The 2017 Lesvos (Midilli) earthquake (Mw 6.3): Earthquake hazard implications from source modeling, numerical waveform simulation with regional 1D velocity structure and static stress field

Abstract

We investigate the earthquake hazard of Lesvos Island and the Turkish coast, considering the source mechanism and rupture propagation of the June 12, 2017 Lesvos (Midilli) mainshock (Mw 6.3), its numerical waveform simulations with regional new 1D deep velocity structures, relocated seismicity, and crustal stress loading due to the destructive earthquakes. The teleseismic body waveform inversion indicates that the strike, dip, and rake of the fault are 127°, 47°, and −97°, respectively. The depth is 9 km, and the seismic moment is 3.4 × 10²⁵ dyne cm. The mainshock ruptures a 12 × 15 km² area with a maximum 1.9 m slip and 3.4 MPa average stress drop. The previous rupture models are evaluated with simulated broadband (0.05–10 Hz) ground motions based on the discrete wavenumber method, considering shallow soil amplifications. The S-wave velocity models used in the simulations between the mainshock and stations are defined with the multiple-filter method. Our bilateral rupture propagation model gives better fits for the waveform arrivals and Fourier spectrum. The waveforms’ frequency with the highest horizontal amplitude is ∼3 Hz, which agrees with the soil fundamental frequency in Vrissa village. It is concluded that the damage in Vrissa is caused by the soil structure, not rupture propagation. The earthquake clusters in the north and south of Lesvos agree with a right-lateral synthetic shear if the Psara-Lesvos and Agia-Paraskevi faults are considered the principal displacement zone of a SW-NE right-lateral strike-slip shear zone. The results infer the possibility of continuing the earthquake hazard for Lesvos Island and the western coast of Türkiye.