The structure of the Archaean crust of the North America has been studied based on the synthesis of geolo‐ gical and geophysical data, including seismic sections along LITHOPROBE Geotransects, magnetic and gravity anomaly maps, and seismic tomography data. The authors rely on the experience gained in the Russian Program of the deep geological and geophysical studies of the East European Craton. The juvenile Neoarchaean crust, containing the frag‐ ments of reworked Meso‐ and Paleoarchaean rocks, forms an asymmetric round‐oval‐shaped domain, wherein the geophysical, structural, and metamorphic parameters display a concentric zoning pattern. The Central zone occupies the Hudson Bay basin. The Internal zone (the northeastern and northern Superior Province) is mainly composed of the granulite facies of metaplutonic, metavolcanic and metasedimentary rocks. The External zone encompasses the southern Superior Province together with Hearne and Rae Provinces. This paper presents 3D crustal models of sou‐ thern Superior Province. The crust development resulted from rifting and a partial disruption of the continental crust, short‐term opening of the linear oceans, successive northward subduction and accretion of the ancient continental and juvenile Neoarchaean oceanic and island‐arc terranes between ~2.78 and ~2.70 Ga. Subsequent events in the epicontinental environment, including formation of the metasedimentary belts, granulite facies metamorphism and intense ore formation processes, took place within the range from ~2.71 to ~2.63 Ga. The SCLM morphology within the limits of the Archaean North American Craton can be represented as a flattened overturned cone with a vertical axis (down to a depth of ~350 km). The Hudson Bay basin is located right above the lithospheric keel. A number of the main features of the structure and evolution of the Archaean crust of the North American Craton, primarily the oval‐ concentric zoning, the important role of high‐temperature magmatic and metamorphic processes and mainly in‐ tracontinental magmatism and sedimentation, indicates the leading role of the mantle‐plume type processes. The Neoarchaean evolution of the North American craton represents the plate‐tectonic processes initiated by a super‐ plume. The Neoarchaean North American Craton is one of a series of similar phenomena that occurred ~2.75 Ga ago in a number of continental regions. The most important features, repeated to a certain degree in tectonic units of this type, are: (1) synchronous formation between 2.79 and 2.58 Ga; (2) mainly intracontinental development; (3) the prevalence of oval‐shaped synformal tectonic structures of different ranks with some form of concentric zoning; (4) high‐temperature magmatism (usually with the participation of enderbite‐charnockites and gabbro‐anorthosites) and metamorphism of the granulite facies; (5) a frequently repeated combination of high‐grade (granulite and high‐ temperature amphibolites facies) and low‐ or moderate‐grade (greenschist and epidote‐amphibolite facies) meta‐ morphic rocks; (6) the lower‐crust granulite‐basaltic layer that had formed and was deformed at the final stage of endogenic activity; (7) a thick lithosphere (the lithospheric keel reaches a depth of 250–350 km).

The rocks from different stages of the geodynamic evolution have been preserved in the Urals. In its geologic history, the least studied is the transition period between continental rifting and the beginning of oceanic spreading. This article presents the geochemical data on the Sr-, Nd-isotopes, zircon U-Pb (SHRIMP) ages for the MesoNeoproterozoic igneous rocks and associated ores from the Bashkir meganticlinorium (BMA) on the Urals western slope. A Large Igneous Province (LIP) formed there as a result of mantle plume activity during the Middle Riphean (1380–1350 Ma). Later on (1200–1100 Ma), short-term rifting took place, as evidenced by the Nazyam graben, which was followed by the complete break-up of the continental crust. For magmatic rocks in the age range of 1750–1200 Ma, the evolition of chemical composition OIB-type → E-MORB →N-MORB is observed. The εNd(t) values for the igneous rocks and the associated BMA ores vary from negative (–6) to positive ones (+5), and thus give evidence of the lithosphere mantle depletion with time. These facts and the Sr-isotope ratios for the magmatic rocks from the subsequent evolution stages confirm that the oceanic basin to the east of the East European platform started to open at the end of the Middle Riphean. For the Vendian-Cambrian, some traces of orogenes (Timanian stage) are observed. The development of the Uralian Paleozoic ocean started in the Ordovican and continued up to the Late CarboniferousPermian.

