EARTHQUAKE FOCAL PARAMETERS in the CRIMEAN-BLACK SEA REGION in 2018–2019

Abstract

The results of calculation and analysis of spectral and dynamic parameters of the sources (М0,r0, , , ησ, r, ū, Eu и Mw) of 24 Crimean earthquakes for 2018–2019 in the range of energy classes KП=5.8–11 are presented. 157 station amplitude spectra of P- and S- seismic waves recorded at seven regional digital seismic stations were used for calculations. The determination of dynamic parameters of the sources was carried out using the Brune theoretical dislocation model. The average values of the dynamic parameters of earthquake sources for 2018–2019 were in most cases estimated for several stations and for different types of waves, which ensured a small value of the degree of scattering of individual estimates. For the studied 2018–2019 earthquakes, the average values of the seismic moment М0, the radius of the circular dislocation r0, and the stress drop  were within the confidence intervals of the long-term dependencies М0(KП), r0 (KП) and (KП). For five strongest earthquakes of 2018 (January 31, April 24, September 9, September 13, and October 15 with KП=10.5–11) and two earthquakes of 2019 (May 8 and December 4), focal mechanism solutions were obtained within the framework of the double dipole model. Type of movement in the source of January 31, 2018 earthquake is a strike-slip with a normal fault component, of September 9 and September 13, 2018 – a normal fault, of April 24 and October 15, 2018, as well as May 8 and December 4, 2019 – a reverse fault. The spectral composition of seismic oscillations was additionally studied from the energy spectra of 15 earthquakes using records at the Alushta station located at distances 5–285 km from source zones. At the qualitative level, a shift of the spectrum maximum (fqmax) towards higher frequencies for weak shocks and close epicentral distances.