Seismic Swarm S20230206.3: Analysis of Activity Near Yeşilyurt, Turkey

The seismic swarm designated S20230206.3 occurred 9 km south of Yeşilyurt in Turkey's Malatya Province, within the tectonically active East Anatolian Fault Zone. This strike-slip fault system accommodates lateral motion between the Arabian and Anatolian plates, producing frequent shallow earthquakes. The region has a documented history of significant seismic events, including the destructive February 2023 Kahramanmaraş earthquakes that originated nearby and caused widespread damage across southeastern Turkey and northern Syria.

The swarm initiated at 02:26 on 6 February 2023 and concluded at 23:53 on 15 February 2023, spanning 237 hours and 27 minutes. During this period, 149 earthquakes were recorded. Analysis of the first 100 events reveals a pattern of moderate-magnitude activity concentrated in the initial days, followed by a gradual decline in both frequency and intensity.

Early events on 6 February included multiple shocks exceeding magnitude 4.0, with the strongest reaching 4.9 at a depth of 14 km. Depths across these events ranged from 2 km to 30 km, indicating activity along both shallow crustal faults and slightly deeper segments of the fault zone. Subsequent days showed a transition to smaller events, predominantly between magnitudes 2.5 and 3.6, with most focal depths around 5 km. By 11 February, activity had notably diminished, featuring isolated events below magnitude 4.0.

This swarm represents one of only two recorded since 1 January 2000, marking the first such sequence in the modern instrumental era for the area. The clustering of events, beginning with a series of magnitude 4+ shocks and transitioning to lower-energy releases, aligns with typical swarm behavior driven by fluid migration or stress redistribution along the East Anatolian Fault. Depths remained predominantly shallow, consistent with the brittle upper crust in this tectonic setting.

Overall, the sequence underscores the ongoing seismic hazard in the Yeşilyurt region, where the interplay of regional plate motions continues to generate episodic activity. Monitoring such swarms provides critical data for understanding fault dynamics and refining hazard assessments in one of Turkey's most seismically vulnerable zones.