The article reports on the geological, mineralogical, geochemical and isotope-geochemical studies of granitoids (charnockites) from the Tatarnikovsky massif located in the northern part of the Baikal uplift of the Siberian craton basement. The age of the studied granitoids is 1.85 Ga. Like other unmetamorphosed granitoids and associated volcanic, the granitoids dated 1.88–1.84 Ga are abundant in the southern area of the Siberian craton. These rocks are a part of the South Siberian post-collisional magmatic belt. The Tatarnikovsky granitoids form a series of small massifs confined to the Davan tectonic zone. However, unlike the rocks of the Davan zone, these granitoids have not been subjected to dynamometamorphism, mylonitization and metasomatism, and seem younger than the geologic structure of this zone. The formation of granitoids coincides in time with the youngest formations in the North Baikal volcanoplutonic belt (1.85–1.84 Ga). The Tatarnikovsky granitoids have two facies varieties – coarse-grained and medium-fine-grained porphyric, the transition being gradual. Considering the mineral composition of the granitoids, specifically the presence of orthopyroxene, these rocks can be classified as charnockites. The research results presented in this article are based on the study of charnockites in the Tatarnikovsky massif, the largest in the Tatarnikovsky complex. The chemical composition of the Tatarnikovsky coarse-grained granitoids corresponds to monzonite and syenite, and fine-grained porphyry granitoids are granosyenite. All the studied granitoids are close to alkaline and calc-alkaline, metaluminous (ASI=0.83–0.97), ferrous (FeO*/(FeO*+MgO)=0.86–0.89) granite, with high concentrations of Nb, Y, Zr, and Ba, and low concentrations of Sr. According to their geochemical characteristics, the Tatarnikovsky granitoids correspond to A-type granite. These rocks show negative values εNd(t)=–1.4…–3.5 and model age ТNdDM=2.4–2.5 Ga. The temperature estimated for the initial stages of crystallization of granitoid melts suggests that granitoids formed at high temperatures, 890–960°С (i.e. the zircon saturation temperature). The granitoid melts crystallized in hypabyssal conditions at the pressure of 2.2–2.9 kbar, as well as in conditions of low or moderate oxygen fugacity. According to the mineralogical, geochemical and isotope-geochemical data, the Tatarnikovsky charnockite could have resulted from melting of mafic rocks from the lower crust (gabbroid, and ferrodiorite) which are products of differentiation of the tholeiitic mantle magmas that had intruded into the base of the continental crust. Taking into account the high concentrations of Ba and the positive anomalies of Eu in the distribution spectra of rare-earth elements (REE) of the coarse-grained granitoids, it can be suggested that these granitoids are the products of partial melting of the crustalmafic source. The fine-grained porphyry granitoids with higher silica contents and lower Ba and Zr contents than those in the coarse-grained granitoids, as well as the negative anomalies of Eu in the REE distribution spectra, are the products of fractional crystallization of the granitoid melt. With regard to formation of the unified structure of the Siberian craton, the geodynamic setting for formation of the Tatarnikovsky charnockite is considered as postcollisional extension due to the fact that these rocks belong to the South Siberian post-collisional magmatic belt. However, on a more local scale of the Baikal uplift of the Siberian craton basement, we suggest that the intercontinental rifting setting was in place during the intrusion of the Tatarnikovsky granitoids, the rocks of the North Baikal volcanoplutonic belt, the granitoids of the Primorsky and Achadsky complexes that cross the rocks of the Akitkan fold belt, collision events in which ceased 1.98–1.97 Ga ago.

The interaction between the Amur, Pacific and Eurasian tectonic plates initiates seismic activity at the plate margins as well as in the plate periphery, as evidenced by intracontinental earthquakes. In the Amur plate, the dynamics of intercontinental seismicity is controlled by deformation wave fronts comprising a regular pattern of equidistant zones [Sherman, 2013]. According to [Trofimenko et al., 2015a, 2015b, 2016], maximum values of seismic activity in the range of magnitudes 2≤M≤4 also form a sequence of spatial cells in the form of seismic clusters from the east (Sakhalin – Sakh) to the west (the western boundary of the Baikal rift zone – BRZ ) (Fig. 1). One of the main characteristics of the seismic process is seismic activity migration given as sequential activation of seismogenic structures within the seismically active zones and on the global scale [Vikulin et al., 2012; Khain, Khalilov, 2008]. Direct observations show that crust deformation migrates from the Japan-Kuril-Kamchatka subduction zone towards the continent, and the estimated migration rates range from 10 to 140 km per year (e.g. [Ishii et al., 1978; Kasahara, 1979; Harada et al., 2003; Yoshioka et al., 2015]). In the Baikal and Amur regions (107–140°E), the fronts of deformation waves migrate at a rate of 5–20 km per year [Sherman, 2007, 2013]. Considering the order of magnitude, this rate is comparable to the rates of crust deformation migration from the Japan-Kuril-Kamchatka zone (10–100 km per year). Our studies show that the sequential activation of the seismic clusters in the northeastern segment of the Amur plate (Sakh – TanLu – Al-St) occurs at a rate of 1000 km per year [Trofimenko et al., 2015a] (Fig. 1). In the meridional tectonic structures, the shifting chains of maximum seismicity values are sequentially replaced by minimum values (i.e. inversion zones). Based on the spatial cycles with the phase shift of the maximum seismic activity values at the rate of 1000 km per year, it is possible to represent the dynamics of seismicity in the form of a process initiated by long-period stress waves/deformations. According to [Mogi, 1968; Kasahara, 1979; Malamud, Nikolaevskii, 1989; Saprygin et al., 1997; Harada et al., 2003; Bykov, 2005, 2014; Sherman, 2007, 2013, 2014; Milyukov et al., 2013], slow deformation waves of the global and regional scale are generated at the margins of lithospheric plates. Under this concept, the migration rate of seismic activity and the spatial extent of seismic cycles can be identified as the velocity and length of deformation waves. Using the data on seismicity of the most active region of the Baikal rift zone – the northwestern segment of the Amur plate, we have studied the periodic components of seismicity along the entire northern boundary of the Amur plate. An indirect evidence of the existence of deformation waves is the migration of anomalies of geophysical fields and its correlation with the migration of seismic activity. The space-time anomalies of the magnetic and gravity fields were studied in the South Yakutian geodynamic polygon [Trofimenko, 1990; Trofimenko, Grib, 2003, 2016], and the indicators of deformation waves were revealed in the seismic regime and the geophysical fields at the northern margin of the Amur plate. The sequential manifestation of anomalies in the magnetic and gravity fields is associated with the activation of latitudinal tectonic structures. Our estimations show that the geophysical anomalies migrate at different rates, from 100 to 1000 km per year. Based on the results obtained in our study and their comparison with other available data, the dynamics of seismicity along the northern margin of the Amur plate is identified as a wave process.

The article presents the results of the study focused on the anisotropic properties of the upper mantle in Central Asia. The study is based on a representative set of the group velocity dispersion curves for Rayleigh and Love waves. The dispersion curves were calculated in the range of 10–250 s. The maps of group velocity distribution pat‐ terns and the horizontal resolution estimates were calculated by the surface‐wave tomography method developed for a spherical surface. Based on the maps, the local group velocity dispersion curves were reconstructed for the given points within the study region, which were then converted into the one‐dimensional velocity sections of SV‐ and SH‐waves, and a vertical anisotropy coefficient was estimated. A three‐dimensional anisotropic model shows the ve‐ locity distribution pattern of S‐waves in the crust and the mantle to the depth of 500 km. According to this model, ver‐ tical anisotropy in the upper mantle is observed to the depth of about 250 km and has maximum values in the depth interval from the crustal bottom to 150 km. The anisotropic properties are unevenly distributed and reflect the geo‐ logical structure of the study area. Therefore, tectonically active regions are characterized by the high values of the anisotropy coefficient and the reduced values of the S‐wave velocities. The presented results can contribute to the further development of more detailed and strictly proved geodynamic models of the study area.

Upper crust fault and fold patterns are studied with an innovative approach of controlled‐source seismic refraction profiling integrated with gravity data. The potentiality of the conventional method based on refrac‐ tion/wide‐angle reflection traveltimes, which has been so far applied to plane‐parallel layered earth, is extended onto deformed crust with lateral and vertical inhomogeneities due to advanced processing technologies. Performance of the approach is tested on data of the 1‐SB transect that traverses geologically studied areas and provides good refer‐ ence. Upper crust features revealed from seismic data agree with known geological structures, this indicating the basic applicability of refraction surveys to tectonically complex areas with 7 to 10 km wide low‐angle dipping fault zones between blocks marked by velocity anomalies to depths of 4–6 km. Joint interpretation of refraction and gravity patterns becomes possible within the limits of a seismic‐gravity model in which both are characterized by seismic‐ density and seismic acceleration values of the same dimension.

