Seismic Swarm S20230303.1: Analysis of Central Turkey Earthquake Activity

Central Turkey occupies a tectonically complex zone at the western edge of the Anatolian Plate, where ongoing convergence between the Arabian and Eurasian plates drives lateral extrusion of the Anatolian block. This motion is accommodated primarily by the North Anatolian Fault Zone to the north and the East Anatolian Fault Zone to the southeast, both major strike-slip systems capable of producing large-magnitude events. The broader region exhibits shallow crustal seismicity, with most earthquakes occurring at depths of 5–15 km along distributed fault networks.

Seismic swarms, characterized by clusters of events without a single dominant mainshock, are documented in the historical record of the area. Since 1 January 2000, two such swarms have been identified, with the first occurring in 2023. These sequences typically involve low-to-moderate magnitudes and shallow focal depths, reflecting fluid migration or aseismic slip along secondary faults rather than primary plate-boundary rupture.

Swarm S20230303.1 began at 13:24 on 2 March 2023 and concluded at 03:51 on 18 March 2023, spanning 374 hours and 27 minutes. During this interval, 153 earthquakes were recorded across central Turkey. Analysis of the first 100 events reveals predominantly small magnitudes, with 92 events below magnitude 3.0 and only one reaching 5.0. Depths remained shallow, averaging 6–8 km, consistent with the regional crustal structure.

The sequence initiated with microseismicity (magnitudes 1.8–2.8) on 2 March, followed by a magnitude-5.0 event at 02:53 on 3 March at 7 km depth. Subsequent activity included multiple events of magnitude 3.0–4.0 clustered within the first 48 hours, after which magnitudes declined while event frequency remained elevated for several days. Notable later shocks included a magnitude-3.9 event on 5 March and isolated magnitude-3.7 events on 7 March. The temporal pattern shows an initial energetic phase decaying into sustained low-level activity, typical of swarm behavior driven by pore-pressure changes or slow slip.

This swarm occurred in the aftermath of the major February 2023 earthquakes that affected southeastern Turkey, highlighting the potential for triggered seismicity on adjacent fault segments. Continued monitoring of central Turkey remains essential given the area’s proximity to densely populated regions and critical infrastructure.