This paper discusses the structure of a geologic medium represented by accessible lithified rocks and provides an overview of methods used to describe its movements. Two basic opinions are considered in the framework of the discussion: (1) an initially homogeneous and continuous geologic medium acquires the structure composed of blocks in the process of the geologic medium’s deformation/destruction/degradation, and (2) a geologic medium is composed of blocks (and often has hierarchic, active, energy-saturated features), and the continuity model is thus not valid for describing the geologic medium’s deformation. Proponents of the first point of view actively apply the standard or modified continuum model of a solid deformed body (SDB) in estimations of the stress-strain state, but the input parameters of this model do not contain any information on discreteness in principle. Authors who support the second opinion, either explicitly or implicitly assume that the block structure of the geologic medium, which is detectable by geological methods, makes a direct and unambiguous impact on all other mechanical properties of the geologic medium and, above all, on the nature of its movements.

Based on results obtained by interpreting the data collected in our long-term field studies of rock fracturing, mathematical processing of GPS-measurements, and theoretical models, we agree with the concept of the geologic medium’s block structure, but argue that the geologic block-structure property is not acquired but congenital. Regarding sedimentary rocks, it means that the discrete structure has been already embodied in the rock before sediment lithification, regardless of the intensity of macroscopic deformations. A discrete structure is the form of the geologic medium existence and a cause of the congenital anisotropy of the geologic medium’s strength characteristics. Due to subsequent deformation of the geologic medium, some elements of the structure can be manifested more clearly, and the structure itself can become more complex due to secondary effects. At the same time, the structure of geologic blocks is not directly manifested in the spatial and temporal features of the recent movements in the geologic medium. However, it is not an obstacle to developing continuum models of such movements in the same way as, for instance, the adequacy of the continuum general theory of relativity is not denied in view of the discrete-hierarchical structure of the Universe.

The key requirements to a model include its applicability, testability, confirmability/deniability of its predictions in the investigated space-time scale, and compliance with conservation laws. This paper briefly discusses the most important aspects of the continuum approach based on the concept of an effective continuous medium and, above all, the Cauchy continuum model, envisaging that the dynamic response of the medium in spatial descriptions is given only by the Cauchy symmetric stress tensor (T). In more general continuum models of the medium (such as moment, micropolar, micromorphic and other models), the dynamics of the medium may be characterized by asymmetric tensors of force and couple stresses.

This paper refutes the unjustified criticism of the continuum model as such criticism is rooted in the mistaken identification of quite special assumptions or ways of setting the problems with the general principles of the continuity model. Special attention is given to critical comments received from supporters of the active geologic medium concept. The paper considers actual difficulties encountered in studies using the continuity model, specifically in coordinated descriptions of the medium containing mobile defects, as well as the medium that is subject to deformation due to movements on its structure, while this structure is hierarchical at any scale level, down to the zero level (which, in particular, concerns the fractal structure). Discussed are causes of some widespread misunderstandings and mistakes in the geoscience literature, as well as the occurrence of conditions facilitating the revival of Aristotle ideas and preNewton concepts in geology, which repeatedly gain the upper hand over the modern ideas of classical physics. The paper considers the problem of reconstruction of stresses in the geologic medium from in-situ kinematic indicators, specifically from irreversible slips. Attention is drawn to the fact that the currently dominating approach ‘imposes’ a priori speculative rules on the geologic medium, such as a relationship between stresses (to be estimated) and the slip directions. Under this approach, the conservation laws are inevitably ignored, which makes it impossible to interpret the obtained results in terms of stress. Under the alternative approach proposed earlier by the author of this paper, the conservation laws being taken into account allows not only to reconstruct the stress tensor field, but also to judge on the geologic medium rheology. It is concluded that rejecting the continuum approach a priori, with a reference to the geologic medium discreteness, is at least unconstructive.

