seismic moment tensor

The parameters and mechanisms of the source of modern earthquakes in the Eastern Baltic region are systematized. The predominant types of focal mechanisms of continental earthquakes are strike-slip and reverse. A generalized map of the orientation of maximum horizontal stresses in the East Baltic region and adjacent territories has been created. To create this map, we utilized the World Stress Map database and added the directions of maximum horizontal stresses in Estonia.

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.

Understanding the source mechanisms of induced earthquakes is important to distinguish them from natural earthquakes. The main objective of our study consists in finding out which parameters of the source mechanism can be used most effectively to identify the induced earthquakes. A possibility is also being explored whether they can be retrieved from data of a limited number of stations or even just one.

Purpose. The paper’s purpose consists in determining the source mechanism of 29.09.2017 earthquake near Stebnyk (21h46m8,4s, = 49,34˚, λ = 23,49˚, h = 1,9 км, MD = 2,9) using two methods – from polarities of first P-wave arrivals and by inversion of wave forms registered at a limited number of stations. Methodology. Seismic waves in the inhomogeneous medium represented by horizontally layered elastic structure are calculated using the matrix method.

For the first time for Transcarpathian region the solution of the focal mechanism of perceptible earthquake was solved. Earthquake occurred under the influence of the horizontal compression, oriented in latitudinal direction and near-horizontal tension of the submeridional orientation. A first-motion type in the source – strike-slip combined with reverse-oblique.

We consider the model of a vertically inhomogeneous medium, when one or more layers are under more stress. We suggested to use the matrix method of Thomson-Haskela for solving the problem to build field movements in order to use relevant analytical relations for solving the inverse problem in respect of stress tensor and / or parameters of the source. The results of mathematical modelling are simple in utilization and can be used for interpretation of seismic records.

The construction of a field displacement on the free surface of layered medium using the matrix method of Thomson – Haskell is considered. The authors show the obtained solution of the direct problem of seismology. The analytical solutions of the direct problem are used for solving the inverse problem. This method of solving of the inverse problem allows the source distributed in time and definition of the time function of the source STF to be considered.

The propagation of seismic waves in homogeneous halfspace is considered in this paper. The source is represented by seismic moment tensor. It is shown that the eigenvalue and eigenvectors problem can be used for seismological problems.

Purpose. The purpose of this paper is to show the importance of the additional information to determine the focal mechanisms of earthquakes in the Carpathian region of Ukraine, and also to determine the focal mechanisms and the spectral parameters of recurrent earthquakes. Methodology. The graphic method is proposed to determine the focal mechanisms of earthquakes in the region with a small seismic activity. This method is based on the distribution of the longitudinal P- wave polarities into compressive and extensive zones devised by nodal planes.