The article presents the general results of medium- and long-term earthquake forecasting with K ≥ 13 (M ≥ 5.0) in the Baikal rift zone. They were obtained in recent years through the joint use of the Prediction geoinformation system and the developed two-stage phenomenological model for the periods of preshock preparation of earthquakes. This model was created based on the analysis of seismological data on the preparation of the most dangerous local earthquakes that occurred in the Baikal rift zone. It is consistent with results obtained in the study of seismic regimes of ice shock preparation on the ice cover of Lake Baikal and in conducting field experiments on fault sections with the aim of clarifying the physical and mechanical conditions for the emergence of sources of seismic-range wave-oscillation generation. The paper provides an example of practical use of the obtained results of earthquake forecasting, as well as methods of clarifying seismic-hazard assessments in relation to infrastructure in the city of Angarsk, located 100 km from the seismically dangerous Main Sayan Fault (MSF), in the zone of which, during the analysis of the seismic regime, a “locked” segment with a seismic gap was identified. In accordance with its linear dimensions with a length of 60 km, according to two assumed equations of relationships L/M, estimates of energy potential were calculated, the maximum values of which correspond to the values Mmax = 7.1 and 7.8. It is shown that the use of the obtained earthquake-forecast results helps to clarify the level of seismic hazard for the nearest time intervals of expectation of earthquakes with different values Mmax. An example of assessing the current seismic hazard using a medium-term forecast for the infrastructure of the city of Angarsk is considered for possible seismic tremors from the south-eastern section of the MSF zone for the next 10 and 50 years. When compared with the OSR-16 map, it is shown that the calculations carried out indicate a relatively lower level of seismic hazard for the city of Angarsk, with waiting times of 10 and 50 years.

The paper presents some multidisciplinary research results on the structure of slip surfaces in segments of tectonic faults in the Baikal region and Mongolia. The properties of subsurface (modern) and deep slickensides exposed after many-kilometer denudation of the Earth’s upper crust are studied at different levels—from macroscale to nanocrystals. Other types of heterogeneities characterizing the structure of fault slip zones are also considered. The presented data indicate a heterogeneous structure of tectonic faults. Their slip zones show both low-friction regions where strong mineral phases are replaced by weak minerals and potentially unstable spots with high friction resistance. Results of the comprehensive study of geological conditions under which different-scale heterogeneities emerge in exhumed fault segments should be taken into account when developing rock mass models suitable for numerical simulation of earthquake preparation processes at the micro-, meso- and macroscales.

Using the developed geoinformation system “Prediction”, an analysis was made of information available from the media on two devastating earthquakes in the Türkiye that occurred in the western segment of the East Anatolian fault on February 6, 2023. The possibilities of recognizing signs of the preparation of earthquake data by means of medium-term forecasting developed for the Baikal rift zone, which are important for assessing seismic hazard and seismic risk, are discussed. Based on the analysis of the consequences of the large-scale destruction of residential and industrial infrastructure in the Türkiye, the causes of the huge damage to the country's economy caused by earthquakes, which are largely due to unfavorable seismotectonic conditions and urbanization problems that arose as a result of insufficient compliance with the necessary requirements and norms of earthquake-resistant construction, are considered.

A special issue of the journal “Geology and Environment” on the topic: “Consequences and assessment of the threat of earthquakes” comes out two months after the catastrophic earthquakes in Southeast Turkey that occurred on February 6, 2023. The issue presents articles on the consequences of these earthquakes and takes steps towards a theoretical understanding the nature of earthquakes, developing methods for predicting earthquakes in the Baikal region and measures to reduce damage.

The methods developed by the world community to date to withstand strong natural and induced destructive earthquakes do not effectively reduce material losses and the number of victims. The authors propose for discussion an integrated approach to solving the problem of ensuring seismic safety, based on the use of new important information about the geological conditions for earthquake generation. This involved the use of results of numerical and physical modeling, as well as physical full-scale experiments in the natural fault areas. The paper analyzes the petrophysical conditions of deep-seated frictional processes in coseismic faults, revealed through detailed studies of the fragments of paleoearthquake centers that became accessible after their exhumation from seismic-focal depths of the Earth’s crust. The collected information allowed the authors to clarify with a high degree of certainty the origin and occurrence of seismic motions. This paper presents briefly the results of the medium-term forecast of earthquakes with M≥5.0 as applied to the seismodynamic regime of the Baikal rift zone. The forecast emphasizes the detection of places for 1–11-year earthquake generation cycles. A comprehensive analysis of the collected information made it possible to substantiate the conclusion about an opportunity to prevent earthquake damage by using hydrodynamic damping of seismically hazardous fault segments. In the last section, consideration is being given to one of the most promising methods of such man-made impacts, which uses modern technological advances in drilling deep multil-branch and directionally inclined wells with horizontal deviation. The paper discusses the techniques that make it possible to prevent episodes of unexpected reactivation of fault segments in the form of excitation of earthquakes with M≥6.0. Attention is drawn to conducting tests at selected sites in order to improve the technology as part of the approach to earthquake damping.

