earthquakes

The accuracy of the focal mechanism solution mainly depends on the number of stations used and becomes problematic especially in the case of weak earthquakes and sparse networks. In our study, we retrieve the seismic moment tensor of the M=5 earthquake on 9 October 2023 (18:23:09 UTC, 21.783°E, 49.086°N, depth 11.5 km) in Eastern Slovakia from its records at only four seismic stations. Our seismic moment tensor inversion is based on the point source approach and the use of only direct waves calculated by the matrix method.

The problem of earthquake prediction, as well as its interrelation with horizontal movements of the Earth’s crust has not still been solved. The purpose of the work is to establish a possible correlation between generalized parameters of horizontal movements of the Earth’s crust and seismicity. The Carpathian-Balkan region in connection with frequent and spatial differentiation of earthquake activity and well-known geological structures is chosen as a field for the research.

Possibility of use of tidal devices for record of seismic waves from earthquakes and other geodynamic events is studied. It is investigated the inertial and gravitational contribution of   seismic signal to pendular seismometers and tidal devices (seismotiltmeter and gravimeter). These are identical devices and differ stability of blocks and in filtration parameters. Tidal devices are more sensitive in over-long-period area where the gravitational contribution is more. It is given examples of record of seismic fluctuations by tidal devices at some earthquakes.

The constructed model for a deep structure of the lithospere under the Neftegorsk earthquake region shows that North Sakhalin consists of the North Sakhalin sedimentary basin, the Deryugin basin and the ophiolite complex located between them. The ophiolite complex composed of the the ultrabasic rocks, fixes the position of the ancient subduction zone which was active about 100-60 million years ago. On a surface the subduction zone manifests itself as deep faults running along Sakhalin.

In the article presented methods of the directed monitoring of acoustic background in an infrasound range by means of the area system of grouping of microbarographs, and also methods of the directed monitoring by the radiotechnical complex of radioroutes of VLF signals. The first results over of remote supervisions of seismoactivity Vranchea region are brought with the use of the considered methods, anomalous effects are distinguished in the looked after fields before earthquakes.

Using methods of factor, correlation and regression analysis anomalous component investigation of temporal variations of geophysical field characteristic (power of local earthquakes, endogenic microseisms, geotemperatures, the Earth's crust deformation, atmospheric pressure and temperature) registered at the Transcarpathian network of regime geophysical stations (RGS) in 1992-1997 have been carried out. To separate anomalous components from series of geophysical field characteristics harmonic components and trend have been excluded by means of filtration in a spectral domain.

Seismogeodynamic conditions, complicating the operation of chinks on an example of Dolyna and Oryv-Ulychnyansk oil-gas deposits are considered. Intensive technology of production of oil on Dolyna deposit in 1974-1976 has provoked a series of appreciable earthquakes with intensity of 5-6 degree (MSK-64 scale).

On the basis of carried out specification of coordinates and depths of local earthquakes sources which was made by using of new methods the general spatial analysis of seismicity of the Ukrainian Carpathians and its concrete structural-tectonic zones was made. The distribution of earthquakes on the depth including on the Mizhgirya – Vyshkov – Shevchenko – Dolyna section was studied and some features of seismotectonics in the area around the north-east of connection of Oash and Transcarpathian deep faults was traced.
 

During the last few years digital seismic apparatus development was provided in the Institute of Geophysics. Some sets of digital seismic apparatus were made and tested at the regional seismic stations of the Carpathian network. The created equipment DAS is reliable and has sufficiently high operational properties due to use of modem chips and replacement of some analog chains (filtering, integrating, etc.) on their program analogues. The flexible algorithms of useful seismic signal detecting was applied.