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天然电场选频法是利用大地电磁场作为工作场源,测量大地电磁场在地面产生的电场,研究地下地电断面的电性变化,以查明水文地质工程问题的一种交流电勘探方法。平面波在各向同性均质中,设波的前进方向与垂直地面的z轴方向一致;波面与x、y轴所在地平面平行。若考虑到当z→∞时,则电场强度E和磁场强度H均→0。因场强系随传播距离的增加而衰减,故当场强衰减1/e倍时,其场强为地面场强的37%。则其传播距离Z_(?)为:
Natural electric field frequency selection method is the use of the earth’s electromagnetic field as a workplace source to measure the electric field generated by the earth’s electromagnetic field on the ground to study the electrical properties of underground geoelectric changes in order to identify hydro-geological engineering problems of an AC exploration method. The plane wave is in isotropic homogeneity, and the advancing direction of the wave is consistent with the z-axis direction of the vertical ground plane; the wave plane is parallel to the plane where the x and y axes are located. If we consider that when z → ∞, then the electric field strength E and the magnetic field strength H → 0. Because the field strength decay with the increase of propagation distance, the strong field strength is 37% of the ground strength when the strong field decay 1 / e times. Then its propagation distance Z_ (?) Is: