Negative structures of the Earth’s crust, including intramountain basins, are key sources of information on the development of the continental crust at the plate and orogenic stages of its evolution. The aim of this study is to give a comparative description of the Mesozoic-Cenozoic basins of the Eurasian intracontinental orogen and identify regional features of the geodynamic development of its various segments. The research methodology included comparative geological analysis, structural and tectonic studies, description of lithological sections, tectonophysical experimental work, analysis of magnetotelluric sounding data. and other investigations.
This article is a logical continuation of the previously published article [Leonov et al., 2025], dealing with the description of the intramountain basins of the Gissar-Alai mountain system and the Central Tien Shan. In this study, consideration has been given to the intramountain depressions of Western Transbaikalia, and analysis has been made of general and individual features of the structure and geotectonic development of all three areas surveyed for the occurrence of similar structural ensembles within the orogenic belt.
The presented data allow us to conclude that the system of intramountain basins and interbasinal highs in Western Transbaikalia, as well as in other considered segments of the Central Asian fold belt, emerged and evolved during the Mesozoic and Cenozoic within a limited tectonic area of shear flow dispersion. A comparative analysis has been carried out to reveal common and individual features of structural evolution, as well as the nature of sedimentation and volcanism in the considered areas; there has been discussion of structural and geodynamic prerequisites for the occurrence of ordered systems of orogenic depressions within the intracontinental orogenic region at the plate stage of its development.

The paper presents the first data on detrital zinc chromites from banded ilmenite-hematite sandstone of the terrigenous Bezymyannaya formation of the Tuva-Mongolian terrane in the eastern part of the East Sayan. The zinc content of the accessory and ore chromites from the ophiolite complexes in the southeastern part of the East Sayan is not high and falls within the range of 0.2 to 1.5 wt. % ZnO. Scanning electronic microscopy has been used to study morphological and structural features and chemical composition of detrital zinc chromites. The study of chemical composition of mineral phases of titanium-ferruginous oxide interlayers, composed of ilmenohematite, Ti-hematite, pseudobrookite, pseudorutile and zinc chromite, has shown that Zn (12–27 wt. % ZnO) is present only in chromite and entirely absent in other ore minerals, i.e. that zinc enrichment in chromite is a feature of the ore body rather than the result of metamorphism or metensomatoses of terrigenous rocks in the source area. The ore bodies of the studied detrital chromites are associated with ultrabasites and basites, their metasomatized varieties, and podiform chromites from the ophiolite complexes in the southeastern part of the East Sayan. Metasomatic changes of mantle peridotites and chromitites and the effects of fluid/hydrothermal solution parameters resulted in substitution of Mg by Zn in the chromite. Zinc could originate from the subducting-slab rocks – volcanic-sedimentary rocks containing the fragments of submarine hydrothermal sulfide ore deposits, zinc-enriched and involved in metasomatic changes of peridotites and chromites.

This study presents the results of an integrated petrographic and U-Pb geochronological investigation of Lower to Middle Carboniferous sandstones from the Volga-Ural petroleum province. The samples were obtained from drill cores collected in the South Tatar Arch and the northeastern flank of the Melekess Depression. The combined data reveal distinct provenance signatures for the Lower and Middle Carboniferous units. The Lower Carboniferous sandstones are characterized by a monomictic composition, dominated by well-rounded quartz grains. The heavy mineral assemblage consists primarily of ultra-stable minerals such as rutile, anatase, and zircon. U-Pb (LA-ICP-MS) dating of detrital zircons indicates a dominant Proterozoic age population, suggesting source areas associated with the Sveconorwegian and Svecofenian orogenic belts. In contrast, the Middle Carboniferous sandstones display a polymictic composition, comprising quartz, feldspar, and lithic fragments with moderate grain rounding. The heavy mineral suite is more diverse and includes both stable (rutile, anatase, zircon, spinel, garnet) and less stable minerals (biotite, amphibole, epidote). U-Pb geochronology reveals a dominant Paleozoic detrital zircon population, pointing to the Uralian orogen as the primary sediment source.

