Зимой 2024 года в районе научно-учебного полигона Геологического факультета МГУ им. М.В. Ломоносова в Калужской области были проведены опытно-методические работы с использованием методики измерений, позволяющей получать одновременно целый набор электроразведочных данных аудиомагнитотеллурического зондирования (АМТЗ), частотного зондирования (ЧЗ) и глубинной электротомографии с измерением вызванной поляризации (ЭТ-ВП). Работы были выполнены по профилю, пересекающему палеодолину р. Угра неогенового возраста. На первом этапе интерпретации была выполнена автоматическая совместная 2D инверсия данных АМТЗ и ЭТ-ВП. Полученная модель использовалась в качестве стартовой для интерактивного двумерного подбора данных ЧЗ. По результатам двухэтапной интерпретации электроразведочных данных была построена глубинная модель удельного электрического сопротивления (УЭС), оценены пространственные границы погребенной долины. В заключении описаны преимущества и недостатки предложенной методики измерений. In the winter of2024, experimental and methodological work was carried out in the area of the research and training fieldcamp of the Faculty of Geology of Lomonosov Moscow State University in the Kaluga Region using a measurement technique that allows obtaining simultaneously a whole set of electrical exploration data - audiomagnetotelluric sounding (AMTS), control source electromagnetic method (CSEM) and deep electrical resistivity tomography with measurement of induced polarization (ERT-IP). The work was carried out on a profile crossing the paleovalleyofthe Ugra River of Neogene age. At the first stage of interpretation, an automatic joint 2D inversion of the AMTS and ERT-IP data was performed. The resulting model was used as a starting point for interactive twodimensional selection of CSEM data. Based on the results of a two-stage interpretation of electrical exploration data, a deep model of electrical resistivity was built, and the spatial boundaries of the paleovalley were estimated. In conclusion, the advantages and disadvantages of the proposed measurement method are described.

В период с 2015 по 2022 год в районе научно-учебного полигона геологического факультета МГУ им. М.В. Ломоносова в Калужской области были выполнены измерения комплексом электроразведочных методов по трем профилям субширотного направления. Комплекс включал в себя вертикальные электрические зондирования с измерением вызванной поляризации, зондирования становлением поля в ближней зоне, аудиомагнитотеллурические зондирования. Эти работы посвящены изучению миоценовой палеодолины, закартированной в среднем течении р. Угры. По результатам комплексной интерпретации электроразведочных данных была построена глубинная модель удельного сопротивления и поляризуемости. На качественном уровне на основе карт кажущихся электроразведочных параметров были оценены пространственные границы палеодолины. From 2015 to 2022 in the area of the research and training fieldcamp “Aleksandrovka” of the Geology Department of the Lomonosov of Moscow State University (Kaluga region) the elecrtomagnetic survey was carried out along three lines with sublatitudinal direction. Survey included a set of electmomagnetic methods: vertical electrical sounding with induced polarization, time-domain electromagnetic sounding and audio magnetotelluric sounding. These surveys were done to study the Miocene paleovalley located in the middle course of the Ugra river. Resistivity and chargeability model was obtained from the joint inversion of EM data. Boundaries of the paleovalley were define more accurately using apparent resistivity and chargeability maps.

The results of magnetotelluric soundings obtained in 2020 along the Rzhev–Velikie Luki profile in the suture zone of three segments of the Precambrian crust of the East European Platform: Fennoscandia, Sarmatia, and Volga-Ural are presented. An anomaly zone of increased conductivity in the crust was revealed in the central part of the profile. The crust conductor is weakly expressed on the components of the telluric tensor due to the screening effect of the conducting sedimentary cover; therefore, the main emphasis in the qualitative analysis of the data and inversion is placed on magnetovariation parameters. According to the results of 2D inversion carried out in A.E. Kaminsky’s ZONDMY2D program, a subvertical zone of low resistivity has been identified on the geoelectric model in the crust, which is assumed to be associated with a paleosubduction zone of the Belarusian Oceanic Plate.

