The 2023 Türkiye earthquake doublet, comprising Mw 7.8 and Mw 7.7 events, resulted in over 59,000 fatalities and $119 billion in damages. These earthquakes occurred along the East Anatolian Fault Zone (EAFZ), a left-lateral strike-slip fault system formed by the collision of the Anatolian, Arabian, and African plates. The EAFZ is segmented, with variations in strike and geometry influencing earthquake characteristics. While less seismically active than the North Anatolian Fault Zone (NAFZ) in the 20th century, geodetic studies indicated significant strain accumulation along the EAFZ, capable of generating large earthquakes. The 2020 Mw 6.7 Doğanyol-Sivrice earthquake was the largest event on the fault before 2023. The 2023 doublet ruptured complex fault networks, prompting the need for detailed kinematic rupture models to understand the ground motion generation and resulting catastrophe. This study uses extensive seismic and geodetic observations, including strong-motion data, to develop these models, providing insights into the rupture processes and the triggering mechanism of the second event.

Previous studies have examined the tectonic setting of the EAFZ, noting its segmented nature and the potential for large earthquakes. Research on past significant events (1513, 1795, etc.) helped to establish the region's seismic history. Geodetic and geological studies have highlighted the role of fault geometry in controlling earthquake size and occurrence. The 2020 Mw 6.7 Doğanyol-Sivrice earthquake served as a significant precursor event, providing insights into the region's seismic behavior. Several studies have modeled the rupture process of the 2023 earthquake doublet using various techniques and data sets, but the complexity of the rupture requires sophisticated approaches to fully resolve the space-time evolution of slip.

The study uses a joint inversion of seismological and geodetic data to constrain the kinematic rupture models. Data included strong-motion recordings, teleseismic waveforms, static and high-rate GNSS data, and coseismic displacements derived from strong-motion observations. A novel baseline correction method was developed for the strong-motion data to enhance the determination of static displacements. The authors constructed multi-segment fault models (six for Mw 7.8, five for Mw 7.7) based on satellite data and relocated aftershocks. A nonlinear finite-fault inversion method was employed to determine the space-time slip distribution for each event. Coulomb stress change analysis was used to investigate the triggering mechanism of the Mw 7.7 earthquake by the Mw 7.8 earthquake. The study also assessed the future seismic hazard by calculating coseismic stress changes from the combined effects of the 2023 doublet and the 2020 Doğanyol-Sivrice earthquake.

The kinematic models reveal complex multi-fault rupture processes for both earthquakes. The Mw 7.8 earthquake initiated on a splay fault and propagated bilaterally along the main EAFZ strand, with rupture velocities ranging from 2.5 to 4.5 km/s and a peak slip of 8.1 m. The Mw 7.7 event showed bilateral supershear rupture velocity (>4 km/s) initially, followed by slower rupture (~3 km/s). A notable paucity of aftershocks in some high-speed rupture regions was observed. The Coulomb stress change analysis indicates that the Mw 7.8 earthquake plausibly triggered the Mw 7.7 event, with stress increases exceeding the minimum triggering threshold. The combined stress changes from the 2023 doublet and the 2020 earthquake reveal potential future rupture zones, particularly along the northeastern EAFZ and the Dead Sea Fault. The study also found that moment-scaled radiated energy estimates for both events were lower than the global mean for similar events, potentially reflecting smoother rupture propagation on straight fault segments.

The findings provide a comprehensive understanding of the complex rupture processes and triggering mechanism of the 2023 Türkiye earthquake doublet. The observed supershear rupture in segments of both events highlights the potential for rapid stress release in regions with favorable fault geometry and stress conditions. The successful triggering of the Mw 7.7 event by the Mw 7.8 event emphasizes the importance of considering stress transfer in seismic hazard assessment. The identification of potential future rupture zones emphasizes the need for targeted mitigation efforts in these regions. The lower-than-average radiated energy suggests factors influencing radiated energy such as slip roughness may play a critical role in future earthquake forecasts and simulations.

This study presents detailed kinematic rupture models of the 2023 Türkiye earthquake doublet, revealing complex multi-fault rupture and supershear phenomena. The Coulomb stress analysis confirms the likely triggering of the second event by the first. The identified potential future rupture zones based on coseismic stress changes highlight the need for continued monitoring and hazard assessment in the region. Future research should focus on refining the 3D crustal models and incorporating more sophisticated rheological properties into dynamic rupture simulations to better understand the complexity of the observed ruptures.

The study acknowledges limitations associated with using a 1D velocity model for Green's function calculations, which might affect the accuracy of waveform fits, particularly at regional distances. Inherent uncertainties in strong-motion baseline correction, GNSS measurements, and satellite-based deformation mapping also contribute to uncertainties in the models. The complexity of the fault system may not be fully captured by the multi-segment fault models. Finally, some regions showed higher uncertainty in slip distribution due to a lack of very near-fault observations.