Near-surface inhomogeneities in the magnetotelluric field. Magnetic polarization

• Autorzy: Miecznik J.
• Języki publikacji: EN

Abstrakty

EN

Near-surface inhomogeneities cause the so-called static shift of amplitude magnetoelectric sounding curves for the magnetic polarization mode, and thus disturb the quantitative interpretation of magnetotelluric data. A number of possible methods for removing the static shift are presented in the geophysical literature; however, they all require data from other geophysical methods. Having known the electromagnetic field distribution in the given geoelectric cross-section, one can determine quantitative relationships between specific resistivities of the near-surface layer and calculated apparent resistivities. This is also an efficient way of removing static shift effects. The presented geoelectric model comprises a non-homogeneous near-surface layer resting over a 1D horizontally layered earth with arbitrary number of layers and the insulating base. The electromagnetic field distribution in such a model was calculated by means of the Fourier transformation with Dirichlet's boundary conditions. A plane electromagnetic wave with normal incidence was the source of electromagnetic field. The solutions are analytic expressions for the electric field at the Earth's surface. Moreover, asymptotic expressions for high-frequency and low-frequency field variations were calculated. In a high-frequency range, the impedance behaves as in the case of a uniform half-space. In a low-frequency range, the impedance depends most of all on the longitudinal conductivity of the layered earth.

Słowa kluczowe

EN

near-surface inhomogenities; Fourier transformation; static shift effect; magnetotelluric sounding

• Wydawca: Instytut Geofizyki PAN
• Czasopismo: Acta Geophysica Polonica
• Rocznik: 2002
• Tom: Vol. 50, nr 2
• Strony: 259--278
• Opis fizyczny: Bibliogr. 11 poz.

Twórcy

autor

Miecznik J.

• Department of Geophysics, University of Mining and Metallurgy, Kraków, Poland