Seismic Swarm S20100524.1: Eastern Turkey, May 2010

A seismic swarm designated S20100524.1 occurred in eastern Turkey between 05:47 on 23 May 2010 and 00:46 on 26 May 2010. Over 66 hours and 58 minutes, the sequence produced 39 earthquakes. Magnitudes ranged from 2.3 to 3.8, with the largest event recorded at 3.8 on 23 May at 19:58:31. Depths remained predominantly shallow, between 0 and 20 km, consistent with crustal deformation in the region.

The sequence began with a 3.1-magnitude event at 05:47:44 on 23 May at 2 km depth. Subsequent events clustered in the first 24 hours, including multiple shocks of 2.5–3.0 magnitude at depths of 2–20 km. Activity continued through 24 May with events such as a 3.5-magnitude quake at 06:57:07 and a 3.0-magnitude shock at 08:04:04. On 25 May, seven additional events occurred, mostly between 2.6 and 2.9 magnitude at 2–10 km depth. The final event, magnitude 2.5 at 2 km depth, marked the swarm’s conclusion on 26 May.

Eastern Turkey lies within the Alpine-Himalayan orogenic belt, where the Arabian Plate converges northward with the Eurasian Plate at rates of approximately 15–20 mm per year. This collision drives deformation across the East Anatolian Fault Zone and associated strike-slip and thrust structures. The area experiences distributed seismicity rather than large single-fault ruptures, producing frequent swarms and moderate events. Shallow focal depths reflect brittle failure in the upper crust above a ductile lower crust influenced by regional compression.

Historical records document recurrent moderate seismicity in eastern Turkey. Instrumental catalogs since the early twentieth century show clusters of events with magnitudes below 4.0 occurring along secondary faults and within deforming blocks. Such swarms typically reflect fluid migration or aseismic slip triggering, without progression to a mainshock of magnitude 6 or greater.

The 2010 swarm fits this pattern of low-to-moderate, shallow activity. No single dominant fault plane is evident from the spatial distribution; instead, the events suggest activation of a network of minor structures under regional stress. Depths concentrated above 10 km indicate failure within the seismogenic zone most susceptible to small-scale stress perturbations.

Seismic hazard assessments for eastern Turkey incorporate these swarm characteristics into probabilistic models. The region’s convergence continues to elevate risk, with potential for larger events along the East Anatolian Fault, yet swarms of this scale remain common background phenomena.

References

USGS Earthquake Catalog (earthquake.usgs.gov)
Turkish Disaster and Emergency Management Authority (AFAD) seismic bulletins
Bird, P. (2003). An updated digital model of plate boundaries. Geochemistry, Geophysics, Geosystems.