In recent decades, seismic observations have been actively expanding all over the world. They are used in a very wide range of tasks: from studying mega-earthquakes over vast areas of subduction zones to assessing local micro-earthquakes in the area of an individual mine or recording weak events accompanying hydrocarbon extraction. More and more temporary and permanent seismic systems are appearing in Russia to monitor nuclear industry facilities and control man-made seismicity in mining areas. The article describes the work that was carried out at the turn of the century during the selection of locations for seismic stations, which later became part of the International Monitoring System (IMS) organized to control nuclear tests. The main principles and algorithms for selecting locations for seismic stations are considered based on the analysis of the experience of work on selecting sites for IMS stations in Russia; some seismic characteristics of the sites are given. A step-by-step analysis of the basic approaches used in the organization of the IMS seismic network may be useful in creating new observation systems to solve various problems.

The results of a joint analysis of catalogs of events associated with the Mikhailovsky GOK explosions according to the data of MSG «Mikhnevo» and stations of the International Monitoring System from 2011 to 2024 using the method of cross-correlation of waveforms are presented. The high quality of the catalog created according to the data of MSG «Mikhnevo» has been confirmed.

In order to study the processes in the geological environment during the preparation of strong earthquakes, monitoring was carried out in 1980–1993 on the territory of Armenia for different geophysical fields (geomagnetic, gravitational, geochemical, and radon). The study of changes in the variable geomagnetic field δT was carried out using the ratios of the amplitudes of synchronously measured variations in the components of the δT field in the northern part of Armenia. To assess the change in the state of the geological environment, the calculated parameter N(A) = Ai/Aj, was used, the ratio of the amplitudes of the variations in the geomagnetic field caused by an external source and measured synchronously at different pairs of stations. The calculated parameter N(A) characterizes the change in the electromagnetic induction (electrical conductivity) of the geological environment. Before the Spitak earthquake, the values of the parameter N(A) decreased by about 35%. Analysis of data before the Paravan earthquake also shows a sharp drop in the values of this parameter by 20–25%. Changes in the calculated parameter N(A) show that the electromagnetic induction or electrical conductivity has changed in the studied geological environment. The concentration of subsurface radon at the Jermuk station before the Spitak earthquake increased by 15%, while at the Leninakan station, on the contrary, it decreased. Several months before the Spitak earthquake, mantle helium appeared in the Kajaran well, which usually appears before strong earthquakes. In the northern part of Armenia, where gravity measurements were taken, anomalous changes were also recorded before the Spitak earthquake. The obtained anomalous changes in geophysical fields are possible geophysical precursors of the Paravan (13.05.1986, M = 5.4) and Spitak (07.12.1988, M = 7.0) earthquakes.

The physical mechanism of propagation of the electromagnetic field disturbance generated by the electric prospecting generator facility ERGU-600-2 located at the Bishkek geodynamic test site of the Research Station of the Russian Academy of Sciences in Bishkek (Kyrgyzstan) into the lower ionosphere is investigated. Within the framework of a simplified model of the medium and the radiation source (grounded dipole powered by the ERGU-600-2 facility), analytical expressions were obtained for the frequency and spatiotemporal distributions of the electromagnetic field components. The numerical results demonstrate that the amplitude of the electric field disturbance in the ULF range at an altitude of 70 to100 km reaches several μV/m. To verify the numerical results on the territory of the Bishkek geodynamic test site, field measurements of the full geomagnetic field vector were carried out at various distances from the radiating dipole during the ERGU-600-2 operation sessions. The results of field measurements are consistent with the results of numerical studies, which allows to apply the proposed numerical method for assessing the electromagnetic pollution of the environment during the operation of man-made sources such as the ERGU-600-2 + dipole system.

We consider the joint variations of the magnetic field and the Earth’s rotation speed. It is shown that in the considered cases, the induction of the geomagnetic field increases with increasing speed of rotation of the Earth and vice versa decreases with its fall. We used the results of instrumental observations performed at magnetic observatories ‒ the Mikhnevo Geophysical Observatory of Sadovsky Institute of Geosphere Dynamics of Russian Academy of Sciences and a number of observatories of the international INTERMAGNET network ‒ located at a distance from the main magnetic anomalies of the Earth, and IERS data on the unevenness of the Earth’s rotation. A quantitative relationship has been obtained between the absolute magnitude of the geomagnetic field induction vector and the LOD value equal to the difference between the observed and ephemeris day duration. 

The time dependences of the energy of tropical cyclones and earthquakes in the northwestern Pacific Ocean over a long-term period are compared. Certain correlations between the dynamics of annual cyclone and earthquake energy values are revealed. The trends in the long-term dynamics of annual cyclone and earthquake energy values are calculated. The obtained results support the information available in the literature on the influence of tropical cyclones on the seismicity of the regions of their activity.