Our detailed study of the crust and upper mantle of the South Baikal basin focused on seismic coda and seismic S-waves attenuation and estimated seismic quality factor (QS and QC), frequency parameter (n), attenuation coefficient (δ), total attenuation (QT), and the ratio of two components the total attenuation: intrinsic attenuation (Qi), and attenuation due to scattering caused by the inhomogeneities of the medium (QSC). We calculated the sizes of inhomogeneities revealed in the block medium, which put their effect on the attenuation of seismic waves in different frequency ranges. The seismic wave attenuation field was analyzed in comparison with the geological and geophysical characteristics of the medium, and a direct relationship was established between attenuation, composition and active processes in the crust and upper mantle of the studied area. According to the estimated intrinsic attenuation (Qi) and scattering attenuation (QSC) contributions into the total attenuation, intrinsic attenuation is generally dominant in the studied area, while the QSC component increases in the areas of large active faults.

Синтезированы ионные комплексные соединения состава [LnL2(NO3)2]2[Ln(NO3)5]⋅3Me2CO (Ln = Sm (1), Eu (2), Tb (3), Dy (4)) с оптически активным лигандом L, содержащим фрагменты 1,10-фенантролина и (+)–3-карена. По данным РСА, кристаллическая структура соединения 2 построена из комплексных катионов [EuL2(NO3)2]+ (полиэдр N6O4) и комплексных анионов [Eu(NO3)5]2– (полиэдр O10), а также молекул Me2CO. Лиганды L и NO3 выполняют тридентатно-хелатную и бидентатно-хелатную функцию соответственно. Комплексы 1—4 изоструктурны и кристаллизуются в нецентросимметричной пространственной группе P1, их магнитные свойства изучены в температурном интервале 2—300 K. Значения μэфф для 1—4 при 300 K составляют 3.14 μB, 6.08 μB, 16.76 μB и 18.30 μB соответственно и характерны для ионов Ln3+. Для комплекса 3 значительная анизотропия приводит к нелинейной полевой зависимости намагниченности при 2 K. Комплексы 1—4 проявляют металл-центри­рованную оранжевую (Sm3+), красную (Eu3+), зеленую (Tb3+) и желтую (Dy3+) люминесценцию в твердом состоянии при комнатной температуре. Квантовый выход люминесценции для твердых образцов уменьшается в ряду 2 > 1 > 3 ≈ 4.

Summary In the report the results of application of modern ways in the tectonophysical analysis of geological and geophysical data for identification of regularities in a fault structure of a platform cover on the Kovykta gascondensate field (GCF) are considered. The basis for research of sedimentary cover are the materials of 3D seismic and electromagnetic survey, the structural data and materials of digital relief model processing. As a result of the complex analysis the zone-block structure (ZBS) of the Kovykta GCF is established. It represents hierarchy of blocks which contact with each other on wide zones of short fractures concentration. The ZBS style is defined by domination of subhorizontal fault zones (layer-by-layer stripping) and subvertical zones of northwest and northeast orientations. The network of the fault zones was formed in four stress fields which correspond with the main stages of an adjacent Baykal- Stanovoy mobile belt development in the Paleozoic- Cenozoic. Some fields are reactivated in the Cenozoic under the influence of the gravitational processes connected with local lifted raisings of a relief. The zone-block structure of the Kovykta GCF is a basis for it's zonation on hydrocarbon productivity, overpressure zones, on degree of fracturing and types of stress state of rocks. The solution of this task will allow to receive additional substantiating for the choice of drilling site which can be passed without geohazards and with the prospect of detection of natural gas accumulation.

The article presents the results of the tectonophysical approach to the analysis of stress fields and the structure of gas–condensate deposits with the complex platform cover. The discussed case is the Kovykta license area (LA) in Eastern Siberia, Russia. In the upper part of the cross section, the network of fault zones was identified from the relief lineaments and structural data. The dynamic conditions for faulting (compression, extension, and strike-slip) were reconstructed by the paragenetic analysis. The state of crustal stresses in the study area was studied by tectonophysical modeling using gelatin as an optically active material. The applied method was successful in distinguishing between the zones of faults in the platform cover, which differ in the degree of their activity in the specified stress fields. The lower part of the cross section in the NE segment of the Kovykta LA is considered as an example of the tectonophysical interpretation of the electrical and seismic survey data in order to identify the fault zones and reconstruct the corresponding stress fields. Based on the synthesis of the analyzed data, it is revealed that the deposits like the Kovykta gas condensate field (GCF) show the zone-block structure of the platform cover formed under the influence of several stress fields closely associated with the stages of tectogenesis in the adjacent mobile belts. The next objective is to enhance the tectonophysical approach in order to develop a hierarchical model of the GCF zone-block structure, which details need to be known for improving the prediction of sites with the complicated stress-strain state of rocks and mitigating the risks associated with drilling exploration and production wells.

