Active Tectonics and Seismicity of the Anatolian Fault Zones

The Anatolian fault system, situated at the junction of the Eurasian, Arabian and African plates, comprises two primary strike-slip structures: the North Anatolian Fault Zone (NAFZ) and the East Anatolian Fault Zone (EAFZ). These major transform faults accommodate westward extrusion of the Anatolian block, producing high strain rates and frequent seismic activity. Historical records document successive large earthquakes migrating westward along the NAFZ over the past century, leaving a seismic gap beneath the Sea of Marmara. The EAFZ, in contrast, exhibits complex segmentation and interactions with subsidiary splays. Contemporary geodetic observations reveal differential slip rates of 20–25 mm/yr on the NAFZ and 10–15 mm/yr on the EAFZ, with intervening transfer zones exhibiting both crustal shortening and extension. Interactions between major events, aseismic creep patches and dynamic stress transfer contribute to irregular rupture propagation and variable recurrence intervals. The region’s dense urban centres and critical infrastructure overlay these active faults, rendering the precise characterisation of strain accumulation, fault geometry and rupture dynamics essential for seismic hazard assessments and resilience planning.

Research from Nature Portfolio

Recent studies have reconstructed the complex 2023 earthquake doublet along the EAFZ, revealing a bilaterally propagating mainshock that broke through multiple fault segments over more than 350 km, followed nine hours later by a second event on a curved splay. Inversion of seismic and geodetic data indicates fluctuating rupture speeds, with early supershear propagation exceeding 4 km/s and peak slips above 8 m. Coulomb failure stress changes imparted by the first event appear to have triggered the subsequent rupture. Complementary analysis emphasises the heightened seismic risk across the region by quantifying directivity effects and stress interactions during multi-segment rupture, underscoring the capacity for cascading failures within an intricate fault network.

Active Tectonics and Seismicity of the Anatolian Fault Zones publication trend

The graph below shows the total number of articles in active tectonics and seismicity of the anatolian fault zones across all publications each year (not limited to Nature Index journals).

Technical terms

Strike-slip fault: A fracture in the crust where blocks move predominantly horizontally past one another.

Seismic gap: A segment of an active fault that has not ruptured for a longer period than adjacent sections and may accumulate high strain.

Coulomb failure stress: A metric quantifying changes in stress on a fault plane that promote or inhibit slip.

InSAR (Interferometric Synthetic Aperture Radar): A satellite technique measuring ground deformation by comparing radar phase differences between repeat passes.

GNSS (Global Navigation Satellite System): A constellation of satellites used to provide precise three-dimensional positions and velocities of ground stations.

Supershear rupture: A rupture propagation regime in which the crack tip advances faster than the shear-wave speed of the surrounding medium.

Fault creep: A gradual, aseismic slip on a fault that releases strain without generating significant earthquakes.

References

1. Complex multi-fault rupture and triggering during the 2023 earthquake doublet in southeastern Türkiye. Nature Communications (2023).
2. High‐Resolution Surface Velocities and Strain for Anatolia From Sentinel‐1 InSAR and GNSS Data. Geophysical Research Letters (2020).
3. Istanbul's earthquake hot spots: Geodetic constraints on strain accumulation along faults in the Marmara seismic gap. Geophysical Research Letters (2014).
4. Rapid Characterization of the February 2023 Kahramanmaraş, Türkiye, Earthquake Sequence. The Seismic Record (2023).