The paper briefly overviews the evolution of ideas concerning causes and mechanisms related to the origin of the Baikal rift zone (BRZ) in the centre of the Eurasian plate, discusses parameters of the recent seismogeodynamic impact on the seismotectonic regime in BRZ due to the Western Pacific subduction and the Indo-Eurasian collision, and attempts at estimating their contributions to the modern geodynamics of rifting processes in Pribaikalie. Seismic migration processes and specific density patterns of the released seismic energy are analyzed for two selected profiles between BRZ and the regions of collision and subduction. A statistical method is proposed to calculate seismic migration from space-time diagrams, and equations are developed to show a decrease in specific density of seismic energy released in the lithosphere at a distance from the interplate boundaries towards the Baikal rift. The modern geodynamic impact on the seismotectonic regime in BRZ due to the Indo-Eurasian collision is reflected in moderate horizontal compression of the lithosphere, mainly in the southwestern BRZ and partly in the central BRZ. In the transition area in this profile, the specific density of released seismic energy is about 1.72×1010 J/km2. The geodynamic impact on the seismotectonic regime in BRZ from the subduction zone (from the Nankai trough) is shown by a significantly lower specific density of released seismic energy, 1.02×1010 J/km2. In the lithosphere of the northeastern BRZ, a weaker geodynamic influence is mainly manifested by responses to strong seismic events and earthquake focal mechanisms with a clear strike-slip component in the Chara and Tokka basins located in the Aldan shield of the Siberian platform.

We discuss a possible mechanism that drives the propagation of the geodynamic impact on BRZ from the interplate contact areas. In our opinion, the geodynamic influence propagates intermittently in the lithospheric plates due to motions of slow-deformation-wave fronts, which are reflected in the diagrams as seismic activity clusters. The longrange propagation of slow waves is realized through triggering of active faults in the lithosphere. Such faults interacting with slow wave deformations may be manifested as excited sources of dissipation of seismic oscillations resulting from a spontaneous release of the energy accumulated in the Earth interior. This mechanism of endogenous energy supply may explain the observed propagation of recordable slow elastoplastic deformations for many thousands of kilometres.

Today, when the new materials are available to show more ancient ages of the early elements of BRZ, and it is established that the tectonic energy is reduced with distance from the interplate boundaries, there is no support for the hypothesis based on the role of the Indo-Eurasian collision in the formation of BRZ. A recordable seismotectonic impact on the seismic regime in BRZ can occasionally occur after a major seismic activity in the regions of collision and subduction. This phenomenon may be used as a criterion for developing medium-term earthquake predictions, taking into account a delay in response.

Short-term cycles observed in the seismic regime of BRZ and its adjacent areas, as well as in the seismic migration processes are considered as a basis for making a conclusion that seismotectonic processes associated with interactions between the plates, as well as the seismic migration processes may be impacted by a potential modulating influence of cosmogenic factors. Such extraterrestrial factors include short-term variations in the Earth’s rotation and orbiting modes, as well as in gravitational interactions between the Earth, Sun and Moon. It is unlikely that the shortterm cycles may result from the slow endogenous processes of thermal convection in the Earth.

Introduction. Studying and mapping of faults in the Earth’s crust is one of the priority objectives in struc‐ tural geology and tectonophysics. Generally, faults are associated with mineral deposits, thermal springs and earth‐ quakes, and fault zones are areas of the most dangerous geological processes and various geophysical anomalies. In this regard, digital maps and databases on faults and fault zones are highly demanded both for science and practical applications. This paper presents a new digital map of the southern East Siberia and the adjacent Northern Mongolia, which shows faults in the crust which were active in the Pliocene‐Quaternary. The map covers the territory between 96–124°E to 49–58°N. An annex to this paper contains files with geospatial data on the mapped faults.

The input data, and their synthesis. We consolidated the database on faults active in the Pliocene‐Quaternary stage of the crust development and mapped the faults on the basis of digital elevation models SRTM 90 m [Consortium for Spatial Information, 2004], space images from Landsat series satellites (Google Earth), electronic bathymetry data on Lake Baikal [Sherstyankin et al., 2006], topographic maps (1:200000 scale), regional and global earthquake cata‐ logs, as well as the publications and maps based on the earlier studies of active tectonics and earthquake traces with the use of the ActiveTectonics Information System developed by the research team lead by the author of this paper [Lunina et al., 2014b]. For the major part of the southern East Siberia, we collected and processed our field observa‐ tion data on faults and related deformation features (Fig. 1). The geographic locations of the faults were mapped with the use of MapInfo GIS. The precise detection of tectonic faults, topographically represented by river lineaments and benching, was ensured by the synthesis of cartographic, literature and field materials. A significant number of the detected lineaments, that were not confirmed by any data due to the poor knowledge of some regions in the southern East Siberia and the adjacent territories, are included in the database with a special mark and shown on the map as inferred faults.