The problem of earthquake forecasting remains challenging, especially considering strong seismic events (M≥8). Strong earthquakes occur most often along the fault planes due to large-amplitude displacements of the contacting blocks. In such cases, the physical parameters of the earthquake foci generation process are estimated on the basis of the concepts describing the destruction of solids. In this paper, we present a new tectonophysical model of strong earthquake foci in the continental lithosphere. In this model, an earthquake focus is viewed as a body whose rheological properties are changing over time throughout the entire seismic period, including the moment of the seismic event initiation, its occurrence and the subsequent stress release in of the geological medium. In the period when a future earthquake source develops and grows, the physical properties of the host rocks are assumed to change substantially, and both the viscosity and the relative shear strength decreases. At the moment of time when a strong earthquake takes place, the viscosity of the rocks in its focus is at its minimum value and thus favorable for high-amplitude interblock shearing under the current regional stress and unchanged geodynamic factors. A decrease in the viscosity is facilitated by an increase in the fault length and leads to weakening of the geological medium and decreases its strength properties. When the earthquake occurs, the viscosity of the rocks in its source is assumed significantly lower than the dynamic viscosity of the lithosphere and not less than one or two orders below the viscosity of the interblock seismically active medium containing the source. It is most likely that at the moment of time when an earthquake takes place, the viscosity in its source is 1017–1019 Pa·s. In our approach, the parameter of viscosity is introduced into the physics of earthquake foci, and the time factor is taken into account when studying the process of earthquake preparation and occurrence, which can be an important step to gaining more knowledge for forecasting of the strongest seismic events (M≥8).

We performed a tectonophysical analysis of earthquake frequency–size relationship types for large Central Asian earthquakes in the regions of dynamical influence due to major earthquake-generating faults based on data for the last 100 years. We identified four types of frequency–size curves, depending on the presence/absence of characteristic earthquakes and the presence or absence of a downward bend in the tail of the curve. This classification by the shape of the tail in frequency–size relationships correlates well with the values of the maximum observed magnitude. Thus, faults of the first type (there are characteristic earthquakes, but no downward bend) with Mmax ≥ 8.0 are classified as posing the highest seismic hazard; faults with characteristic earthquakes and a bend, and with Mmax = 7.5–7.9, are treated as rather hazardous; faults of the third type with Mmax = 7.1–7.5 are treated as posing potential hazard; and lastly, faults with a bend, without characteristic earthquakes, and with a typical magnitude Mmax ≤ 7.0, are classified as involving little hazard. The tail types in frequency–size curves are interpreted using the model of a nonlinear multiplicative cascade. The model can be used to treat different tail types as corresponding to the occurrence/nonoccurrence of nonlinear positive and negative feedback in earthquake rupture zones, with this feedback being responsible for the occurrence of earthquakes with different magnitudes. This interpretation and clustering of earthquake-generating faults by the behavior the tail of the relevant frequency–size plot shows raises the question about the physical mechanisms that underlie this behavior. We think that the occurrence of great earthquakes is related to a decrease in effective strength (viscosity) in the interblock space of faults at a scale appropriate to the rupture zone size.

Based on the data on seismically active faults of Central Asia, the authors apply the Gutenberg‐Richter law to study regularities of seismicity in large seismically active fault zones. Cumulative recurrence plots are constructed for earthquakes recorded only in the areas of active dynamic influence of the specified faults. Special attention is paid to changes in slope angles of the recurrence plots at the transition to the area of strong magnitudes. It is noted that the right‐side end of the plot (i.e. distribution tail) becomes steeper or less steep relative to the main distribution for small magnitudes. The degree of non‐linearity and the forms of the recurrence plot tail are used to rank the faults of Central Asia by potential relative seismic hazard. It is shown that the highest seismic hazard is associated with the faults that control earthquakes with magnitudes M≥7.5, which recurrence plots show a trend to decrease the slope angle of the regression line in the area of strong magnitudes. It is highly probable that such earthquakes may reoccur in the fault zones in the next 50–100 years.