This article solves the task of selecting and describing methods for assessing the social and economic indicators of seismic risk using the example of the town of Angarsk in Irkutsk oblast, which is located dangerously close (100–120 km) to seismically dangerous faults in the Eastern Sayan uplift and the Baikal Rift Zone characterized by magnitudes M = 6.5–8.0. The relevance of the study is determined by the demand for clarifying the seismicity of an actively developing region and the declaration of the Sendai Framework for Disaster Risk Reduction 2015–2030, which calls for improving risk assessment methods and implementing measures to mitigate it. The goal is to obtain reliable estimates of risk indicators that are necessary and sufficient for making the decision to mitigate. The scientific novelty is due to the fact that, for the first time, as part of one work for a single town, the results of all stages of the study are presented, including updating the assessment of seismic hazard, the vulnerability of risk elements, and the calculation of various indicators of possible damage associated with the risk. In addition, a joint analysis of all values has been performed for the first time. To assess the risk indicators, methods of computer simulation using the GIS Extremum, developed with the participation of the authors of this paper, were applied. In addition to describing methodological techniques, the article provides a rationale for the parameters of the possible and most dangerous seismic events. For the town of Angarsk, these are 8 and 9 grades of the MMSK-86 scale. An assessment of the social and economic indicators of seismic risk has been performed, the values of which are the highest in the microdistricts of Baikalsk, Staro-Baikalsk, Kitoy, and Novy-4, which implies the need for special measures, including the inspection and strengthening of the seismic resistance of buildings.

Abstract—A joint analysis of seismicity in the Baikal Rift Zone (BRZ) is carried out using modern instrumental data (Baikal Branch of the Federal Research Center “Geophysical Survey of the Russian Academy of Sciences,” 1963–2021) combined together with historical and paleoseismological data on earthquakes. The structure of the seismicity field within BRZ is studied by the new statistical methods. The spatial resolution in the seismically active areas attained 100–120 km. The analysis revealed patches of seismic activity alternating with areas of relative seismic quiescence (seismic gaps). The seismic patches form a hierarchical structure. At the highest level (a spatial scale of 500–1800 km and a lifetime of 300 years and longer), three main patches of seismicity are identified within BRZ, defining the Sayan, Baikal, and Severomuiskii (North Muya) subregions. Smaller patches form a structure with a spatial scale of 100–500 km and a lifetime of 50–200 years. The patches of seismic activity reflect the segmentation of active faults during the seismotectonic evolution of the Earth crust. The estimates of the maximum regional magnitude Mmax from instrumental data for 1963–2021 and from seismogeological data are compared. It is shown that quantile estimates Qq(T) of the maximum earthquakes in the future time interval T are preferable to the Mmax estimates for the seismic risk problems.

The paper discusses the results of studying the regimes of preparation and implementation of high-energy dynamic phenomena in the freshwater ice cover of Lake Baikal, namely the seismodynamic destruction (icequakes) similar to strong tectonic earthquakes in the Earth's crust. We analyze the causes and mechanisms of the formation of multi-kilometer main cracks in the ice cover, which are the sources of seismic impulses with energies up to 105–108 J. The energies of such events are comparable with the characteristic energies of minor earthquakes and moderate rock bumps. Analysis of seismic emission in the ice cover recorded by seismographs on the ice and the coast shows the similarity of the spatio-temporal and physicomechanical conditions for the preparation of main cracks in the ice cover and earthquake sources in tectonic faults. The results of the study are relevant for the development of new methods and improvement of existing methods for strong icequake forecast as well as for planning measures to prevent or mitigate the destruction of coastal engineering infrastructure and for improving the methods for forecasting tectonic earthquakes in seismically active zones of the Earth's crust including Baikal rift zone.

