SEISMICITY OF THE ANDAMAN &
NICOBAR ISLANDS
EARTHQUAKE
HISTORY
The map
to the left shows all historically recorded earthquakes in the
Andaman & Nicobar Islands. Earthquakes having magnitudes greater
than 4.0 since 1973 are also shown. Two prominent red triangles
visible to the north-east of Port Blair, i.e. in the top half of the
map, are the only volcanoes in India. The northernmost of the two is
the Barren Island Volcano. This volcano has erupted in recent times,
the last being in 1996. The other volcano is called Narcondam and is
dormant. The Andaman and Nicobar Islands are located near the
boundary of the Indian plate and the Burmese Microplate. The Andaman
Trench marks this boundary and lies in the Bay of Bengal to the west
of the archipelago (Blue teethed line). Another prominent feature is
the north-south West Andaman fault which is strike-slip in nature
and lies in the Andaman Sea, to the east of this island chain (Red
line). The Andaman Sea, just like the Atlantic Ocean, is presently
being widened by a tectonic process called "Sea Floor spreading".
This is taking place along undersea ridges
(Yellow lines) on the seafloor. The Indian plate is diving beneath
the Burmese Microplate along the Andaman Trench in a process known
as "Subduction". Shallow and occasional intermediate-depth
earthquakes delineate the subducted slab under the Andaman-Nicobar
islands joining the seismicity trend of the Indo-Burman ranges. In
recent and historic times only two high magnitude earthquakes have
occurred in this region. The first of these was in 1881, in the
Andaman Sea, near the Nicobar Islands and the second, off the west
coast of Middle Andaman Island in June 1941.
LARGEST
INSTRUMENTED EARTHQUAKE IN THE ANDAMAN &
NICOBAR ISLANDS
26 June 1941 - West of
Middle Andaman Island, India, Mw 7.7
11:52:03 UTC, 12.50 N, 92.50 E
This is
strongest earthquake on record in this region to be recorded
instrumentally. It caused damage in the Andaman Islands, including
at Port Blair, destroying many of its major buildings. The quake
also spawned a tsunami in the Bay of Bengal which was recorded along
the Coromandel Coast.
SEISMIC
HAZARD
All of the
Andaman & Nicobar Islands lie in Zone V. This makes them
extremely vulnerable to major earthquakes with an MM intensity
greater than IX.
The entire island chain is also
susceptible to tsunamis both from large local quakes and also from massive
distant shocks. No warning system is presently in place for any of
the islands in this chain.
SIGNIFICANT EARTHQUAKES IN
THE ANDAMAN & NICOBAR
ISLANDS
Both
instrumented and non-instrumented events may be listed below.
Reported magnitudes are listed for instrumented events while maximum
observed intensities are listed for non-instrumented shocks. Some of
the latter might also have magnitudes assigned to them by various
authors, in which case the reference is stated. Please note that
Magnitude and Intensity are NOT THE SAME.
31st December
1881 - NNW of the Andaman
Islands, India, Mw 7.9 (Bilham et al 2000)
No recording
stations were present at the time, though calculations were made by
various agencies of the seismic vertical from the time of the shock
recorded at different locations including Kolkata (formerly
Calcutta), Vishakhapatnam, Chennai and Port Blair. They also
recorded the arrivals of tsunamis at different points on the eastern
coast of India. The tsunami had a maximum run-up of 1.2 meters on
the Coromandel coast. Damage occurred to masonry buildings at Port
Blair.
16 November 1914 - South-west of Barren Island, India, Ms 7.2,
16:17:06.0
UTC, 12.00 N, 94.00 E
28
June 1925 - SE of Little
Andaman Island, India
13:41:35.0 UTC, 10.20 N, 92.80
E
1 August
1929 - Andaman Sea, ESE of
Barren Island, India, Ms 6.5
05:01:48.0 UTC, 12.00 N, 95.50
E
9 December 1929
- SSE of Great Nicobar, India,
Ms 6.7, Mb 7.2
06:49:54.0 UTC, 04.50 N, 94.50
E
19 March
1936 - Little Andaman Island,
India, Ms 6.5
09:04:05.0 UTC, 10.50 N, 92.50
E
14 September
1939 - Andaman Sea, SE of
Barren Island, India, Ms 6.0
09:00:58.0 UTC, 11.50 N, 95.00
E
26 June
1941 - West of Middle Andaman
Island, India, Mw 7.7
11:52:03 UTC, 12.50 N, 92.50 E
This is strongest
earthquake on record in this region to be recorded instrumentally.
It caused damage in the Andaman Islands, including at Port Blair,
destroying many of its major buildings. The quake also spawned a
tsunami in the Bay of Bengal which was recorded along the Coromandel
Coast.
8 August
1945 - North of Little Andaman
Island, India, Ms 6.7
09:53:40.0 UTC, 11.00 N, 92.50
E
23 January
1949 - Andaman Sea, East of Car
Nicobar Island, India, Ms 7.2
06:31:13.0 UTC, 09.50 N, 94.50
E
17 May
1955 - Off the east coast of
Great Nicobar Island, India, Mw 7.0, Ms 7.2
14:49:49 UTC, 07.00N,
94.00E
18 June
1957 - Andaman Sea, ENE of
Narcondam Island, India, Ms 6.5
14:48:17.0 UTC, 14.00 N, 96.00
E
14 February
1967 - Andaman Sea, West of the
Mergui Archipelago, 6.8
01:36:04 UTC, 13.70N,
96.50E
20 January
1982 - 8.5 kilometers east of
Bananga, Great Nicobar Island, Mw 6.2
04:25:11 UTC, 06.95N,
94.00E
Followed by a Mw 6.1 quake at 07:09:17 UTC which had its
epicentre 8
kilometers south-east of Laful, Great Nicobar Island. Some injuries and considerably damage occurred
in the Nicobar Islands due to both these quakes.
20 January 1982 - 8 kilometers south-east of Laful, Great Nicobar Island, Mw
6.1
07:09:17 UTC, 07.12N, 93.94E
Followed the Mw 6.2 quake at
04:25:11 UTC which had its epicentre 8.5 kilometers east of
Bananga, Great
Nicobar Island. Some injuries and
considerably damage occurred in the Nicobar Islands due to both
these quakes.
14 September 2002 -
23.6
kilometres SSE of Diglipur (North Andaman), India, Mw
6.5
22:28:31 UTC,
13.087 N, 93.112 E
This earthquake caused damage on North Andaman
and was felt as far south as Port Blair. A tsunami was experienced
on the a few islands of North Andaman's eastern and northern coasts.
There were two unconfirmed fatalities at Rongat. |
