Izvestiya, Physics of the Solid Earth最新文献

—As is known, earthquake sources result from destructive geological processes within the Earth’s lithosphere. As part of an international collaboration, we conducted a detailed petrophysical, geological, and structural study of the preparation conditions for exhumed paleoseismic ruptures in the Baikal Rift Zone and Mongolia. Alongside routine seismological data analysis, we utilized numerical simulations and physical-mechanical experiments on fault segments for medium-term forecasting and seismic hazard assessment. Methodologically, particular attention was paid to the influence of fluid-mechanical processes on both the occurrence of coseismic displacements in fault zone segments and the subsequent healing of these displacements at various crustal depths. Synthesizing the collected data and incorporating global data on the variety of geodynamic regimes of earthquake preparation, we identify a significant diversity in the thermodynamic factors governing crustal failure, accounting for fluid saturation within intraplate environments and interplate boundary zones. We analyze the key role of fluid flows at different crustal depths, where their influence largely dictates the observed variety of geomechanical conditions during earthquake source preparation. Furthermore, we consider the seismogeological features governing the nucleation of local earthquakes with magnitudes M ≥ 5.5 across various segments of the Baikal Rift Zone. Accounting for the totality of these factors improved the accuracy of medium-term forecasts for hazardous earthquake sources to 70%. Ultimately, these findings substantiate the advantages of constructing and implementing regional models of earthquake source preparation that comprehensively incorporate local seismogeological conditions.

This study presents a comparison between previously published deep seismic sounding (DSS) results and three one-dimensional velocity models obtained using the receiver function (RF) method in the Kola region. The RF models were derived from long-term datasets (>15 years) from global network permanent seismic stations. DSS profiling provides significantly higher resolution of crustal structure than the RF method. The boundaries and characteristics of the crust–mantle transition obtained by the two methods are fully consistent. The upper-mantle discontinuity depths identified by DSS experiments involving peaceful nuclear explosions also closely match the RF results. The study demonstrates a high structural consistency between lithospheric features reconstructed using DSS and RF methods.

Many earthquakes occur unexpectedly: their impact exceeds the expected level based on standard seismic hazard estimates adopted for the region. For strong earthquakes (magnitude 6 and greater), current hazard assessments rely primarily on historical records, paleoseismological data, and information on active faults. In contrast, data on smaller earthquakes are largely disregarded, even though moderate earthquakes are assessed precisely on the basis of such smaller events. This study aims to determine whether a high level of seismicity, expressed through the activity of weak earthquakes, can—accounting for the Gutenberg–Richter law—serve as an indicator of possible future strong earthquakes, and conversely, whether a low level of seismicity implies a low probability of a strong event. We analyzed the strongest earthquakes worldwide from 2001 to 2025, including those for which the hazard was underestimated by national (regional) seismic hazard maps. For each earthquake, we estimated the 50‑year probability of an event of that magnitude within a region containing its rupture zone. Assuming a stationary Poisson process, we used the number of seismic events of magnitude of completeness and greater during the 20 years preceding the target earthquake, scaled to the number of events of magnitude equal to or larger than that of the target earthquake over 50 years. For the vast majority of events, the estimated probability exceeded 10%. This threshold—a 10% probability over 50 years—is the typical benchmark used in seismic hazard mapping. Thus, our results demonstrate that seismic hazard assessment, particularly in delineating potential source zones for strong earthquakes, must include a statistical analysis of weaker earthquakes. Such an approach will reduce the number of “unexpected” earthquakes in the future and improve the accuracy of probabilistic seismic hazard assessments.

By applying surface-wave tomography (SWT) and receiver function (RF) methods, new estimates of the V_S velocity distribution in the Earth’s crust and upper mantle down to depths of approximately 300 km have been obtained beneath the eastern part of the Kharaulakh segment of the Verkhoyansk fold belt. In addition, the radial anisotropy parameters of the medium were evaluated. The RF and SWT methods were applied independently to enhance the reliability of the resulting estimates, yielding mutually consistent results. The analysis identified three crustal layers with a combined thickness of 30 km, which are underlain by a 30–35 km thick crust–mantle transition zone. In the upper mantle, a complex low-velocity zone was detected at depths of 90–180 km, which may feature a two-layer structure.

This study was performed within the framework of the problem of diagnosing, monitoring, and predicting the state of geotechnical systems and natural objects. It focuses on the substantiation and laboratory testing of an approach for establishing quantitative relationships between the parameters of stochastic fields in geo-objects under heterogeneous stress conditions. Experiments on diametrical compression of rock disk specimens were conducted with synchronous recording of microdisplacements on their surfaces using digital image correlation. Interpretation of the obtained data allowed us to identify emerging surface microfractures at each loading stage. It was established that even at the initial stage, statistically significant relationships arise between disturbances (characterized by the number of microfractures per unit area) in different parts of the specimen, and the closeness of these relationships increases with growing load. Correlations were found between the load level and the number of microfractures in different parts of the specimen, which enable predictive assessments of the disturbance of the latter.