The paper discusses the basic principles underlying a new approach to the control of seismic activity in tectonic fault zones. A key component of the approach is the use of controlled man-made impacts on highly stressed fault segments. The applicability of the approach was verified in field experiments on seismically active fault segments of the Baikal rift zone and collision structures of Mongolia. The paper reports the most striking examples of applying man-made pulsed vibrational impacts to highly stressed fault segments in combination with controlled fluid injection into deep wells. The results of impacts on the studied fault segments are discussed in the light of new geological data on physicochemical processes in the zones of ancient seismically active faults and recent advances in deep drilling for hydrocarbon exploration and production. A justification is provided for the concept of controlled shear stress relaxation in potentially hazardous fault segments showing the signs of earthquake preparation. The possible implementation of the proposed concept in the near future is discussed.

The paper deals with the methodological features of drilling and completion of wells in the fractured natural reservoirs containing oil and gas accumulations with different reservoir pressures of fluid-pressure systems from abnormally high to abnormally low. The authors had studied the fluid-pressure systems of industrial lithium-bromine brines, oil and gas fields and accumulations in the south of the Siberian platform for the period from 1983 to 2019. The article summarizes the main results, including new technical solutions protected by the Russian Federation patents. The authors proposed and patented a series of new technical solutions for the immediate consolidation of natural permeable fractures during the primary opening of the reservoir by drilling, as applied to a fractured reservoir. The main task of the study is to preserve the permeability of the fractured system in the bottomhole formation zone under the action of compressive stresses (rock mass) that increase with the formation of a drawdown cone, primarily in the bottomhole formation zone with the increase in the drawdown (ΔP) above critical values. Such an area is the bottomhole formation zone within a radius of the first meters around the well that penetrated the fractured reservoir. Practice has proved that the use of innovative solutions through the advanced consolidation of permeable fractures in the bottomhole formation zone (of fluid-producing oil- and gas-bearing, water-bearing reservoir) in the open (initial natural) state ensures the preservation of natural permeability of natural filtering fractures of the reservoir with the fluid system reservoir pressure from anomalously low to abnormally high. The solution ensures constant permeability of the fractured filtration system throughout the cleaning cycles of the bottomhole formation zone rocks from drilling mud, obtaining of the true calculated hydrodynamic parameters based on the results of well testing in the modes of the “steady-state production method” and well flow rate (productivity) stabilization under further well operation.

AbstractThe authors outline the results of long-term interdisciplinary research aimed at identifying the possibility and the methods of controlling tangential displacements in seismically dangerous faults to reduce the seismic risk of potential earthquakes. The studies include full-scale physical and numerical modeling of P-T conditions in the earth’s crust contributing to the initiation of displacement in the stick-slip regime and associated seismic radiation. A cooperation of specialists in physical mesomechanics, seismogeology, geomechanics, and tribology made it possible to combine and generalize data on the mechanisms for the formation of the sources of dangerous earthquakes in the highly stressed segments of faults. We consider the prospect of man-caused actions on the deep horizons of fault zones using powerful shocks or vibrations in combination with injecting aqueous solutions through deep wells to manage the slip mode. We show that such actions contribute to a decrease in the coseismic slip velocity in the fault zone, and, therefore, cause a decrease in the amplitude and energy of seismic vibrations. In conclusion, we substantiate the efficiency of the use of combined impacts on potentially seismically hazardous segments of fault zones identified in the medium-term seismic prognosis. Finally, we discuss the importance of the full-scale validation of the proposed approach to managing the displacement regime in highly-stressed segments of fault zones. Validation should be based on large-scale tests involving advanced technologies for drilling deep multidirectional wells, injection of complex fluids, and localized vibrational or pulse impacts on deep horizons.

The paper is devoted to the discussion of promising methods of man-caused impacts on highly stressed and potentially seismically dangerous segments of faults using the injection of drilling fluids through deep wells. We expect that fluid injection will make it possible to transfer displacements in the principal slip zone into the accelerated creep mode and thereby to exclude dynamic coseismic slip accompanied by high-amplitude elastic (seismic) waves. To substantiate the approach, we briefly analyze the information obtained from field experiments as well as physical and numerical modeling aimed to study the modes of generation of seismic impulses during dynamic slip events in fault segments. We also discuss the potential consequences of fluid injection into fault segments through deep wells.

