GPR AS A PROSPECTIVE METHOD FOR STUDYING THE RITMICAL STRUCTURE OF QUATERNARY DEPOSITS (FOR EXAMPLE, SAISARY LAKE IN YAKUTSK)

(Neradovskii L.G. )

The spectral analysis of GPR signals recorded on Saisary lake in Yakutsk was performed. Three periodic generations of time series of pulses were detected in the GPR signals. According to drilling data of the support well, they correspond to three rhythmic structures of sediments of different genesis. According to the drilling of the reference borehole, they correspond to three rhythmic structures of sedimentary deposits of different genesis. In silt-peat deposits and clay deposits of lake-swamp genesis with a thin- layer rhythmic structure to a depth of 2,0 m pulses follow each other with periods 0,41-0,20-0,15 m. In the transitional zone with the appearance of sandy material in lake-swamp deposits, the period of pulses repetition at the depth of 2,0-3,4 m increases to 0,67-0,34-0,22 m. Below 3,4 m, where the basal sandy thickness of alluvial genesis begins with thick-layer rhythmic structure of sands of different grains, the pulse period reaches the maximum values 0,84-0,43-0,31 m. The GPR method is recommended for use in permafrost studies in order to solve stratigraphy problems, as a promising auxiliary tool for rapid and non-destructive study of the rhythmic structures of Quaternary deposits.......

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  • 2020  № 4, pp. 25-33

THE RESULTS OF EXPERIMENTAL AND METHODOLOGICAL SURVEYS OF ELECTRICAL PROSPECTING AT THE SITE OF THE MSU IN ALEXANDROVKA (KALUGA REGION)

(Kulikov V.A. Ermolin E.Y. Melnikov A.V. Asoskov A.E. Polikarpova V.A. )

The results of experimental and methodological surveys which were conducted in the spring of 2019 at the “Alexandrovka”, the scientific and educational geophysical base of the Geological Faculty of Lomonosov Moscow State University in the Kaluga region is presented in the article. The testing work included several tasks. One of them consisted in comparing the results of measurements of induced polarization (IP) carried out in the time domain with the registration of the total decay of the IP field, with the results of frequency domain measurements by using the differential phase parameter (DPP). The question of the applicability of the empirical formula A.V. Kulikov (Kulikov A.V., 1978) for the calculation of DPP into apparent polarizability was raised repeatedly by many geophysicists, and this question remains open. The second task of the experimental surveys was to compare the results of geometric soundings performed with different arrays along the profile. At the last stage, along the profile, audiomagnetotellurics measurements were performed by using MTU-5A equipment and a joint inversion of the audiomagnetotellurics data and electrotomography data was applied. The result was compared with a priori geological information that is available for the area of the scientific and educational base.......

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  • 2020  № 4, pp. 34-42

NEGATIVE INDUCED POLARIZATION ANOMALY AND ITS POSSIBLE ORIGIN

(Bobachev A.A. Shevnin V.A. )

Negative IP anomalies sometimes can be found during field survey. In publications their origin explain by the influence of contrast horizontal layering of type K and Q or by the influence of lateral resistivity contrast that influence in IP anomalies according to J.R. Wait. Exists one other hypothesis of negative IP anomalies origin as intrinsic property of pure clay with definite humidity and in case of rather high current density of polarizable current (Brandes, 2003, 2005). The authors found IP anomaly at student field practice in Kaluga region and studied its space position, lithological characteristic and relation with close laying layer of highly resistive sand. Though negative IP anomaly was found in loam layer its probable origin resulted from closely situated highly resistive sand layer.......

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  • 2020  № 4, pp. 43-49

EARTHSCOPE ARRAY OF SIMULTANEOUS MAGNETOTELLURIC SOUNDINGS: MULTI-SITE METHOD TO ESTIMATE TRANSFER FUNCTIONS IN THE ACTIVE CORDILLERA REGION (NORTHWESTERN USA)

(Lozovsky I.N. Varentsov Iv.M. Gracheva D.A. )

The paper presents the results of data processing for the array of simultaneous magnetotelluric and magnetovariational soundings held in the northwestern part of the United States in the frames of the EarthScope research program. The innovative PRC_ MTMV software system developed in the GEMRС IPE RAS has been applied. This technique allowed to obtain high-quality estimates of the impedance and tipper, superior in quality to the early available simultaneous processing results. The most important achievement is the implementation of procedures for the estimation of horizontal magnetovariational responses and obtaining valuable data early absent for this region. These responses are free of near-surface galvanic distortions and provide direct mapping of deep conductive structures.......

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  • 2020  № 4, pp. 50-57

ON JOINT INVERSION APPROACH IN 1D GEOELECTRICAL PROBLEMS

(Pushkarev P.Yu. Zhuravlev S.D. Budennyy S.A. )

The article demonstrates an effect of inversion accuracy in joint inversion approach for 1D geoelectric problems and shows case for formulation of joint target function for CSEM and MT methods. The algorithm is verified on two models with different problem formulation for each. The first one assumes fixation of layers thickness and the second - usage of general regularization coefficient without any hard boundaries on thicknesses and resistivities. The application of joint inversion approach provides better accuracy of models regarding to real ones than results of separate inversions in every case.......

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  • 2020  № 4, pp. 58-67
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