ИСТИНА

The reliability of earthquake hypocenter coordinates is a pressing issue for any seismically active region. The accuracy and completeness of pertinent data are essential determinants for solving a wide spectrum of problems in contemporary seismology, notably the design of seismic-resistant facilities, regional seismic zoning, the development of earthquake forecasting techniques, and the construction of geodynamic models of the Earth's crust and upper mantle [1, 2, 3]. The Caucasus region, in which the Republic of Armenia is located, is characterized by high seismic activity. The region's current geodynamics are manifested by slow surface deformation, the presence of faults and lithospheric blocks, and rapid seism genic displacements along faults and at their intersections. Earthquakes with magnitudes up to 7.0, which are considered catastrophic, have been recorded in the region. The Spitak earthquake of December 7, 1988, is particularly notable [4, 5, 6]. In seismological studies, the degree of reliability of the results obtained is largely determined by the characteristics of the seismological catalogues used, among which the completeness, accuracy and reliability of the data are of particular importance. Earthquake catalogs compiled for Armenia are primarily based on data obtained using instrumental recording methods. Preliminary assessments of the results presented by various researchers indicate that the quality of Armenian earthquake bulletins and corresponding catalogs is currently insufficient to fully utilize the information contained within them in solving contemporary problems in modern geophysics. To confirm this statement, it is enough to analyze the distribution of epicenters and hypocenters of earthquakes on the territory of Armenia, as well as the distribution of points on the Wadati graph [1, 3]. As numerous studies have shown, the initial seismological data contained in bulletins and catalogs exhibit significant heterogeneity. This heterogeneity is primarily due to the uneven geographic distribution and number of seismic networks over the entire observation period [3, 7, 8]. The paper presents a comparative analysis of two leading international seismological catalogues, NEIS (USA) and ISC (UK), for the territory of Armenia (latitude range 39–41° N,longitude range 43–47° E) for the period 1991–2024. Their advantages and disadvantages are considered, and practical recommendations for the use of these catalogues in regional studies are offered. The ISC catalog is characterized by the widest time coverage, dating back to 1960, and a high degree of completeness for events with magnitudes less than 4. However, the quality of hypocenter determinations within it is uneven due to differences in observation systems and data processing methods. Improving the accuracy of determining earthquake hypocenter coordinates, particularly focal depths, requires modernizing national seismic networks. Responsibility for the completeness, quality and relevance of seismological data lies with the relevant national services, ensuring the timely registration, processing and publication of information on earthquakes. The main goal of this work is to explore the following objectives: 1. Comparison of earthquake origin times, locations, and magnitudes in different catalogues. 2. Comparison of the number of events represented in the NEIS and ISC catalogues. 3. Analysis of time series in both catalogs. These and other objectives will help identify both differences and similarities in the data presented in the NEIS and ISC catalogues. Solving these problems will help determine which of these two catalogues should be used for seismic hazard assessment in specific regions and for global studies.