The data bank has been created to address the tensor of the seismic moment of earthquakes that occurred in the Altai-Sayan seismically active region in the period 1978–2025. The scalar seismic moment M0 for these events was already known from the CMT catalog. This paper presents estimates of the following dynamic parameters: source radius r, shear stress drop ∆σ, and reduced seismic energy ePR using a phenomenological approach based on previously obtained regression relationships between the source radius r and the scalar seismic moment M0. Stress drop and reduced seismic energy estimates have been obtained for 69 earthquakes with a magnitude MW 3.5–7.2. Thus, it allows to significantly expand the data bank on these earthquake parameters for the Altai-Sayan seismically active region. Maps have been drawn of the areally averaged estimates of stress drop and reduced seismic energy.

This paper mainly considers seismicity in the Kamchatka region. Based on 60-year-long instrumental observations, there were seven seismic layers identified according to depth distribution of seismic energy. For each layer, there were obtained seismicity characteristics: a number of events in a layer, depth of peak energy penetration, total energy in a layer, slope of a trend line in recurrence plots, ratio of the total energy of earthquakes with a K-value greater than 14 to that of earthquakes with a K-value between 10 and 14. The slope of the trend line in recurrence plots decreases with depth from 0.63 to 0.36. Almost half of the total seismic energy fell within the depth greater than 50 km.

The change in seismic layers during the instrumental observations is shown on plots of deviations from uniform increase in the accumulation of cumulative energy over time and cumulative total amount of events. The movement on the plots allows making an assumption about the constancy of subduction velocity and stability of background seismic energy dissipation for the Kamchatka region on the intervals with a linear increase in the accumulation of cumulative energy over time.

An increase in the accumulation rate of the cumulative total amount of earthquakes at depths greater than 550 km was subsequently followed by an increase in the accumulation rate of the cumulative total amount of events in 0–35 and 80–130 km layers. It is shown that since the 2000s there has been an increase in seismic activity in seismic focal zone of the Kamchatka region.

The article assesses the possibility of influence of changes in the electrical resistivity of the upper horizons of the Earth’s crust on the formation of large-scale anomalies of the ionospheric total electron content (TEC), recorded before strong earthquakes in various seismically active regions of the world. The results of monitoring the ionospheric TEC at the final preparatory stages of the Zhupanov (January 30, 2016, M_w=7.2) and Shipunsky (August 17, 2024, M_w=7.0) earthquakes were compared with changes in the electrical resistivity of the geomedium in the Petropavlovsk-Kamchatsky geodynamic polygon. The presented results allow us to conclude that the changes in the ionospheric TEC at the final preparatory stages of these earthquakes are significantly correlated with the changes in the electrical resistivity of the upper (up to approximately 1000 m) part of the Earth’s crust in the corresponding subionospheric regions. The paper discusses a possible physical basis for the obtained results.

A short sequence of aftershocks of the mb=4.2 earthquake associated with volcanic and tectonic processes in the North Atlantic was used to evaluate the efficiency of the waveform cross-correlation method (WCC) in detecting weak signals and events at teleseismic distances. The results of the WCC application are compared with those obtained at the International Data Center (IDC) and presented in the Standard Event Bulletin (SEB). The WCC method allows spatially close repeating-signal detection threshold to be several times lower when compared to energy detectors. It has already been applied at the IDC to aftershock sequences of large and moderate earthquakes with relatively high signal-to-noise ratios for event-associated signals. 50 to 70 percent of events, defined as true by the IDC, were found in addition to those listed in the SEB. All hypotheses, automatically generated for the earthquake under consideration by the WCC, were processed by an experienced IDC analyst, which made it possible to generate events according to strict IDC quality criteria. 38 seismic events listed in the SEB were supplemented with 26 aftershocks trough the WCC method, with an iterative procedure applied to search for all possible sources using the newly found aftershocks for the repeated application of the WCC. High efficiency in detection of low-magnitude events in the North Atlantic at teleseismic distances from the recording stations applies also to seismicity studies in other regions, including subarctic and arctic.

