The article presents major results which have been obtained during 30 years of researches conducted by the Laboratory of Tectonophysics at the Institute of the Earth’s Crust.

General regularities in organization of fault-block structures in the brittle lithosphere are established. Relations between main parameters of faults are investigated, and their connection with the lithospheric structure and recent crustal movements is shown. A rheological model of vertical zoning of faults is proposed. Internal structures of faults are studied; stages in faulting are generally defined in terms of time; regularities of patterns of joints inside faults are described; and original methods of mapping such joints are proposed to reveal tectonic conditions of faulting.

Based on seismic monitoring, new methods of quantitative assessment of relative activity rates of faults in real time are developed. Such methods are applied to delineate zones of recent destruction of the lithosphere in the Central Asian region. The state of stresses of the lithosphere is mapped, and the new map allows us to reveal regularities in the spatial mosaic of regions differing by types of stress fields.

Our physical experiments conducted in compliance with similarity conditions are aimed at studying faulting mechanisms with regard to variable loads. A special set of experiments is devoted to the Baikal rift system. Cases of application of tectonophysical methods to study fault tectonics, the state of stresses and seismicity of the lithosphere are described. Prospects of tectonophysical researches conducted in the Laboratory and potentials of integration with studies of other research teams are considered.

The article presents results of experimental studies using a bi-axial servo-control system to apply load on samples with extensional and compressional en echelon faults. During the experiments, variations of temperature and thermal images were recorded synchronously by a multi-path contact-type thermometric apparatus and a thermal image system, respectively. A digital CCD camera was employed to synchronously collect images of specimens’ surfaces. The digital speckle correlation method (DSCM) was utilized to analyze the images and to define displacements and strain fields. Our experimental results show that temperature fields have clear responses to opposite stress states in the jog areas of both types of the en echelon faults. Prior to failure of the jog area, its temperature is the highest at the compressional en echelon faults and the lowest at the extensional en echelon faults. Records by DSCM give evidence that mean strain of the jog area is the highest at compressional en echelon faults and the lowest at the extensional en echelon faults. It is revealed that deformation of the en echelon faults occurs in two stages, developing from stress build-up and fault propagation in the jog area to unstable sliding along the fault. Correspondingly, the mechanism of heating-up converts from strain heating into friction heating. During the period of transformation of the temperature rising mechanism, three events are observed in the jog area and its vicinity. Analyses of our experimental results demonstrate that variations of temperatures in the jog area can be indicative of fault sliding and suggest sliding directions. Observations and studies of temperature changes during transformation of the temperature rising mechanism at sensitive portions of faults are of great importance for early detection of precursors of unstable slip on active faults.

The article highlights the importance of researching earthquake which occurred in the Sakhalin and Kuril Islands in combination with studies of seismic dislocations and tectonic movements caused by such earthquakes. It is shown that seismic dislocations and tectonic movements can be studied from focal mechanisms of earthquakes. Data on the crustal structure and earthquake sources are valuable for finding solutions of fundamental problems of geotectonic and geodynamics; therefore, it is challenging to juxtapose such data while studying the transition zone from the Eurasian continent to the Pacific Ocean.

The crustal structure and distribution of earthquake are considered along the Shantar-Matua profile which runs from the western border of the Tatarsky Strait (the Primorie coast) through South Sakhalin and the Okhotsk Sea up to the Matua Island. Based on the NEIC catalogue, a depth profile showing earthquake hypocenters is constructed for a zone which widths on both sides of the Shantar-Matua profile amounted to 200km. This allows us to consider specific features of the deep structure of the crust and positions of the earthquake sources in the crust and in the upper mantle along the uniform profile (Fig. 1, a, b).

Data on catastrophic earthquakes with magnitudes of 8.3 and 8.1 that occurred on 15 November 2006 and 13 January 2007 in the region of the Simushir Island are collated with results of onshore and marine deep seismic researches by DSS, CMRW, MSWE, MEW methods in the region of the Middle Kurils. The structure of the crust and focal zones of these earthquakes are considered in conjunction (Figures 2–8).

Cyclic changes in the state of stresses of the lithosphere and corresponding seismic dislocations in the focal zone of the catastrophic Shikotan earthquake of 04 October 1994 (M=8.1, depths 0-150km) are revealed (Table 1, Fig. 9).

