Source Parameters of Strong Turkish Earthquakes on February 6, 2023 (Mw = 7.8 and Mw = 7.7) from Surface Wave Data

Abstract

Based on the amplitude spectra of surface waves, the source parameters of the strong Turkish earthquakes on February 6, 2023 (M_w = 7.8 and M_w = 7.7) were calculated in two approximations: an instantaneous point source and an elliptical shear dislocation. As a result, fault planes were identified, data were obtained on the scalar seismic moment, moment magnitude, focal mechanism, and source depth of the considered seismic events, and the integral parameters characterizing the fault geometry and its development in time were estimated. It is shown that the sources of the earthquakes under study were formed under the action of the regional stress field and their focal mechanisms were sinistral strike-slips with a strike direction close to the strike of the East Anatolian fault zone for the first event and close to the strike of the Sürgü-Çardak fault system for the second one. For the first earthquake, our estimates of the rupture duration and its length (t = 52.5 s, L = 180 km) probably refer not to the entire rupture, but only to its main phase, confined to the northeastern segments of the East Anatolian Fault and characterized by maximum displacements and values of the released seismic moment. The values of t = 30 s and L = 180 km that we obtained for the second earthquake fully characterize the entire rupture.