Summary In 2019, comprehensive geophysical work was completed on the regional 22 km profile across the Ugra river. The work was carried out for several years by a group of employees and postgraduate students of the Department of Geophysics of the Geological faculty of Lomonosov Moscow state University during educational and optional geophysical practices [Kulikov et al., 2016]. The geophysical complex included works using audio-magnetotellurics sounding (AMTS), time domain electromagnetic (TDEM), and vertical electric sounding with measurement of induced polarization (VES-IP). Based on the results of a complex interpretation of electrical data, a deep resistivity model was constructed. The most interesting result is the allocation in the Central part of the profile multi-tiered system of paleovalleys with different ages ‒ Visean, Neogene, Quaternary.

Summary In recent years representatives of the Department of Geophysics of the geological faculty of Moscow State University carried out geological-geophysical investigations of buried river valleys in the territory of Kaluga region. When solving this task, the most effective is the complex of methods, including geometrical soundings (VES) and induction low-frequency methods electromagnetic survey (TEM). As a result of joint interpretation of VES and TEM data within the horizontally layered subsurface the geoelectrical section satisfying observed data of both methods was obtained. Preliminary results of the interpretation show that the buried paleovalleys of different age represented mainly by sands appear in the geoelectrical model in the form of local objects of high resistivity against the background of a horizontally layered host section.

WE PRESENT THE RESULTS OF A JOINT INTERPRETATION OF THE DATA SETS FROM SEVERAL COMPLEXES OF ELECTRIC PROSPECTING METHODS AIMED AT STUDYING THE MAJOR MIOCENE PALEOVALLEY, LOCATED IN THE MIDDLE REACHES OF THE UGRA RIVER IN THE KALUGA REGION. THESE METHODS INCLUDED VERTICAL ELECTRICAL SOUNDING WITH INDUCED POLARIZATION (VES-IP), TIME-DOMAIN ELECTROMAGNETIC SOUNDING (TEM), AND AUDIOMAGNETOTELLURIC SOUNDING (AMT). THE UPPER PART OF THE GEOELECTRICAL MODEL WAS DERIVED BY FITTING A SINGLE MODEL, A COMBINATION OF THE VES-IP AND TEM DATA, IN A SPECIAL VERSION OF THE IPI2WIN PROGRAM. THIS MODEL, CORRESPONDING TO THE UPPER PART OF THE SECTION, WAS USED AS THE STARTING POINT FOR THE SELECTION OF AMT DATA. THUS, THE DEPTH OF THE MIOCENE PALEOVALLEY MODEL WAS OBTAINED ON THE BASIS OF MAGNETOTELLURIC DATA, AND THE UPPER PART WAS BASED ON LESS DEEP ELECTRICAL METHODS - VES AND TEM.

Since May 2011 we have collected long-period magnetotelluric (MT) data in non-magnetic pavilion on geophysical base of Moscow University in Kaluga region. Three sets of electrical lines with different types of electrodes were installed. Different groups of authors have made processing of MT records, calculation of apparent resistivity curves. These curves were compared with apparent resistivity curve obtained on magnetovariational data of Moscow observatory. The 1D inverse problem was solved for the deep part of the generalized curve (T > 30 s). In particular we succeeded in finding preliminary conductivity values on the depth of crust, upper and middle mantle.

Since May 2011, long-period magnetotelluric (MT) data have been collected in the non-magnetic pavilion at the geophysical base of Moscow University in the Kaluga Region. The non-magnetic pavilion was constructed in compliance with the following conditions: selection of non-magnetic materials, control of local magnetic field anomalies, and setting the basement for magnetometers separately from the main build-ing. Recording equipment with fluxgate and optomechanical magnetometers with three sets of electric lines with different electrodes was installed. The parallel testing of channels was performed. Currently, the seismo-logical equipment and meteorological station are being prepared for installation.