DETERMINATION OF EARTHQUAKE SOURCE PARAMETERS BASED ON DATA FROM A LIMITED NUMBER OF SEISMIC STATIONS

Background. This paper presents a method for determining the seismic moment tensor using only direct P- and S-waves, which are less sensitive to modeling effects of wave propagation than reflected and refracted waves, significantly improving the accuracy and reliability of the method. The earthquake source is considered as a point source with a known location and origin time. Methods. Wave propagation in a medium modeled as a set of horizontally homogeneous elastic layers is calculated using the matrix method, which allows isolating only direct waves. Based on the forward problem and the solution of the generalized inversion, an inversion algorithm for observed waveforms to determine the components of the seismic moment tensor M(t) is presented. The analysis is conducted based on records of the earthquake that occurred on February 22, 2024, in Eastern Slovakia, using data from only two seismic stations of the Slovak network: sk19 (49.25°N, 21.93°E) and sk20 (49.21°N, 21.61°E). Results. To verify the reliability of the obtained earthquake source parameters, a comparative analysis was conducted between synthetic seismograms, calculated using the wavefield modeling methodology based on the matrix method, and observed records of direct P- and S-waves at station sk19. A correlation analysis of direct P- and S-waves for observed and synthetic seismograms was performed. The results of the analysis demonstrated a high reliability of the determined seismic moment tensor for the February 22, 2024 earthquake (Eastern Slovakia), obtained through inversion using only direct waves. Conclusions. The use of a point source represented by a seismic moment tensor, placed within a horizontally stratified half-space, is an effective approach for determining earthquake focal mechanisms. The study results confirm the feasibility of using only direct P- and S-waves for determining the seismic moment tensor, which enhances computational accuracy and reduces the impact of modeling effects on wave propagation.