East Anatolian Fault Shielding Effect on Ground Shaking in Eastern Türkiye

Rufus D. Catchings

Submitted August 30, 2026, SCEC Contribution #15421, 2026 SCEC Annual Meeting Poster #238

The 6 February 2023 Mw 7.8 and Mw 7.6 Kahramanmaraş earthquake sequence in eastern Türkiye was responsible for over 60,000 fatalities and $160 billion in damage in Türkiye and Syria (Milat Internet Archive, 2023; last accessed September 22, 2025), as strong shaking occurred along much of the length of the East Anatolian and Dead Sea Transform faults (EAF and DST, respectively). To better understand the connectivity of the fault system, regional seismic wave propagation, and seismicity in the region, the U.S. Geological Survey (USGS) and the Turkish Disaster and Emergency Management Authority (AFAD) recorded aftershocks from July 2023 until December 2023 using an evenly spaced grid of nodal seismometers that covered much of southeastern Türkiye. We evaluated regional shaking intensity generated by small- to moderate-magnitude earthquakes that were recorded by the nodal seismometers. Our data show that shaking varies with both the magnitude and the location of the earthquakes. We observe that, at similar epicentral distances, earthquakes with epicenters on the southeastern side of the EAF generate stronger regional shaking on the southeastern side of the fault, and epicenters on the northwestern side of the EAF generate stronger regional shaking on the northwestern side of the fault. We also find this pattern for the east-west-trending Sürgü-Çardak fault (the Mw 7.6 causative fault) and for smaller faults that are subparallel to the EAF. This suggests that the faults act as shields, limiting efficient cross-fault propagation of seismic energy resulting from small and moderate-magnitude earthquakes. The same may hold for larger magnitude earthquakes, as strong-motion records from the Mw 7.8 earthquake, which had an epicenter on the southeastern side of the EAF, resulted in stronger shaking on the southeastern side relative to the northwestern side of the EAF (Chen et al., 2025). Although the large-magnitude earthquakes caused damage on both sides of the EAF, damage may have been partially muted for areas on opposite sides of the EAF during the two mainshocks. We observe a large velocity contrast across the EAF, which may be responsible for the apparent shielding effect.

Key Words
East Anatolian, Ground Shaking, Fault Shielding

Citation
Catchings, R. D. (2026, 08). East Anatolian Fault Shielding Effect on Ground Shaking in Eastern Türkiye. Poster Presentation at 2026 SCEC Annual Meeting.

Related Projects & Working Groups
Ground Motions (GM)