Location:

Period:

15 Feb 2005 20:08:43 - 16 Feb 2005 13:03:29 (16 hours 54 minutes)

Volcanoes in 100km radius:

None

Earthquakes:

17 swarms found nearby.

2004

PS20041226.8(127.1km)

26 Dec

3 days 5 hours

41 earthquakes

PS20041226.5(67.0km)

26 Dec

1 day 11 hours

20 earthquakes

PS20041226.7(190.6km)

26 Dec

11 hours

16 earthquakes

PS20041226.1(130.8km)

26 Dec

2 days 23 hours

30 earthquakes

2005

PS20050101.3(184.1km)

1 Jan

1 day 1 hours

6 earthquakes

S20050127.1(51.5km)

26 Jan

4 days 22 hours

168 earthquakes

S20050127.2(79.9km)

26 Jan

3 days 18 hours

105 earthquakes

PS20050126.1(51.6km)

26 Jan

5 days 20 hours

98 earthquakes

S20050128.1(93.0km)

27 Jan

2 days 5 hours

44 earthquakes

S20050129.1(81.4km)

28 Jan

1 day 12 hours

33 earthquakes

PS20050202.1(170.4km)

1 Feb

14 hours

5 earthquakes

PS20050205.1(35.7km)

4 Feb

2 days 6 hours

10 earthquakes

2014

PS20140321.1(116.3km)

21 Mar

7 hours

7 earthquakes

PS20141111.1(111.3km)

11 Nov

3 hours

5 earthquakes

2019

PS20190401.1(111.2km)

31 Mar

8 hours

12 earthquakes

2021

PS20210803.1(55.9km)

3 Aug

2 hours

5 earthquakes

2023

PS20230409.1(78.1km)

9 Apr

13 hours

5 earthquakes

AI-generated article — for informational and entertainment purposes only. May contain inaccuracies. Full disclaimerFound an error?

Seismic Swarm PS20050216.1 in the Nicobar Islands Region

A notable seismic swarm occurred in the Nicobar Islands, India region, between 20:08 on 15 February 2005 and 13:03 on 16 February 2005. Over 16 hours and 54 minutes, five earthquakes were recorded as part of this swarm sequence. The events ranged in magnitude from 4.5 to 5.9, with focal depths between 11 km and 33 km. Specific occurrences included a magnitude 5.2 event at 20:08:43 on 15 February at 33 km depth, followed by a magnitude 5.3 at 20:20:44 on the same day at 33 km depth. On 16 February, a magnitude 5.9 at 08:19:41 occurred at 11 km depth, closely followed by a magnitude 5.8 at 08:19:44 at 30 km depth, and concluding with a magnitude 4.5 at 13:03:29 at 30 km depth.

The Nicobar Islands form part of the Andaman-Nicobar archipelago, situated along a tectonically active convergent margin in the eastern Indian Ocean. This region lies at the boundary where the Indian Plate subducts beneath the Burma Plate along the Sunda Trench, producing frequent seismic activity including both shallow crustal events and deeper subduction-related earthquakes. The islands themselves are underlain by a mix of sedimentary, volcanic, and ophiolitic rocks, reflecting their position on an accretionary complex. Historical seismicity in the broader Andaman-Nicobar zone has included great earthquakes, such as the 2004 Sumatra-Andaman event of magnitude 9.1–9.3, whose rupture extended northward and influenced subsequent stress patterns in the Nicobar segment.

Swarm activity in this setting often reflects fluid migration or stress triggering along fault systems associated with the subduction interface and overlying crustal faults. The February 2005 swarm took place in the aftermath of the 2004 megathrust rupture, consistent with patterns of aftershock and swarm sequences observed in the region. Since 1 January 2000, twelve such swarms have been documented in the Nicobar Islands area, with four occurring in 2004 and eight in 2005, underscoring episodic clustering of moderate-magnitude events.

Geological monitoring of the Nicobar region continues to highlight its elevated seismic hazard due to ongoing plate convergence at rates of approximately 5–6 cm per year. The combination of shallow and intermediate-depth events within the swarm indicates activation across multiple structural levels within the subduction system.

References

USGS Earthquake Hazards Program: Andaman-Nicobar seismicity reports
Geological Survey of India: Tectonic framework of the Andaman-Nicobar Islands
International Seismological Centre: Earthquake catalog data for the eastern Indian Ocean