We apply the method of cataclastic analysis (MCA) of fractures to assess the state of stresses of the crust in the area of the Shikotan earthquake. This method is the basis for new experimental studies of the state of tectonic stresses and deformations and properties of rocks in their natural bedding. The method of reconstruction of tectonic stresses was designed by Yu.L. Rebetsky. Stresses are reconstructed from Centroid Moment Tensor data (СМТ), i.e. solutions for earthquakes recorded in NEIC catalogues (Figures 10–15). Based on reconstructed parameters of the recent state of stresses of the crust and the upper mantle of the Southern Kurils, there are grounds to conclude that spacious areas of stable stress tensor parameters are present in the region under studies, along with local sites wherein these parameters are subject to anomalously fast changes.

In the Pribaikalie and adjacent territories, seismogeological studies have been underway for almost a half of the century and resulted in discovery of more than 70 dislocations of seismic or presumably seismic origin. With commencement of paleoseismic studies, dating of paleo-earthquakes was focused on as an indicator useful for long-term prediction of strong earthquakes. V.P. Solonenko [Solonenko, 1977] distinguished five methods for dating paleoseismogenic deformations, i.e. geological, engineering geological, historico-archeological, dendrochronological and radiocarbon methods. However, ages of the majority of seismic deformations, which were subject to studies at the initial stage of development of seismogeology in Siberia, were defined by methods of relative or correlation age determination.

Since the 1980s, studies of seismogenic deformation in the Pribaikalie have been widely conducted with trenching. Mass sampling, followed with radiocarbon analyses and definition of absolute ages of paleo-earthquakes, provided new data on seismic regimes of the territory and rates of and recent displacements along active faults, and enhanced validity of methods of relative dating, in particular morphometry. Capacities of the morphometry method has significantly increased with introduction of laser techniques in surveys and digital processing of 3D relief models.

Comprehensive seismogeological studies conducted in the Pribaikalie revealed 43 paleo-events within 16 seismogenic structures. Absolute ages of 18 paleo-events were defined by the radiocarbon age determination method. Judging by their ages, a number of dislocations were related with historical earthquakes which occurred in the 18th and 19th centuries, yet any reliable data on epicenters of such events are not available. The absolute and relative dating methods allowed us to identify sections in some paleoseismogenic structures by differences in ages of activation and thus provided new data for more accurate definitions of epicenters and magnitudes of the paleo-earthquakes. In some cases, it was revealed that neighboring dislocations of seismogenic structures, which were previously considered independent, had been subject to simultaneous opening.

The article presents a new approach to selecting regression equations to estimate paleo-magnitudes with regard to specific geodynamic conditions as well as to levels of available knowledge on seismodislocations and reliability of available data parameters.

The late Cretaceous-Cenozoic sediments of fossil soils and weathering crusts of the Baikal rift have been subject to long-term studies. Based on our research results, it is possible to distinguish the following litho-stratigraphic complexes which are related to particular stages of the rift development: the late Cretaceous–early Oligocene (crypto-rift Arheo-baikalian), the late Oligocene–early Pliocene (ecto-rift early orogenic Pra-baikalian), and the late Pliocene-Quaternary (ecto-rift late orogenic Pra-baikalian – Baikalian) complexes. Changes of weathering modes (Cretaceous-quarter), soil formation (Miocene-quarter) and differences of precipitation by vertical and lateral stratigraphy are analysed with regard to specific features of climate, tectonics and facial conditions of sedimentation. Tectonic phases are defined in the Cenozoic period of the Pribaikalie.

Geochemical features for volcanic rocks and petrologic data for deep-seated inclusions, which can be used to infer mass transfer between different geospheres, are reviewed. It is typically believed that slabs can subduct as deep as the core-mantle boundary with the following recycling by plumes coming up to the sublithospheric regions of magma generation. However, the petrologic evidence of the deepest accessible material is limited by the depth of the uppermost lower mantle (~650–700km), i.e. by the depth of the deepest earthquakes. Ferropericlase inclusions in some diamonds do not exclude involvement of deeper mantle horizons, yet do not unambiguously support it. No unambiguous confirmation of involvement of the lower mantle into magma generation underneath volcanically active regions is obtained from geochemical data either, while the geochemical data suggest complete chemical isolation of the Earth’s core from the upper mantle processes.

In the state-of-the-art geology, concepts of evolution of interrelated geodynamic and biotic events throughout the history of the Earth have been developed (Fig. 1). Research results on sediments, bio-stratigraphy and geodynamics of the southern fragment of the Siberian craton (SSC, Fig. 2) provide for more or less reliable assessments of the status and evolution of ancient landscapes and biotas from the Lower Proterozoic to the Cenozoic.