At the Bishkek geodynamic test area in the Northern Tien Shan, complex electromagnetic monitoring was conducted, including a wide frequency range by magnetotelluric sounding in various modifications and induction sounding with a controlled impulse source (method of sounding in the far zone, SFZ). The geoelectrical sections of the lithosphere were constructed for the study area. Based on the geophysical monitoring data and the profile MT moni‐ toring data on the Baitik depression, the main faults belonging to the Northern Tien Shan fault system were detected: Shamsi‐Tyundyuk (Predkirgizsky), Baitik, Chonkurchak, and Issyk‐Ata. From the geoelectrical data, we obtained new information that is independent of other geophysical methods used for studying the deep structure of the Earth – the hidden fault structures and the geoelectrical segmentation of the study area were revealed. The latter reflects the main elements of the block structure of the junction zone of the Chuya basin and the Kirghiz ridge. This information needs to be taken into account when constructing a comprehensive model showing the geological, geophysical and geodynamical features of the development of the Tien Shan, a vivid example of an intracontinental orogen. The MTS, FS and SFZ data from the Ak‐Suu and Chon‐Kurchak electromagnetic monitoring stations were interpreted. Based on the representative array of experimental electromagnetic data, we analyzed the effective depths of field penetration, which are most sensitive to changes in the electromagnetic parameters of the medium for the stationary and routine observation sites with respect to the clusters of seismic events. This paper discusses the development of the azimuth MT monitoring technique and the analysis of the time series of electromagnetic parameters, which were used for de‐ termining the contribution of each component of the impedance tensor to the informativeness of the monitoring stu‐ dies. The data from the 2004–2016 KNET Catalogue of the Research Station of RAS were analyzed in order to investi‐ gate the relationship between the space‐time seismicity distribution and the electrical conductivity variations that correspond to the features of the seismicity pattern at depth. Examples discussed are the time‐frequency series of MT monitoring in 2007 and 2016 at the Ak‐Suu and Chon‐Kurchak stations that identified anomalous electromagnetic parameters corresponding to the fluid redistribution model for the pore‐cracked medium: syn‐phase decreasing and increasing values of the parameter by the orthogonal azimuths. Thus, a phenomenological model has been tested. It relates the change in the stress‐strain state of the medium with the redistribution of fluids between the systems of fractures, which causes variations in the active and reactive components of the electrical resistance.

The data from the regional magnetotelluric sounding profiles Severny and Yuzhny (northern and southern, respectively) was analyzed and interpreted. The profiles were located on several sites of the eastern coast of Kam‐ chatka, which differ in tectonic structure and geodynamic conditions. The southeastern region covers the Kuril‐ Kamchatka segment of the Pacific transition zone, which corresponds to the active continental margin, while the northeastern region includes the passive continental margin. Geoelectrical sections were obtained along the regional profiles to a depth of about 80 km. The identified anomalies of electrical conductivity were compared with the data obtained by other geophysical methods (specifically, the data on gravity and anomalous magnetic fields). The com‐ parative analysis of the geoelectrical sections shows that electrical conductivity changes gradually in the northeastern region, while the structure of the southeastern region is represented by blocks differing in geoelectrical properties. The conducting horizon of the lithosphere lies at different depths in different parts of East Kamchatka. The south‐ eastern section shows the roof of the lithospheric layer closest to the land surface.

The earth surface deformation was modeled for the North, Central and South Sakhalin on the basis of de‐ formation velocities recorded by the GPS stations of the Sakhalin Geodynamical Network. A pattern of contemporary horizontal deformation is intricate in the vicinity of the main submeridional faults of the island. On the island surface, the dominant deformation regime is compression; however, the spatial distribution of deformation is heterogeneous. The horizontal compression is mainly sublatitudinal and SW‐NE‐trending. In addition to compression, there are zones of rather intense right‐lateral strike‐slip in the northern and central parts of the island, while stretching dominates in the south‐eastern parts. The regional geodynamic setting is reflected in the seismicity of the island. Recently, the seismic activity has been increased in the areas characterized by intensive surface deformation, while the areas of low deformation rates correlate with the zones of weak and sparse seismicity.