The construction of an earthquake source zones (ESZ) model is an important step in seismic hazard assessment. Earthquakes occur mainly on pre-existing faults; therefore, the strongest earthquakes are generally considered to be confined to extended linear structures. However, a significant number of earthquakes occur outside such structures and are classified as so-called scattered seismicity. Historically, in ESZ models, scattered seismicity has been represented by a uniform distribution of epicenters within areas considered relatively homogeneous, known as “domains.” The domain boundaries are defined by experts. This approach was developed in the late 1960s and was justified by the short period of instrumental observations and the insufficiently high quality of earthquake parameter determination in catalogs. In modern conditions, high-quality data are quite sufficient for more detailed modeling of scattered seismicity in the form of local estimates on a regular grid. Various approaches exist for such modeling. The aim of this work is to select or develop an optimal method for spatially local estimates of the number of earthquakes at or above the magnitude of completeness. Obviously, the goal of an optimal model is to predict the locations of epicenters (hypocenters) of future earthquakes. Therefore, the main criterion for selecting the optimal method is the best fit of the model to real data that were not used in constructing the model or estimating its parameters. The maximum likelihood method is used to determine the degree of correspondence between the model and the data. Another selection criterion is the minimization of subjective assumptions in model construction, ensuring full reproducibility of the model using only observed data.

The aim of this article is to test the fractal dimension of relief as a new parameter for recognizing ore-bearing morphostructural nodes in the Caucasus and Altai–Sayan regions. Polymetallic deposits of various sizes known in these regions were considered. The objects of recognition are morphostructural nodes, the positions of which were determined in previous studies using the method of morphostructural zoning, where it was shown that the spatial localization of polymetallic deposits in these regions is controlled by morphostructural nodes. For each node, the fractal dimension (FD) was calculated from SRTM digital elevation models using the box-counting method. The informativeness of FD was assessed a priori using a discretization procedure, which made it possible to determine characteristic FD value intervals for nodes hosting known polymetallic deposits and for nodes where such deposits are unknown. Together with morphometric and geological–geophysical parameters of the nodes, the FD parameter was used to recognize ore-bearing nodes using the Kora-3 pattern recognition algorithm. The obtained results were compared with the classification of nodes into ore-bearing (class O) and non-ore-bearing (class NO) that had been previously identified in the study regions without using the FD parameter. It is shown that the fractal dimension of relief is an informative parameter for recognizing potentially ore-bearing morphostructural nodes in the regions considered.

A distributed slip model of the source of the July 29 (30), 2025 Kamchatka earthquake (M_w = 8.8) was constructed based on coseismic displacements recorded by GNSS stations. To verify the obtained source model, numerical tsunami modeling was performed using the calculated vertical coseismic seafloor displacements. The resulting mareograms were compared with observations from DART bottom pressure recorders that were not used in the inverse modeling procedure. It is shown that the source model developed in this study reproduces the amplitude characteristics of the first tsunami wave at the considered DART stations and does not lead to the pronounced overestimation of amplitudes observed for the USGS model. However, at stations located in the eastern sector relative to the source, the simulated tsunami signal produced by this model is delayed, whereas the USGS model more accurately reproduces the observed wave arrival times. Overall, the comparison demonstrates that each of the two models has distinct advantages in reproducing different characteristics of the observed tsunami signal. The results suggest that DART data may serve as an independent diagnostic constraint for the assessment and further refinement of earthquake source models.

This study presents an analysis of direct numerical modeling of fluid injection in the vicinity of an active tectonic fault. The objective is to refine the initiation criteria for induced seismic events by considering both the absolute pore pressure and its rate of change. We simulate a scenario of fault hydraulic unloading where elevated pore pressure reduces effective normal stresses and initiates slip along fault segments. Utilizing a rate-and-state friction framework, we analyze the transition from steady (aseismic) slip to an unstable, seismogenic regime as a function of the pore pressure buildup rate. The results demonstrate that the characteristics of induced slip are governed not only by the pore pressure level reached but also by its rate of increase. Within the considered modeling framework, the final slip zone length scales almost linearly with the initial length of the unstable fault segment, while the maximum slip velocity is highly sensitive to the pore pressure growth rate, exhibiting an exponential increase followed by saturation. A comparative analysis of different methodologies for estimating seismic moment and equivalent magnitude reveals a consistent threshold structure in the relationship between magnitude and the pore pressure growth rate.

The article examines the consequences of scenario earthquakes for settlements of Krasnodar Krai, including the cities of Krasnodar and Tuapse. The aim of the study is to provide realistic estimates of damage and risk indicators resulting from predicted strong and felt earthquakes in the study area. The tools and simulation methods used to assess the potential impact of scenario earthquakes on buildings and the population of the region are described. The paper presents methodological materials and the results of calibrating seismic intensity attenuation models based on an analysis of historical seismicity data for the region. Baseline data have been updated to account for the specific building stock characteristics of Krasnodar Krai settlements. Maps of potential damage to the building stock, maps of individual seismic risk, and economic vulnerability at the regional and urban levels are presented. Particular attention is paid to the rapid modeling of the consequences of a felt earthquake that occurred near the city of Krasnodar on January 24, 2024. This event was used to verify the models and assess the accuracy of the obtained results. It is confirmed that the models adequately reflect the extent of potential damage and meet the specified requirements. The obtained data can be used for planning risk mitigation measures and increasing regional resilience to potential natural disasters.