INFLUENCE OF "GEOLOGIC NOISE" ON MAGNETOTELLURIC-SOUNDING DATA AND METHODS FOR TAKING IT INTO ACCOUNT
A.V. Pospeev1,2, E.A. Sen'1,3
1Institute of the Earth’s Crust, Siberian Branch of the Russian Academy of Sciences, ul. Lermontova 128, Irkutsk, 664033, Russia
2Irkutsk Scientific Center, Siberian Branch of the Russian Academy of Sciences, ul. Lermontova 134, Irkutsk, 664033, Russia
3OOO SIGMA-GEO, ul. Zvezdinskaya 6, Irkutsk, 664011, Russia
Keywords: Magnetotelluric sounding, induction and galvanic effects, impedance, conductivity, interpretation, quasi-longitudinal curve
Abstract
The paper deals with the problem of interpreting magnetotelluric data in the differentiated low-conductivity upper part of the section. An observation network often makes it impossible to describe a spatial irregularity spectrum completely; so, using 3D data inversion comes across a significant spatial equivalence of the solution. The effect of irregular conductivity of the upper part of the section at one of the sites is considered by the comprehensively studied near-field transient electromagnetic sounding in dense 3D networks. A technique is proposed for choosing the directions of the minimum gradient of anomaly-causing conductivity and for selecting corresponding quasi-longitudinal curves for estimating the deeper parameters of the model. The advantage of using quasi-longitudinal curves is shown, and the high geological efficiency of the developed technique for interpreting magnetotelluric data is demonstrated at one of the sites of the Siberian Platform.
DOI: 10.15372/RGG2019181
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