Seismic Swarm S20240617.1 in Central Turkey: Characteristics and Regional Context

Central Turkey experienced a notable seismic swarm designated S20240617.1 between 09:32 on 16 June 2024 and 16:34 on 19 June 2024. Over this 79-hour period, 58 earthquakes were recorded, providing valuable data on localized seismic activity within the Anatolian tectonic framework.

The swarm initiated with a magnitude 1.9 event at 7 km depth. Activity intensified later that day, culminating in the largest event—a magnitude 4.4 earthquake at 5 km depth at 17:24:52. Subsequent events remained predominantly below magnitude 2.0, with depths consistently ranging from 4 to 12 km. Notable later shocks included magnitudes of 2.8, 2.5, 2.9, and several around 2.0, all occurring at shallow crustal levels. This pattern reflects typical swarm behavior, characterized by numerous small-magnitude events without a dominant mainshock-aftershock sequence.

Geologically, Central Turkey occupies a critical position on the Anatolian Plate, which moves westward due to the northward collision of the Arabian Plate with the Eurasian Plate. The region is bounded by the North Anatolian Fault Zone to the north and the East Anatolian Fault Zone to the southeast, both major strike-slip systems accommodating regional deformation. Shallow crustal depths observed in the swarm align with active faulting in this compressional-transpressional regime, where accumulated strain releases through distributed microseismicity.

Historical records indicate seismic swarms are infrequent in Central Turkey. Since 1 January 2000, only three such swarms have occurred, with the first documented in 2023. The current event represents continued monitoring of this phenomenon, highlighting episodic clustering rather than isolated large-magnitude ruptures.

Analysis of the event timings shows peak activity concentrated within the first 48 hours, followed by a gradual decline. Magnitudes clustered between 0.9 and 2.0 for the majority of events, underscoring low-energy release overall. Depths remained stable in the upper crust, consistent with brittle failure along pre-existing fault planes influenced by regional tectonics.

This swarm contributes to understanding seismic hazard in Central Turkey, where ongoing plate interactions sustain background seismicity. Continued observation supports refined models of fault behavior in the Anatolian interior.

References

SeismoSight internal swarm classification S20240617.1 dataset.
USGS Earthquake Catalog (regional Anatolian tectonics summaries).
Peer-reviewed literature on Anatolian Plate kinematics (e.g., recent updates through 2024).