Ground Motion Variability During the February 6, 2023 M7.8 Kahramanmaraş Earthquake, Türkiye

On February 6, 2023, two catastrophic earthquakes struck the Kahramanmaraş region, marking some of the most destructive seismic events in modern Turkish history. These earthquakes caused extensive loss of life and widespread destruction across southeastern Türkiye and northwestern Syria. The two earthquakes ruptured different fault segments with comparable magnitudes, generating exceptionally strong ground motions. Particularly, in the southern section of the fault rupture along the Amos fault segment, extreme ground motions were recorded. The earthquakes' complex rupture processes, characterized by sequential bilateral ruptures, varying rupture velocities and geometries, across branched fault segments, provide crucial insights into rupture dynamics and seismic hazard. Understanding the spatial variability of ground motions and the directivity effects associated with these complex rupture dynamics is essential.

This study focuses on analyzing the spatial variability of ground motions generated by the Mw 7.8 mainshock. By simulating ground motions on a regular grid across the affected region, we investigate the spatial distribution of ground motion intensity measurements and the rupture directivity effects. Using advanced kinematic rupture modeling techniques, simulations were performed with the Graves and Pitarka (2016) hybrid-source method, combined with Frequency-Wavenumber (FK) 1D Green’s functions computed for a regional velocity model. High-slip patches and stochastic small-scale slip variations were incorporated to create hybrid rupture models.

The simulations, validated against strong-motion data, effectively reproduced near-fault ground motions within the 0–3 Hz frequency range, allowing for near-fault ground variability analysis. This study provides valuable insights into the spatial variability of ground motion amplification patterns and their relationship with rupture directivity, enhancing our understanding of earthquake ground motion variability and seismic hazard.