Seismic Swarm S20070221.1: Eastern Turkey, February 2007

Eastern Turkey lies within the Alpine-Himalayan orogenic belt, where the Arabian Plate converges with the Eurasian Plate at rates of approximately 15–20 mm per year. This tectonic interaction produces a complex network of strike-slip and thrust faults, including the East Anatolian Fault Zone and the Bitlis-Zagros suture. The area experiences frequent seismic activity due to these active structures, with historical records documenting destructive events dating back centuries.

The seismic swarm designated S20070221.1 began at 11:05 UTC on 21 February 2007 and concluded at 16:12 UTC on 26 February 2007. Over 125 hours and 6 minutes, 124 earthquakes were recorded. The sequence opened with a magnitude 5.7 event at 6 km depth, followed by a rapid succession of smaller shocks. Analysis of the first 100 events reveals predominantly shallow hypocenters, with depths ranging from 2 km to 30 km and the majority clustered between 2 km and 15 km. Magnitudes after the initial shock remained below 4.0, peaking at 3.8, indicating a mainshock-aftershock pattern within an overall swarm classification.

Temporal distribution showed highest activity in the first 48 hours, with event rates declining steadily thereafter. Depths remained consistent across the period, suggesting a localized crustal volume under stress without significant migration. The sequence aligns with regional tectonics driven by oblique convergence and lateral escape along major fault systems.

Since 1 January 2000, this remains the sole swarm recorded in the internal classification for the region, underscoring its relative rarity amid background seismicity.

References

• United States Geological Survey Earthquake Catalog
• European-Mediterranean Seismological Centre Data Archive
• Active Tectonics of the Eastern Mediterranean Region (peer-reviewed geological syntheses)