Studying locations of strong earthquakes (М≥8) in space and time in Central Asia has been among top prob-lems for many years and still remains challenging for international research teams. The authors propose a new ap-proach that requires changing the paradigm of earthquake focus – solid rock relations, while this paradigm is a basis for practically all known physical models of earthquake foci. This paper describes the first step towards developing a new concept of the seismic process, including generation of strong earthquakes, with reference to specific geodynamic features of the part of the study region wherein strong earthquakes were recorded in the past two centuries. Our analysis of the locations of М≥8 earthquakes shows that in the past two centuries such earthquakes took place in areas of the dynamic influence of large deep faults in the western regions of Central Asia. In the continental Asia, there is a clear submeridional structural boundary (95–105°E) between the western and eastern regions, and this is a factor controlling localization of strong seismic events in the western regions. Obviously, the Indostan plate’s pressure from the south is an energy source for such events. The strong earthquakes are located in a relatively small part of the territory of Central Asia (i.e. the western regions), which is significantly different from its neighbouring areas at the north, east and west, as evidenced by its specific geodynamic parameters. (1) The crust is twice as thick in the western regions than in the eastern regions. (2) In the western regions, the block structures re-sulting from the crust destruction, which are mainly represented by lense-shaped forms elongated in the submeridio-nal direction, tend to dominate. (3) Active faults bordering large block structures are characterized by significant slip velocities that reach maximum values in the central part of the Tibetan plateau. Further northward, slip velocities decrease gradually, yet do not disappear. (4) In the western regions of Central Asia, the recurrence time of strong earthquakes is about 25 years. It correlates with the regular activation of the seismic process in Asia which is mani-fested in almost the same time intervals; a recurrence time of a strong earthquake controlled by a specific active fault exceeds seems 100–250 years. (5) Mechanisms of all the strong earthquakes contain a slip component that is often accompanied by a compression component. The slip component corresponds to shearing along the faults revealed by geological methods, i.e. correlates with rock mass displacements in the near-fault medium. (6) GPS geodetic meas-urements show that shearing develops in the NW direction in the Tibet. Further northward, the direction changes to the sublatitudinal one. At the boundary of ~105°E, southward of 30°N, the slip vectors attain the SE direction. Further southward of 20°N, at the eastern edge of the Himalayan thrust, the slip vectors again attain the sublatitudinal direc-tion. High velocities/rates of recent crust movements are typical of the Tibet region. (7) The NW direction is typical of the opposite vectors related to the Pacific subduction zone. The resultant of the NE and NW vectors provides for the right-lateral displacement of the rocks in the submeridional border zone. (8) The geodynamic zones around the cen-tral zone (wherein the strong earthquakes are located) are significantly less geodynamically active and thus facilitate the accumulation of compression stresses in the central zone, providing for the transition of rocks to the quazi-plastic state and even flow. This is the principal feature distinguishing the region, wherein the strong earthquakes are loca-ted, from its neighboring areas. In Central Asia, the structural positions of recent strong earthquakes are determined with respect to the following factors: (1) the western regions separated in the studied territory; (2) the larger thickness of the crust in the western regions; (3) strong submeridional compression of the crust and upper lithosphere in combination with shear stresses; (4) high rates of recent crustal movements; and (5) the rheological characteristics of the crust.

The first tectonophysical model of the Baikal seismic zone represents a separate complex region of the lithosphere. It has a pinnate structure with a backbone belt of current deformation, which is a concentrator of largest earthquakes, and branching, repeatedly reactivated large and small faults. In its vertical section, the seismic zone is tree-like, the stem and the branches being faults of different size ranks which can generate earthquakes when reactivated. The real-time short-period fault motions and the respective seismicity occurring at a certain time and in certain places are triggered by strain waves, which disturb the metastable state of the faulted lithosphere subject to regional stress. The modeling work includes developing general requirements for tectonophysical models of continental rifts and special methods for identifying the faults that become active within short historic time spans, as well as techniques for locating potential events in space and time in specific active faults. The methods and model testing for medium-term earthquake prediction are described by the example of the well-documented Baikal seismic zone, which is the most active part of the Baikal rift system. The tectonophysical model for the Baikal zone is statistically supported by field data, and this allows estimating the velocities and periods of strain waves for different zone segments and faults, with implications for nearest-future earthquake prediction.

