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Neotectonic activity in the area of the Salair Ridge (southern West Siberia) rejuvenated a system of large arc-shaped faults separating the Salair tectonic arc from the adjacent tectonic units. These regional faults, which make up the general tectonic framework of the Altai-Sayan folded area, originated in the late Paleozoic and were repeatedly reactivated in the Mesozoic. The deformation within the major Salair thrust sheet is mainly brittle and follows small fault planes that crosscut the margins of Paleozoic thrusts. The neotectonic faulting controlled the erosion pattern of the territory and produced a reticulate drainage system. The Salair tectonic unit is a single 80 × 250 km block comprising multiple neotectonic blocks, with a relative vertical offset of no more than 100 m in the block interior and 100-200 m at its southern, northern, and eastern borders. The northwestern and southeastern border faults have reverse slip geometry, while the motions on the en-echelon northeastern fault boundary include reverse and right-lateral strike-slip components. The thickness of the Salair thrust sheet estimated from magnetotelluric (MT) data increases in the western direction from 5 to 15 km in the northern block part and from 10 to >20 km in the south. The allochthon base is delineated by a low-resistivity zone interpreted as a horizontal detachment. This boundary formed in the Mesozoic and was rejuvenated at the neotectonic stage. The lithology and deformation of Jurassic sediments filling piedmont basins around the Salair Ridge indicate that the Cenozoic fault pattern generally inherits the Mesozoic framework but differs in about ten times smaller vertical offset.

We present results of petrographic, geochemical, and isotope-geochemical (Sm-Nd) studies of the Paleoproterozoic terrigenous rocks of the Urik-Iya graben, which formed during three successive stages of extension. We have established that these rocks are both petrogenic (Ingashi and Daldarma formations) and lithogenic (Ermosokha Formation) sediments. It is concluded that the rocks in the lower and, partly, middle parts of the Urik-Iya graben section (Ingashi Formation and Lower Daldarma Subformation) resulted mostly from the disintegration of felsic igneous rocks. The terrigenous rocks in the middle part of the section (Upper Daldarma Subformation) might have formed through the disintegration of both felsic and mafic igneous rocks. The rocks in the upper part of the section (Ermosokha Formation) probably formed from the underlying terrigenous rocks of the Ingashi and Daldarma formations. The Nd model age (2.3-2.5 Ga) estimated for the rocks of the three studied sections points to a predominance of rocks of the Neoarchean and Paleoproterozoic upper continental crust in the provenance.

A model of the deep electrical conductivity of the Altai-Sayan folded region is presented, which was compiled from the results of three-dimensional inversion of the invariant values of the impedance matrix and three-dimensional impedance data fitting, using the trial-and-error procedure. The obtained electrical-resistivity values were used to estimate the fluid saturation of the Earth’s crust by applying the Shankland-Waff equation. The NaCl salinity of the aqueous solution is taken equal to 170 g/L, for which the fluid saturation is most consistent with the seismic data. The electrical conductivity and fluid saturation of focal zones of earthquakes, activated blocks of the region, and deep faults were studied. Most of the earthquake hypocenters are located above the top of conductors and near deep low-resistivity faults. The position of low-resistivity anomalies correlates with the position of domains with the enhanced attenuation of converted earthquake waves and reduced velocities of compressional waves. The Teelin, Samagaltai, and Kaa-Khem earthquake sources are characterized by maximum fluid contents (0.5-0.9 %), and the Altai, Shapshal, Shagonar, and Bolsheporoshskii sources, by minimum ones (0.1-0.2 %). The fluid saturation of deep faults reaches 1.2 %. The faults characterized by tensile stresses oriented orthogonally to their strike, show the highest fluid contents. A similar pattern is observed for the crustal blocks located beneath depressions. The high fluid contents beneath the Kyzyl Basin and its surroundings correlate with the major compressional-wave velocity deficit beneath it.

Electrical resistivity tomography has been widely applied in prospecting and exploring gold deposits, but its potential for studying placers has not been sufficiently revealed. It is shown on the basis of numerical simulation and the example of field studies that linear anomalies with high electrical resistivity identified in floodplains correspond to gold-promising stream pool and riffle facies. It is concluded from working with alluvial placers in Kamchatka, Altai, and the Baikal Region that electrical resistivity tomography has a high resolution for solving geological problems, which means that it can be used as the main method for prospecting and exploring placers.

The efficiency of the development of an oil and gas field is largely determined by the knowledge of its geologic structure. In the recent decade, complex fractured carbonate reservoirs have attracted more and more attention. This paper is concerned with a new technology for constructing 3D images of complex reservoirs, based on Gaussian beam processing of scattered seismic waves. This technology was developed at OOO RN-KrasnoyarskNIPIneft’ in cooperation with the Trofimuk Institute of Petroleum Geology and Geophysics. To test it, a special synthetic model was constructed, which is analogous to one of the licensed objects of PAO NK Rosneft’. For this purpose, a full-scale 3D seismic modeling was performed, which provided us with synthetic wave fields and made it possible to carry out well-controlled numerical experiments for reconstructing the geologic structure of the object of study. One of the distinctive features of the constructed digital model (digital twin) is the presentation of faults not as some ideal slip surfaces but as 3D geologic bodies filled with tectonic breccias. A series of numerical experiments was performed to simulate such breccias, the geometry of these bodies, and the geomechanical processes of fault formation. To select the parameters of the used method of discrete elements, we used the information obtained by geophysical studies in horizontal wells crossing the fault within the geologic prototype of the constructed digital model.

An implicit scheme of the discontinuous Galerkin method for solving gas dynamics equations on unstructured triangular grids is constructed. The implicit scheme is based on the representation of a system of grid equations in the so-called «delta» form. To solve the resulting SLAE for each moment of time, solvers from the NVIDIA AmgX library are used. To verify the numerical algorithm, a series of calculations were performed for the flow over the NACA0012 symmetric airfoil profile at various angles of attack, and the problem of the flow over the RAE2822 airfoil profile was solved. The results of calculations are presented.

This paper proposes a method for the numerical solution of the direct one-dimensional problem of magnetotelluric sounding. The construction of difference schemes is realized by the local integral equations method. A natural variant of the interpolation of an approximate solution is considered. The estimate of convergence of the approximate solution to the exact one and the estimate of the interpolation error are proved.

By an example of the investigation of the Euler equations on Lie algebras, we discuss an approach to the qualitative analysis of differential equations arising in a number of problems of mathematical physics, including rigid body dynamics. The approach proposed is based on a combination of methods of computer algebra and qualitative analysis of differential equations. We consider the applications of computer algebra in the problems of finding stationary invariant sets and studying their stability. For the equations under study, stationary invariant sets of various dimension have been found and their stability in the Lyapunov sense has been investigated.

A method for the search for numerical solutions to the Dirichlet boundary value problems for nonlinear partial differential equations of the elliptic type and of an arbitrary dimension is proposed. It ensures low consumptions of memory and computer time for the problems with smooth solutions. The method is based on the modified interpolation polynomials with the Chebyshev nodes for approximation of the sought for function and on the new approach to constructing and solving the problems of linear algebra corresponding to the given differential equations. The analysis of spectra and condition numbers of matrices of the designed algorithm is made by applying the interval methods. The theorems on approximation and stability of the algorithm proposed for the linear case are proved. It is shown that the algorithm ensures an essential decrease in computational costs as compared to the classical collocation methods and to finite difference schemes.