For a long time, foreshocks have been highly anticipated for the development of short-term earthquake prediction methods. However, the wide variety of their manifestations has not yet allowed these expectations to be realized. This article analyzes the nature and parameters of the foreshock sequences of more than 60 major earthquakes with magnitudes ranging from 4.7 to 9.1, which occurred in various regions of the world under different tectonic conditions. The analysis showed that the size of the zone of manifestation of foreshocks, localized in a limited area within a few days or hours before the main shock, depends on the magnitude of the strongest foreshock in the sequence. Moreover, the maximum dynamic deformation from the strongest foreshock in the vicinity of the hypocenter of the future main shock is a stable value. As a possible interval for the manifestation of the strongest «immediate» foreshock, it is proposed to use a time period of 30 days before the main shock.

This paper presents a new approach to locating acoustic emission sources based on a supervised machine learning (ML) method. A distinctive feature of the proposed approach is the use of a synthetic data catalog – comprising source locations and signal arrival time differences at several acoustic emission (AE) sensors – to train the localization algorithm. When the configuration of AE sensors changes, the routine collection of experimental data to generate the ML training set can be replaced by a numerical simulation. Data variability is provided by introducing a random delay in arrival time detection, determined by the signal-to-noise ratio.The ML algorithm, trained on synthetic data, improves location accuracy and successfully resolves the location problem for a larger number of pulses compared to the classical approach of solving elastic wave propagation equations via the residual method. The proposed ML algorithm is applicable to various laboratory experimental setups as well as to seismic monitoring, provided the velocity profile is well-defined.

The problem of the movement of the decomposition front of intra-permafrost metastable gas hydrate into ice and gas is considered. A mathematical model is formulated, an analytical solution is obtained, and various scenarios are investigated. Cases are examined where the triggers are a pressure drop below the critical value, a temperature rise above the critical value, or both simultaneously. Estimates are obtained for the propagation velocity of the gas hydrate destabilization front and the rates of methane discharge through the upper boundary of the formation.

The results of complex instrumental observations of geophysical effects in the surface atmosphere during the period of increased solar activity on January 18‒21, 2026, which manifested itself in the form of a powerful solar flare of class X1.9 on January 18, 2026 and followed by a strong geomagnetic storm on January 19‒21, 2026 with a K_p = 8.8. Based on the results of the analysis of digital recordings, it was shown that the solar flare and storm were accompanied on Earth by increased amplitude variations in the electric and magnetic fields, temporary changes in the thermobaric state of the atmosphere, microbaric variations, as well as an increase in GPS positioning errors. The ionospheric effect of a solar flare and a magnetic storm, which manifested themselves as variations in the critical frequency of the ionospheric F2 layer, was also noted.

We study the spatiotemporal heterogeneity of PM2.5 mass concentrations in Moscow and the surrounding region using data from a sensor network and the Center for Geophysical Monitoring in Moscow of the Sadovsky Institute of Geospheres Dynamics of Russian Academy of Sciences. An analysis of hourly averages and first differences in PM2.5 concentrations revealed that PM2.5 concentrations in Moscow are generally determined by a combination of the general urban/regional background and local anomalies. Hierarchical clustering of observation points revealed that clusters of local anomalies only partially coincide with regional groups identified by the geographic location of the points relative to central Moscow. The weekend effect was found not to be the dominant factor in shaping the diurnal variations in PM2.5 concentrations in Moscow›s urban environment. The diurnal variation in PM2.5 concentrations, both for the geographically defined regions and for the clusters identified through cluster analysis, is generally similar and consistent with the daily variation in PM2.5 concentrations typical for the Moscow region for fair weather. An analysis of the concentration of microfine particles in the Moscow atmosphere depending on the season showed that concentrations are higher in winter than in summer.

In geophysics, the problem of classifying triggers of dynamic processes in the lithosphere, hydrosphere, atmosphere, ionosphere, and magnetosphere has arisen and requires a solution. Triggers that induce catastrophic events, such as destructive earthquakes, require particular attention. Classification is necessary to express the diversity of triggers in a limited number of organized and clearly identifiable types. This article proposes a collaborative project to systematize triggers, i.e. to develop a unified classification and nomenclature. A simplified (basic) and an expanded classification tables are proposed. The basic matrix uses the principle of binary opposition. It contains three categories of descending rank: type (natural, artificial), class (endogenous, exogenous), and species (periodic, aperiodic). The expanded classification table adds a category of lower rank than species. The result is 32 trigger varieties. The heuristic value of systematizing triggers is emphasized. New phenomena discovered during the classification process are identified: the excitation of a strong aftershock by a circumnavigational seismic echo, the modulation of global seismicity by the Earthʼs spheroidal oscillations, and the weekend effect in earthquake activity. A causal chain of triggers, termed a trigger cascade, is identified in the magnetosphere. The existence of so-called antitriggers is noted; they do not excite, as is usually the case, but rather interrupt an ongoing dynamic process.

In this paper we develop an understanding of the proper time the earthquake source using catastrophic Tohoku earthquake. The paper is dedicated to the 120th anniversary of Einstein’s theory of relativity, but the dedication is symbolic, since we are investigating a purely non-relativistic geophysical object. We still found it possible to borrow the terms «time relativity» and «proper time» from the theory of relativity. The concept of the proper time of the source is developed by us within the framework of the phenomenological theory of earthquakes. The paper describes a procedure for measuring proper time using observation data of foreshocks and aftershocks. We synchronized the imaginary «underground clock» that counted the proper time and the clock that showed world time. The idea of a hypothetical underground clock turned out to be effective. We have shown that the proper time of the source flows unevenly relative to the flow of world time. Two phases of the evolution of the source before the main shock of the earthquake were discovered. This complements the picture of three-phase relaxation of the source after the main shock, which we established earlier. The uneven flow of proper time relative to world time indicates the non-stationarity of the source parameters. The overall conclusion is that the concept of the proper time of the source has enriched the possibilities of experimental study of earthquakes.