In the Lower Proterozoic, the geodynamic regime of the Urik-Iyskiy graben was similar to those of the westernpacific island-arc systems, which resulted in the orogen formation and established post-orogen granitoids of 1.86 bln years of age. At the beginning of the Early Riphean, volcano-sedimentary masses were accumulated in continental basins (Fig. 2, 3A). Collision orogenesis also resulted in the occurrence of the terrigeno-volcanogenic complex of the Akitkanskaya suite in the Western Pribaikalie and the transecting Irelskiy granitoids, aged 1.86 bln years, at the edge of the craton. Later on, most probably before the Riphean, peneplanation took place, and a shallow peripheral sea was formed with highly-mature sediments of the Purpolskaya suite. Different environments are reconstructed in the KodarUdokan zone. Sediments of the Udokanskaya suite, varying in thicknesses from 11 to 14 km, suggest a complicated evolution of sedimentation in the peripheral marine basin. Dozens of radiochronological datings of granitoids of the Chuiskiy and Kodarskiy complex which transect the Udokanskaya suite are within the range from 1.7 to 2.0 bln years. From the deposit composition and texture, it can be suggested that the middle, Chineiskaya sub-suite was formed under island-arc conditions; and glacial phenomena occurred in the late Udokan time.

Further geological history of the SSC can be described only within the period after the Late Riphean sedimentations (see Fig. 3Б, В). The SSC evolution in the Neo-Proterozoic began with divergence events, which most probably occurred in the period of 1000–850 mln years in the east, and in the interval of 780–730 mln years in the west of the territory. The latest period is logically aligned with disintegration of Rodini, the super-continent. The period of 780–680 mln years in the eastern part of the region can defined by the beginning of convergency processes, formation and evolution of the island arc and the back-arc basin. It is supposed that basal layers of the Baikalskaya and Oselokskaya suites and their analogues occurred 730 mln years ago, and evidences of glacial processes in these series correlate with the global Sturtian glaciations. The period of 680–630 mln years was characterized by formation of the foreland-type peripheral basin which was then replaced by a system of orogen-type submontain troughs in the Early Vendian (from 630 mln years, see Fig. 3Г). The second half of the Vendian in various zones of SSC was distinguished by shallow-water carbonate-terrigenous sediments of a similar type. Compensatory sedimentation occurred in residual valleys of the basin. Fast infill of the basin and leveling of the relief resulted in the stationary regime of the relatively shallow, yet vast basin. In the Early Cambrian, carbonate sedimentation occurred throughout the Siberian Platform and in the area adjacent to the SSC (see Fig. 3Д).

The Paleozoic sediments preserved mainly in the central and northern regions of the Siberian Platform reflect a complex evolution of internal and epicontinental seas and shallower basins of the Siberian continent named Angarida. In the Ordovician, predominating were carbonate rocks with marine fauna. In the Silurian was characterized by a variety of sediments formed in different marine environments, ranging from distal shelf to shallow water and salted gulfs. In the Late Silurian and the Early Devonian, the territory of Angarida was land. Local volcanism with mafic lava eruptions through fractures took place at the background of sub-continental sedimentation. In the Late Paleozoic, the geologic development was marked by major transformation of the pattern of tectonic structures, that was most likely related to inside-plate extension and thinning of the continental crust. In the Mid and Late Carbon (Fig. 4A), the integrated Tungusskiy sedimentation basin was formed as a result of continuous and uniform bending. In the Early Permian (see Fig. 4Б), positive tectonic movements led to significant dewatering of the Paleozoic basins, so that they turned into a washed-out area. Overall raising of the Siberian Platform preconditioned climate changes, such as aridization and climate cooling. In the Mesozoic, landscapes were presented by a combination of flat uplands, wide river valleys with swampy plains and lakes wherein carbonous sediments were accumulated. Basic volcanism with shield eruptions and sub-volcanic rocks was typical then. In the Jurassic (see Fig. 4B), elements observed in the recent topography of the Siberian Platform were formed. In that period, major structural transformation occurred in association with the largest diastrophic cycles in the territory of the Eastern Asia, including formation of the Baikal rift and its branches.

From the analyses of the available data which are briefly presented above, it is obvious that the period of two billion years in the Earth history includes numerous epochs of diastrophic processes of tremendous destructive capacity. Unconformities of formations differing in ages by millions and even hundreds of million years, as those dating back to the Pre-Cambrian, suggest quite realistic yet astounding visions. At the background of scenarios of floods, rock up-thrusts, volcanic explosions and earthquakes evidenced from the very remote past, the current geological and climatic phenomena may seem quite trivial.