We discuss the relationship of solar activity with the seismicity of Earth and reasons for the differences in the results of studies of various authors. Using the epoch superposition method, we analyze the differences in seismic activity distribution over phases of the 11-year solar cycle for the whole world, hemispheres, sectors, latitudinal belts, and individual regions. The northeastern sector of Earth has been shown to make the main contribution to the planetary distribution of seismic activity over phases of the 11-year solar cycle. We have revealed a pattern in the distribution of seismic activity over latitudinal belts: the solar cycle phases, at which the main maximum of seismic activity occurs, increase with increasing latitude in both hemispheres. For some regions, the results may differ from the generalized results for Earth due to the influence of local geodynamic conditions during the destruction of the earth's crust. In middle latitudes, the maximum number of earthquakes is shifted to the later phases of the solar cycle from west to east, which was not found for the northern regions. We discuss possible reasons for various manifestations of solar-terrestrial relationships for different regions, taking into account their different structure and geodynamic development modes. The presence of pronounced maxima of the seismic activity distribution over the 11-year solar cycle phases allows us to use them for refining the “time” parameter in the medium-term prediction of dangerous earthquakes.

The results are discussed of using a complex geological-geophysical approach directed towards detecting and studying deep paleo seismic dislocations (PSD), i.e., ancient coseismic ruptures, at the example of investigations performed at exhumed segments of a marginal suture of the Siberian craton in the Western Baikal region. The obtained data testify that there is a possibility to reconstruct the P–T conditions and regimes of fluid activity in PSDs that had developed in powerful earthquakes in previous seismically and tectonically active eras at focal depths of about 10–25 km. The possibility of absolute dating over syn-metamorphic newly formed minerals, “geo-barometers”, using the Ar40/Ar39 method, have also been demonstrated. Studying deep P–T conditions of PSD emergence using the above approach has a key importance for the cognition of geological factors and petrophysical mechanisms that promote triggering coseismic displacements in faults during seismic source nucleation. The information obtained in studying deep PSDs is actual for developing geomechanical models of seismogenic faults and elaborating methods of their relaxation using preemptive complex anthropogenic actions on potentially dangerous segments of active faults.

In the paper, we discuss an approach to the development of methods for managing seismotectonic deformation processes in a multiscale block-structured Earth's Crust from the viewpoint of the concept of physical mesomechanics. To date, there are no convincing results of many year researches in the fields of earthquake prediction and prevention of the dangerous man-caused and tectonic earthquakes. Therefore, in recent decades, there has been an increasingly active search for new ways to solve the problem of seismic safety. The aim of our research team's activity is to provide a scientific rationale for a multidisciplinary approach to reduce the excess level of shear stresses in the fault zones to a safe background level by "spending" it on mechanical destruction and thermal processes in rocks during aseismic and co-seismic slip. The authors summarize the main results of modeling of geological and geophysical processes in the field of preparation of different scale seismogenic events, as well as the results of complex man-made impacts on segments of seismically active faults. The data obtained on segments of different scale faults within the Baikal rift zone and Mongolia confirm the possibility of implementing such an approach. For the practical implementation of such a project at highly stressed fault zones, it is necessary to carry out vertical, oblique and horizontal multilateral drilling with an injection of fluids of different compositions in combination with vibro-pulse stimulations to achieve safe relaxation of shear stresses.

Frictional instability is the most likely mechanism of shallow earthquakes. For better understanding fault behavior we have conducted field experiments on shear deformation of a model fault. This study has focused on revealing the seismic-acoustic signatures of fault behavior. The entire spectrum of sliding regimes has been realized in the course of 1-m scale experiments—from a stable creep to a regular stick–slip, and their seismic-acoustic characteristics were investigated. It is shown that seismic pulses with characteristic frequencies less than 500 Hz are emitted only during slip events. The acoustic emission (AE) is observed both during slip events and at the stage of their preparation. Statistical analysis has shown that the AE distribution is generally a superposition of a power law distribution for low-energy pulses and a peak-like distribution for the largest pulses. The distribution with a characteristic peak prevails in regular stick–slip, while (quasi)stable creep is characterized by the power law distribution over the entire range of amplitudes. Both distributions—“with peak” and “without peak”—are observed for irregular sliding regime (random slip events with various amplitudes). Applying the nonlinear Grassberger-Procaccia algorithm to the analysis of time-series of AE data has allowed to rank the fault sliding regimes. The calculated correlation dimension characterizes the dynamics of the fault. The highest dimension is typical for stable sliding. A decrease of the correlation dimension indicates an enhanced probability of high-amplitude slip events. Nucleation of largest slip events is observed for the regular stick–slip with the least correlation dimension.

This paper reports data on the structure of the central zone of the seismogenic fault in the originally deep segments of the fault zone. The isotopic analyses have made it possible to estimate the absolute age of the ancient coseismic faults at 673 ± 5 Ma, which is indicative of seismic activation of deep faults in the studied segment of the marginal suture of the Siberian Craton in the Neoproterozoic.