Seismic hazard assessment with the use of an integrated approach is discussed on the case of the left bank of the Angara river in Irkutsk, Russia. Potential earthquake focal zones have been identified in the study area. A brief overview of fault tectonics, seismology and seismogeology of the study area is presented. The map of the epicenters of local earthquakes and the map of active faults in the study area show the magnitudes of potential seismic events in the potential earthquake focal zones. The methodology of instrumental measurements and the methods of seismic hazard assessment are considered in detail. Calculations are based on the data obtained by the instrumental methods of seismic microzoning. Theoretical seismic effects on typical ground conditions are calculated, and the estimations are obtained with reference to maximum accelerations for predicted strong earthquakes. Estimated are potential seismic effects of probable strong earthquakes on the foundations of structures in the study area. Based on the estimations, an initial signal is formed (taking into account the potential earthquake focal zones, their parameters and the spectral composition of vibrations corresponding to the local earthquakes), and a required set of seismic models is developed in order to quantify the parameters of soil motions that may take place in the event of a strong earthquake. The experimental methods provided the data on the seismic properties of the reference and investigated soils, the propagation rates of seismic waves in such soils, and the pattern of microseism levels, as required for a valid estimation of seismic effect parameters by the seismic rigidity method and the microseism technique. Currently, both methods are by far the most effective in determining the seismic hazard of the territories. Statistical analysis was carried out using the calculations and the simulation data to more clearly determine the scatter of the results obtained. The seismic hazard of the study area is assessed based on the results of this study.

Our study aimed to clarify the seismic potential of the Severobaikalsk fault and to discover the structural features of active faults on the NW shores of Lake Baikal. Seismogenic faults and large seismogravitational structures were mapped in the area of the Srednekedrovaya paleoseismodislocation, one of the most remarkable seismotectonic structures in the Baikal region. During the field trip, we tested the capacities of an OKO‐2 georadar and an ABDL‐ Triton antenna used to study cross‐sections of the Baikal ridge. Its slopes are steep, covered with Pinus pumila and abundant screes, many of which developed into boulder streams (‘kurumnik’). The first studies of the Sredneked‐ rovaya paleoseismodislocation were conducted by V.P. Solonenko and his team in 1964–1965. To some extent, this zone can be viewed as a reference object that can provide much information and thus deserves an in‐depth investiga‐ tion using new technologies. Our study combined the field observation and the interpretation of high‐resolution satel‐ lite images provided by DigitalGlobe (US) and downloaded by SAS.Planet. The consolidated database was sufficient for constructing a new schematic map showing the seismogenic faults associated with the Srednekedrovaya paleoseis‐ modislocation. The cumulative length of the ruptures observed on the surface amounted to almost 29.5 km. Some ruptures are separate from each other, and the rupture spacing ranges from the first tens of meters to the first kilome‐ ters. The width of the widest rupture zone is 1.9 km. The length of individual ruptures varies from 5.0 m to 2.7 km. Morphologically, the Srednekedrovaya paleoseismodislocation is represented by ledges and ditches that often comprise complex grabens disturbing the bedrock and slope deposits. The fault structure of this zone is a typical set‐ ting of orthogonal and slightly oblique crustal stretching, but its manifestation differs in the zone segments. In general, it is a combination of steeply dipping and listric faults traced to the depth of 13 m. In plan, the faults are observed to form the systems of subparallel ruptures that mainly strike at 30°. A linear relationship is established between the heights of the seismogenic ledges and the throws estimated from the ground‐penetrating radar data. The former are larger by 0.5–2.0 m than the throw measured from the radargrams. Apparently, this reflects the magnitude of expan‐ sion of the ledge upward along the sloping slope. In the zone of the main fault plane coinciding with the main ledge, the maximum and mean arithmetic throws are 8.3 and 4.93 m, respectively. On other fault planes, the throws range from 0.4 to 4.6 m. The paleoearthquake magnitude ranges from 6.8 to 7.6, according to the estimations from the seis‐ mic rock collapse volume, fault length, and the displacements. Our study of the Srednekedrovaya paleoseismodisloca‐ tion confirms that listric normal faulting is widespread along the western side of the North Baikal basin and gives in‐ direct evidence that conditions for accumulation and release of seismic energy are different on the western and east‐ ern shores of Lake Baikal. It should be noted, however, that in the studied near‐surface layer of the crust, the blocks of loose material may move along the flat planes due to gravitational sliding that increases under the impact of cryogenic processes on the steep slopes of the Baikal ridge.

This paper presents the experimental results of analyzing the quantitative correlation of fracture distribu‐ tion at 10 survey sites on the Co To‐Thanh Lan islands, Quang Ninh province, Viet Nam. The obtained results show that most fracture correlation coefficients are over 0.80. The high correlation values among the survey sites reflect well the geodynamic conditions of the tectonic activity phases. These results confirm the significance of the correla‐ tion method in analyzing the structural geology and geotechnics.