Seismic Swarm S20231123.1 in Eastern Turkey
Eastern Turkey lies within a highly active tectonic zone shaped by the ongoing collision between the Arabian and Eurasian plates. This region forms part of the Alpine-Himalayan orogenic belt, where compressional forces drive crustal deformation along major fault systems, including the East Anatolian Fault Zone and associated strike-slip structures. Historical seismicity reflects this activity, with frequent moderate earthquakes occurring at shallow depths typically between 5 and 15 kilometers.
Swarm S20231123.1 began at 21:56 on 22 November 2023 and concluded at 10:08 on 1 December 2023, spanning 204 hours and 11 minutes. During this period, 162 earthquakes were recorded in eastern Turkey. The sequence represents one of three swarms documented since 2000, marking the first such event in that timeframe.
Analysis of the first 100 events reveals a clear temporal pattern. The sequence initiated with low-magnitude tremors around 1.0 to 2.2, concentrated at depths of 5 to 12 kilometers. A notable escalation occurred on 23 November at 14:46 with a magnitude 5.3 event at 10 kilometers depth, followed closely by a magnitude 4.7 shock at the same depth. Subsequent activity included multiple events between magnitudes 2.0 and 3.4, with the majority clustered at 5 to 7 kilometers depth. Later events in the initial 100 showed continued small-magnitude releases, predominantly below 2.5, interspersed with occasional peaks reaching 3.0. Depths remained shallow throughout, rarely exceeding 12 kilometers, consistent with the region's upper-crustal faulting.
This distribution indicates a swarm characterized by a mainshock-aftershock progression rather than purely uniform microseismicity. The 5.3 magnitude event appears to have triggered an elevated rate of smaller quakes, with most activity decaying rapidly after the initial 24 hours. Depths averaging near 7 kilometers suggest rupture within brittle crustal layers influenced by regional plate convergence.
Such swarms contribute to understanding stress accumulation along the East Anatolian Fault system. Eastern Turkey's geology features ophiolitic mélanges and volcanic arcs overlying metamorphic basement, which accommodate both strike-slip and thrust motions. Updated monitoring since the major 2023 regional events has improved detection of these low-magnitude sequences.
References
- United States Geological Survey Earthquake Catalog
- European-Mediterranean Seismological Centre Data Archive
- Turkish Disaster and Emergency Management Authority Seismic Reports