水平层状电各向异性介质大地电磁正演研究

Magnetotelluric forward research on horizontal layered electric anisotropic media

电各向异性现象在地球内部是普遍存在的,通过理论上推导的电各向异性介质的张量电导率的表达式及水平层状电各向异性介质的大地电磁正演公式,对一些地电模型进行数值计算,同时与电各向同性地电模型进行对比分析。结果表明,电各向异性介质的张量电导率的大小不仅与介质的固有电阻率性质有关,还与测量的方向有联系;电各向异性系数和相对测量角的变化都对地层的视电阻率和相位曲线振幅有较大的影响,但其曲线形态基本保持不变;当野外观测方向和电各向异性介质的电性主轴重合时,电各向异性介质模型可以看成两个独立的电各向同性介质模型。这些结果有助于以后的电各向异性介质实验研究和其大地电磁反演研究。

The electrical anisotropic phenomena is universal in the earth interior.We theoretically derived tensor conductivity expressions for the electrical anisotropic media and formula of magnetotelluric forward modeling in layered electrical anisotropic media which was used for numerical calculating some geoelectric models and comparing with electric isotropic geoelectric model.It shows that the tensor electrical conductivity of anisotropic media is not only related with its inherent resistivity properties,but also measuring direction;The amplitude value of the apparent resistivity curve changes significantly when one of the electric anisotropy coefficient and the relative measurement angle changes,while the shape of the apparent resistivity curve basically remain unchanged;When the measuring direction is the same as electrical spindle orientation of electric anisotropic medium in the field of electromagnetic exploration,electric anisotropic medium model can be seen as two independent electric isotropic medium model.This study,hopefully,will contribute to the research and application of future electric anisotropic media magnetotelluric inversion.