Location:

Period:

14 Nov 2011 11:15:03 - 19 Nov 2011 12:13:49 (5 days 58 minutes)

Volcanoes in 100km radius:

Tenduruk Dagi(82km)

Earthquakes:

M 7.0+:

M 7.1; 27 km NNE of Van, Turkey; (23 Oct 2011) (11km from the swarm center)

8 swarms found nearby.

2011

PS20111023.1(36.6km)

23 Oct

1 day 4 hours

10 earthquakes

S20111023.2(4.2km)

23 Oct

14 days 17 hours

739 earthquakes

S20111024.1(25.9km)

23 Oct

4 days 0 hours

78 earthquakes

S20111029.1(9.0km)

28 Oct

8 days 13 hours

155 earthquakes

S20111030.1(24.0km)

29 Oct

2 days 2 hours

46 earthquakes

S20111109.1(26.5km)

9 Nov

11 days 2 hours

333 earthquakes

S20111129.1(18.5km)

28 Nov

35 days 13 hours

454 earthquakes

2022

S20220613.1(26.4km)

12 Jun

3 days 2 hours

44 earthquakes

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Seismic Swarm S20111115.1 in Eastern Turkey: Geological Context and Event Analysis

Eastern Turkey lies within the Alpine-Himalayan orogenic belt, where ongoing convergence between the Arabian and Eurasian plates drives intense seismic activity. The region features a complex network of strike-slip and thrust faults, including segments of the East Anatolian Fault Zone. This tectonic setting produces frequent moderate earthquakes and occasional swarms of low-to-moderate magnitude events.

Swarm S20111115.1 occurred in this seismically active zone, centered near Van Province. It began at 11:15 on 14 November 2011 and concluded at 12:13 on 19 November 2011, spanning 120 hours and 58 minutes. During this interval, 63 earthquakes were recorded, with magnitudes ranging from 1.9 to 4.2 and focal depths predominantly between 2 and 20 km, indicating shallow crustal sources.

The sequence exhibited typical swarm characteristics: a gradual increase in event rate without a single dominant mainshock, followed by a steady decline. The largest event reached magnitude 4.2 at a depth of 5 km on 14 November. Subsequent activity included multiple events of magnitude 3.0–3.2, clustered in the first 48 hours. Depths remained consistently shallow, consistent with the brittle upper crust in this compressional regime.

This swarm took place approximately one month after the magnitude 7.1 Van earthquake of 23 October 2011, whose epicenter lay 27 km NNE of Van and only 11 km from the swarm centroid. The proximity suggests possible static or dynamic stress triggering from the mainshock, a common phenomenon in tectonically active regions following large ruptures.

Historical records since 2000 indicate six seismic swarms in the broader area, with S20111115.1 representing the earliest documented case. Such swarms reflect episodic fluid migration or aseismic slip along fault segments within the plate-boundary zone.

The combination of swarm activity and the preceding major event underscores the elevated seismic hazard in eastern Turkey. Continued monitoring of microseismicity remains essential for understanding stress evolution along regional faults.

References

SeismoSight internal swarm classification database
USGS Earthquake Catalog (events since 2000)