Results and discussion. The digital map (Fig. 2) shows 1678 faults composed of 2315 segments, including 1097 true, and 1218 inferred ones, identified by the fault strike changes or fragmentation. Using the consolidated fault da‐ tabase, we constructed maps showing fault segments differing in the degree of activity (Fig. 3), displacement types (Fig. 4 and 7), and ages of the last activations (Fig. 8). Besides, we constructed a map of seismically active faults that can generate M≥5.5 earthquakes. The analysis of the thematic maps of faults gives grounds to conclusions that have been either partly supported or controversial, yet now are based on the factual justification of the faults in the Ac‐ tiveTectonics Information System database. It is shown that the Baikal rift zone is bordered in the southwest by the Busiyngol basin and the West Belino‐Busiyngol fault, and in the northeast by the Olyokma and Nyukzha faults located in the basins of the same‐name rivers. In the areas located westward and eastward of these boundaries, the rift re‐ gime (crustal stretching, extension with strike‐slip faulting, and shearing) is abruptly changed to transpression. In general, similar activation features are typical of the southern East Siberia in the Holocene and the present time. Such features include seismogenic activation episodes when mainly the faults of the NE–SW and sublatitudinal strike are renovated – normal faults, left‐lateral normal faults with a strike‐slip component, left‐lateral strike‐slip faults, left‐ lateral strike‐slip faults with a normal component, and left‐lateral strike‐slip faults with a reverse component. The NE‐ striking faults are insignificant to the west of 98° meridian.

Conclusion. The digital fault map (Fig. 2) and the thematic maps (Fig. 3, 4, 7, 8 and 9) can be used as a tectonic ba‐ sis for the synthesis of geological, geophysical, hydrogeological and geodetic data in studies aimed at forecasting of hazardous endogenic and exogenic geological processes. The undoubted advantage of this digital fault map over other regional fault maps is its integrated mapping framework that consolidates a large amount of data (collected mostly by the Siberian scientists) in the uniform information space. Newly gathered data can be input in the map’s database that is available for off‐line viewing on html‐pages.

The paper presents the results of comprehensive study of the primary diamond deposit of the Nyurbinskaya pipe in the Yakutian diamondiferous province. It is established, that the pipe is confined to the fault junction of four directions and is composed of the kimberlite of four phases. Analysis of different faults and tectonic fracturing allowed to reconstruct the tectonic stress fields acting at the stage of the kimberlite body formation and to determine their occurrence sequence in time. The data obtained about regularities of the Nyurbinskaya pipe compositional structure and results of geologo-structural studies are combined in a single structural-compositional model of the deposit formation. Peculiarities of the fault network operation during the deposit formation stage are confirmed by experimental results using polarization-optical method. The model allowed to formulate the basic structural characteristics of the prospecting works object within which the formation of kimberlite body type of the Nyurbinskaya pipe is possible and to determine the elements of the fault network which are promising for the kimberlite pipes discovery.

Equations of state of corundum (α-Al2O3), eskolaite (Cr2O3), hematite (α-Fe2O3), and magnetite (Fe3O4) are constructed based on the Helmholtz free energy by simultaneous optimization of ultrasonic, X-ray diffraction, dilatometric, and thermochemical measurements. The magnetic contribution to Cr2O3, α-Fe2O3, and Fe3O4 Helmholtz free energy was determined via the A.T. Dinsdale model [Dinsdale, 1991]. The calculated thermodynamic properties of rock-forming oxides of aluminum, chromium, and iron are in good agreement with the reference data and experimental measurements at room pressure, as well as with P-V-T measurements at high temperatures and pressures. Thermodynamic functions (x, α, S, CP, CV, KT, KS, γth, G) of corundum, eskolaite, hematite, and magnetite are calculated at different pressures (up to 80, 70, 50 and 20 GPa, respectively) and temperatures (up to 2000 K), and the results are tabulated. The calculated Gibbs energy of rock-forming oxides can be used to construct the phase diagrams of mineral systems, which include the oxides under the conditions of the Earth’s mantle.

This study aimed to provide a systematic overview of water sources in the Baikal region and Transbaikalia by the content of radon (Q) and establish regularities in variations of Q values in space and time.

We collected and analyzed our evaluations of Q and the available published Q values for many dozens of water sources in the study area (Fig. 1), and reviewed the monitoring data of eight water sources that belong to the Angarsky fault impact zone in Southern Priangarie (Fig. 5). Radon content in water samples was measured in accordance with the standard procedure using a RRA-01M-03 radiometer (sensitivity of at least 1.4∙10–4 s–1∙Bq–1∙m3; maximum allowable relative error of 30 %).

