Location:

Period:

30 Oct 2020 11:56:04 - 7 Nov 2020 00:01:28 (7 days 12 hours 5 minutes)

Volcanoes in 100km radius:

None

Earthquakes:

185

M 7.0+:

M 7.0; 13 km NNE of Néon Karlovásion, Greece; (30 Oct 2020) (8km from the swarm center)

4 swarms found nearby.

2020

S20201030.2(18.9km)

30 Oct

24 days 12 hours

881 earthquakes

S20201031.1(25.4km)

30 Oct

2 days 16 hours

47 earthquakes

S20201031.2(24.2km)

31 Oct

15 hours

27 earthquakes

S20201102.1(28.7km)

1 Nov

6 days 5 hours

153 earthquakes

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Seismic Swarm S20201030.3 in the Dodecanese Islands, Greece

A seismic swarm designated S20201030.3 occurred in the Dodecanese Islands region of Greece, beginning at 11:56 on 30 October 2020 and concluding at 00:01 on 7 November 2020. Over approximately 180 hours and five minutes, the swarm produced 185 recorded earthquakes. The events were concentrated in an area known for active tectonics within the Aegean Sea, where the convergence of the African and Eurasian plates drives frequent seismic activity along the Hellenic Arc.

Analysis of the first 100 events reveals a rapid onset with an initial magnitude 4.8 earthquake at 17 km depth. Subsequent activity included numerous events between magnitudes 2.0 and 4.2, with depths predominantly ranging from 1 km to 34 km. The sequence featured several magnitude 4.0 events at shallow depths of 2–10 km, alongside clusters of lower-magnitude tremors at 5–10 km. Magnitudes generally declined after the first day, though occasional peaks above 3.5 persisted into early November. Depths showed variability, with many events occurring at 5–10 km, indicating shallow crustal involvement typical of the region’s fault systems.

This swarm aligns with the area’s established seismic character. The Dodecanese Islands lie near major fault zones associated with the subduction of the African plate beneath the Aegean microplate, producing both shallow crustal earthquakes and deeper events. Historical records indicate elevated seismicity, with the swarm representing the sole such episode documented since 1 January 2000. The preceding activity in this classification also dates to 2020.

A notable strong earthquake of magnitude 7.0 occurred on 30 October 2020, located 13 km north-northeast of Néon Karlovásion and approximately 8 km from the swarm center. This event likely influenced the swarm’s initiation and intensity, as aftershock sequences commonly follow large shocks in tectonically active zones.

The overall pattern underscores the Dodecanese region’s ongoing potential for clustered seismic activity driven by plate-boundary dynamics. Monitoring such swarms provides valuable data on stress accumulation and release along regional faults.

References

SeismoSight internal swarm classification data for S20201030.3.
Geological Survey of Greece regional tectonic summaries.