New methods are proposed for registering deformation waves and assessing their phase (vector) velocities based on earthquake monitoring in dynamic influence areas of active faults. Active faults in Central Asia are classified on the basis of the vector velocities of deformation waves. The complex parameters of the presently active faults and the vector velocities of the deformation waves are used for the geodynamic zoning of Central Asia. Such an approach offers new opportunities for the more extensive investigation of the geodynamic characteristics of spacious intracontinental structures that were tectonically active in the Cenozoic.

We used the Digital Faults geoinformation system that we developed to propose an algorithm for quantitative estimation of seismic activity on faults. The resulting technique was used to study the spatiot-emporal patterns in the present-day activity of faults in Central Asia. Fault activity was found to vary at frequencies of a few years and cannot be explained by changes in the regional stress fields. We studied the tendency of seismic events to be localized to areas of dynamic influence due to faults. The active faults were grouped by the criteria of seismicity organization in the influence areas of these faults. It was shown that fault activity and its comparatively high frequency on real time scales are caused by strain waves, which may be generated by interplate and interblock movements in the brittle lithosphere. Judging by the speed of strain waves, the active faults are classified into groups that differ in their geological and geophysical parameters. They can be used to estimate the directions of strain wave fronts and to identify areas of dominant fault activation over intervals of real (geologically speaking) time. We give a map showing active faults in Central Asia, plots of a quantitative index of their seismic activity, and the directivity vectors of strain waves that excite fault activity. The methods we developed for classifying active faults by the quantitative index of seismic activity and for determining the vectors of strain waves that excite fault activity are all tools that significantly expand our possibilities when developing tectonophysical models of the seismic process in earthquake-generating zones of the lithosphere and open new methods for attacking problems in intermediate-term earthquake prediction.

The available geological and geophysical methods fail to estimate variations of fault activity in real time intervals, such as, months, years or decades. Using geo-informational technologies, this challenge can be resolved with an algorithm and software based on a quantitative index of seismic activity. Such an approach has been applied to studies on the Baikal rift system (BRS) and its adjacent territories. It is discovered that fault activity is variable in intervals of several years, which cannot be attributed to changes in regional stress fields. An active fault map of BRS and curves of the quantitative index of seismic activity of faults are constructed for the BRS cross-section. The proposed method ensures a detailed classification of active faults by the quantitative index of seismic activity, and thus significantly extends options for finding solutions of problems related to the middle-term forecast of earthquakes. This method has been applied to study spatial and temporal variations, sources, and mechanisms of the recent fault activation. It is shown that fault activation has a relatively high frequency on the real time scale because of the slow deformation waves of disturbance that are generated by inter-plate and intra-block movements of the brittle lithosphere. Throughput velocity of deformation waves allow classification of active faults into groups that differ in geological and geophysical parameters. They also allow an estimation of the direction of the deformation wave's front and identification of an area of dominating fault activation in real time (geologically instant) intervals.

The Darzens reaction of dihaloacetic acid esters with aromatic aldehydes produces either arylhaloglycidic or arylhalopyruvic esters depending on the nature of the substituent in the aromatic ring. Alkyl p-methoxyphenylchloropyruvates undergo spontaneous intermolecular cyclocondensation to form pyranone or furanone derivatives depending on the character of the alkyl fragment.

Alkylation of 3-benzoylquinoxalin-2(1 H )-one with 1,5-dibromo-3-oxapentane, 1,8-dibromo-3,6-dioxaoctane, and α,ω-dihaloalkanes with different lengths of the polymethylene chain gave the corresponding quinoxaline podands. In the reaction with 1,2-dibromoethane, the N,O-rather than N,N′-alkylation product was obtained. The reaction of the obtained quinoxaline-based podands with benzene-1,2-diamine followed the quinoxaline-benzimidazole rearrangement pattern with formation of 2-(3-phenylquinoxalin-2-yl)benzimidazole-based podands.

AbstractFor Abstract see ChemInform Abstract in Full Text.

3-α-Chlorobenzyl- and 3-benzoylquinoxalin-2-ones react with benzylamine in DMSO to give intermediate 3-(α-benzyliminobenzylidene)quinoxalin-2-one which is capable of existing in several tautomeric forms. The subsequent oxidative cyclocondensation leads to imidazo[1,5-a]quinoxalin-4-one. This new procedure for building up imidazo[1,5-a]quinoxalin-4-one system has been applied to the synthesis of various bis(imidazo[1,5-a]quinoxalin-4-ones).