depth of exploration on the same transceiver distance. The method just needs to measure one component of the electromagnetic fields on wild working, and can acquire the signal of multiple frequencies at one measurement, which improve accuracy and efficiency of the measurement. Frequency domain electromagnetic methods all have static effect, so does wide field electromagnetic method. Static effect is a difficult problem in data processing of wide field electromagnetic method, and affects the results of the data interpretation seriously, so we need to do static correction in wide field electromagnetic to improve the quality of data interpretation.The paper briefly introduces the basic principle, characteristics and working ways of wide field electromagnetic method, and analyzes" the mechanism of the static effect, and introduces the correlation coefficient method and the wavelet transform method to identify the static effects, and describes some methods of the static corrections, such as curve shift method, spatial filtering method, median filtering method, electromagnetic array arrangement method, phase conversion method, the joint inversion method, direct two-dimensional inversion methods, and puts emphasis on the theory of continuous media inversion, and simulate s the static effect under some different theoretical models, such as the uniformity half space, two-story D curve, three H-type curve, three K-type curve, three Q-curve, and using spatial filtering method, median filtering method, phase conversion method, and two-dimensional inversion method for static correction, and tries to use Gaussian filtering method in static correction, and comprehensively analyzes the effect of various methods of correction. Finally, the paper conducts static correction of a two-dimensional inversion using the data of a Lead-zinc-silver mine in Inner Mongolia and coal mine in Anhui by using Wide field electromagnetic method, and eliminates the static effect effectively.The paper has won the support and funding of National natural science foundation project, the basis research of wide field electromagnetic system (40827002).