A Trial for Introducing 6-Element Tensor Impedance in Magnetotelluric Method and Its Application
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摘要: 在经典大地电磁(MT)理论中,张量阻抗[ Z ]定义为电场分量和磁场分量之间的线性关系.估算张量阻抗[ Z ]及和它有关的其他参数(例如视电阻率、相位、倾子等)是MT数据处理中的一个重要环节.引入了六元素张量阻抗[ R ]的全新概念,并开发了相应的处理方法.为检验本方法的特征和抗噪性能,对采集自朝鲜的MT野外资料进行了分析.分析结果表明在MT资料处理中新定义的六元素张量阻抗[ R ]比传统的四分量张量阻抗[ Z ]提高测深曲线的相干度至少0.1以上,并且改善了大地电磁资料处理的质量.Abstract: The conventional magnetotelluric method is theoretically based upon definition of impedance tensor[ Z ] and the relationship between the electrical and magnetic components Ex, Ey, Hx, Hy, Hz of MT field, the main purpose of MT data processing is to obtain inpedance tensor, apparent resistivity, phase, tipper, skewness and other parameters. In this paper, we propose the definition of 6-elements tensor impedance and briefly describe its some characteristics and determination techniques in the comparison with the former impedance tensor[ Z ]. Furthermore, we explain the necessity of the proposed method and demonstrate its applicability by some field tests conducted in Democratic People's Republic of Korea.
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Key words:
- magnetotelluric exploration /
- impedance tensor /
- signal to noise ratio /
- geophysics
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表 1 MT时间序列中磁场分量的振幅比较
Table 1. Comparison of amplitudes of magnetic components from MT records
频率段 采样率t(s) 磁场分量平均振幅(mA/m) Hx Hy Hz 1 6.510 4×10-4 0.562 1.893 0.560 2 1.016 7×10-2 0.078 0.041 0.063 3 0.166 667 0.183 0.149 0.350 4 2.666 67 6.279 10.748 17.410 平均 1.775 3.208 4.596 表 2 图 1中的测点Ei(i=x, y)和Hj(j=x, y, z)之间的平均相干度
Table 2. Coherencies between Ei(i=x, y) and Hj(j=x, y, z) components
Coh(Ex, Hx) Coh(Ex, Hy) Coh(Ex, Hz) Coh(Ey, Hx) Coh(Ey, Hy) Coh(Ey, Hz) 0.488 0.456 0.409 0.473 0.419 0.405 表 3 图 1中的MT测点中用[Z]和[R]时Ei, Eip之间平均相干度
Table 3. Comparison of coherencies between Ei, Eip components when using [Z] and [R]
相干度 Coh(Ex) Coh(Ey) [Z] 0.659 0.641 [R] 0.692 0.692 -
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