On August 18, 2020, an M_W 6.8 earthquake occurred ~130 km southwest of Bengkulu. In this study, we used the static GNSS data from continuously monitoring stations, surrounding the epicentre, to obtain the data from 10 days before to 10 days after the earthquake. We estimate the coseismic slip distribution with two models of nodal planes from the USGS. The coseismic slip was calculated using an elastic half-space model with inversion best-fit displacement. The GNSS displacement data with values less than ~5 mm indicate an insignificant displacement and the best model arameters of strike of 313° and dip of 8°, with a misfit value of ~0.4 mm. This study suggests that the 2020 Bengkulu earthquake occurred due to the subduction of the Indo-Australian plate underneath the Eurasian plate with a cumulative seismic moment of 1.73·10¹⁹ N·m, equivalent to magnitude 6.76.

Like the entire Fennoscandian Shield, Karelia is a low-seismicity region. Fenoscandia displays numerous geological evidence of the Holocene natural disasters, which followed the last ice sheet degradation. Holocene paleoseismic dislocations have been revealed in some parts of Karelia. However, none of them have been found in southeastern Karelia – the junction zone between the Fennoscandian Shield and the Russian Plate. The 2023 field studies near Kubovo village, Pudozh District, Republic of Karelia, have revealed for the first time three local paleoseismic dislocations. The fault zone in which these study objects are located was previously assumed to be active prior to the Proterozoic. The available paleoseismic records disprove this assumption and provide evidence on the Holocene activation of these faults. These studies led to the conclusion that, after the glacial retreat and the removal of the glacial load, the study area experienced an earthquake of no less than VIII intensity degrees on the MSK-64 scale, which produced local paleoseismodisocations generating seismotectonic, seismogravitational, and shaking-induced deformations. The radiocarbon date obtained from the organic layer of the reservoir in the immediate vicinity of the paleoseismodislations suggests that they were formed no earlier than 11350±230 years ago.

Heavy rainfall on the night of August 31 – September 1, 2023, caused massive mudflows in the area of the Susunai range near Yuzhno-Sakhalinsk. Such large-scale mudflows have not occurred since 1981. Another intense rainfall in early October 2023 has once again resulted in mudflows. This paper describes the condition of 13 mudflow channels after these events, presents the mudflow parameters, and provides a list of mudflow-caused damages. Special attention has been given to the mudflow initiation mechanism. The paper also confirms the data on recurrence frequency of massive large-scale mudflows in the Susunai range area.

A study has been made of the morphological characteristics of the Upper Proterozoic rocks and their shear sense indicators in the island-arc complex of the northeastern Central Taimyr tectonic zone near the Main Taimyr fault. The structural kinematic studies have made it possible to identify, to characterize and to specify the geodynamic position of the first-stage deformations related by the authors to the Late Neoproterozoic (Ediacaran) orogeny. The first-stage deformation structures are common in the Upper Neoproterozoic metamorphic rocks and represented by the northwest-overturned folds, complex shear zones with C/S structures, and sheath folds indicative of the northwest-trending thrusting. The preserved first-stage deformation structures may be a relic of the suprasubduction accretionary prism formed in the Late Neoproterozoic. The deformations are almost absent in tectonic plates of the upper part of the accretionary prism, being more common in its deeper part. The second-stage (Late Paleozoic) structures are characterized by the east-southeast right-lateral reverse thrust movement along the NE-SW faults and are superimposed on the firststage structures. The third-stage structures, corresponding to the Mesozoic orogeny for the study area, are a local occurrence and have the displacement similar to that of the first deformation stage, though they are represented by brittle left-lateral strike-slip deformations. Besides, at the third stage there is a partial reactivation of the earlier faults.