Based on the frequency patterns of Q values measured in the Baikal region and Transbaikalia (Fig. 2) and the analysis of the known classifications of the water sources by radioactivity, we propose a uniform regional classification of groundwaters with respect to 222Rn content (Table 1). In seismically active Baikal region, wherein water sources with Q>185 Bq/l are practically lacking, we distinguish the first three groups with the following Q ranges: Group I – Q≤15 Bq/l, Group II – 16≤Q≤99 Bq/l, and Group III – 100≤Q≤184 Bq/l. Most of the water sources sampled in the Baikal region and Transbaikalia belong to Groups I and II, which allows us to recommend an objectively existing value of 100 Bq/l as the level of intervention in the preparation of drinking water in this region, instead of the limit of 60 Bq/l that is now approved in Russia.

In order to identify the special patterns of groundwater sources in the Baikal region and Transbaikalia, which belong to different radioactivity groups, we sampled these sources along the transect from Bayanday to Muhorshibir, across the Baikal rift and other large regional tectonic structures (Fig. 4). On a larger scale, we analysed the radon content variability in the groundwater sources within the zones influenced by the Tunka normal fault (Fig. 3), Primorsky normal fault, Angarsky strike-slip fault with a normal component, and other active faults located in the study region. 

Within the framework of the spatial aspect, the material and structural factors determining the radioactivity of groundwaters in the study region are identified. Our data support the results of the previous studies showing a generally lower radon content in groundwaters in the Baikal region in comparison with those in Transbaikalia that is characterized by a higher radioactivity due to the abundant granitoids of different types. The background concentrations of the radioactive gas in the Baikal region correspond to Group I, and in those in Transbaikalia to Group II. The boundary between the regions with different levels of radioactivity of groundwaters is shifted southeastward from the central structures of the Baikal rift. Within the Bayanday–Muhorshibir transect, it coincides with the known boundary between the Transbaikalia province of cold carbonic acid waters and the Baikal province of nitrogen and methan terms (see Fig. 4). The structural factor of formation of the emanation field refers to an increase in radioactivity of water associated with the faults, whereat an increased permeability and higher geodynamic activity cause a more intensive radon emanation and/or the occurrence of emanating reservoirs (see Fig. 3, and 4). In the Baikal region, water sources of Group II are generally associated with faults, while in Transbaikalia, groundwater sources belonging to groups III and VI are typically related to faults.

To clarify the pattern of temporal variations in groundwater radioactivity, we analysed long rows of the monitored Q values (9 to 30 months) in eight water sources in the Angarsky fault zone in Southern Priangarie (see Fig. 5, and 6).According to the adopted classification (see Table 1), three water sources belong to the near-surface sources (Group I), and there are five deeper near-fault water sources (Group II). Despite the distinct variations in radioactivity, the Q values recorded through most of the monitoring time do not exceed the threshold Q values for the respective groups. It appears that the observed periodic anomalously high and low contents of radon are due to seasonally variable meteorological parameters (see Fig. 6).

The correlation analysis of Q values and atmospheric pressure (P), air humidity (U) and temperature (T) shows a clear dependence of the content of radon in groundwater on T and P values (Table 3). Following the major seasonal trend of air temperature, the level of radioactivity is increased in the water samples taken in winter and decreased in summer (see Fig. 6). Q values are indirectly influenced by parameter T via changes of water temperature, variations in flow rates of water sources, freezing of the top layer of soil and other processes, which parameters require further research.

According to the monitoring data (see Table 3, and Fig. 6, A), the content of radon in near-surface water sources (Group I) can vary by a few and the first dozens of units, while changes by tens of becquerel per liter are recorded in the deeper near-fault water sources (Group II). As a consequence, in short periods of extreme Q values, the content of radon in a water source may increase or decrease to a value corresponding to a neighbouring radon-radioactivity group.

This paper provides an overview of the radon activity of groundwater in the Baikal region and Transbaikalia with a focus on regularities in the spatial and temporal patterns of 222Rn in the water sources with Q<185 Bq/l. The nonradon waters are more abundant in the Baikal region, including areas of active use of natural resources. Although the content of 222Rn in low, such waters should be a target of further research aimed to explore medicinal water sources, assess drinking water quality, and discover the emanation precursors of strong earthquakes in the study region.