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Last update: T_KG (03.05.2002)
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Last update: T_KG (02.04.2008)
The lecture presents the electrical conductivity as one of the fundamental physical parameters of the Earth?s interior, which plays a significant role in geophysical studies of the temperature distribution, mineral composition, structural setting, fluid content and of specific assemblies of electronic conductors due to tectonic processes in the Earth. The lecture presents models of the electromagnetic induction in the Earth due to natural time variations of the external geomagnetic field. By presenting details of the magnetotelluric and geomagnetic depth sounding methods, the lecture demonstrates basic principles of the electromagnetic induction experiments, of the statistical data processing and analysis, as well as of the physical and geological interpretation of the depth electromagnetic soundings. |
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Last update: prof. RNDr. František Gallovič, Ph.D. (10.06.2019)
Oral exam |
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Last update: T_KG (26.03.2008)
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Last update: T_KG (11.04.2008)
Lecture |
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Last update: T_KG (19.01.2003)
Subject of geoelectricity as a geophysical discipline. Classification of geoelectrical methods. Electrical conductivity of the earth's materials Physical principles of the electrical conductivity. Electrical conductivity of minerals, rocks, fluids and melts. Mechanisms of the electrical conductivity in the earth, mixture laws. Electric macro-anisotropy and its possible geodynamical interpretation. Relation of the electrical conductivity to other geophysical parameters. Other electromagnetic parameters - permitivity, permeability, electrochemical parameters. Primary sources of the natural electromagnetic field of the Earth Frequency range of geoelectrical induction methods, sources of the primary electromagnetic field in radio-, audio- and helio-frequency bands, their structure in time and space. Electromagnetic plane wave in a layered conductor - Cagniard-Tikhonov magnetotelluric model Direct and inverse magnetotelluric problem. Plain wave impeding on the surface of a layered conductor. Cagniard-Tikhonov fundamental model of the magnetotelluric problem, impedance of a layered earth, apparent resistivity and impedance phase. Long period asymptotics of magnetotelluric curves. Analytical properties of the magnetotelluric impedance. Electromagnetic induction in a layered earth due to spatially non-uniform sources Maxwell's equations in a wave number domain. Magnetotelluric and magnetic spectral impedances for a layered conductor. Magnetotelluric and geomagnetic induction soundings. Limitations of the Cagniard-Tikhonov model with a non-uniform source field. Generalization to spherical conductors - global electromagnetic soundings into the mantle depths. Electromagnetic field in laterally inhomogeneous structures Classification of lateral inhomogeneities (local, regional, 2-D, 3-D). Modelling of electromagnetic fields in horizontally inhomogeneous structures (laboratory models, numerical models). Impedance tensor. Approximate models, Born approximation and its extensions, induction in a thin sheet. Distortions of the magnetotelluric curves due to lateral inhomogeneities, local/regional composite models of the magnetotelluric field. Deep geomagnetic soundings - geomagnetic transfer functions and induction arrows. Magnetotelluric practice, geoelectrical models Practical aspects of magnetotelluric and geomagnetic depth soundings (instrumentation, data acquisition, data processing, interpretation). Geoelectrical projects. Electrical anomalies within the earth, their explanation in terms of thermodynamic, structural and tectonic conditions. Estimates of the electrical conductivity of the lower mantle and the earth's core. |