Seismic Activity in Eastern Turkey: Analysis of Swarm S20241016.1

Eastern Turkey occupies a tectonically active zone shaped by the ongoing collision between the Arabian and Eurasian plates. This convergence drives deformation along major structures, including the East Anatolian Fault Zone and the Bitlis-Zagros suture. The region experiences frequent earthquakes due to strike-slip and thrust faulting, with crustal depths typically ranging from 5 to 20 kilometers. Historical records document significant events, such as the 2023 magnitude 7.8 and 7.7 earthquakes that originated near the East Anatolian Fault, underscoring the area's persistent seismic hazard.

Seismic swarms represent clusters of earthquakes occurring in rapid succession without a single dominant mainshock. Swarm S20241016.1 began at 02:57 on 16 October 2024 and concluded at 05:42 on 2 November 2024. Over 410 hours and 44 minutes, the sequence produced 357 events. This marks only the second swarm recorded in the region since 1 January 2000, following an earlier episode in 2023.

Analysis of the first 100 events reveals a rapid onset with magnitudes spanning 0.7 to 6.0 and focal depths concentrated between 5 and 14 kilometers. The largest event, magnitude 6.0, occurred at 07:46 on 16 October at 10 kilometers depth, followed closely by several magnitude 3 events within minutes. Subsequent activity consisted predominantly of microearthquakes below magnitude 2.0, clustered at depths around 7 kilometers. The sequence displayed a typical swarm pattern of declining event size after the initial peak, with most activity remaining shallow and consistent with brittle failure in the upper crust.

Such swarms can arise from fluid migration, stress transfer along fault networks, or aseismic slip episodes. In the Eastern Turkey setting, they often align with segments of the East Anatolian Fault system, where accumulated strain is released in diffuse clusters rather than isolated large ruptures. The 2024 swarm's parameters align with regional norms for depth distribution and magnitude-frequency relations observed in prior instrumental records.

Continued monitoring remains essential given the region's proximity to populated centers and critical infrastructure. Future studies integrating geodetic and seismic data could clarify whether this swarm reflects transient tectonic loading or longer-term fault behavior.

References

USGS Earthquake Hazards Program regional reports on Anatolian tectonics.
SeismoSight internal swarm classification database.