Seismic Swarm S20230207.1: Analysis of Central Turkey Seismicity in February 2023

Central Turkey occupies a tectonically active zone at the western edge of the Anatolian plate, where ongoing convergence between the Arabian and Eurasian plates drives lateral extrusion. This setting produces frequent strike-slip and normal faulting along major structures such as the North Anatolian Fault and subsidiary segments of the East Anatolian Fault system. The region’s crust is relatively thin and fragmented, allowing stress to redistribute through distributed microseismicity when larger events occur nearby.

Swarm S20230207.1 began at 11:30 on 6 February 2023 and concluded at 23:24 on 14 February 2023, spanning 203 hours and 53 minutes. During this interval, 108 earthquakes were recorded. The first 100 events exhibited magnitudes between 2.5 and 4.5 and focal depths predominantly between 2 km and 14 km, with a smaller number reaching 22 km. The largest event reached magnitude 4.5 at 10 km depth on 6 February at 14:41:57 UTC. Activity showed a typical swarm pattern: an initial energetic phase followed by a gradual decline, without a single dominant mainshock.

Temporal distribution indicates peak rates on 6–8 February, after which event frequency decreased steadily. Depths clustered around 5–10 km, consistent with brittle failure within the upper crust of central Anatolia. No events exceeded magnitude 5.0, distinguishing the sequence from mainshock-aftershock sequences associated with the region’s larger fault systems.

According to internal records maintained since 1 January 2000, only two swarms have been identified in the area. Swarm S20230207.1 represents the first such sequence. This scarcity underscores that clustered microseismicity of this type remains uncommon relative to the background rate of isolated events.

The swarm’s timing coincides with a period of elevated regional strain following the 6 February 2023 magnitude-7.8 Kahramanmaraş earthquake approximately 150 km to the south. Although direct triggering cannot be confirmed from the provided data alone, the spatial and temporal proximity suggests possible stress perturbation transmitted through the Anatolian crust. Continued monitoring is warranted to assess whether residual stress may influence future activity along nearby fault segments.

References

SeismoSight internal swarm catalogue (S20230207.1 parameters and event list).
Regional tectonic summaries from the Turkish Mineral Research and Exploration Institute (MTA) and peer-reviewed literature on Anatolian plate kinematics (updated through 2023).